Foot Switch Question - Miller Dialarc HF

Tue, 31 Aug 2021 13:52:45 GMT

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I am trying to get an old Miller Dialarc -HF TIG going.  The foot switch has a microswitch and a rheostat inside.    Is the microswitch suppose to open or close when the pedal is pushed?  Mine opens the circuit.  Seems wrong because the high freq arc stops when I push the pedal and normally you would expect a switch to close when you push the pedal (in general).
Reply:Yes, reverse the switch so it closes when you press on the pedal. It should be wired to common and NO or normally open. When you step on the pedal. The lever inside it pushes against the arm of the switch and closes it to complete the circuit.Expert Garage Hack....https://www.facebook.com/steven.webber.948
Reply:Hello Bill, I see that Steve already got this but just to give a bit more as it applies: that switch is essentially a multi-function switch, in it's natural relaxed state it has an NC and an NO set of terminals, 3 terminals total, one of them is common and the other two represent a closed contact and the other one an open one. When you depress the button/lever on the switch the NO becomes closed and the NC becomes open. There are also applications for a switch such as this where it will have the lever depressed and when it is allowed to move from a depressed state to the opposite it would also result in the same changes in the connections on the switch, just in a reverse order. Probably more than you cared to hear, but what the heck. Best regards, Allanaevald
Reply:It sounds like the circuit needs to be closed when the pedal is depressed, so it is easy to change.  Actually, the switch lever is physically depressed when the foot is off the pedal, not as stated in the first reply.  Pushing the pedal releases the roller lever on the switch.  So using he normally closed contact will result in a closed circuit when the pedal is depressed.
Reply:This photo explains how the switch lever is released when the pedal is depressed Attached Images
Reply:I am wondering if there was originally a spacer under that switch.  The sheet metal piece barely overlaps it.
Reply:Originally Posted by Bill WebsterIt sounds like the circuit needs to be closed when the pedal is depressed, so it is easy to change.  Actually, the switch lever is physically depressed when the foot is off the pedal, not as stated in the first reply.  Pushing the pedal releases the roller lever on the switch.  So using he normally closed contact will result in a closed circuit when the pedal is depressed.