By activating S1 the relay closes its contacts only after a certain time interval that depends on C1. Fractional seconds up to a few seconds can be obtained. The circuit works with 5 to 12 V relays and currents of 100 mA or slightly more for the BD135. Diode D1 can be 1N4148 or any other general purpose. The circuit is from the book Robotics, Mechatronics and Artificial Intelligence by Newton C. Braga.
