Welding positioner problem

By Dwill63 Date 03-01-2016 02:09

Hello new to here with a question, I have a homemade welding positioner with a 12 volt dc geared motor with a pulse width modulator for the speed control, forward and reverse switch, and on off switch, my problem is when I'm welding in Ac tig the positioner shuts off after a handful of seconds of welding, it's never consistent when it shuts off, sometimes you can make a full rev other times not even a few degrees. I have all the electronics and the motor insulated with non conductive plastic from the rest of the frame work. My only guess is either static electricity or the frequency of the welder is interfering with the pwm causing it to **** off. Any help will greatly be appreciated!! Thanks

Devin Redemske

By Trackergd (**)

Date 03-01-2016 11:31

Is the plastic case and the 12v power wire(s) shielded?

By Dwill63 Date 03-02-2016 15:44

I will add pictures this evening to better help explain what I have, the motor and wires are separated from any welding current.

Attachment: image.jpeg - Control box insulated, plastic bolted to positioner, box bolted to plastic (927k)

Attachment: image-1.jpeg - Wires are not touching any metal (927k)

Attachment: image-2.jpeg - Plastic bolted to hub of the motor, sprocket bolted to the plastic (929k)

Attachment: image-3.jpeg - Plastic motor mounts (929k)

By Trackergd (**)

Date 03-03-2016 14:58

OK. I "think" I see the problem. Think of the Welding Machine as being a big Tesla Coil putting out high frequency waves (and in reality, the little adjustable arc gap inside the welder is almost identical to what you see on a Tesla Coil). If the electronic components are not shielded, the waves are picked up by the electronic components and the wires leading to and from the motor and control box. I would run shielded wire between the motor and the control box that are grounded at both ends as well as wire mesh shielding in the box, however it looks like the box is aluminum(?). Can you remove the box from the unit and move it further away? Another thought is to make sure you have a good ground on the entire unit, not just through the power cord.

By Dwill63 Date 03-09-2016 16:10

I will try moving the box further away, yes it is aluminum with plastic between it and we're it mounts. I get the tesla idea, which makes sense why it only shuts off on Ac current and not on dc current. I will look into sheilded wire and the mesh. And by shielded wire if I know what your talking is a wire with a type of foil or braided copper jacket? Also I clamp it down on the welding table when in use.

Thanks again!!

By Trackergd (**)

Date 03-10-2016 13:09

Yes, either foil or braided wire shield. If the box is all aluminum except for the display, you might not need to shield it, however if you do I suggest using copper window screen as it will not get the white oxidation the aluminum screen gets, but either will work. Let me know how it works out!

By 60John

Date 03-10-2016 13:41

You are getting HF interference coming through the electrical circuit ground you need an equipment ground on the welder. So all the HF goes directly to ground like they do with the electrical box it has a wire running to a rod driven into the ground.

By Trackergd (**)

Date 03-10-2016 17:41

Correct 60 John. I was focused on the positioner and did not think to include the welder in the discussion, other than the source of the HF. The ground pin on the welder (and the entire neutral/ground buss) becomes the ground. In some states (or localities) the code requires the neutral leg and ground buss to be connected, in other states they must be independent. Better to have everything high voltage grounded to earth....otherwise you might become the ground at some inconvenient moment. :eek: