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  1. #1
    Join Date
    Jun 2007
    Location
    Vic
    Age
    48
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    544

    Default Tig pedal for a poor man

    I can't afford $240 for the Unimig razor foot pedal hence making my own instead.

    -Old sewing machine pedal at TnT market: $5

    -10K potentimeter off ebay $7 with postage https://www.ebay.com.au/itm/10K-SLID...53.m2749.l2649

    -Socket $25: https://www.ebay.com.au/itm/Amphenol...53.m2749.l2649

    5m cable $10

    Total: is under $50


    A adjustable linkage
    20180721_170755.jpg



    Micro switch, normally on and off when the red button is pressed
    20180721_170746.jpg

    potentimeter is 10K when pedal is fully pressed. "0" when fully depressed
    20180721_170828.jpg


    20180721_175637.jpg

    20180721_175645.jpg

    20180721_181023.jpg


  2. #2
    Join Date
    Jun 2010
    Location
    Canberra
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    Default

    Nice work.

    I have the Unimig pedal (got it as a deal with the machine), while it works, it's not the nicest piece of engineering.

  3. #3
    Join Date
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    Vic
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    Default

    I still need to wire the other end of the cable to the plug. It has 7 pins and I am guessing maybe 4 or 5 will be used?
    2 for the micro switch. Them maybe 2 or 3 for the potentiometer. i don't know, I might have to open the hand piece to have a look.

  4. #4
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    Canberra
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    Default

    While I remember, my Razor 200 AC/DC actually came with a spare 7 pin plug, I assume to facilitate hooking up a 3rd party pedal.

  5. #5
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    Default

    I opened the plug and here is the connection for the tig torch which has the amperage adjuster incorporated.

    20180722_193550.jpg

  6. #6
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    Default

    Hi RustArc,

    Do you have to hold the foot pedal down for 5 seconds for the Remote function to activate on the machine or it detects by itself once you plug it in?

  7. #7
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    Canberra
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    You still have to do the 5 second (or however long it takes until it beeps) thing to toggle between panel and remote.

  8. #8
    Join Date
    Sep 2009
    Location
    Sydney
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    Default

    Sorry to revive an old thread but I’ve just upgraded from a basic Unimig scratch start to a Razor 200 DC TIG.

    I was keen to add a foot pedal but the $250 seems a very steep price to pay for a 10k pot and switch so I’ve purchased a cheap one to see if I can make something work.

    I haven’t got a variable amperage torch so cannot check how that works but I have pulled the case off and I can see 2 pairs of wires attached to the connector.

    Red/Green - pins 1/2 (main switch)
    Black/Red - pins 2/4 (I assume the amperage control)

    My understanding of potentiometers is that they have 3 wires. So wiring it up has me confused.

    I was wondering if one side of the switch would provide a voltage to provide the potentiometer and the other 2 wires are the ground and wiper?

    Anyone help?

  9. #9
    Join Date
    Dec 2018
    Location
    NSW
    Posts
    586

    Default

    I've been digging thru the schematics to make a rarely used MMA machine a foot controlled DC TIG Rig.
    I have also dug into the diagrams for my AC TIG to see what I can make to get this functionality (A later version used a 7 pin pedal control). This is an ongoing project.

    In your case am I right in understanding that you have a 4 pin plug- 2 for the Pot, and 2 for the arc initiation switch?
    On the pot / 2 pin quandary-
    While I don't condone you start poking about a welder and get yourself zapped, if one were to consider getting a multimeter on the machine ground and probing one of the 2 switches for the pedal, you'd probably find that one is a 5V or 24V signal, and the other is the output voltage to the machine amperage control. So after this point the machine control board just gets a reference voltage that relates back to the amperage control circuitry... just like it would for a panel mounted amp control dial.

  10. #10
    Join Date
    Sep 2009
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    Sydney
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    Default

    Quote Originally Posted by Commander_Keen View Post
    In your case am I right in understanding that you have a 4 pin plug- 2 for the Pot, and 2 for the arc initiation switch?
    On the pot / 2 pin quandary-
    While I don't condone you start poking about a welder and get yourself zapped, if one were to consider getting a multimeter on the machine ground and probing one of the 2 switches for the pedal, you'd probably find that one is a 5V or 24V signal, and the other is the output voltage to the machine amperage control
    The welder has a 7 pin plug (single plug). I’ll get a meter on it today as my suspicion was that the switch must have a voltage on it and maybe that was driving the amperage control voltage too?

    https://unimig.com.au/wp-content/uploads/2019/08/RAZOR-TIG-200-DC-Manual.pdf

    I will check all the pins to see what they’re doing.

    Might grab a 2W 10k pot too so I can test a few things.

    Oddly you’re supposed to hit the switch for 5 seconds to activate remote control. But hitting the switch just activated the weld cycle and gas solenoid.

  11. #11
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    Sep 2009
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    Sydney
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    Measuring DC voltage I can’t really pick up anything on any of the pins. 1/2/3/4 all measure 0.001v.

    I assume they should be DC?

  12. #12
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    Jun 2010
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    Canberra
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    Default

    I have one of these machines, and the foot pedal - when I get a moment I'll have a look at how it's connected up and take some measurements.

  13. #13
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    Quote Originally Posted by RustyArc View Post
    I have one of these machines, and the foot pedal - when I get a moment I'll have a look at how it's connected up and take some measurements.
    You’re a legend. Thanks!

    The questions I have are:

    1. What connections are the switch on
    2. Is there continuity between the switch (either side) and pin 3, is so which one?

    Plus any other details you feel are useful

    My assumptions are:
    1/2 are the torch switch with one side being “hot”
    This hot side is also sending voltage to the potentiometer via pin 3 (connecting either pin 1 or 2, whichever is hot to pin 3)
    Pin 2 is the potentiometer wiper
    Pin 5 is the ground side of the potentiometer

  14. #14
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    Jun 2010
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    Had a quick measure:
    1 & 2 are a normally open switch, closing when pedal starts to move.
    4 & 5 are either side of a 10k pot
    3 is the wiper, starting at 5 and going towards 4 as the pedal is pressed.

    Didn't observe any linking of pins, but then again, didn't test that thoroughly as it's very fiddly.

  15. #15
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    Quote Originally Posted by RustyArc View Post
    Had a quick measure:
    1 & 2 are a normally open switch, closing when pedal starts to move.
    4 & 5 are either side of a 10k pot
    3 is the wiper, starting at 5 and going towards 4 as the pedal is pressed.

    Didn't observe any linking of pins, but then again, didn't test that thoroughly as it's very fiddly.
    Thank you very much!

    I will have to open up the machine again and check the 7 pin wiring. Your wiring makes sense to me and yet I only have 4 wires going to the socket. It looks like the wiper is missing which would be essential for any potentiometer regulation.

    Can you see inside the machine at all? Do you have 2 pairs of wires coming from the plug?

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