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light sensitive BEAM robot
First off, this project requires no programming. No code.
The full robot is two identical circuits, one for each side of the robot. If the left-side photoresistor senses light the right-side motor turns on, and vice versa. This way the robot will always turn towards a light. If the light is even on both sides (meaning the robot is facing straight at the light source) the robot will drive straight ahead.
How it works. 1) The variable resistor should be adjusted so the motor is just below the point of turning on in normal light.
2) When a light is shined on the photoresistor (LDR1), it's resistance drops and a current begins to flow in the base of T3 causing it to start to turn on and draw a current from the base of T1 (through R3). This in turn, causes a larger current to flow through T1 and into the motor M1.
3) The LED (LD1) will also begin to light up. The brighter the light on the sensor, the more the transistors will turn on and the faster the motor will spin.