Multifunction Power Supply
Petre tzv Petrov
Many embedded systems these days need +5V power supply with some special functions such as power-fail detection, zero-crossing signals for mains power supply and possibility to maintain the charging of built-in batteries.
Presented here is the circuit of such a power supply for embedded systems. It provides +5V, battery charger, zero-crossing signals and power-fail signal. The circuit is based on popular low-cost components. It needs simple adjustment with potmeter POT1 to immediately get you started.
Circuit and working
The circuit shown in Fig. 1 is built around a step-down transformer (X1), two bridge rectifiers(BR1 and BR2), adjustable voltage regulator LM317 (IC1), 5V voltage regulator 7805 (IC2), hex inverter Schmitt trigger 74HC14 (IC3) and a few discrete components.
The mains power supply 230V AC, 50Hz is applied to connector CON1. Fuse F1 protects the input from overloads. Resistor R1 and capacitor C1 filter some of the noise coming from the mains power supply. The secondary of power transformer X1 is 12V, 2.5A.
CON3 provides +5V, 1A power supply using standard 5V regulator IC2. Rectifying bridge BR1 is of 2.5A. The value of the main filtering capacitor (C4) should be at least 4700 µF. IC2 provides regulated +5V with output current up to 1A. If a higher current is needed, regulators like 78T05 (3A, 5V) or 78S05 (2A, 5V) can be used. In practice, it is better to limit the load for 78XX up to around 0.7-0.8A. The unregulated output at CON4 provides voltage of 10V to 18V depending on the transformer used and the current consumption from the power supply. This unregulated voltage can be used for peripheral functions. Fuse F2 is used to protect the output.
The power supply incorporates battery charger with adjustable regulator IC1. A 6V rechargeable battery is used to provide power supply to some parts of the system when the mains power supply does not function properly. The maximum voltage level across the rechargeable battery is adjusted using potmeter POT1. The maximum charging current is limited by resistor R7. Regulator IC1 can provide output voltage of +1.25V to +8.2V, adjustable with potmeter POT1.
Diodes D1, D2 and D3 protect regulators IC1 and IC2. Bridge rectifier BR2 is used only to provide signals around the zero crossings. Capacitor C2 should have a small value. It is intended to cut only the very high frequency, not to filterthe mains power supply. The values of R2 and R3 can be changed depending on IC3 and parameters of the produced pulses.
CON5 provides power-fail signal when the voltage at test point TP2 falls below approximately 8V. Transistor T1 stops conducting and the control unit is intimated the same by a high signal at pin 3 of CON5.
The threshold voltage of the power-fail signal is regulated with zener diode ZD2 (7.5V) and resistors R4 and R5. Transistor T1 should preferably be switching type, but most of the npn silicon transistors with a high gain will also work well.
The outputs from pins 2, 3 and 4 of connector CON6 provide different signals with a frequency that is double the frequency of the mains power supply (100 Hz). These signals are active near zero crossings of the mains power supply and can be used for several purposes, such as:
1. The control unit can use them to measure the frequency of the mains power supply.
2. These can be used to synchronise the operation of the control unit with zero crossings of the mains power supply.
3. Тhe amplitude of signal TP4 is proportional to the secondary voltage of the transformer. The control unit can measure it and determine the secondary voltage of X1.
4. Outputs TP5 and TP3 are TTL- or CMOS-compatible depending on IC3. IC3 can be CMOS or TTL; e.g., 74HC14, 74HCT14, 74LS14, etc. It should have built-in Schmitt trigger.
Construction and testing
Use individual heat-sinks for IC1 and IC2. The size of the heat-sink should be calculated according to the dissipated heat for each particular case; e.g., the thermal resistance should be below 5°C/W for each heat-sink. The metallic part of 7805 is connected to the ground pin, while the metallic part of LM317 is connected to the output pin.
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Circuit and working
The circuit shown in Fig. 1 is built around a step-down transformer (X1), two bridge rectifiers(BR1 and BR2), adjustable voltage regulator LM317 (IC1), 5V voltage regulator 7805 (IC2), hex inverter Schmitt trigger 74HC14 (IC3) and a few discrete components.
 Fig. 1: Circuit of multifunction power supply |
CON3 provides +5V, 1A power supply using standard 5V regulator IC2. Rectifying bridge BR1 is of 2.5A. The value of the main filtering capacitor (C4) should be at least 4700 µF. IC2 provides regulated +5V with output current up to 1A. If a higher current is needed, regulators like 78T05 (3A, 5V) or 78S05 (2A, 5V) can be used. In practice, it is better to limit the load for 78XX up to around 0.7-0.8A. The unregulated output at CON4 provides voltage of 10V to 18V depending on the transformer used and the current consumption from the power supply. This unregulated voltage can be used for peripheral functions. Fuse F2 is used to protect the output.
The power supply incorporates battery charger with adjustable regulator IC1. A 6V rechargeable battery is used to provide power supply to some parts of the system when the mains power supply does not function properly. The maximum voltage level across the rechargeable battery is adjusted using potmeter POT1. The maximum charging current is limited by resistor R7. Regulator IC1 can provide output voltage of +1.25V to +8.2V, adjustable with potmeter POT1.
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CON5 provides power-fail signal when the voltage at test point TP2 falls below approximately 8V. Transistor T1 stops conducting and the control unit is intimated the same by a high signal at pin 3 of CON5.
The threshold voltage of the power-fail signal is regulated with zener diode ZD2 (7.5V) and resistors R4 and R5. Transistor T1 should preferably be switching type, but most of the npn silicon transistors with a high gain will also work well.
The outputs from pins 2, 3 and 4 of connector CON6 provide different signals with a frequency that is double the frequency of the mains power supply (100 Hz). These signals are active near zero crossings of the mains power supply and can be used for several purposes, such as:
1. The control unit can use them to measure the frequency of the mains power supply.
2. These can be used to synchronise the operation of the control unit with zero crossings of the mains power supply.
3. Тhe amplitude of signal TP4 is proportional to the secondary voltage of the transformer. The control unit can measure it and determine the secondary voltage of X1.
4. Outputs TP5 and TP3 are TTL- or CMOS-compatible depending on IC3. IC3 can be CMOS or TTL; e.g., 74HC14, 74HCT14, 74LS14, etc. It should have built-in Schmitt trigger.
Construction and testing
Use individual heat-sinks for IC1 and IC2. The size of the heat-sink should be calculated according to the dissipated heat for each particular case; e.g., the thermal resistance should be below 5°C/W for each heat-sink. The metallic part of 7805 is connected to the ground pin, while the metallic part of LM317 is connected to the output pin.
 Fig. 2: An actual-size, single-side PCB for the multifunction power supply |
 Fig. 3: Component layout for the PCB |
An actual-size, single-side PCB for the multifunction power supply is shown in Fig. 2 and its component layout in Fig. 3. After assembling the circuit on a PCB, enclose it in a suitable case. Fix all the connectors at the rear side of the cabinet for connecting the mains and taking the outputs.
To test the circuit, switch on switch S1 and check various voltages as indicated in the test-points table. LED1 indicates the availability of 5V.
To test the circuit, switch on switch S1 and check various voltages as indicated in the test-points table. LED1 indicates the availability of 5V.
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Designing A Cost-Effective and Versatile Home Area Network Device
The device proposed here integrates seamlessly with a home area network and keeps a tab on the energy consumption and operation of electrical equipment while acting as a low-cost energy meter
Manish sharma, Manish Jindgar and Biswaprakash Navajeevan
The sky-rocketing cost of energy production has necessitated a more efficientenergy consumption process. This has brought revolution in electrical equipment manufacturing and energy metering infrastructure. Home area network (HAN) is an advanced electrical ecosystem in which a smart utility meter and HAN devices communicate with each other to control the energy consumption profile. Armed with the latest technological advancements in the fieldof energy utilisation, HANs are ready to supplant the traditional electrical ecosystems at home.
A basic HAN device has a two-way communication link with a utility meter and optionally with other devices in a HAN ecosystem, sharing energy consumption data of the equipment it is connected to and also receiving commands to turn off or hibernate the equipment when unused.
 Fig. 1: Application diagram of HAN device |
A basic HAN device has a two-way communication link with a utility meter and optionally with other devices in a HAN ecosystem, sharing energy consumption data of the equipment it is connected to and also receiving commands to turn off or hibernate the equipment when unused.
