Car anti theft wireless alarm

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This FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system. The mini VHF, FM transmitter is fitted in the vehicle at night when it is parked in the car porch or car park. The receiver unit with CXA1019, a single IC-based FM radio module, which is freely available in the market at reasonable rate, is kept inside. Receiver is tuned to the transmitter's frequency. When the transmitter is on and the signals are being received by FM radio receiver, no hissing noise is available at the output of receiver. Thus transistor T2 (BC548) does not conduct. This results in the relay driver transistor T3 getting its forward base bias via 10k resistor R5 and the relay gets energised. When an intruder tries to drive the car and takes it a few metres away from the car porch, the radio link between the car (transmitter) and alarm (receiver) is broken. As a result FM
radio module gene-rates hissing noise. Hissing AC signals are coupled to relay switching circ- uit via audio transformer. These AC signals are rectified and filtered by diode D1 and capacitor C8, and the resulting positive DC voltage provides a forward bias to transistor T2. Thus transistor T2 conducts, and it pulls the base of relay driver transistor T3 to ground level. The relay thus gets de-activated and the alarm connected via N/C contacts of relay is switched on. If, by chance, the intruder finds out about the wireless alarm and disconnects the transmitter from battery, still remote alarm remains activated because in the absence of signal, the receiver continues to produce hissing noise at its output. So the burglar alarm is fool-proof and highly reliable.
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40 meter Direct Conversion Receiver

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Using the circuit of 40-metre band direct-conversion receiver descr- ibed here, one can listen to amateur radio QSO signals in CW as well as in SSB mode in the 40-metre band. The circuit makes use of three n-channel FETs (BFW10). The first FET (T1) performs the function of ant./RF amplifier-cum-product detector, while the second and third FETs (T2 and T3) together form a VFO (variable frequency oscillator) whose output is injected into the gate of first FET (T1) through 10pF capacitor C16. The VFO is tuned to a frequency which differs from the incoming CW signal frequency by about 1 kHz to produce a beat frequency in the audio range at the output of transformer X1, which is an audio driver transformer of the type used in transistor radios. The audio output from transformer X1 is connected to the input of audio amplifier built around IC1 (TBA820M) via volume control
VR1. An audio output from the AF amplifier is connected to an 8-ohm, 1-watt speaker. The receiver can be powered by a 12-volt power-supply, capable of sourcing around 250mA current. Audio-output stage can be substituted with a readymade L-plate audio output circuit used in transistor amplifiers, if desired. The necessary data regarding the coils used in the circuit is given in the circuit diagram itself.

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Coilless FM transmitter !

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The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength. Since the output of N4-N6 is square wave there will be a lot of harmonics in it. The 9th harmonics of 10.7Mhz (96.3Mhz) will hence be at the center of the FM band .
N1 is working as an audio amplifier. The audio signals from the microphone are amplified and fed to the varycap diode. The signal varies the capacitance of the varycap and hence varies the oscillator frequency which produce Frequency Modulation.

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Color Sensor

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Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only ‘AND’ gates and ‘NOT’ gates.

When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corres- ponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.
When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :
1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.
2. Common ends of the LDRs should be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions.
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Metal Detector

