This NodeMCU Circuit Finder Takes the Yelling out of Finding the Right Circuit Breaker

Pseudonymous maker "ThinkLearnDo" and his father have turned to a pair of NodeMCU microcontroller development boards to assist with a home improvement task: figuring out which circuit breaker goes with a given socket.

"My dad was having to deal with finding out which plug receptacle is connected to which circuit at work," ThinkLearnDo explains. "He came up with a simple idea of using NodeMCUs to help solve that problem. This is the result."

The idea is relatively simple: One of the two NodeMCU boards, which include Wi-Fi connectivity on-board, is configured as an access point and listens out for UDP packets sent to its address; the other NodeMCU connects to said access point and begins transmitting the packets.

So long as the stream of packets is uninterrupted, the NodeMCU's on-board LED will remain lit. Should one of the two NodeMCUs switch off — because, say, you've toggled the circuit breaker controlling the power socket to which it's connected — the LED goes out.

It's a neat solution to the problem, though one which has long been solved by commercial socket testers with audible "everything's fine" alarms — or the low-tech alternative of someone shouting to tell you when a lamp goes off.

ThinkLearnDo's version, though, has a couple of advantages: It's silent and won't disturb others in a shared environment, though flipping circuit breakers randomly until you find the one you need might; and it works through walls and closed doors where an audible version might not be so noticeable.

A video demonstration of the project is available on ThinkLearnDo's YouTube channel, with code for the server and client published to GitHub under an unspecified open source license.