This low-cost device can be hooked in the existing electrical infrastructure without the need to replace, renovate, alter or rework the infrastructure. The power consumption is very low (in microamperes) when it’s not in use. The following sections describe certain enhancements to the basic HAN device architecture which extend its capability and feature-set.
Architecture
The HAN device can be considered as an intelligent power socket, which at one end connects to the normal power socket and on the other end offers pluggable connection interface for home appliances, e.g., microwave and air-conditioner. It can be controlled directly by the utility meter over wireless interfaces like radio frequency (RF) or wired interfaces like power line communication (home plug, etc). Additionally, its firmwarecan be upgraded over the RF/programmable logic controller (PLC) interface by the utility meter. Various energy parameters of the device can be displayed on the LCD. It also supports battery backup option for maintaining the time and date.
Fig. 1 shows the application diagram of the HAN device. The device consists of a microcontroller, 230V-3.3V converter, relay, signal conditioning circuitry, infrared (IR) interface (supporting both transmitter and receiver), LCD panel and RF/power-line communication physical layer.
Its main operational features are:
- Very low current consumption (10 μA) when it’s not functional
- Very low run current (10 mA); 40 mA at full load
- Fully controlled by the energy meter
- High-voltage cut-off to save the appliances
- Wireless communication over 2.4GHz Zigbee
- Month-wise information storage of the power consumed
- Fully-functional system starting from 90V AC to 300V AC
- Easy to hook on to the network
- Compact in size
Role of various components
Fig. 2 shows the block diagram of the device components. The role of these components is described below:
Microcontroller. The microcontroller or system-on-a-chip (SoC) plays a pivotal role in the device operation. In addition to controlling other components, it stores the application firware in its internal Flash memory. For supporting various functionalities of the HAN device, the microcontroller should be equipped with the following features:
- Low-power processing core with the capability to perform complex arithmetic operations required for energy calculation
- Suitable physical-layer communication interface for RF or power-line communication, if used
- On-chip Flash memory and static random-access memory for storing application firmware and faster operation
- LCD driver for LCD display
- Interfaces like universal asynchronous receiver/transmitter, which can support infrared communication
- High-resolution analogue-to-digital converters (ADCs) with programmable gain amplifierfor voltage and current measurements
- Input/output (I/O) ports for driving relays
- Real-time counter for time keepingThe microcontroller senses the voltage and current through the signal conditioning circuit along with the ADC and programmable gain amplifierto calculate root mean square (RMS) voltage and current values, instantaneous energy consumed and total energy consumed over a period of time (one month or longer). It then sends this data to the utility meter through RF or power line communication and also displays it on the LCD. When a command to turn off the device is received, it drives suitable logic on its I/O ports to operate the relay.
The microcontroller gets its power supply from the power line through a 230V-3.3V converter. The converter can be suitably configuredaccording to the operating voltage of the microcontroller. The on-chip Flash firware can be updated over the RF or PLC interface by the utility meter. The protocol and exact details of frmware updation depend on specific implementations.
 Fig: 2: Block diagram of HAN device |
Compared to voltage measurement, current measurement is less involved. First, the line current is downsized using a current transformer and then passed through a small value of high-precision shunt resistor. The voltage drop across this shunt resistor gives a measure of the line current. As this voltage drop is very small, it is suitably amplifiedbefore being fed to the ADC.
The amplifierconsists of programmable gain stages for amplificationof only the alternating-current (AC) components, thus preventing the amplifie output from saturation.
Infrared interface. The infrared interface can be configuredsuitably according to the range and power consumption. It provides remote configurationsupport for the HAN device, enabling the user to remotely turn on/off the home appliance connected to the HAN device. The protocol and exact details of operation can be flexiblychosen for particular implementations.
LCD panel. The LCD panel displays the instantaneous energy consumed, total energy consumed last/current month, date and time of the day, RMS voltage and RMS current. It inherits some of the utility meter display, thus acting as a low-accuracy but smart AC energy meter.
In a nutshell, the above architecture conceptualises a cost-effective and extremely versatile HAN device, which is replete with all the essential HAN device features along with the support for advanced features like firmwar upgrade and full control of appliances over RF/PLC interface. It also doubles as a low-cost smart AC energy meter, providing round-the-clock energy consumption details of the home appliance.
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Remember your childhood, when a bucket of Lego bricks was like having infiniteammo for your imagination? Growing up doesn’t mean you have to give up those moments. In fact, you can now use your imagination and make stuff that is much more complex and has far greater capabilities. In this article, we discuss an interesting kit that will allow you to create a myriad of robotic structures to perform various functions.
Merlyn TRN-1
At its simplest, it is a robotic kit that helps you design up to 28 different types of fundamental robots, be it a linear moving robot, rotary robotic arm or even a robot with cylindrical axis. If you dig beneath the surface a little, it is a completely modular, electronic, rugged kit that not only allows you to create robots but also helps you add new features to them. This one kit allows a huge array of possibilities to create, control and reconfigure robots—wha-ever be the need.
It is basically a gadget, the parts of which can be attached together to create any kind of motion. You can add your regular devices to this gadget. The best part is that you can use it to perform functions required for industrial automation—such is the flexibilit of this device.
This kit is the brainchild of Biju Ronnie Varkey, owner of Designs and Projects Development (DPD), Patiala. A robotics enthusiast himself, Varkey worked on this product for two long years, making sure that it is built and functions exactly the way it is meant to be.
On asking what drove this idea in his mind, Varkey says, “While teaching robotics at engineering colleges, I noticed that there was nothing available at hand to teach students in a way that they would not only remember but also enjoy learning robotics. The most I saw anywhere was a couple of microcontrollers, line follower robots and the like. I sincerely felt that this was a huge waste of engineering talent and hence I started working on this project two years ago by designing and then fine-tuningthe initial design according to the feedbacks I received from students and teachers, who are as much responsible for the finaldesign as anyone who worked on it.”
“Apart from generating an interest in robotics, I also wanted students, who come out having learnt the basics of robotics, to be able to say that they had an employable education,” he adds.
Features of Merlyn TRN-1
The kit is basically divided into three parts: electronics, which includes microcontrollers, motors and drivers for motors; mechanical part, which comprises all the axes; and software segment, which controls microcontrollers used in the kit.
The kit uses a stepper motor for movement along all the axes, including the rotary axis that has a geared set-up. The motor used is a 2A stepper motor with independent drivers for each of the motors. These drivers are controlled by a microcontroller; in case of TRN-1, an Arduino Mega 2560 board. You can also drive it by connecting it to your PC or laptop.
“Using an Arduino board provides a good number of inputs/outputs (useful for attaching a number of sensors) and is also easy to program, highly stable and extremely flexible.Stepper motors can easily be replaced with DC motors or servo motors, and all of them can be controlled directly by the board without much fuss,” Varkey says.
The Arduino board is capable of driving up to eight axes (eight stepper motors) at the same time. Hence your system has around eight degrees of freedom. You can add a proximity sensor, IR sensor or what-ever suits you. The different motors are con-nected to each other to help the robot move the way you like.
Each of the three parts of the kit can be customised to a great degree, enabling smooth functioning and lending great frequency to the robot that you want to design.
Obstacles
Talking about the problems encountered during the materialisation of the idea, Varkey says, “Since the idea was already in my head after the visits to engineering colleges, I spent a lot of time listening to the target users of our system, making notes of the problems they were facing, what they wanted and things they wanted in the solution. Then, it took us nearly a year to reach the point where we are today. This model is actually based on the 10th prototype we rolled out. The firstone we made could only be turned into a single basic robotic system.”
“To add value, Merlyn TRN-1 was worked on extensively to enable it to be turned into 28 fundamentally different types of robotic systems. You can cascade different kits together to increase the envelope in which you are working along with the range/scope of the work you are doing. The best part is that you are not limited by the mechanical, electronics or software scheme of things utilised in the robot,” he adds.
The components were especially made from anodised aluminium, ensuring a rugged yet light design.
Spreading the wings
The kit was premiered at the EFY Expo 2013, held recently in New Delhi, as a project concept for students.
Varkey shares, “A trial run for the product has already been done at some engineering colleges by way of live demonstrations, and almost all of those colleges have placed orders for our product. They said that this is something very new and they would love to have such a useful product in their college.”
Varkey plans to market the product by directly contacting the engineering institutes, through dealers who are already selling kits in the market, and by seeking help of media outlets like Electronics For You and the likes to spread word about this product.