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The circuit described here is that of a metal detector. The opera- tion of the circuit is based on superheterodyning principle which is commonly used in superhet receivers. The circuit utilises two RF oscillators. The frequencies of both oscillators are fixed at 5.5 MHz. The first RF oscillator comprises transistor T1 (BF 494) and a 5.5MHz ceramic filter commonly used in TV sound-IF section. The second oscillator is a Colpitt’s oscillator realised with the help of transistor T3 (BF494) and inductor L1 (whose construction details follow) shunted by trimmer capacitor VC1. These two oscillators’ frequencies (say Fx and Fy) are mixed in the mixer transistor T2 (another BF 494) and the difference or the beat frequency (Fx-Fy) output from collector of transistor T2 is connected to
detector stage comprising diodes D1 and D2 (both OA 79). The output is a pulsating DC which is passed through a low-pass filter realised with the help of a 10k resistor R12 and two 15nF capacitors C6 and C10. It is then passed to AF amplifier IC1 (2822M) via volume control VR1 and the output is fed to an 8-ohm/1W speaker. The inductor L1 can be constructed using 15 turns of 25SWG wire on a 10cm (4-inch) diameter air-core former and then cementing it with insulating varnish. For proper operation of the circuit it is critical that frequencies of both the oscillators are the same so as to obtain zero beat in the absence of any metal in the near vicinity of the circuit. The alignment of oscillator 2 (to match oscillator 1 frequency) can be done with the help of trimmer capacitor VC1. When the two frequencies are equal, the beat frequency is zero, i.e. beat frquency=Fx-Fy=0, and thus there is no sound from the loudspeaker. When search coil L1 passes over metal, the metal changes its inductance, thereby changing the second oscillator’s frequency. So now Fx-Fy is not zero and the loudspeaker sounds. Thus one is able to detect presence of metal
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Radio Remote Control using DTMF

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H ere is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a very confined area and line-of-sight. However, this circuit makes use of radio frequency to transmit the control signals and hence it can be used for control from almost anywhere in the house. Here we make use of DTMF (dual-tone multi frequency) signals (used in telephones to dial the digits) as the control codes. The DTMF tones are used for
frequency modulation of the carrier. At the receiver unit, these frequency modulated signals are intercepted to obtain DTMF tones at the speaker terminals. This DTMF signal is connected to a DTMF-to-BCD converter whose BCD output is used to switch-on and switch-off various electrical applicances (4 in this case). The remote control transmitter consists of DTMF generator and an FM transmitter circuit. For generating the DTMF frequencies, a dedicated IC UM91214B (which is used as a dialler IC in telephone instruments) is used here. This IC requires 3 volts for its operation. This is provided by a simple zener diode voltage regulator which converts 9 volts into 3 volts for use by this IC. For its time base, it requires a quartz crystal of 3.58 MHz which is easily available from electronic component shops. Pins 1 and 2 are used as chip select and DTMF mode select pins respectively. 
When the row and column pins (12 and 15) are shorted to each other, DTMF tones corresponding to digit 1 are output from its pin 7. Similarly, pins 13, 16 and 17 are additionally required to dial digits 2, 4 and 8. Rest of the pins of this IC may be left as they are. The output of IC1 is given to the input of this transmitter circuit which effectively frequency modulates the carrier and transmits it in the air. The carrier frequency is determined by coil L1 and trimmer capacitor VC1 (which may be adjusted for around 100MHz operation). An antenna of 10 to 15 cms (4 to 6 inches) length will be sufficient to provide adequate range. The antenna is also necessary because the transmitter unit has to be housed in a metallic cabinet to protect the frequency drift caused due to stray EM fields. Four key switches (DPST push-to-on spring loaded) are required to transmit the desired DTMF tones. The switches when pressed generate the specific tone pairs as well as provide power to the transmitter circuit simultaneously. This way when the transmitter unit is not in use it consumes no power at all and the battery lasts much longer. The receiver unit consists of an FM receiver (these days simple and inexpensive FM kits are readily available in the market which work exceptionally well), a DTMF-to-BCD converter and a flip-flop toggling latch section. 
The frequency modulated DTMF signals are received by the FM receiver and the output (DTMF tones) are fed to the dedicated IC KT3170 which is a DTMF-to-BCD converter. This IC when fed with the DTMF tones gives corresponding BCD output; for example, when digit 1 is pressed, the output is 0001 and when digit 4 is pressed the output is 0100. This IC also requires a 3.58MHz crystal for its operation. The tone input is connected to its pin 2 and the BCD outputs are taken from pins 11 to 14 respectively. These outputs are fed to 4 individual ‘D’ flip-flop latches which have been converted into toggle flip-flops built around two CD4013B ICs. Whenever a digit is pressed, the receiver decodes it and gives a clock pulse which is used to toggle the corresponding flip-flop to the alternate state. The flip-flop output is used to drive a relay which in turn can latch or unlatch any electrical appliance. We can upgrade the circuit to control as many as 12 channels since IC UM91214B can generates 12 DTMF tones. For this purpose some modification has to be done in receiver unit and also in between IC2 and toggle flip-flop section in the receiver. A 4-to-16 lines demultiplexer (IC 74154) has to be used and the number of toggle flip-flops have also to be increased to 12 from the existing 4

