Remote Foot Control

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Hi Guys!I'm a pretty new member to the forum, so Hi!. Having finally moved home from university, ive set myself up with a secondhand Newarc (small uk brand) 200amp AC/DC TIG unit and have been trying to sort out a foot control for it.  After going to see them, they're foot controls have the same plug, but different wiring, and as they dont sell my machine anymore im at a bit of a dead end.  Here's where im hoping you guys might be able to help please!  Ive added pics below to help.  It looks like the machine is German made (from all the german serials, etc) and then rebranded.  The Remote connector is 7pin and all pins are wired back to the control PCB (which is a bit of an end to my usefulness).  I used a multimeter to measure the voltage across the pins, relative to the central pin, all the outer pins are at 10v DC, not sure if thats any use.  Does anyone have any ideas on how to figure out what each pin is meant for?  I have a foot control from an older machine i was hoping to hook up.Thanks In advanceMichael Attached Images
Reply:That does sound like an interesting project...  My guess is two wires are to tell the machine that there IS a foot control attached, two to run the 'contactor', and the remaining 3 to control amperage.See if you can follow the wires from the board's control pot to the plug on the board.Do some searching on the board looking for power supply and ground.Also, keep googling... amazing what you can find on the 'net.My method of following the traces may not work.  But it's where I would start.  Also, if you have a control from another machine, measure it.  That *might* give you an idea where to start too.WELCOME to the forum.  Theres more information here than should be legally allowed!!
Reply:Cheers and thanksI did try tracing the circuit on the PCB but ran into one of those pesky microchips, which stumped me.  its all black magic and voodoo with wires attached to me
Reply:What is stamped on the microchip that you traced to? All microchips are different. Try to take a clear picture with your camera in macro mode of the top of the ic chip and then once we know what the ic (chip) is then we can source the datasheet and then you will know what the wires are for. Good luck!Miller Synchrowave 180SDLincoln WeldPak 100HD w/gas conversionPowermate 230A AC Arc Welder circa 1980
Reply:one pair of wires are to turn the gas solenoid on/off and one pair of wires controls the amperage ( at least that is the way it is on my tig)  You can figure yours out if you can turn off the remote (so amperage is controled by the front panel and measureing the reostat (potentiometer, or varible resistor)  You want a foot pedal with the same ohm reading.  The other pair you hook up to the on off switch of your foot pedal (look where the wires for your gas solenoid are connected)  Hope this is of some helpThermal Arc 185 TigHTP 200 MigCraftsman O/A1942 Bridgeport Mill12 Ton Hyd PressConsew Walking Foot
Reply:Try contacting Newarc.http://www.newarc.co.uk/frames.htm
Reply:Thanks for the responses guys,I get the feeling it all more complicated than i can cope with!!  ive tried speaking to newarc, but they've not managed to turn up any information so far.  I resorted to trying shorting pins together and tried every combination which would imply that as mentioned above two pins may be there to enable the foot pedal while two others are the contactor. which would make a complicated pin shorting combination (plus im worried about damaging the unit).  I took out the circuit boards and did my best tracing but got lost when the tracks split and dissapeared underneath a couple of the chips and various other components.  I thought id narrowed it down to 5 pins but that didnt seem to work out.  will i do any damage by shorting lots of pins together? (i wont hold you responsible!).  it could be taht the foot control uses the same contactor as the the torch button (different connector) which would mean i have 7 pins to guess which ones are for the potentiometer.  as you can tell ive been pulling my hair out over this for a while now!!! and there aint much left as it is! Im thinking of wiring in tht foot control manually, hopefully you can follow my little drawing, which would allow me to set the max. current, then allow the foot control to work within that range.  would i be right in saying i dont need to match the potentiometer resistance of the machine either?  I cant see why this wouldnt work if the current is controlled by a simpel potential divider, but knowing my luck its probably more complicated!Let me know what you all think, thanks once agian in advance! my right foot is itching!edit... just had a thought it might not work without a double pole switch to isolate the ground...  would i be better off just making a switch to make the standard potentiometer remote? Attached ImagesLast edited by psychosis; 01-08-2007 at 11:09 AM.
Reply:http://www.iwelding.net/main%204.htmCould this be a re-branded chinese (or some other asian) welder?  I just found this.  If so, you might contact these folks...Smithboy...if it ain't broke, you ain't tryin'.