Adding a PWM to welder wire feed roller

Discussion in 'General Electronics Chat' started by nick9one1, Mar 22, 2016.

  1. nick9one1

    Thread Starter New Member

    Mar 22, 2016

    I have a SIP migmate welder which are renowned for having poor wire feed control. For anyone that doesn't know, when you pull the trigger on a MIG welder, a motor should feed wire based on the speed set by a pot.
    I'd like to improve mine.

    A few people have replaced the DC power supply to the motor with good results. but I'd like to go one further and replace the power supply and add a PWM.
    Compared to what I can see on this forum, my knowledge of circuitry is low, so I'd like to get some feedback on my proposed change to the circuit.
    Does the modification look OK?

  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Does the added mains-to-DC device provide mains isolation? If not, the circuit could be LETHAL.
    If it were me, I'd omit that device and take the PWM supply off the transformer secondary, at CN5.
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
    Most MIG machines already use PWM to control the wire feed. The usual problem for erratic wire feeding problems, is either the feed rolls themselves or the torch liner. Over time the torch liner gets grit and or copper from the filler wire built up in it. Every so often I have to pull the liner from my machine (MillerMatic 135) and soak it over night in kerosene. Then blow it out with an air hose. The kero both cleans and lubricates the liner.
  4. nick9one1

    Thread Starter New Member

    Mar 22, 2016
    Thanks for the replies.

    Yes the additional power supply is is isolated, its a laptop 19.5v switched mode power supply I have spare.
    I'm using a second power supply as other users of the SIP migmate have connected a replacement supply for the wire feed control and have had massive improvements. They haven't gone as far as adding PWM, but as I can get one for less than a fiver, it seems worthwhile.

    I've attached another picture of a modification someone else made.

    Unfortunately not the SIP migmate. Like I said I'm not an electronics engineer, but from what I can see it isnt PWM circuit.
    I've already replaced the main liner, gooseneck liner, and rollers. From all I've read about this welder, the wire feed circuit is the culprit.
    shortbus likes this.