The electronic device described in mi readers, you can install on the toy, equipped with a separate drive for each caterpillar: tank, lunar Rover, Lunokhod. The model moves with headlights on in a darkened room, and set PA her the photodiodes capture the reflection of the headlights from obstacles. The appropriate commands to the drive engines on the basis of the received data takes the logical unit. Here’s how it works.
When the photodiode V1 is shaded, its resistance is high and, consequently, it creates a high potential which is fed simultaneously at the two inputs 1, 2 of the chip D1. Output 3 a logical 0, transistor V3 is opened and the relay K1 includes an electric motor.
The illuminated photodiode has a small resistance, the voltage drop across it is small. Therefore, the inputs 1, 2 is fed a logic 0, and the output 3 appears a logic 1: transistor VЗ closed, de-energizing relay K1 and the motor stops.