In this quick Arduino tutorial I will explain how you can control a relay using the Arduino Board, one 1K and one 10K resistors, 1 BC547 transistor, one 6V or 12V relay, one 1N4007 diode and a 12V fan ...

This prevents A17 Q3 from discharging the +160 volt supply into the A1through A12 Q2 transistors. The coil in the added relay is paralleled with the coil of K4, through a 120 ohm 2 watt resistor as ...

This, in turn, switches on the transistor and the following relay, with the relay coil supply to the slave I/O boards restored. So during power-on and power-off transient, this circuit minimizes ...