Power supply resets when aircon comes on

[new299]

I have a E6340, every time my aircon comes on (portable unit on the same circuit). The E6340 resets. I assume this is something to do with the inrush current to the aircon. But what exactly is happening? And how to I rectify the situation?

[electr_peter]

Few possible causes:

• AC line is dragged down too low by the inrush current
• spikes on AC line manage to get though (conducted emission)
• RF noise emission induces noise around MCU forcing a reset

More detailed investigation is needed to know for sure. Check AC line, add noise filters, ...

[new299]

Few possible causes:

• AC line is dragged down too low by the inrush current
• spikes on AC line manage to get though (conducted emission)
• RF noise emission induces noise around MCU forcing a reset

More detailed investigation is needed to know for sure. Check AC line, add noise filters, ...

Thanks, I'd guess not RF as it's a few meters away, and I'd would have thought I'd see other effects if it was that serious. Would adding ferrite cores to the power supply and aircon possibly help? This would provide some filtering?

[flynwill]

Most likely it's the voltage sagging when the AC compressor kicks in.  An easy test:  plug a small incandescent lamp into the same circuit and watch as AC kicks in.  You'll likely see it dim. 

As to whether or not it is an issue: probably not.  If the dip is really bad it might be indicative of a bad splice somewhere in that circuit that's on the edge of going up in smoke, or that the AC's compressor is on it's last legs.  More likely it's just a long wiring run.

[TimFox]

I agree about voltage sag.
40 years ago, my apartment shared a utility transformer with a townhouse that had a badly-maintained central air unit.  Whenever that unit cycled on, there was a serious transient sag in the voltage at my apartment, that screwed up my audio amplifier temporarily.