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Remote control using VHF modules

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A few designs for remote control switches, using VG40T and VG40R remote control pair, are shown here.
The miniature transmitter module shown in Fig. 1, which just measures 34 mm x 29 mm x 10 mm, can be used to operate all remote control receiver-cum-switch combinations described in this project. A compact 9-volt PP3 battery can be used with the transmitter. It can transmit signals up to 15 metres without any aerial. The operating frequency of the transmitter is 300 MHz. The following circuits, using VG40R remote control receiver module measuring 45 mm x 21 mm x 13 mm, can be used to:
(a) activate a relay momentarily,
(b) activate a relay for a preset period,
(c) switch on and switch off a load.

To activate a relay momentarily (see Fig. 2), the switch on the transmitter unit is pressed, and so a positive voltage is obtained at output pin of VG40R module. This voltage is given to bias the relay driver transistor. The relay gets activated by just pressing push-to-on micro switch on the transmitter unit. The relay remains energised as long as the switch remains pressed. When the switch is released, the relay gets deactivated. Any electrical/electronic load can be connected via N/O contacts of the relay.
To activate a relay for a preset period (refer Fig. 3), the switch on the transmitter unit is pressed momentarily. The transistor gets base bias from VG40R module. As a result the transistor conducts and applies a trigger pulse to IC 555, which is wired as a monostable multivibrator. The relay remains activated till the preset time is over. Time delay can be varied from a few seconds to a few minutes by adjusting timing components.
To switch on and switch off a load (refer Fig. 4), a 555 IC and a decade counter 4017 IC are used. Here the 4017 IC is wired as a flip-flop for toggle action. This is achieved by connecting Q2 output to reset terminal while Q1 output is unused. Q0 output is used for energising the relay. The relay is activated and deactivated by pressing the transmitter switch alternately. So, to activate the load, just press the transmitter switch once, momentarily. The relay will remain activated. To switch off the relay, press the transmitter switch again. This process can be repeated. Time delay of monostable multivibrator is set for about one second.
Note: Short length of shielded wire should be used between VG40R receiver module output and the rest of the circuit. The transmitter with 9V battery must be housed inside a nonmetallic (say, plastic) cabinet for maximum range of operation.

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This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the TV detecting a channel-change or any other command. This allows you to watch your own program without anyone changing the channel !!    The circuit is adjusted to produce a 38kHz signal. The IR diode is called an Infra-red transmitting Diode or IR emitter diode to distinguish it from a receiving diode, called an IR receiver or IR
receiving diode. (A Photo diode is a receiving diode). There are so many IR emitters that we cannot put a generic number on the circuit to represent the type of diode. Some types include: CY85G, LD271, CQY37N (45¢), INF3850, INF3880, INF3940 (30¢). The current through the IR LED is limited to 100mA by the inclusion of the two 1N4148 diodes, as these form a constant-current arrangement when combined with the transistor and 5R6 resistor.

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FM Transmitter

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100 meter FM transmitter

Frequency Range: 85-110 MHz

This is tested project and verified by me..........

Simplest FMT can be used with number of low amplitude audio output devices for transmission up to 100 m. Audio Input can be a Microphone,PC, DVD, TV,Mobile any other sound output device.,

Stop disturbing others while watching TV and go Wireless .

Hardware Description:

BC108 act as buffer amplifier to isolate the frequency generating and modulating stage.

2N2369 is a RF amplifier and RF generator to modulate the Input signal at 85-110 MHz.

C5 trimmer to change the frequency and C6 to vary the power output.

L1 can be 1 uH fixed resistor or can be made at home by using 24SWG wire having 4 turns on 6 mm diameter former.

