Have you ever needed to power a 12-volt relay in a circuit but only had 6 or 9 volts available? This simple circuit will solve that problem. It allows 12-volt relays to be operated from 6 or 9 volts, ...

The real core of engineering, in addition to technical expertise, is the ability to articulate the inevitable tradeoffs and pros/cons of design alternatives, and then weigh these relative to each ...