29 December 2021 By Julian Spina 1

ACS712 Module problems – 30A version

Module melts under high current

I had a problem with an ACS712 30A module completely melting at a a current of 15-18A for a bunch of seconds. Smoke was everywhere and I probably risked a fire.

I made this small module based on a Digispark ATTINY85 board to measure my house’s AC current usage. The house isn’t big and my electricity needs could go from 0.5A to 15A. The energy meter mounted by the electric company will allow an overcurrent for maybe 10-20 seconds, and will trip after that time.

Reference: Here’s the link to the DC version of the board I made some time ago http://electronic.acca3.it/2021/03/21/arduino-measure-current-problem/

This is the module, it sits between the main energy meter and the RCBO:

Very briefly: it’s powered by AC 220V current, AC-DC transformer and fuse are visible at the bottom. Digispark ATTINY board reads current via ACS712, 30A version top part of photo, and sends the measurement using 433MHz board (with external aerial).

Now what happens is this: you buy a nice ACS712 30A module but the plastic connector where you connect the power line is rated 10A! That is what I discovered on my ACS712 module, check yours out, there’s a writing on the green connector, mine says “10A”. So when current sits around 15A for 10 or 20 seconds the connector will meltdown creating a serious fire risk.

Now, as you can see in the photos all wire, plastic container and ACS712 module connector melted down. It’s so important to use components which are fire-resistant (or fire-retardant) to avoid even more serious damage when failures like this happen.

The solution I adopt now is to remove the green connector and directly solder my 14AWG wires to the board. So I’m sure this problem won’t happen again. Next photo shows the result of direct soldering the wires.

A part from that, ACS712 modules are good litlle modules… Enjoy!