Varkey adds, “Another way we have thought of is by utilising the open source way. Our kit is open for all sorts of customisation. If a software guy comes up with a neat applet that can be integrated into the robot to perform some particularly specificfunction, we will work out some sort of revenue sharing method. If a mechanical guy comes up with an end effector that works great, he can put it on our website and we can look at the revenue sharing angle with him as well.”
Patents and future additions
DPD has applied for three patents covering the drive mechanisms. One is for the drive mechanism being used, which deals with how different mechanisms can be put together on the same axis. Another patent is for the direct drive mechanism that allows any linear member of the kit to become a linear axis. For example, consider the making of a box-type robot. In this case, the 12 sides of the box now become 12 axes of the robot. The last one is regarding the specificdrive mechanism where you can use any member of the kit and drive it directly through the stepper motor without using any type of belt. In the system, you can have a linear drive with the stepper motor using a screw-drive while having a DC motor on another axis, which has a wire-drive to move around—all of them independently working together on different fields and different actuations.
Regarding additions to the design, Varkey says, “Adding new features is the basis of all innovations and we at DPD are no different. We have plans to increase the amount of customisation available and improve the graphical user interface of the microcontroller and a host of other features.”
IEEE 802.16 standard essentially specified two aspects of the air interface for WiMAX—the physical layer (PHY) and the media access control layer (MAC) (refer Fig. 1). The physical layer defnes electrical and physical specification for devices, establishment and termination of a connection to a communication medium, communication flow control, modulation, coding, etc. On the other hand, MAC layer is further divided into three sub-layers—convergence, common part, and security or privacy.
The convergence sub-layer de-scribes how wireline technologies such as asynchronous transfer mode (ATM), Ethernet, 802.1 (LAN/MAN) and Internet protocol (IP) are encapsulated on the air interface and how data is classified.The common part sub-layer is responsible for idle-mode processes like cell selection, paging structures and location-area updates. This layer is also responsible for sleep-mode processes, handover procedures, multicast and broadcast services, quality-of-service (QoS) class and automatic repeat request (ARQ) processes. It also does header suppression, packing and fragmentation for efficient use of spectrum.
The security sub-layer provides subscribers with privacy, authentication or confidentiality across the broadband wireless network. It is accomplished by applying crypto-graphic transforms to MAC packet data units carried across connections between the subscriber station and the base station. Secure communications are delivered by using secure key exchange during authentication, and encryption using advanced encryption standard (AES) or data encryption standard (DES) during data transfer. The MAC layer incorporates privacy key management version 2 (PKMv2) for MAC layer security. PKMv2 incorporates support for extensible authentication protocol (EAP).
In addition, the security sub-layer provides operators strong protection from theft of service. The base station protects against unauthorised access to data transport services by securing the associated service flowsacross the network. The security sub-layer employs an authenticated client/server key management protocol in which the base station server controls distribution of keying material to the client subscriber station. Additionally, the basic security mechanisms are strengthened by adding digital certificate-basedsubscriber station device authentication to the key management protocol.
Security components
WiMAX security uses two component protocols—encapsulation protocol and privacy key management (PKM) protocol. The encapsulation protocol is used for securing packet data across the wireless network. This protocol defines a set of supported cryptographic suites, i.e., pairings of data encryption and authentication algorithms and the rules for applying these algorithms to a MAC packet data unit payload.
On the other hand, the PKM protocol is used for secure distribution of keying data from the base station to the subscriber station. Through this key management protocol, the subscriber station and the base station synchronise keying data. In addition, the base station uses the protocol to enforce conditional access to network services. The stack of security components of the system is shown in Fig. 2.
Key management protocol. There are two PKM protocols supported in IEEE Standard 802.16—PKM version 1 (PKMv1) and PKMv2 with more enhanced features such as new key hierarchy, advanced encryption standard (AES)-cipher message authentication code, AES-key-wraps, and multicast and broadcast services. PKM protocol allows mutual authentication, unilateral authentication, periodic re-authentication/re-authorisation and key refresh.
Key management protocol uses either extensible authentication protocol, or X.509 digital certificatestogether with Rivest-Shamir-Adlerman (RSA) public-key encryption algorithm or a sequence starting with RSA authentication and followed by extensible authentication protocol authentication. It uses strong encryption algorithms to perform key exchanges between a subscriber station and base station. RSA protocol support is mandatory in PKMv1 but optional in PKMv2. However, extensible authentication protocol support is optional in both the versions of key management protocol, unless specifically required.
PKM’s authentication protocol establishes a shared secret, called authorisation key, between the subscriber station and base station. The shared secret is then used to secure subsequent PKM exchanges of trafficencryption keys. This two-tiered mechanism for key distribution permits refreshing of trafficencryption keys without incurring the overhead of computation-intensive operations.
The authorisation key is derived by the base station and subscriber station from the pre-authorisation key (in case of RSA-based authorisation procedure) and/or the PMK (in case of extensible authentication protocol-based authorisation procedure). The exclusive-or (XOR) value of primary authorisation key and pairwise master key is mainly used to generate the authorisation key. The Dot16KDF algorithm is used for authorisation key derivation.
The base station authenticates a client subscriber station during the initial authorisation exchange. Each subscriber station presents its credentials, which is a unique X.509 digital certificateissued by the subscriber station’s manufacturer (in case of RSA authentication) or an operator-specified credential (in case o EAP-based authentication).
The base station associates the subscriber station’s authenticated identity to a paying subscriber and hence to the data services that the subscriber is authorised to access. Thus, with the authorisation key exchange, the base station determines the authenticated identity of a client subscriber station and the services (i.e., specifictrafficencryption keys) the subscriber station is authorised to access. Since the base station authenticates the subscriber station, it may protect against an attacker employing a cloned subscriber station masquerading as a legitimate subscriber.
Privacy key management RSA authentication. The PKM RSA authentication protocol uses X.509 digital certifcates—the RSA public key encryption algorithm that binds public RSA encryption keys to MAC addresses of subscriber stations. The digital certificat contains the subscriber station’s public key and MAC address. When requesting an authentication key, a subscriber station presents its digital certificateto the base station. The base station verifies the digital certificateand then uses the verifiedpublic key to encrypt an authentication key, which the base station then sends back to the requesting subscriber station (refer Fig. 3).
All subscriber stations using RSA authentication have factory-installed RSA private/public key pairs or provide an internal algorithm to generate such key pairs dynamically. If a subscriber station relies on an internal algorithm to generate its RSA key pair, it generates the key pair prior to its firstauthorisation key exchange. All subscriber stations with factory-installed RSA key pairs also have factory-installed X.509 certificates.
PKM extensible authentication protocol authentication. This authentication uses extensible authentication protocol (EAP) in conjunction with an operator-selected EAP method (e.g., EAP-transport layer security (TLS) or EAP-tunnelled TLS with Microsoft challenge handshake authentication protocol version 2 (TTLS MS-CHAPv2)). The method uses a particular kind of credential—X.509 certificate in case of EAP-TLS, o a subscriber identity module in case of EAP-SIM (refer Fig. 4).
EAP authentication provides dynamic encryption keys to wireless users. These are more secure than static encryption keys. If an intruder passively receives enough packets encrypted by the same encryption key, he can perform a calculation to learn the key and use it to join a network. Because dynamic encryption keys change frequently, these prevent intruders from performing the calculation and learning the key.
After successful EAP-based authorisation, if the subscriber station or base station negotiates authorisation policy as ‘authenticated EAP after EAP’ mode, the authenticated EAP messages carries the second EAP message. It cryptographically binds previous and following EAP authentication sessions, while protecting second EAP messages. In order to prevent ‘man-in-the-middle attack,’ the firstand second EAP methods should fulfil the mandatory criteria.
During re-authentication, the EAP transfer messages are protected with a hashed message authentication code or cipher message authentication code protocol. The base station and subscriber station discard unprotected EAP transfer messages or EAP transfer messages with invalid hashed message authentication code or cipher message authentication code digests during re-authentication.
Message authentication code keys are used to sign management messages in order to validate the authenticity of these messages. The message authentication code to be used is negotiated at a subscriber station’s basic capabilities negotiation request. There are different keys for uplink and downlink messages. For a multicast message (in down-link only) and for a unicast message, a different message authentication key is generated. In general, message authentication keys used to generate the cipher message authentication code value and the hashed message authentication code-digest are derived from the authorisation key.
Cryptographic method of data encryption
Encryption services are defined as a se of capabilities within the MAC security sub-layer. Encryption information is allocated in the generic MAC header format and applied to the MAC packet data unit payload when required by the selected ciphersuite while the generic MAC header is not encrypted.
