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 Post subject: MOT Spot welder controller
PostPosted: Sat Jun 23, 2012 5:13 am 

Joined: Fri Dec 19, 2008 2:29 pm
Posts: 1
I want to build a battery pack spot welder by hacking a Microwave transformer.
Lots of Utube and Instructable on physical construction.

Now I want to talk about control.
The input is 120vac @ 1-2 A / output about 4-5vac @ ??? amps.
I would like to set up a varible timer to limit my on time .1 to 2 sec (probably use 555 timer circuit).


I'm assuming the best idea would be to control the primary of the transformer
but how would be the best way to do that. I dont know about inruse current etc.

What ya got in your little bag of tricks


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 Post subject: Re: MOT Spot welder controller
PostPosted: Sat Jun 23, 2012 7:52 pm 

Joined: Wed Nov 24, 2004 1:01 am
Posts: 2285
Location: ASHTABULA,OHIO
In a nut shell - Timer controls on / off of an opto coupler (maybe MOC 3000 series), Opto's output enables relay or triac in series with primary winding. Thats the skinny, but as usual it will take some extra design work to fit it to your requirements. Don't really know what your initial configuration looks like.


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 Post subject: Re: MOT Spot welder controller
PostPosted: Fri Jan 02, 2015 12:49 pm 
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Joined: Thu Oct 26, 2006 7:11 pm
Posts: 1316
Location: Maryland
I know this is a late posting but I would use an industrial 'hockey puck' Solid State Relay'
There is going to be way more current than a common opto device can handle!
Most of these are triac based and designed for pretty big current, like full wave motor control, at line voltages, They can be used like an AC relay that is turned on with an isolated low voltage (TTL) input.
PM me if you need one!



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“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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