Antenna 1-2 m copper wire.
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communication using visible light

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Wireless optical communication using visible light is one of the emerging green technologies that has not been fully utilized. Many versions of white-LED transceivers have been built, but mainly due to the high cost of good photodiodes and the existing popularity of fluorescent lamps, visible-light communication (VLC) only receives luke-warm attention to date. I shall introduce two low-cost and efficient transceiver circuit designs that can be constructed using on-the-market components.
They can be applied in moderate-speed data communications such as smart phones and tablets for ad-hoc transmission of photos and files. The potentials for these designs are wide if we are able to scale down the circuits to tiny PCBs or manufacture them at IC level.


LED is a very green technology. Since very little heat is produced, it can reduce interior temperatures by 1 to 2 degrees, thus lowering air-conditioning costs and carbon dioxide emissions. LED lighting is also much safer for the living and working environment because it is mercury free and does not produce IR or UV rays which can be harmful to human eyes and skin [1].
White LED communication uses light in the visible spectrum as the carrier medium. The functional duality of LEDs - both as a light source and a communication medium - creates many new and interesting applications [2][3][4][5][6][7][8][9] based on the fast-switching characteristic of LEDs and the ability to modulate lightwave for free-space communications. In this kind of technology, it is possible to achieve high-speed data transmission for high data loads with low implementation complexity. Also, lightwave cannot penetrate walls, thus making it easy to secure transmissions against casual eavesdropping. Furthermore, unlike radio frequencies, the visible-light spectrum does not need licensing.
Given the strengths of LEDs [10] - long lifetime, high tolerance to humidity, small size, and low power consumption - a white-LED communication system is therefore potentially feasible for indoor wireless networks. VLC is somewhere between Bluetooth and WLAN, but in the near future, it will replace these two technologies if the transceiver circuit can be fabricated with the LED and photodiode together on a single chip. We should expect a sudden burst of popularity in white-LED communication in the next generation of personal computers after IBM and Intel have successfully fabricated and tested their new optical core processors. Optical I/O ports would most probably replace our LAN and USB interfaces. These ports would be able to connect to ceiling lights, wall lights, or desk lamps via a repeating adaptor.
In the following sections, two types of transceiver circuit prototypes are introduced. The design principles in this work are based on cost cutting, simplicity, and the most common electronic components on the market. The intended application is serial peer-to-peer, ad-hoc communication.

Hardware Description: Prototype 1

The components of Prototype 1 (Fig. 1) consist mainly of a microcontroller, a repeater, and a USB-RS232 converter. The transmitter consists of a microcontroller PIC12F508 which is used for the modulation of the TX signal from the µUSB-MB5 (USB-RS232 converter). When the TX pin transits from logic low to logic high, the 12F508 generates a 40 kHz carrier. During low periods, the carrier is suppressed. After the modulation of the signal, the output of the microcontroller is passed on to an NPN darlington transistor to drive the white LEDs.
The repeater receives white-light signals using the BS520 eye-response photodiode and retransmits them at a higher power. Signals received by the BS520 is usually weak and easily affected by ambient light. The repeater circuit is used to shape and boost the received signal from the photodiode before passing it to the IR transmitter. The other use of the repeater is to fine-tune the signal to the correct frequency, so that it can be readily accepted by the IR receiver. The path between the IR transmitter and the IR receiver must be enclosed to ensure that the receiver does not receive reflected signals from the transmitter. Alternatively, an optoisolator IC (e.g. 4N25) can also be used in place of the IR transmitter and receiver.
After the IR receiver receives signals from the repeater and demodulates them, the demodulated signals are sent to the RX pin of the µUSB-MB5, which then passes the converted signals back to the computer. The µUSB-MB5 RS232-to-USB converter is one of the more expensive items in the transceiver (USD $58), but there should be less expensive serial converters out there in the market.
The design of Prototype 1 is based on the established IR technology by creating a hybrid combination (Fig. 2) of IR and visible-light devices. The components are cheap and widely available.