With advanced encryption standard’s counter with cipher block chaining-MAC mode (an authenticated encryption algorithm designed to provide both authentication and confidentiality),the packet data unit payload (after encryption) has a format as shown in Fig. 5. Here packet data unit payload is prepended with a 4-byte packet number. The packet number is transmitted with the least significantbit firstand the packet number itself is not encrypted. The packet number associated with a security association is set to ‘1’ when the security association is established and a new trafficencryption key installed. After each packet data unit transmission, the packet number is incremented by ‘1.’
On uplink connections, the packet number is XORed with 0x80000000 prior to encryption and transmission. On downlink connections, the packet number is used without such modifiction. The ciphertext message authentication code is transmitted such that byte index ‘0’ is transmitted firstand byte index ‘7’ transmitted last.
The result
WiMAX users should feel confdent that their transmitted data is free from eaves-dropping or manipulation and only authorised users can access WiMAX services. The improved WiMAX technology implements improved security architecture. Thus the operator ensures that only authorised subscribers access the network and use appropriate services subscribed by them.
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Say hello to ToucHb—a prick-free blood testing device brought to you by Biosense Technologies. ToucHb can measure your blood hae-moglobin, oxygen saturation, temperature and pulse rate all without pricking for blood. A team of three—engineer Myshkin Ingawale and doctors Abhishek Sen and Yogesh Patil—was behind making this product from the ground up.
What led the team to come up with this idea? Myshkin narrates, “In 2009, I had gone to visit my friend Abhishek in Parol—a two-hour drive from Mumbai. He was interning at the place and when I reached Parol, I had to wait for him as he was busy helping deliver a baby. Afterwards, he came out ashen-faced and informed me that both the mother and baby had died of something called post-partum haemorrhage, which is basically uncontrollable bleeding. What was shocking was that it was caused by undiagnosed anaemia.”
The news that someone could die of anaemia—a completely diagnosable and curable disease—shocked Myshkin and made him look for a solution. He asked his mother, a paediatrician, and found that testing for anaemia involves sending a blood sample through a Coulter counter. But the nearest such machine was in Mumbai and it wasn’t a viable solution to keep using the machine to have every person tested for anaemia. He contacted his two friends and started searching for practical designs for the device.
Dr Sen says, “In India, public healthcare runs on the ASHA worker and not on the doctor. So when our team convened to design a solution for this problem, we knew that whatever we created had to be prickless (to avoid medical waste), simple enough for the ASHA worker to operate and small enough for her to carry in her kit.”
ToucHb features
ToucHb is a handheld battery-operated device. Total blood haemoglobin is used for the diagnosis of anaemia. (The WHO qualifies any pregnant woman with Hb level of less than 11 grams per decilitre of blood as anaemic.)
TouchHb works on the principle of ‘photoplethysmography.’ Basically, it works by radiating light of three different wavelengths onto the finger, and through the tissue of the patient’s finger. Once this is done, based on the amount of light transmitted, absorbed and scattered, one can figure out the amount of haemoglobin in blood. Haemoglobin has a characteristic absorbance. For estimation of oxygen saturation, the technique is similar to the one used in pulse oximeters. While a pulse oximeter is not able to measure total haemoglobin, ToucHb is designed to do that.
Obstacles
Since non-invasive procedures for the masses is still a field in its infancy, developing the device was not without its share of challenges.
Dr Abhijeet says, ”We often joke that we failed 32 times but in reality we probably failed many more times—maybe many times each day! First, the basic science—the core R&D itself—was a challenge. All this ‘optical’ stuff for a bunch of relatively inexperienced doctors and engineer meant that we were walking in the dark.”
Dr Yogesh adds, “There were small nitty gritties related to production and assembly lines—a millimetre here and a rupee difference there—and suddenly we were struggling both on the technical and costing sides! We had to learn as we went along—how to identify signs of error, rectify and make the hardware reliable. We learnt the best way—by being wrong!”
Roadmap
ToucHb is being produced and sold directly to clinics, which then use it for screening and monitoring of anaemia in their patients. But the team has a bigger plan—to scale up the production from 30-40 a batch to more than 1000 a batch. This will involve putting in place a quality management system, something which will take time.
“Apart from scaling up the production, one of the big steps for us is to partner with different international and national health agencies to under-stand the best way to create an impact with this device. The healthcare ecosystem is a complex thing—protocols are designed for good reasons, and we need to work jointly with experienced public health experts to modify the existing system and make small incremental tweaks in the way point-of-care community health works,” says Dr Patil.
The ToucHb Version 1 has already been released. So what next?
Myshkin shares, “As with any technology, you have to keep upgrading, making it better to avoid obsolescence. So watch out for even more feature-rich Version 2, a few months down the road! I would love to tell you about the features we are planning to introduce in subsequent versions, but we ourselves are not sure about which ones will make the cut.”
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2.A Truly Modular Robotic Kit
Always wanted to get into the exciting field of robotics but didn’t know where to start? Let us introduce you to one of the most innovative robotic kits of the decade—it could very well be described as the Lego set of the engineering community
Ashwin Gopinath
Ashwin Gopinath
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Merlyn TRN-1
At its simplest, it is a robotic kit that helps you design up to 28 different types of fundamental robots, be it a linear moving robot, rotary robotic arm or even a robot with cylindrical axis. If you dig beneath the surface a little, it is a completely modular, electronic, rugged kit that not only allows you to create robots but also helps you add new features to them. This one kit allows a huge array of possibilities to create, control and reconfigure robots—wha-ever be the need.
It is basically a gadget, the parts of which can be attached together to create any kind of motion. You can add your regular devices to this gadget. The best part is that you can use it to perform functions required for industrial automation—such is the flexibilit of this device.
This kit is the brainchild of Biju Ronnie Varkey, owner of Designs and Projects Development (DPD), Patiala. A robotics enthusiast himself, Varkey worked on this product for two long years, making sure that it is built and functions exactly the way it is meant to be.
On asking what drove this idea in his mind, Varkey says, “While teaching robotics at engineering colleges, I noticed that there was nothing available at hand to teach students in a way that they would not only remember but also enjoy learning robotics. The most I saw anywhere was a couple of microcontrollers, line follower robots and the like. I sincerely felt that this was a huge waste of engineering talent and hence I started working on this project two years ago by designing and then fine-tuningthe initial design according to the feedbacks I received from students and teachers, who are as much responsible for the finaldesign as anyone who worked on it.”
“Apart from generating an interest in robotics, I also wanted students, who come out having learnt the basics of robotics, to be able to say that they had an employable education,” he adds.
Features of Merlyn TRN-1
The kit is basically divided into three parts: electronics, which includes microcontrollers, motors and drivers for motors; mechanical part, which comprises all the axes; and software segment, which controls microcontrollers used in the kit.
The kit uses a stepper motor for movement along all the axes, including the rotary axis that has a geared set-up. The motor used is a 2A stepper motor with independent drivers for each of the motors. These drivers are controlled by a microcontroller; in case of TRN-1, an Arduino Mega 2560 board. You can also drive it by connecting it to your PC or laptop.
“Using an Arduino board provides a good number of inputs/outputs (useful for attaching a number of sensors) and is also easy to program, highly stable and extremely flexible.Stepper motors can easily be replaced with DC motors or servo motors, and all of them can be controlled directly by the board without much fuss,” Varkey says.
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Each of the three parts of the kit can be customised to a great degree, enabling smooth functioning and lending great frequency to the robot that you want to design.
Obstacles
Talking about the problems encountered during the materialisation of the idea, Varkey says, “Since the idea was already in my head after the visits to engineering colleges, I spent a lot of time listening to the target users of our system, making notes of the problems they were facing, what they wanted and things they wanted in the solution. Then, it took us nearly a year to reach the point where we are today. This model is actually based on the 10th prototype we rolled out. The firstone we made could only be turned into a single basic robotic system.”
“To add value, Merlyn TRN-1 was worked on extensively to enable it to be turned into 28 fundamentally different types of robotic systems. You can cascade different kits together to increase the envelope in which you are working along with the range/scope of the work you are doing. The best part is that you are not limited by the mechanical, electronics or software scheme of things utilised in the robot,” he adds.
The components were especially made from anodised aluminium, ensuring a rugged yet light design.
Spreading the wings
The kit was premiered at the EFY Expo 2013, held recently in New Delhi, as a project concept for students.
