This is circuit can be used for sensing the distance between
the rear bumper of the car and any obstacle behind the car. The
distance can be understood from the combination of the LEDs (D5 to D7) glowing.
At 25cm D7 will glow, at 20 cm D7&D6 will glow and at 5cm D7, D6
and D5 will glow. When the obstacle is beyond 25 cm none of the above
LEDs will glow.
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Car Parking Sensor circuit
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Note:
- D1 & D2 must be mounted close (~2cm)
- D1 can be a general purpose IR LED.
- D2 can be general purpose IR photo diode with sun filter.
- Transmitter as well as receiver can be powered from the car battery.
- For proper working of the circuit, some trial and error is needed with the position of D1 and D2 on the dash board.
Two
ICs are used in the circuit. The IC1 (NE555) is wired as an astable
multivibrator for driving the IR Diode D1 to emit IR pulses. The
operating frequency of the transmitter is set to be 120Hz.The IR pulses
transmitted by D1 will be reflected by the obstacle and received by the
D2 (IR photo diode).The received signal will be amplified by IC2a.The
peak of the amplified signal will be detected by the diode D4 and
capacitor C4.R5 and R6 compensates the forward voltage drop of D4.The
output voltage of the peak detector will be proportional to the distance between
car’s bumper and obstacle. The output of peak detector is given to the
inputs of the other three comparators IC2b,IC2c and IC2d inside the
IC2(LM324).The comparators switch the status LEDs according to the input
voltage their inverting inputs and reference voltages at their non
inverting inputs. Resistances R7 to R10 are used to set the reference
voltages for the comparators.
Lay out IC LM324
Features
Internally frequency compensated for unity gain
Large DC voltage gain 100 dB
Wide bandwidth (unity gain) 1 MHz (temperature compensated)
Wide power supply range:Single supply 3V to 32V or dual supplies ±1.5V to ±16V
Very low supply current drain (700 μA)—essentially
independent of supply voltage
Low input biasing current 45 nA (temperature compensated)
Low input offset voltage 2 mV and offset current: 5 nA
Input common-mode voltage range includes ground
Differential input voltage range equal to the power supply voltage
Large output voltage swing 0V to V+ − 1.5V.
