SIP mod - Pulse Width Wire Controller

I fitted that pulse width modulation (PWM) wire controllor (bought from eBay - search 30 amp motor controller) to the SIP 130. It comes with it's own circuit board and is a fairly direct swap out for the wire feed circuit on a PCB.

My worry was the choice of inputs are 12V or 24V (select via a jumper) and I wanted the wire speed to change with power setting which maybe varies from somewhere like 13V to 22V.

Plugged it in across the torch and earth anyway and it works (for now at any rate)!



You'd expect more low speed torque from a PWM controller, or so I'm led to believe.

It doesn't make a lot of difference to the ease of welding. Possibly the starting is slightly quicker on the lowest setting, but there's no real improvement to the jerkiness. Would probably need the smoothing transformer for that.

Here are before and after welds on the lowest setting on 0.8mm sheet with argoshield (thanks for the adapter weldequip):



In summary there doesn't appear to be any real advantage to doing this mod.

One thought - I never find the lowest settings of these mig welders quite low enough for 0.8mm. Would it be possible to fit a step down transformer after the main transformer? Or would that create nasty resonances in the electrics?

By having the speed roughly selected with the power switch you're still reducing the voltage to the circuit, which is defeating the object of having the PWM controller to some extent.

I'd be inclined to use the seperate transformer (connected to the mains after the contactor) & rectifier as suggested by Bump, to supply 24v DC to the controller and motor.

You'd scarifice the rough speed selection though.

One thing I noticed was the knob on the controller is very sensitive, maybe more so than the standard SIP one. Was thinking that would be worse with a constant supply, but thinking about it it's not going to be a big change in sensitivity. Could add some gearing.

I'll get one of Bump's transformers. Interested to see the effect that has, and it would allow a 24V feed for max torque which would be fun to try.

To make the knob less sensitive you could replace the potentiometer with a combination of switched resistances and a variable resistance.

Use the switch to get near & trim with the pot. With a bit of genius you could choose the switched resistors to correspond to the power selector knob.

pmw controler

Just reading this thread saw that malcome has bought one of those motor controle thingys. Did you set the jumpers on it to 12V or 24v? I bought one it a 15A version
and intend on doing a simular thing I am also doing the wire feed mod with 24v transformer . Bit confused as I think feed to motor is only 12v and if I do the 24v mod will the pcb still only send 12v to the feed motor?
Nick

You need to match the supply to the motor. The output of the PWM controller goes from zero to supply voltage.

so 12v then?

nicho215 said:

so 12v then?

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If it's a 12v motor, set the PWM to 12v and provide a 12v supply

will this work on a sip 80

oneeyeguy said:

will this work on a sip 80

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Bear in mind:

malcolm said:

In summary there doesn't appear to be any real advantage to doing this mod.

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In answer to the same question posted elsewhere - How old is the SIP 80? It's not a model I'm familiar with. If it's really really old then it might be a good one and not need all these mods.

Post a photo of the machine so we can identify it.

When is the last time you changed the wire liner? Probably needs one of those if the wire feed is playing up. See http://www.mig-welding.co.uk/sip-wirefeed.htm

well i just got it new from ebay a week ago iv put in a steel liner

heres the inside aswell its only got a on off switch and a high and low on out side

So what's the trouble with the SIP? Or are you just doing a bit of tuning? I see you've already beefed up the top roller mounting.

i just a bit of tuning it was crap with the plastic liner in even new and i read about steel ones and its alot better

Malcolm, you said "Plugged it across the torch and earth" You do mean before the reactor?

As the output is just rectified AC with no smoothing, I bet the PWM controller will be unstable. You need a good DC source for it. Could do with a diode and a large capacitor. I bet the speed range will be more controllable.

rtbcomp said:

You'd scarifice the rough speed selection though.

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eh? I though that because you take the negative for the transformer from the pcb, it is steped down by your power setting... What
I can say is that my baby welds like a dream even in my novice hands the wire speed knob is sensative but ive got used to it tbh -but you could put a bigger knob on it to increase the finger travel (increased circumference) for the same ajdustment