Varkey shares, “A trial run for the product has already been done at some engineering colleges by way of live demonstrations, and almost all of those colleges have placed orders for our product. They said that this is something very new and they would love to have such a useful product in their college.”
Varkey plans to market the product by directly contacting the engineering institutes, through dealers who are already selling kits in the market, and by seeking help of media outlets like Electronics For You and the likes to spread word about this product.
Varkey adds, “Another way we have thought of is by utilising the open source way. Our kit is open for all sorts of customisation. If a software guy comes up with a neat applet that can be integrated into the robot to perform some particularly specificfunction, we will work out some sort of revenue sharing method. If a mechanical guy comes up with an end effector that works great, he can put it on our website and we can look at the revenue sharing angle with him as well.”
Patents and future additions
DPD has applied for three patents covering the drive mechanisms. One is for the drive mechanism being used, which deals with how different mechanisms can be put together on the same axis. Another patent is for the direct drive mechanism that allows any linear member of the kit to become a linear axis. For example, consider the making of a box-type robot. In this case, the 12 sides of the box now become 12 axes of the robot. The last one is regarding the specificdrive mechanism where you can use any member of the kit and drive it directly through the stepper motor without using any type of belt. In the system, you can have a linear drive with the stepper motor using a screw-drive while having a DC motor on another axis, which has a wire-drive to move around—all of them independently working together on different fields and different actuations.
Regarding additions to the design, Varkey says, “Adding new features is the basis of all innovations and we at DPD are no different. We have plans to increase the amount of customisation available and improve the graphical user interface of the microcontroller and a host of other features.”
3.Why WiMAX Will Not Fail
WiMAX provides robust access control, data privacy and data integrity using sophisticated authentication and encryption technologies. This article investigates the architecture enabling the high-level security
Rajiv Kumar Singh
Rajiv Kumar Singh
In today’s fast-paced lifestyle, consumers want communication at faster speed and lower cost, more broadband capabilities as well as nomadic and mobility support. Keeping these demands in mind, IEEE 802.16 working group has come up with a new wireless communications standard called the broadband wireless access (BWA). Commonly known as WiMAX (worldwide interoperability for microwave access), this is a fast evolving technology used to form wide-range wireless networks with high data rate of information transfer.
We live in a variety of networking environments for using Internet-based services and applications. Data security becomes an important issue in such interconnected networks in order to safely transmit or receive information. Due to this, different security protocols are designed and deployed with network standards.
The latest update given by WiMAX Forum—the IEEE 802.16m—claims to offer up to 100Mbps mobile and 1Gbps fixedspeeds. The update is added to the WiMAX standard in both its versions—fixed(IEEE 802.16d-2004) and mobile (IEEE 802.16e-2005) broadband wireless access.
WiMax protocol
We live in a variety of networking environments for using Internet-based services and applications. Data security becomes an important issue in such interconnected networks in order to safely transmit or receive information. Due to this, different security protocols are designed and deployed with network standards.
The latest update given by WiMAX Forum—the IEEE 802.16m—claims to offer up to 100Mbps mobile and 1Gbps fixedspeeds. The update is added to the WiMAX standard in both its versions—fixed(IEEE 802.16d-2004) and mobile (IEEE 802.16e-2005) broadband wireless access.
WiMax protocol
IEEE 802.16 standard essentially specified two aspects of the air interface for WiMAX—the physical layer (PHY) and the media access control layer (MAC) (refer Fig. 1). The physical layer defnes electrical and physical specification for devices, establishment and termination of a connection to a communication medium, communication flow control, modulation, coding, etc. On the other hand, MAC layer is further divided into three sub-layers—convergence, common part, and security or privacy.
 Fig. 1: WiMAX protocol layers |
 Fig. 2: WiMAX security sublayer |
The security sub-layer provides subscribers with privacy, authentication or confidentiality across the broadband wireless network. It is accomplished by applying crypto-graphic transforms to MAC packet data units carried across connections between the subscriber station and the base station. Secure communications are delivered by using secure key exchange during authentication, and encryption using advanced encryption standard (AES) or data encryption standard (DES) during data transfer. The MAC layer incorporates privacy key management version 2 (PKMv2) for MAC layer security. PKMv2 incorporates support for extensible authentication protocol (EAP).
 Fig. 3: Public key exchange |
 Fig. 4: Authentication using extensible authentication protocol |
Security components
WiMAX security uses two component protocols—encapsulation protocol and privacy key management (PKM) protocol. The encapsulation protocol is used for securing packet data across the wireless network. This protocol defines a set of supported cryptographic suites, i.e., pairings of data encryption and authentication algorithms and the rules for applying these algorithms to a MAC packet data unit payload.
On the other hand, the PKM protocol is used for secure distribution of keying data from the base station to the subscriber station. Through this key management protocol, the subscriber station and the base station synchronise keying data. In addition, the base station uses the protocol to enforce conditional access to network services. The stack of security components of the system is shown in Fig. 2.
Key management protocol. There are two PKM protocols supported in IEEE Standard 802.16—PKM version 1 (PKMv1) and PKMv2 with more enhanced features such as new key hierarchy, advanced encryption standard (AES)-cipher message authentication code, AES-key-wraps, and multicast and broadcast services. PKM protocol allows mutual authentication, unilateral authentication, periodic re-authentication/re-authorisation and key refresh.
Key management protocol uses either extensible authentication protocol, or X.509 digital certificatestogether with Rivest-Shamir-Adlerman (RSA) public-key encryption algorithm or a sequence starting with RSA authentication and followed by extensible authentication protocol authentication. It uses strong encryption algorithms to perform key exchanges between a subscriber station and base station. RSA protocol support is mandatory in PKMv1 but optional in PKMv2. However, extensible authentication protocol support is optional in both the versions of key management protocol, unless specifically required.
 Fig. 5: Encrypted payload format in counter with cipher block chaining-MAC mode of AES |
The authorisation key is derived by the base station and subscriber station from the pre-authorisation key (in case of RSA-based authorisation procedure) and/or the PMK (in case of extensible authentication protocol-based authorisation procedure). The exclusive-or (XOR) value of primary authorisation key and pairwise master key is mainly used to generate the authorisation key. The Dot16KDF algorithm is used for authorisation key derivation.
The base station authenticates a client subscriber station during the initial authorisation exchange. Each subscriber station presents its credentials, which is a unique X.509 digital certificateissued by the subscriber station’s manufacturer (in case of RSA authentication) or an operator-specified credential (in case o EAP-based authentication).
The base station associates the subscriber station’s authenticated identity to a paying subscriber and hence to the data services that the subscriber is authorised to access. Thus, with the authorisation key exchange, the base station determines the authenticated identity of a client subscriber station and the services (i.e., specifictrafficencryption keys) the subscriber station is authorised to access. Since the base station authenticates the subscriber station, it may protect against an attacker employing a cloned subscriber station masquerading as a legitimate subscriber.
Privacy key management RSA authentication. The PKM RSA authentication protocol uses X.509 digital certifcates—the RSA public key encryption algorithm that binds public RSA encryption keys to MAC addresses of subscriber stations. The digital certificat contains the subscriber station’s public key and MAC address. When requesting an authentication key, a subscriber station presents its digital certificateto the base station. The base station verifies the digital certificateand then uses the verifiedpublic key to encrypt an authentication key, which the base station then sends back to the requesting subscriber station (refer Fig. 3).
All subscriber stations using RSA authentication have factory-installed RSA private/public key pairs or provide an internal algorithm to generate such key pairs dynamically. If a subscriber station relies on an internal algorithm to generate its RSA key pair, it generates the key pair prior to its firstauthorisation key exchange. All subscriber stations with factory-installed RSA key pairs also have factory-installed X.509 certificates.
PKM extensible authentication protocol authentication. This authentication uses extensible authentication protocol (EAP) in conjunction with an operator-selected EAP method (e.g., EAP-transport layer security (TLS) or EAP-tunnelled TLS with Microsoft challenge handshake authentication protocol version 2 (TTLS MS-CHAPv2)). The method uses a particular kind of credential—X.509 certificate in case of EAP-TLS, o a subscriber identity module in case of EAP-SIM (refer Fig. 4).
EAP authentication provides dynamic encryption keys to wireless users. These are more secure than static encryption keys. If an intruder passively receives enough packets encrypted by the same encryption key, he can perform a calculation to learn the key and use it to join a network. Because dynamic encryption keys change frequently, these prevent intruders from performing the calculation and learning the key.
