Blog

Articles on the interesting parts of electrical engineering, each with circuits you can open and try.

1. Why does my RCD trip? How a residual current device works, and what the test button really checks

   An RCD compares the current going out on the line with the current coming back on the neutral. Here is why it trips, the wiring mistakes that make it trip for no obvious reason, and what pressing TEST does and does not prove.

   1 October 2026 · 7 min read