If you’re interested in connecting a new circuit, here’s how to do it. A simple circuit tester with two probes can help ...

Making a device to test an RCD is easy; a resistor between hot and the protective ground circuit would do. [Callan] over-engineers. He used a 50 W resistor where 30 W would do under the worst ...

Here's what to do: First, verify that the tester works by checking a known live circuit. Hold the tester to a powered ...

and in fact that’s what [Dave]’s first LED tester was, in essence. Set an LM317 circuit up to output 10mA, say, and you can safely test out about any LED. Read off the operating voltage ...