After successful EAP-based authorisation, if the subscriber station or base station negotiates authorisation policy as ‘authenticated EAP after EAP’ mode, the authenticated EAP messages carries the second EAP message. It cryptographically binds previous and following EAP authentication sessions, while protecting second EAP messages. In order to prevent ‘man-in-the-middle attack,’ the firstand second EAP methods should fulfil the mandatory criteria.
During re-authentication, the EAP transfer messages are protected with a hashed message authentication code or cipher message authentication code protocol. The base station and subscriber station discard unprotected EAP transfer messages or EAP transfer messages with invalid hashed message authentication code or cipher message authentication code digests during re-authentication.
Message authentication code keys are used to sign management messages in order to validate the authenticity of these messages. The message authentication code to be used is negotiated at a subscriber station’s basic capabilities negotiation request. There are different keys for uplink and downlink messages. For a multicast message (in down-link only) and for a unicast message, a different message authentication key is generated. In general, message authentication keys used to generate the cipher message authentication code value and the hashed message authentication code-digest are derived from the authorisation key.
Cryptographic method of data encryption
Encryption services are defined as a se of capabilities within the MAC security sub-layer. Encryption information is allocated in the generic MAC header format and applied to the MAC packet data unit payload when required by the selected ciphersuite while the generic MAC header is not encrypted.
With advanced encryption standard’s counter with cipher block chaining-MAC mode (an authenticated encryption algorithm designed to provide both authentication and confidentiality),the packet data unit payload (after encryption) has a format as shown in Fig. 5. Here packet data unit payload is prepended with a 4-byte packet number. The packet number is transmitted with the least significantbit firstand the packet number itself is not encrypted. The packet number associated with a security association is set to ‘1’ when the security association is established and a new trafficencryption key installed. After each packet data unit transmission, the packet number is incremented by ‘1.’
On uplink connections, the packet number is XORed with 0x80000000 prior to encryption and transmission. On downlink connections, the packet number is used without such modifiction. The ciphertext message authentication code is transmitted such that byte index ‘0’ is transmitted firstand byte index ‘7’ transmitted last.
The result
WiMAX users should feel confdent that their transmitted data is free from eaves-dropping or manipulation and only authorised users can access WiMAX services. The improved WiMAX technology implements improved security architecture. Thus the operator ensures that only authorised subscribers access the network and use appropriate services subscribed by them.
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3.Prick-free Blood Tester from India
Many of us are terrified of blood tests, where skin is pricked with a needle to get the blood for testing. A solution to this problem has come in the form of ToucHb—a prick-free blood testing device
Ashwin Gopinath
Ashwin Gopinath
 The inside of ToucHb |
What led the team to come up with this idea? Myshkin narrates, “In 2009, I had gone to visit my friend Abhishek in Parol—a two-hour drive from Mumbai. He was interning at the place and when I reached Parol, I had to wait for him as he was busy helping deliver a baby. Afterwards, he came out ashen-faced and informed me that both the mother and baby had died of something called post-partum haemorrhage, which is basically uncontrollable bleeding. What was shocking was that it was caused by undiagnosed anaemia.”
The news that someone could die of anaemia—a completely diagnosable and curable disease—shocked Myshkin and made him look for a solution. He asked his mother, a paediatrician, and found that testing for anaemia involves sending a blood sample through a Coulter counter. But the nearest such machine was in Mumbai and it wasn’t a viable solution to keep using the machine to have every person tested for anaemia. He contacted his two friends and started searching for practical designs for the device.
| Photoplethysmography basics |
| Photoplethysmography (PPG) is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non-invasively to make measurements at the skin surface. The PPG waveform comprises a pulsatile (AC) physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying (DC) baseline with various lower-frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. PPG technology is used in a wide range of commercially available medical devices to measure oxygen saturation, blood pressure and cardiac output, assess autonomic function and also detect peripheral vascular disease. |
Dr Sen says, “In India, public healthcare runs on the ASHA worker and not on the doctor. So when our team convened to design a solution for this problem, we knew that whatever we created had to be prickless (to avoid medical waste), simple enough for the ASHA worker to operate and small enough for her to carry in her kit.”
ToucHb features
ToucHb is a handheld battery-operated device. Total blood haemoglobin is used for the diagnosis of anaemia. (The WHO qualifies any pregnant woman with Hb level of less than 11 grams per decilitre of blood as anaemic.)
TouchHb works on the principle of ‘photoplethysmography.’ Basically, it works by radiating light of three different wavelengths onto the finger, and through the tissue of the patient’s finger. Once this is done, based on the amount of light transmitted, absorbed and scattered, one can figure out the amount of haemoglobin in blood. Haemoglobin has a characteristic absorbance. For estimation of oxygen saturation, the technique is similar to the one used in pulse oximeters. While a pulse oximeter is not able to measure total haemoglobin, ToucHb is designed to do that.
Obstacles
Since non-invasive procedures for the masses is still a field in its infancy, developing the device was not without its share of challenges.
 ToucHb device |
Dr Yogesh adds, “There were small nitty gritties related to production and assembly lines—a millimetre here and a rupee difference there—and suddenly we were struggling both on the technical and costing sides! We had to learn as we went along—how to identify signs of error, rectify and make the hardware reliable. We learnt the best way—by being wrong!”
Roadmap
ToucHb is being produced and sold directly to clinics, which then use it for screening and monitoring of anaemia in their patients. But the team has a bigger plan—to scale up the production from 30-40 a batch to more than 1000 a batch. This will involve putting in place a quality management system, something which will take time.
“Apart from scaling up the production, one of the big steps for us is to partner with different international and national health agencies to under-stand the best way to create an impact with this device. The healthcare ecosystem is a complex thing—protocols are designed for good reasons, and we need to work jointly with experienced public health experts to modify the existing system and make small incremental tweaks in the way point-of-care community health works,” says Dr Patil.
The ToucHb Version 1 has already been released. So what next?
Myshkin shares, “As with any technology, you have to keep upgrading, making it better to avoid obsolescence. So watch out for even more feature-rich Version 2, a few months down the road! I would love to tell you about the features we are planning to introduce in subsequent versions, but we ourselves are not sure about which ones will make the cut.”
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4.SCHOOL/COLLEGE QUIZ BUZZER
GOVINDA RAJU TEKUMUDI
Manual buzzers used for quiz competitions in schools and colleges create a lot of confusion in identifying the first respondent. Although there are circuits using PCs and discrete ICs, they are either too expensive or limited to only a few number of players.
The quiz buzzer circuit given here can be used for up to eight players, which is maximum in any quiz competition. The circuit uses IC 74LS373 and a few passive components that are readily available in the market.
The circuit can be divided into two sections: power supply and quiz buzzer. Fig. 1 shows the power supply section. The regulated 5V power supply for the quiz buzzer section is derived from AC mains. The 230V AC mains is stepped down to 7.5V AC by transformer X1, rectified by bridge rectifier BR1, filtered by C1 and regulated by regulator IC1. Capacitor C2 bypasses ripples in the regulator output.
Fig. 1: Power supply
Fig. 2 shows the quiz buzzer section. At the heart of this section is IC 74LS373, an octal latch that is used to transfer the logic state at data input pins D0 through D7 to the corresponding Q0 through Q7 outputs. Data pins D0 through D7 are normally pulled low by resistors R1 through R8, respectively.
Fig. 2: Circuit of school/college quiz buzzer
As soon as a contestant momentarily presses his respective switch, the corresponding output data pin goes high. This triggers the corresponding SCR and the respective bulb glows. At the same time, the piezobuzzer (PZ1) sounds as transistor T1 conducts.
The quiz buzzer circuit given here can be used for up to eight players, which is maximum in any quiz competition. The circuit uses IC 74LS373 and a few passive components that are readily available in the market.
The circuit can be divided into two sections: power supply and quiz buzzer. Fig. 1 shows the power supply section. The regulated 5V power supply for the quiz buzzer section is derived from AC mains. The 230V AC mains is stepped down to 7.5V AC by transformer X1, rectified by bridge rectifier BR1, filtered by C1 and regulated by regulator IC1. Capacitor C2 bypasses ripples in the regulator output.
Fig. 1: Power supply
Fig. 2 shows the quiz buzzer section. At the heart of this section is IC 74LS373, an octal latch that is used to transfer the logic state at data input pins D0 through D7 to the corresponding Q0 through Q7 outputs. Data pins D0 through D7 are normally pulled low by resistors R1 through R8, respectively.
