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vacuum pump regulator switch

PostPosted: Wed Oct 27, 2010 1:03 am
by disco stu
Finally got vac pump and regulator up and going and glassed up a tail last night. Apart from the leaks (5min for the pump to cycle on again in dry run, 30sec this time :twisted: Why oh why does it always work perfect on the dry run), started having trouble with the switch a little.

I always pictured this but it seemed to be fine on all the dry runs I did. Its a micro switch, with a big washer that pushed down on the lever from the switch when it gets pulled down with the vacuum diaphram (at work so can't get picture).

This is the type of micro switch I'm using:
Image

Anyway, it gets down to where its at that point where the vac is almost enough, , starts pushing the switch down and drops the power to the pump but not fully. What I end up with was that welding arc sound, the pump groaning and maybe switching on for a sec then off, and cycling like that till I would give it a kick and then it would depress the switch properly and it would switch it off until vac had dropped 10 odd kpa and cycle properly.

It was switching on my wifes touch lamp and had me out of bed at 3am trying to fix it (after an already bad start to the sleeping), cause it just kept going, and was making some bad sounds through all the wiring.

Any thoughts on trying to fix it? Is the lever from the switch too long allowing too small a movement (to high a resolution sort of thing) meaning it will almost switch off?

Any help would be great

Cheers, Stu

Re: vacuum pump regulator switch

PostPosted: Wed Oct 27, 2010 9:03 pm
by RCModelReviews
With my (home-built) vacuum pump, I had similar problems so I used the microswitch to control a TRIAC (solid state) switch. That way the microswitch itself only carried a tiny amount of current and didn't suffer from contact-arcing.

Re: vacuum pump regulator switch

PostPosted: Wed Oct 27, 2010 11:29 pm
by disco stu
So without the load it would switch fine under the exact same circumstances?

Worth using a relay, or is one of these TRIAC switches better? I think the micro switch is rated for 4a or so, and this little pump I'm using is 100w so is pulling less than 0.5a (I'm assuming it would pull a lot more on start up etc)

Re: vacuum pump regulator switch

PostPosted: Thu Oct 28, 2010 6:47 am
by RCModelReviews
I just ended up using a regular microswitch on my pump and found it switched far more reliably when it wasn't asked to handle any significant amount of current or voltage.

You have to appreciate that all microswitches have quite a degree of hysteresis though.

Re: vacuum pump regulator switch

PostPosted: Thu Oct 28, 2010 1:15 pm
by disco stu
I'll see what I can dig up. Would much rather be running on 12v, got plenty of relays for that sitting around. Thanks for the help