Power Supply Issues | Home Automation Tech Blog

Fun with Embedded Electronics

Power Supply Issues

It turns out that the power supply I used for the home automation modules has a serious issue with dropouts when the AC load is switched. I found the details on the Itead Studio website and the image I capture on the scope was identical to the one show on there.


This is the capture from my testing.


What was happening is that as the relay switched on the load, on a random number of times, it would reset the EPS12 due to the drop shown above. This only happened when the load was connected to the output.

With help from a friend he pointed to the fact the reason for the randomness was that the load was probably switching on when the AC waveform was near or at the peak and not close to the zero crossing.

Itead Studio have a replacement module but it is much large width wise so they are not going to fit. I decided to try a Solid State Relay in place of the standard one and I happened to have one lying around so this was used. By bending the leg on the + lead outwards and then back down, I can get this to drop directly into the G6D relay position on the PCB.


A simply track cut to insert a 120R resistor to limit the current to the LED within the SSR I now have a silent switch that no longer drops out and causes a reset. I setup a test within Node-red to switch the LED on and off 50 times and it never failed once so this is now installed and it just so happens that is fits in the original housing.


This is the housing and the next image shows the original board with the G6D relay on the left.


I have ordered more of the SSR’s so I should have the rest of the lights in the house fully under control this coming week. For the plug in modules I needed to find a suitable replacement for the relay used on that and I found this one. It is lower current rated but I don’t need to switch anything higher than 500W with these anyway.


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