Help with power interference?

[tribble222]

Sorry if this is a very beginner question, but I can't figure this one out.   

I've built a device that plugs into the wall outlet and uses the Recom RAC04-05SA (http://www.recom-international.com/pdf/Powerline-AC-DC/RAC04-SA.pdf) to power an atmega328p chip that drives an LCD.

Everything works fine unless I have it plugged into the same outlet as my mini-fridge. As soon as the mini fridge starts up my LCD becomes all garbled and never recovers until I turn my device off and back on.

I assume there's some kind of power supply problem with surges or voltage dips or something. Any idea how I can fix this? I have it set up just like the bottom of page 2 in the datasheet. I tried adding the optional capacitors they show in the datasheet but it is still having the same problem.

Thanks in advance 

[amspire]

First thing I would try a much bigger electrolytic capacitor across the output.  It looks like that supply can handle up to 8000uF, but something like 1000 or 2000uF should be fine. The capacitor can be any voltage rating as long as it is above 5V.

Normally, the 47uF should be fine.

Richard

[Psi]

yeah, fridges (or anything with a motor) are really bad on the power when they start.

I agree with amspire, try a bigger output cap.

Also make sure you have a dedicated 0.1uF cap for your micro and your lcd controller power channels (and any other ICs you have) mounted next to the power pins of the IC. It could be that the LCD controller is crashing from the power glitch, might not be the mcu at all.

[IanB]

What about some input filtering like a ferrite bead on the mains lead?

[tribble222]

A bigger capacitor did the trick! Thanks!