Fig. 2: Circuit of school/college quiz buzzer
One terminal of push-to-on switches S1 through S8 is connected to +5V, while the other terminal is connected to the respective data input pins. The switches are to be extended to the players through cord wire. The torch bulbs BL1 through BL8 can be housed in boxes with the front side of the boxes covered with a white paper having the name or number of the contestant written over it for easy identification. Place the boxes above the head level so that these can be seen by the audience also.
When the power is switched on using switch S9 (provided terminals ‘A’ and ‘B’ of both the power supply and quiz buzzer sections are interconnected), the circuit is ready to use. Now all the switches (S1 through S8) are open and Q0 through Q7 outputs of IC 74LS373 are low. As a result, the gates of silicon-controlled rectifiers SCR1 through SCR8 are also low.
As soon as a contestant momentarily presses his respective switch, the corresponding output data pin goes high. This triggers the corresponding SCR and the respective bulb glows. At the same time, the piezobuzzer (PZ1) sounds as transistor T1 conducts.
Simultaneously, the base of transistor T2 becomes high to make it conduct. Latch-enable (LE) pin 11 of IC2 is tied to ground to latch all the Q0 through Q7 outputs. This restricts further change in the output state due to any change in the state of switches S1 through S8 by any other contestant. Only one of the eight torch bulbs glows until the circuit is reset by on/off switch S9.
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SCHOOL PROJECT PDF
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Pradeep G.
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SCHOOL PROJECT PDF
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5.Audible IR Proximity Detector
Pradeep G.
This circuit gives an audible indication when any object comes in front of the infrared reflecting sensor (containing IR LED and phototransistor). The sound generated by the sensor will be louder if the object close to the reflecting sensor is opaque.
The home-made reflecting sensor contains a 5mm IR LED and a phototransistor. It can detect up to a longer range than commercial sensors like HO-4R. It can be used for indoor IR proximity detection.
The circuit uses an IC 555 wired as astable multivibrator. The 10kHz signal produced by the multivibrator is fed to the base of transistor T1. This signal is further fed to the IR transmitting LED used in the sensor. When an object comes in front of the sensor, modulated light emitted by the transmitting LED of the sensor is reflected back and sensed by the phototransistor of the same sensor.
The signals sensed by the phototransistor of the sensor are amplified by transistor preamplifier T2. These are further fed to a power amplifier based on IC LM386 to drive a speaker. The tone of sound can be varied by changing the value of tone capacitor C3 of IC1 (NE555).
To make a home-made sensor place the IR transmitting LED and the phototransistor in a piece of bakelite, parallel to each other such that the transmitted IR beam, after reflection, can be received by the phototransistor.
The circuit works off a 9V battery. Assemble it on a general-purpose PCB and enclose in a suitable cabinet. Connect the sensor such that it is oriented towards an approaching object.
The home-made reflecting sensor contains a 5mm IR LED and a phototransistor. It can detect up to a longer range than commercial sensors like HO-4R. It can be used for indoor IR proximity detection.
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The signals sensed by the phototransistor of the sensor are amplified by transistor preamplifier T2. These are further fed to a power amplifier based on IC LM386 to drive a speaker. The tone of sound can be varied by changing the value of tone capacitor C3 of IC1 (NE555).
To make a home-made sensor place the IR transmitting LED and the phototransistor in a piece of bakelite, parallel to each other such that the transmitted IR beam, after reflection, can be received by the phototransistor.
The circuit works off a 9V battery. Assemble it on a general-purpose PCB and enclose in a suitable cabinet. Connect the sensor such that it is oriented towards an approaching object.
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Audible IR detector
6.Versatile Cmos/ttl Logic and Clock Probe
For fault diagnosis of any logic circuit, you need a probe that can test the logic level or existence of clock activity. The circuit shown here can be used to test CMOS and TTL logic circuits for logic states and also for the presence of clock activity from a few hertz to more than 10 MHz, at any point of the logic circuit.
Supply for the probe circuit is taken from the circuit under test using alligator clips. In the circuit, LM319 dual-comparator is connected as a window detector. The non-inverting pin of comparator N1 is biased to nearly 2V when switch S1 is in TTL position and 80 per cent of Vcc in CMOS position. The output of N1 goes low only when logic input at the probe tip exceeds the biasing voltage and, as a result, the red LED lights up to indicate logic 1 state at the probe tip.
Similarly, the inverting pin of comparator N2 is biased at nearly 0.8V (in TTL position of switch S1) and 20 per cent of Vcc (in CMOS position of switch S1). Only when the input voltage at probe tip is less than the biasing voltage, will its output drop low to light up the green LED to indicate logic 0 state.
The probe tip is also connected to the input of CD4049 (N3) via capacitor C1 to pass AC/clock signals. It simply acts as a buffer and couples only the high-to-low going signals at the input/output of the gate to the input of next gate N4.
The output of gate N4 is further coupled to gate N5, which is wired as a monostable. A positive feedback from the output of gate N5 to the input of gate N4 ensures that unless capacitor C4 (0.47µF) discharges sufficiently via 4.7-mega-ohm resistor, further clock pulses at the input of N4 will have no effect.
Gate N6 is used for driving a yellow LED (indicating oscillatory input at probe tip), which will be switched on for a brief period. The output of gate N6 is further used to inhibit/enable the oscillator formed by gates N7 and N8. It briefly activates the buzzer to beep during mono period, indicating oscillatory input at the probe tip. Thus we have audio-visual indication during clock/oscillatory input at the probe tip.
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Supply for the probe circuit is taken from the circuit under test using alligator clips. In the circuit, LM319 dual-comparator is connected as a window detector. The non-inverting pin of comparator N1 is biased to nearly 2V when switch S1 is in TTL position and 80 per cent of Vcc in CMOS position. The output of N1 goes low only when logic input at the probe tip exceeds the biasing voltage and, as a result, the red LED lights up to indicate logic 1 state at the probe tip.
Similarly, the inverting pin of comparator N2 is biased at nearly 0.8V (in TTL position of switch S1) and 20 per cent of Vcc (in CMOS position of switch S1). Only when the input voltage at probe tip is less than the biasing voltage, will its output drop low to light up the green LED to indicate logic 0 state.
The probe tip is also connected to the input of CD4049 (N3) via capacitor C1 to pass AC/clock signals. It simply acts as a buffer and couples only the high-to-low going signals at the input/output of the gate to the input of next gate N4.
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Gate N6 is used for driving a yellow LED (indicating oscillatory input at probe tip), which will be switched on for a brief period. The output of gate N6 is further used to inhibit/enable the oscillator formed by gates N7 and N8. It briefly activates the buzzer to beep during mono period, indicating oscillatory input at the probe tip. Thus we have audio-visual indication during clock/oscillatory input at the probe tip.
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VERSALITE CMOS /TTL
The Bluetooth SIG is a global trade association with more than 17,000 member companies. It was formed with five companies in 1998, and today, has a member-ship that surpasses 17,000 companies worldwide.
Last year, Apple announced that the iPhone 4S will support Bluetooth v4.0 and become the first Bluetooth Smart Ready phone. The SIG adopted 29 new Bluetooth v4.0 profiles, services, protocols and prototyping specifications, creating the infrastructure for Bluetooth Smart devices.
Elaborating on the Bluetooth 4.0 technology, Suke Jawanda, chief marketing officer, Bluetooth SIG, shared that it was a revolutionary update for Bluetooth as its low-power feature enable whole new categories of devices to become part of the connected world.
“As these devices can now run for months or years on a tiny battery, it is now feasible to liberate data from just about any electronic device you can imagine (security sensor, athletic equipment and apparel, toothbrush, thermostat, heart rate monitor) and send that data to applications that are on the ubiquitous Bluetooth hub devices like smart phones or tablets, or to the cloud,” he said.
Where is Bluetooth 4.0 being used?
Bluetooth 4.0 is currently appearing in hub devices and edge devices. The Bluetooth SIG refers to hub devices using Bluetooth 4.0 as ‘Bluetooth Smart Ready,’ as these are ‘ready’ to connect to the entire universe of Bluetooth devices in the market. Examples of Bluetooth Smart Ready products in the market are the iPhone 5 and 4S, new iPad, Motorola RAZR and Samsung Galaxy, just to name a few.
Low-energy edge devices are referred to as Bluetooth Smart. Examples of Bluetooth Smart devices are the Polar H7 heart rate monitor, the Wahoo Fitness Blue HC Cycling monitor and the Casio G-Shock GB-6900 smart watch.
