Discrete Robot

This simple robot, which responds to light and avoids obstacles, can be built without using a microcontroller, programmer or PC. The only ‘special’ component in the circuit is a window discriminator (a fancy version of a window comparator).Resistors R1 and R2 in combination with light-dependent resistors LDR1 and LDR2 form a voltage divider (with the current being limited by R1 and R2 for bright light). Window discriminator TCA965 compares the mid-point voltage with an upper threshold value (adjustable using P1) and a lower threshold value (adjustable using P2). Outputs AU, AI, AO, and AA go High if the voltage lies below, inside, above or outside this window, respectively; otherwise they remain Low. Output AA switches transistor T1, which drives the right-hand motor.