# Selecting A Power Relay Rc Arc Snubber



## countryguy (Jun 16, 2015)

Snubber?   Now that is a cool tech word!      The thermolyne muffle furnace/oven is done and running.  I used a cool power contractor from the original gear Rather than SSRs.    It does sound cool with all the snapping noise.  But the noise has bounced the rs485 comms at times.  It cannot be good for thee PID controller when that field collapses.     Does anyone recall what the formula is for an AC snubber ?   120vac coil.  Passing two legs for a totally of  24 amps thru the contacts. No more than an amp on the coil I would say.     

Digikey has these:
http://www.digikey.com/product-highlights/us/en/cornell-dubilier-quencharc-caps/744

Any help appreciated!    Cannot wait to get some metal in this thing!


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## Tony Wells (Jun 16, 2015)

http://www.cde.com/resources/catalogs/igbtAPPguide.pdf


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## JimDawson (Jun 17, 2015)

I might use one of these guys http://www.digikey.com/product-detail/en/ERZ-V14D201/P7217-ND/137368

Or just cannibalize a surge protector power strip.


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## brino (Jun 17, 2015)

One of the beauties of RS485 is that it's differential, a balanced two-wire system that should mean that coupled noise is "common mode" and appears equally on both wires, and so would get cancelled out at the receiver. Is your system two wire?

-brino


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## countryguy (Jun 17, 2015)

No question I need to do some clean-up as I simply wanted to "fire it up!"   I need to setup a ground point for the shielded braid on the 485 and the USB/485 comms.  It's quite possible that I'm taking a hit anywhere in the AutomationDirect equipment path to power. PID controller, Comms, to converter, USB to the free SOLO freeware app that locks up often!  

  I took 1 leg from the 220Vac and used it to power the PID.    I'll pull apart the surge protector!  Love free!   Good call JD .

The circuit write up was well written!  I enjoyed the review of the material for a snubber!  Thanks Tony. 
Brino- Agreed  - Should hold out to various noise - It's sporadic and possibly due to other causes.  Thanks for the post!


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