LIE DETECTORS CIRCUITS DIAGRAM

LIE DETECTOR-1

This circuit detects the resistance between your fingers to provide an oscillation. The detection-points can detect resistances as high as 300k and because the resistance decreases, the frequency increases.

Separate the 2 bit pads and fasten them to the back of every hand. because the subject feels nervous, he can sweat and alter the frequency of the circuit.The photos show the circuit engineered on computer boards

with separate bit pads.

LIE DETECTOR-2

This circuit detects the resistance between your fingers to turn on the FALSE LED. The circuit sits with the TRUE LED illuminated. The 47k pot is adjusted to permit the LEDs to change state when touching the

probes. 

LIE DETECTOR-3

This circuit detects the resistance between your fingers to show the four LEDs. As you press tougher, more

LEDs are illuminated.

LIE DETECTOR-4

his circuit detects the resistance between your fingers to show the 3LEDs. As you press harder, a lot of LEDs are illuminated. Thecircuit is less complicated than Lie Detector-3. 

Sourced By: www.circuitsproject.com

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Invisible Broken Wire Detector Circuit Diagram

Portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug. Due to prolonged usage, the power cord wires are subjected to mechanical strain and stress, which can lead to internal snapping of wires at any point. In such a case most people go for replacing the core/cable, as finding the exact location of a broken wire is difficult.

In 3-core cables, it appears almost impossible to detect a broken wire and the point of break without physically disturbing all the three wires that are concealed in a PVC jacket. The circuit presented here can easily and quickly detect a broken/faulty wire and its breakage point in 1-core, 2-core, and 3-core cables without physically disturbing wires. It is built using hex inverter CMOS CD4069.

Gates N3 and N4 are used as a pulse generator that oscillates at around 1000 Hz in audio range. The frequency is determined by timing components comprising resistors R3 and R4, and capacitor C1. Gates N1 and N2 are used to sense the presence of 230V AC field around the live wire and buffer weak AC voltage picked from the test probe. The voltage at output pin 10 of gate N2 can enable or inhibit the oscillator circuit.

When the test probe is away from any high-voltage AC field, output pin 10 of gate N2 remains low. As a result, diode D3 conducts and inhibits the oscillator circuit from oscillating. Simultaneously, the output of gate N3 at pin 6 goes ‘low’ to cut off transistor T1. As a result, LED1 goes off. When the test probe is moved closer to 230V AC, 50Hz mains live wire, during every positive half-cycle, output pin 10 of gate N2 goes high.

Thus during every positive half-cycle of the mains frequency, the oscillator circuit is allowed to oscillate at around 1 kHz, making red LED (LED1) to blink. (Due to the persistence of vision, the LED appears to be glowing continuously.) This type of blinking reduces consumption of the current from button cells used for power supply. A 3V DC supply is sufficient for powering the whole circuit.

Invisible Broken Wire Detector Circuit Diagram

AG13 or LR44 type button cells, which are also used inside laser pointers or in LED-based continuity testers, can be used for the circuit. The circuit consumes 3 mA during the sensing of AC mains voltage. For audio-visual indication, one may use a small buzzer (usually built inside quartz alarm time pieces) in parallel with one small (3mm) LCD in place of LED1 and resistor R5. In such a case, the current consumption of the circuit will be around 7 mA.

Alternatively, one may use two 1.5V R6- or AA-type batteries. Using this gadget, one can also quickly detect fused small filament bulbs in serial loops powered by 230V AC mains.
The whole circuit can be accommodated in a small PVC pipe and used as a handy broken-wire detector. Before detecting broken faulty wires, take out any connected load and find out the faulty wire first by continuity method using any multimeter or continuity tester.

Then connect 230V AC mains live wire at one end of the faulty wire, leaving the other end free. Connect neutral terminal of the mains AC to the remaining wires at one end. However, if any of the remaining wires is also found to be faulty, then both ends of these wires are connected to neutral. For single-wire testing, connecting neutral only to the live wire at one end is sufficient to detect the breakage point.

In this circuit, a 5cm (2-inch) long, thick, single-strand wire is used as the test probe. To detect the breakage point, turn on switch S1 and slowly move the test probe closer to the faulty wire, beginning with the input point of the live wire and proceeding towards its other end. LED1 starts glowing during the presence of AC voltage in faulty wire. When the breakage point is reached, LED1 immediately extinguishes due to the non-availability of mains AC voltage.

The point where LED1 is turned off is the exact broken-wire point. While testing a broken 3-core rounded cable wire, bend the probe’s edge in the form of ‘J’ to increase its sensitivity and move the bent edge of the test probe closer over the cable. During testing avoid any strong electric field close to the circuit to avoid false detection.

Author: K. Udhaya Kumaran

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DTMF Proximity Detector Circuit Diagram

A DTMF-based IR transmitter and receiver pair can be used to realize a proximity detector. The circuit presented here enables you to detect any object capable of reflecting the IR beam and moving in front of the IR LED photo-detector pair up to a distance of about 12 cm from it. The circuit uses the commonly available telephony ICs such as dial-tone generator 91214B/91215B (IC1) and DTMF decoder CM8870 (IC2) in conjunction with infrared LED (IR LED1), photodiode D1, and other components as shown in the figure. A properly regulated 5V DC power supply is required for operation of the circuit.