All of the devices on the market can be found at www.bluetooth.com/Pages/Bluetooth-Smart-Devices-List.aspx
Almost no power requirement!
It seems that Bluetooth 4.0 is targeted for small, battery-operated devices and similar products that require almost no power. Jawanda agrees, adding that Bluetooth 4.0 uses a small fraction of the power consumed by previous versions of Bluetooth and many other wireless technologies.
Since it has been optimised for transmitting small bursts of data very efficiently, devices and sensors using Bluetooth 4.0 can run for years at a stretch without requiring a recharge or battery change. This dramatically increases the number of potential devices that can use wireless connectivity.
For example, wireless keyboards that run on two AA-size batteries and last up to six months without a recharge/replacement can now last over six years if they are a Bluetooth Smart device, given the ultra low-power performance of Bluetooth v4.0.
More applications and range!
It would be interesting to note some of the other applications suitable for Bluetooth 4.0.
According to Jawanda, virtually anything that needs to send relatively small burst of data (vs a constant stream like audio and video) at various times can be a suitable application for Bluetooth 4.0. Heart rate monitors, glucose meters, pedometers, cycling sensors, running sensors, running shoes, golf clubs, security and home automation sensors, watches and irrigation controllers are examples of Bluetooth Smart products coming to the market.
The range covered by Bluetooth 4.0 is approximately 30 metres, typically. “There is nothing inherent in the specification itself that limits the range. Range is a function of the environment the wireless device is operating in and the device hardware itself (for example, how powerful the antenna is),” Jawanda adds. There are industrial applications of Bluetooth that have a range of approximately 1 kilometre.
New use-cases
Does Bluetooth 4.0 open up new usecases, much more than Bluetooth 3.0 ever did?
The answer is ‘yes,’ and that’s because of Bluetooth 4.0’s ultra-low power consumption. Bluetooth is the key technology to bring billions of disconnected devices into the connected world. The technology is already transforming industries like sports and fitness today.
Bluetooth is enabling manufacturers to efficiently embed their power-sensitive products with a high-performing and secure sensor technology that allows them to securely send data to devices their customers already have (their phones, tablets, PCs) and feed the applications on these devices or in the cloud.
The data coming from the Blue-tooth sensor is then turned into information by the application, delighting end-users and allowing OEMs to have a deep service relationship with their customers.
Jawanda says, “We see this transformation happening in massive verticals like healthcare, smart home and industrial automation. The ‘Connected things’ are all part of the bigger movement towards the ‘Internet of things’ or IoT, and Bluetooth technology is considered as the backbone wireless technology to connect the billions of power-sensitive sensors ultimately to Web services.
“The proliferation of Bluetooth technology is booming, and ABI Research expects two billion Bluetooth-enabled products to be shipped in 2012 alone. The figure will grow to approximately 5 billion per year within the next few years.”
A total of ten billion Bluetooth products have already been shipped since inception. This massive network of connected devices will double by 2017. The new use-cases stimulated by Bluetooth v4.0 (and its hallmark low-energy feature) are driving much of this growth.
Bluetooth 4.0 also complements the continued proliferation of Bluetooth Basic Rate/Enhanced Data Rate (BR/EDR) that has and will continue to power wireless audio devices like wireless headsets, speakers and headphones.
7.Bluetooth 4.0: Low-power Feature Enables Revolutionary Uptake
Bluetooth 4.0 uses a small fraction of the power consumed by previous versions of Bluetooth and many other wireless technologies. Since it has been optimised for transmitting small bursts of data very efficiently, devices and sensors using 4.0 can run for years at a stretch without requiring a recharge or battery change
Pradeep Chakraborty
Pradeep Chakraborty
 (Image courtesy: Bluetooth Special Interest Group (SIG)) |
Last year, Apple announced that the iPhone 4S will support Bluetooth v4.0 and become the first Bluetooth Smart Ready phone. The SIG adopted 29 new Bluetooth v4.0 profiles, services, protocols and prototyping specifications, creating the infrastructure for Bluetooth Smart devices.
Elaborating on the Bluetooth 4.0 technology, Suke Jawanda, chief marketing officer, Bluetooth SIG, shared that it was a revolutionary update for Bluetooth as its low-power feature enable whole new categories of devices to become part of the connected world.
“As these devices can now run for months or years on a tiny battery, it is now feasible to liberate data from just about any electronic device you can imagine (security sensor, athletic equipment and apparel, toothbrush, thermostat, heart rate monitor) and send that data to applications that are on the ubiquitous Bluetooth hub devices like smart phones or tablets, or to the cloud,” he said.
Where is Bluetooth 4.0 being used?
Bluetooth 4.0 is currently appearing in hub devices and edge devices. The Bluetooth SIG refers to hub devices using Bluetooth 4.0 as ‘Bluetooth Smart Ready,’ as these are ‘ready’ to connect to the entire universe of Bluetooth devices in the market. Examples of Bluetooth Smart Ready products in the market are the iPhone 5 and 4S, new iPad, Motorola RAZR and Samsung Galaxy, just to name a few.
Low-energy edge devices are referred to as Bluetooth Smart. Examples of Bluetooth Smart devices are the Polar H7 heart rate monitor, the Wahoo Fitness Blue HC Cycling monitor and the Casio G-Shock GB-6900 smart watch.
All of the devices on the market can be found at www.bluetooth.com/Pages/Bluetooth-Smart-Devices-List.aspx
Almost no power requirement!
It seems that Bluetooth 4.0 is targeted for small, battery-operated devices and similar products that require almost no power. Jawanda agrees, adding that Bluetooth 4.0 uses a small fraction of the power consumed by previous versions of Bluetooth and many other wireless technologies.
Since it has been optimised for transmitting small bursts of data very efficiently, devices and sensors using Bluetooth 4.0 can run for years at a stretch without requiring a recharge or battery change. This dramatically increases the number of potential devices that can use wireless connectivity.
For example, wireless keyboards that run on two AA-size batteries and last up to six months without a recharge/replacement can now last over six years if they are a Bluetooth Smart device, given the ultra low-power performance of Bluetooth v4.0.
More applications and range!
It would be interesting to note some of the other applications suitable for Bluetooth 4.0.
According to Jawanda, virtually anything that needs to send relatively small burst of data (vs a constant stream like audio and video) at various times can be a suitable application for Bluetooth 4.0. Heart rate monitors, glucose meters, pedometers, cycling sensors, running sensors, running shoes, golf clubs, security and home automation sensors, watches and irrigation controllers are examples of Bluetooth Smart products coming to the market.
The range covered by Bluetooth 4.0 is approximately 30 metres, typically. “There is nothing inherent in the specification itself that limits the range. Range is a function of the environment the wireless device is operating in and the device hardware itself (for example, how powerful the antenna is),” Jawanda adds. There are industrial applications of Bluetooth that have a range of approximately 1 kilometre.
New use-cases
Does Bluetooth 4.0 open up new usecases, much more than Bluetooth 3.0 ever did?
The answer is ‘yes,’ and that’s because of Bluetooth 4.0’s ultra-low power consumption. Bluetooth is the key technology to bring billions of disconnected devices into the connected world. The technology is already transforming industries like sports and fitness today.
 Bluetooth Smart Ready Apple iPhone 5 (Image courtesy: Bluetooth Special Interest Group) |
The data coming from the Blue-tooth sensor is then turned into information by the application, delighting end-users and allowing OEMs to have a deep service relationship with their customers.
Jawanda says, “We see this transformation happening in massive verticals like healthcare, smart home and industrial automation. The ‘Connected things’ are all part of the bigger movement towards the ‘Internet of things’ or IoT, and Bluetooth technology is considered as the backbone wireless technology to connect the billions of power-sensitive sensors ultimately to Web services.
“The proliferation of Bluetooth technology is booming, and ABI Research expects two billion Bluetooth-enabled products to be shipped in 2012 alone. The figure will grow to approximately 5 billion per year within the next few years.”
A total of ten billion Bluetooth products have already been shipped since inception. This massive network of connected devices will double by 2017. The new use-cases stimulated by Bluetooth v4.0 (and its hallmark low-energy feature) are driving much of this growth.
Bluetooth 4.0 also complements the continued proliferation of Bluetooth Basic Rate/Enhanced Data Rate (BR/EDR) that has and will continue to power wireless audio devices like wireless headsets, speakers and headphones.
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