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Help with Triac based Temerature Controller

I've built a kit (Silicon Chip June 2005 "Tempmaster Temperature Controller") to run my a fridge as a wine fridge.

The fridge is a 240v (Australia) commercial "cool drink" type fridge drawing about 600W. I've replaced the old 'mechanical' thermostat with this new electronic one to run is at a higher and more accurate temperature.

The "output" is essentially a MOC3021 opto coupler driving a BT137F triac.

However when the controller switches on the condenser / fan it often clicks a few times (like its taking a few attempts to start it).

I've already tried incorporating a LC line filter without luck. A TVR fitted between the active / switched active gets really hot (obviously dissipating quite some power).

Any ideas what else I should be looking at?

Cheers, Antony

Reply to
Antony N. Lord
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Can you post a link to a schematic? It's almost surely electrical noise getting back into the control circuitry, although if the power supply is not robust enough it could also be the dip in supply voltage due to the surge when the compressor turns on.

This kind of thing is not good for the compressor.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

You should probably use a mechanical relay to switch the refrigerator. Triacs are rather poor choices for highly inductive loads. If you're intent on using solid state switching, I recommend that you switch from a triac to an alternistor, which is essentially a couple of inverse-parallel connected SCRs, which avoid the commutating problems of the triac.

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Reply to
DaveM

Check the magazine web site for updates.

Reply to
Homer J Simpson

"Homer J Simpson"

** Nothing in the notes and errata of interest.

BTW The article is called:

" Coolmaster Fridge/Freezer Temperature Controller ".

....... Phil

Reply to
Phil Allison

Oh yea, the alternistor !!

Never made it in the market place, I wonder why ??

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Reply to
Donald

"Donald" <

** Called " snubberless triacs " by many makers.

...... Phil

Reply to
Phil Allison

That's easily tested.

How do I prevent contact arcing?

Cheers, Antony.

Reply to
Antony N. Lord

With a snubber. Designing an actual snubber is somewhat of an arcane black art - I've seen people just pick values out of the air, but I've also heard that the resistance should be equal to the inductive reactance of the load, but I'm not sure how to choose a cap value - I'm sure someone will chime in here.

Cheers! Rich

Reply to
Rich Grise

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