Published:2009/7/17 3:30:00 Author:Jessie | From:SeekIC
In order to add some realism to a model sports car, this simple circuit can be built into virtually any type of toy car, battery-operated or not. The design uses a CD4020 14-stage binary counter to operate LED tum indicators (D5 to D8), taillights (D9 and D10), and headlights (D11 and D12). The counter IC1 is clocked by a unijunction oscillator based around TR1. The red taillights and the yellow headlights draw a small current, supplied constantly by resistors R7 and R8. For added re-alism, this current is supplemented through resistors R1 and R2 to give an impression of headlights dipping and taillights braking. The model's turn indicators flash whenever they are enabled, and so the cathodes (k) of D5 to D8 are taken to another output (Q3, pin 7) of IC1. With their anodes (a) taken positive via resistors R3/R4 and the relevant counter output, they flash at the rate determined by Q3. The result is that one set of indicator lights flashes, then the other set, followed by both. The circuit is powered by a PP3-type or MN1604 9-V battery, and a small slide switch S1 can be mounted on the vehicle's underside.
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