The transmitter part is configured around dialer IC1. Its row 1 (pin 15) and column 1 (pin 12) get connected together via transistor T2 after a power-on delay (determined by capacitor C1 and resistors R1 and R16 in the base circuit of the transistor) to generate DTMF tone (combination of 697 Hz and 1209 Hz) corresponding to keypad digit “1” continuously. LED 2 is used to indicate the tone output from IC3. This tone output is amplified by Darlington transistor pair of T3 and T4 to drive IR LED1 via variable resistor VR1 in series with fixed 10-ohm resistor R14. Thus IR LED1 produces tone-modulated IR light.

Variable resistor VR1 controls the emission level to vary the transmission range. LED 3 indicates that transmission is taking place. A part of modulated IR light signal transmitted by IR LED1, after reflection from an object, falls on photodetector diode D1. (The photodetector is to be shielded from direct IR light transmission path of IR LED1 by using any opaque partition so that it receives only the reflected IR light.) On detection of the signal by photodetector, it is coupled to DTMF decoder IC2 through emitter-follower transistor T1.

When the valid tone pair is detected by the decoder, its StD pin 15 (shorted to TOE pin 10) goes ‘high’. The detection of the object in proximity of IR transmitter-receiver combination is indicated by LED1. The active-high logic output pulse (terminated at connector CON1, in the figure) can be used to switch on/off any device (such as a siren via a latch and relay driver) or it can be used to clock a counter, etc. This DTMF proximity detector finds applications in burglar alarms, object counter and tachometers, etc.

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Simple Electromagnetic Field Detector Schematic

This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer. Pickup is by a radial type inductor, used as a probe which responds well to low frequency changing magnetic and electric fields. Ordinary headphones are used to for detection. The field that surrounds a transformer is heard as a 50 or 60Hz buzz. The circuit is below:-

Electromagnetic Field Detector Circuit Diagram

Notes:

I threaded a length of screened cable through an old pen tube and soldered the ends to a radial type can inductor. I used 1mH. The inductor fitted snugly into the pen tube. The opposite end of the cable connects to the input of the op-amp. Any op-amp should work here, possibly better results may be achieved with a low noise FET type such as the LF351. The 2M2 potentiometer acts as a gain control and the output is a pair of headphones. Stereo types can be used if they are wired as mono. I used an 8 ohm type, but the circuit should work equally well with higher impedance types. The probe (shown below) may be connected via screened cable and a 3.5mm stereo plug and socket.

Detection:

The sensitivity of this circuit is good. Mains wiring buried an inch in plaster can be detected with precision. A small load on the electric supply is all that is needed; a 20 watt desk lamp or similar will suffice. The hum field surrounding a transformer can be detected oat over 7 inches. Domestic appliances such as videos and alarm clocks all produce interference which can be heard with the probe. The electric field surrounding a loudspeaker or earpiece can also be heard. Try lifting a telephone and place the probe near the earpiece. A telephone pickup coil can be used in place of the inductor if desired. I will make an improved version of this circuit with a meter output later. Link

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Versatile Proximity Detector with Auto Reset

Electrochemical processes taking place in our body generate complex sig-nals (hum) that are continuously being passed along the nerve fibres throughout the body. Any physical activity such as muscle movement increases hum.

Here’s a circuit that operates when it detects hum generated by the human body in proximity. Its versatility lies in the fact that you don’t need to touch the metal plates for detection. Just the presence of your hand/body within 1 cm of the sensing loop triggers the circuit. The activation of the circuit is indicated by the glowing of an LED and an audible beep. The circuit continues to glow and beep until the hand is within 5 cm of the loop. Beyond 5 cm, it resets automatically.

Here IC2 (555) simplifies the circuitry otherwise needed to achieve this. Regulator 7809 (IC1) supplies 9V DC to the circuit.

Versatile Proximity Detector with Auto Reset Circuit Diagram

When power is turned on, capacitor C3 (47 kpF) charges through resistor R1 (1 mega-ohm). Output pin 3 of IC2 remains high as long as the voltage at its pin 2 is below 2/3Vcc; the buzzer beeps for this period. Beyond that voltage, the output resets (goes low).

Transistors T1 and T2 (each BC548) form a Darlington pair. As long as T1 and T2 remain in cut-off condition, capacitor C3 retains the charge and the buzzer is off. When you take your hand within 1 cm of the loop wire, T1 conducts due to the noise picked up by its base. So capacitor C3 gets a discharge path, and the voltage at pin 2 of IC2 going below 1/3Vcc sets output pin 3 high. As a result, the buzzer sounds.

The beep continues until C3 charges to 2/3Vcc due to gradual withdrawal of the hand from vicinity of the loop wire.  The series combination of capacitor C5 and resistor R3 within dotted lines is optional and reduces hum at the base of T1. The values of C5 and R3 to be used for varying the sensitivity of the circuit are given in the table.

For calibration, wire the circuit and use a 7cm hook-up wire at the base of T1. When you place your hand over the wire insulation, the buzzer should beep. If it doesn’t, check connections. Now connect the loop wire. If beep continues even when there is no person within 20 cm, use a suitable combination of C5 and R3 from the table to reduce the circuit sensitivity.

The suggested PCB size for the circuit (excluding power supply) is 4 cm×3 cm. Solder the loop wire directly. A small hook-up wire was used in the prototype.

Do not remove insulation of the wire. Keep the circuit away from mains wiring and large metal objects.

Sourced by: EFY. Author:  Kaushik Hazarika

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