This is the circuit of a robot published in the June 1992 issue of Radio Electronics magazine. The sensors are used to drive 2 motors with reduction gears. The power is provided by batteries.
This detector with ultra-low deviation was found in an American documentation from the 90s....
This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even...
This is the configuration of this type of oscillator given in an article in Electronics Now...