Using 5 V relays, this circuit can be used as a control shield for microcontrollers. The circuit uses relays, and the motor voltage is independent of the control voltage.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...