Electrical transients and EMI/RFI

[SScnc]

I've been noticing problems with my setup, when I would switch on or off my exhaust fan, coolant pump (which generally is on long before and after I laser) and small air assist compressor, I would hear the sound from my PC as if I had pulled the USB cable then plugged it right back in.

And, sometimes, my DSP would reset as well as my PIC controlled LCD/relay flow and cooling status monitor. I have been very concerned this was going to harm these circuits and started leaving them on and only turning them off after the DSP was turned off.

So I finally figured out what to do about it, I installed "snubbers" across the switches and the problems are completely gone now.

I don't know if anyone else has had or noticed similar problems on their machines but wanted to post this just in case this happens in the future. Below are pics of the type that I used and a schematic of how I connected them across each switch...

HTH

[seeigecannon]

That looks good. Something I can suggest is to use is things like this: http://www.digikey.com/product-detail/e ... -ND/206389 Normal relays can create arcs as they open and that is where RF noise is generated. These will only turn on and off when the power cycle is at 0 volts, so no power spikes or anything like that.

Also, I love the face of your laser.

[Techgraphix]

I, almost always, use solidstate relays with a zero detection circuit.. These are much cheaper than the average relays, much more reliable and your switches only have to handle something like 5V/10mA...
Kees

[SScnc]

I, almost always, use solidstate relays with a zero detection circuit.. much more reliable and your switches only have to handle something like 5V/10mA...
Kees

True, but the loads my switches are controlling are very low but I think with high inductance. I probably will use the SSR zero's on future projects. Thanks to both of you for making me aware of these.

[Techgraphix]

With very small loads or inductive one's, you could place a resistor of ~10K/5W parallel to your load.. I have an airpump that didn't stop after it was started.. The resistor did the trick..

Kees

[SScnc]

Kees, you state SSR zero's cheaper than standard relays. Can you (or anyone) advise which of these you recommend ?