Stop coil whining on Gosund SP111

The Gosund SP111 is a great wireless plug with an ESP8266 controller built in that can switch and measure mains power. It can be flashed OTA with tuya-convert so you don’t even need to do any soldering to get custom firmware such as tasmota on it. The form-factor is also impressive being so small and at about €12/piece the price is hard to beat. The only major downside is that with low/no load it can have that annoying beep / whistle / whining that comes from a badly positioned / not fixed coil (“coil whining”).

Please be careful – you’re dealing with mains electricity here, so unless you know what you are doing and are ok loosing your guarantee for opening and meddling with the insides of a device PLEASE STOP HERE!

The process is the same for both the V1 or V2 SP111, but you can tell if you have a V2 because they are rated to the much higher 3450W.
Unscrew with a phillips screwdriver (PH 0x50 is about the right size)
Pull off the clear plastic cap
Unscrew the board from the plug pins (one screw in each hole) and and remove the purple rubber pad
Unclip the antenna from the board
Carefully pull the board out of the housing. Pull the antenna cable to the little gap on the side as you are doing this so that it does not get jammed between the board and the housing
This is the coil which is whines…
Put a dab of hot-glue on the coil affixing it to the relay (white block in the centre) behind. Be careful that the glue does not stick out further than the coil or it may jam when you are trying to re-insert the board into the housing.

Now re-assemble everything again carefully remembering all the screws, clipping on the antenna again and the purple pad which keeps the antenna connector in place. When you plug it in again you should find that it no longer whines. 🙂

Pro-tip: this method (putting a dab of hot-glue on the coil) is the solution for nearly all whining power supply issues – the only difficulty is getting them open non-destructively and identifying the offending coil.

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