Infrared Toy Car Motor Controller


This add-on circuit
enables remote switching on/off of battery-operated toy cars with the
help of a TV/video remote control handset operating at 30–40 kHz. When
the circuit is energised from a 6V battery, the decade counter CD4017
(IC2), which is configured as a toggle flip-flop, is immediately reset
by the power-on-reset combination of capacitor C3 and resistor R6. LED1
connected to pin 3 (Q0) of IC2 via resistor R5 glows to indicate the
standby condition. In standby condition, data output pin of the
integrated infrared receiver/demodulator (SFH505A or TSOP1738) is at a
high level (about 5 volts) and transistor T1 is ‘off’ (reverse biased).

Circuit

Circuit diagram

The monostable wired around IC1 is inactive in this condition. When
any key on the remote control handset is depressed, the output of the IR
receiver momentarily transits through low state and transistor T1
conducts. As a result, the monostable is triggered and a short pulse is
applied to the clock input (pin 14) of IC2, which takes Q1 output (pin
2) of IC2 high to switch on motor driver transistor T2 via base bias
resistor R7 and the motor starts rotating continuously (car starts
running). Resistor R8 limits the starting current. When any key on the
handset is depressed again, the monostable is retriggered to reset
decade counter IC2 and the motor is switched off.

Standby LED1 glows again. This circuit can be easily fabricated on a
general-purpose printed board. After construction, enclose it inside
the toy car and connect the supply wires to the battery of the toy car
with right polarity. Rewire the DC motor connections and fix the IR
receiver module in a suitable location, for example, behind the front
glass, and connect its wires to the circuit board using a short 3-core
ribbon cable/shielded wire. Note. Since the circuit uses modulated
infrared beam for control function, ambient light reflections will not
affect the circuit operation. However, fluorescent tubelights with
electronic ballasts and CFL lamps may cause malfunctioning of the circuit.


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