SCR Welder amperage controller circuit

[wilt6496]

Has anybody got the Mike W. SCR controller circuit to work on a welder with a variable reactance type amp dial such as an old Dialarc AC/DC or airco welder? These older style transformers will only allow control down to 35amps, and the Mike W. circuit will allow a much lower amperage control (down to 5 or 10 amps). much better for welding thin sheet metal.

[Timinmb]

Has anybody got the Mike W. SCR controller circuit to work on a welder with a variable reactance type amp dial such as an old Dialarc AC/DC or airco welder? These older style transformers will only allow control down to 35amps, and the Mike W. circuit will allow a much lower amperage control (down to 5 or 10 amps). much better for welding thin sheet metal.

It works on my welder that has the slide type inductive amp control. I put one pot in a foot pedal and a second pot on the side of the case containing the circuit. I can flip a switch so that the foot controller is no longer active but the dial on the box is. That way I can fine tune at lower amperages. You're best to run the welder set at the highest current you will need, that use the circuit to back it off slightly as needed, or shut it down completely when you let off the pedal.

[ohmthis]

I've been fighting this control for a while now. I had problems from the beginning to get it to work with my welder. I will post the circuit I built, I would love to see what you guys have used to make it work. Hope to get this working if for just my own sanity!!!!

[J0K3R-X]

Hope this helps?

[J0K3R-X]

This is using an IRKT91 SCR, the configuration maybe be different with other comparable SCR's!

[ohmthis]

This just may be my ticket. I had the 240v from the switch to #1 on the SCR, I had #1 and #2 bonded, but I had the transformer lead off of #2 not #3. I will try this when I can and get with you.....This could fix a 4 year headache. Thanks!

[J0K3R-X]

ohmthis - It should have worked with it coming from 2 or 3 since they are bridged? What scr do you have? I can pull up the data sheet and see how the internals are configured. If I can see the scr part# I can re-draw it for your setup.

Another thing to keep in mind is that for higher powered welders that run on 240, the standard light dimmer might not give you very much control since most of them only have 500k potentiometer. I have rebuilt my dimmer with a 1 megohm potentiometer. It affects the range of control that you have by turning the potentiometer from zero to 100%. Too low of resistance in this component (fewer ohms) results in the low end of the dial not being as low as you may want it. If you mess with the output of the welder and set it to the lower amp setting you may be able to dial it in where you want?

[ohmthis]

I have a powerex pow-r-blok CD43_60A SCR. I am using the drawing that Mike W had on this site. The problem I am having is that when hooked up to the welder it makes one **** of a racket (IE a real aggressive hum) until it trips out the breaker. I measured like over 100A on the input line when trying to use this. It's almost like it's trying to run the welder with only one leg of my 240v. Hope this helps some. Thanks!

[J0K3R-X]

You do have this hooked up to one leg of the input going into the transformer and not one of the output leads right? From what you are describing it sounds like it is a dead short. The worst that should happen is either your welder doesn't power up or it runs as if your scr is not even installed. You don't have both power lines hooked up to it do you? My drawing and the Mike W schematic are for one leg of power going into the welding transformer. Maybe you could post some pics of your setup.

[ohmthis]

I'll post some pics today I hope. Only one lead from the load side of the switch is connected to the scr circuit. It's not a dead short as the welder powers up, but as you push the pedal down the noise gets worse and the amp draw goes up until the breaker trips. I will put up pictures here shortly. Thanks!

[ohmthis]

Here are two first one is the whole set up, Next is just the SCR. I need to redo the wiring as I blew a cap. trying different things to try and fix it. It may be hard to follow, if so I'll take pictures as I redo everything.

[J0K3R-X]

ohmthis and mikehussy1990,

You guys might want to start over and try my diagram? Not saying that Mike W. SCR controller circuit won't work but the way I have it there is much less to go wrong. It is a very basic configuration and I have built 4 of them now with various welders and it worked each time. I have installed it on a Lincoln tombstone and a couple others with the sliding shunt amp control with no problems. Since this only controls the power going to the primary of the welder transformer you should be able to use it on about any welder as long as your SCR is rated for that amperage and voltage. Start with just the dimmer and if that works for you, incorporate it into a foot pedal.

ohmthis - your SCR is the same configuration as the one in my diagram and it seems to be rated for what you are doing.

[ohmthis]

ohmthis and mikehussy1990,

You guys might want to start over and try my diagram? Not saying that Mike W. SCR controller circuit won't work but the way I have it there is much less to go wrong. It is a very basic configuration and I have built 4 of them now with various welders and it worked each time. I have installed it on a Lincoln tombstone and a couple others with the sliding shunt amp control with no problems. Since this only controls the power going to the primary of the welder transformer you should be able to use it on about any welder as long as your SCR is rated for that amperage and voltage. Start with just the dimmer and if that works for you, incorporate it into a foot pedal.

ohmthis - your SCR is the same configuration as the one in my diagram and it seems to be rated for what you are doing.

I don't have a problem with using your circuit, my problem may be installing the dimmer into my existing pedal. I'm using a miller HF box Its a HF-251D-1. It hold all of the HF stuff as well as a gas solenoid. It cam with a miller factory pedal in which I just swapped out the pot. I really don't want to lose this pedal or make another one.....Any suggestions?

[ohmthis]

Hey any thoughts JOK3R-X. just trying to bring this back up to the top!!!

[ohmthis]

I'm trying to find a 600v rotary dimmer, so far no luck. If anyone has a link or a possible place please let me know. Thanks!