VLC Transceiver: Prototype 1

VLC Transceiver: Prototype 2

Prototype 2

In Prototype 2 (Fig. 3), a PIC12F508 microcontroller is used to generate a 40 kHz clock which is passed to the one-shot IC DM74121N. The TX signal from the USB-MB5 is then pulse-position modulated (PPM) by the one-shot device 74121 before being transmitted out through the LEDs.
The receiver consists of a Centronic OSD50-E eye-response photodiode, a preamplifier KA2181, a phase-locked loop MM74HC4046N, and an inverter 74LS04. Light signals received by the photodiode is preamplified and shaped by the preamplifier before being demodulated by the phase-locked loop. For the KA2181 circuit, the user must find its optimal inductor value which determines the receiver's sensitivity.

Both Prototype 1 and 2 can only operate at 9600 bps.

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High Durability of Nanotube Transistors in Harsh Space Environment Demonstrated

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U.S. Naval Research Laboratory electronics science and technology engineers demonstrate the ability of single walled carbon nanotube transistors (SWCNTs) to survive the harsh space environment, investigating the effects of ionizing radiation on the crystalline structures and further supporting the development of SWCNT-based nanoelectronics for use in harsh radiation environments.

"One of the primary challenges for space electronics is mitigating the susceptibility of prolonged exposure to radiation that exists in the charged particle belts that encircle Earth," said Cory Cress, materials research engineer. "These are the first controlled demonstrations showing little performance degradation and high tolerance to cumulative ionizing radiation exposure."
Radiation effects take two forms, transient effects and cumulative effects. The former, referred to as single effect transients (SETs), result from a direct strike by an ionizing particle in space that causes a current pulse in the device. If this pulse propagates through the circuit it can cause data corruption that can be extremely detrimental to someone that relies on that signal, such as a person using GPS for navigation. NRL researchers have recently predicted that such effects are nearly eliminated for SWCNT-based nanoelectronics due to their small size, low density, and inherent isolation from neighboring SWCNTs in a device.
The cumulative effects in traditional electronics results from trapped charges in the oxides of the devices, including the gate oxide and those used to isolate adjacent devices, the latter being primary source of radiation-induced performance degradation in state-of-the-art complementary metal-oxide semiconductor (CMOS) devices. The effect is manifested as a shift in the voltage needed to turn the transistor on or off. This initially results in power leakage, but can eventually cause failure of the entire circuit.
By developing a SWCNT structure with a thin gate oxide made from thin silicon oxynitride, NRL researchers recently demonstrated SWCNT transistors that do not suffer from such radiation-induced performance changes. This hardened dielectric material and naturally isolated one-dimensional SWCNT structure makes them extremely radiation tolerant.
The ability for SWCNT-based transistors to be both tolerant to transient and cumulative effects potentially enables future space electronics with less redundancy and error-correction circuitry, while maintaining the same quality of fidelity. This reduction in overhead alone would greatly reduce power and improve performance over existing space-electronic systems even if the SWCNT-based transistors operate at the same speed as current technologies. Even greater benefits are foreseeable in the future, once devices are developed that exceed the performance of silicon-based transistors.

A locally etched back-gated field effect transistor (FET) structure with a deposited dielectric layer. Thick dielectric layers are highly susceptible to radiation induced charge build-up, which is known to cause threshold voltage shifts and increased leakage in metal-oxide semiconductor (MOS) devices. To mitigate these effects, the dielectric layer is locally etched in the active region of the back-gated FET. A gate dielectric material is then deposited (depicted in red) over the entire substrate. (Credit: U.S. Naval Research Laboratory)

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Professional electronics projects

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Hello! etheory users might be pretty much busy doing your works.Meanwhile take a look at this::::

                        We have a collection of Professional Projects for electronics final year students, while building and studying these projects you would touch almost every concept you have studied in last  three years.Basic practical electronics to professional techniques, Diodes to Microprocessors, C to COMSOL , PCB to Multilayer 3D PCBs, AM Radio to Space Communication and Much more to learn.
All these projects are Licensed under GNU License.
          We are unable to post all the projects because they are not free ......(some of them will be posted as samples)........but costs 10$ to 100$.

 List of project can be emailed on demand:
  1.  Please specify your budget.
  2.  email id or Ph. no. to contact.
for payment options and other queries 
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           If you want the full written material about project . Please email us at:                       or
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