Ho-hum, another microwave oven transformer spot welder, right? Nope, not this one — [Kerry Wong]’s entry in the MOT spot welder arms race was built with safety in mind and has value-added features.
As [Kerry] points out, most MOT spot welder builds use a momentary switch of some sort to power the primary side of the transformer. Given that this means putting mains voltage dangerously close to your finger, [Kerry] chose to distance himself from the angry pixies and switch the primary with a triac. Not only that, he optically coupled the triac’s trigger to a small one-shot timer built around the venerable 555 chip. Pulse duration control results in the ability to weld different materials of varied thickness rather than burning out thin stock and getting weak welds on the thicker stuff. And a nice addition is a separate probe designed specifically for battery tab welding — bring on the 18650s.
Kudos to [Kerry] for building in some safety, but he may want to think about taking off or covering up that ring when working around high current sources. If you’re not quite so safety minded, this spot welder may or may not kill you.
12 thoughts on “Dual-Purpose DIY Spot Welder Built With Safety In Mind”
I believe “angry pixies” is a [thisoldtony] trademark term.
I’m sure you will hear from his lawyer if he ever gets around to getting one????
I think you mean AvE. But he’s probably a bad influence on tony too
Actually it only puts 3V AC open circuit to the fingies. I used to use a big ol’ 50kW spot welder that was donated to my college after being used at a Ford plant, and used it with both my bare hands on the part. Big foot actuated clamp/trigger switch.
I still have those hands
“I still have those hands”
Mounted in a display case?
The dangerous part is on the AC side though a good insulated case for the switch and good grounding would solve the angry pixie problem.
Though the 555 one shot timer also would help make the welds more consistent.
You do not want this 3V on your wedding ring. It’s bad when it melts on your finger.
Well my ring is Tungsten Carbide so I guess my finger will melt first.
Safety in mind, but not really so much in practice. It appears that the mains terminals are insulated by a strip of duct tape from an ungrounded metal box. It would be way safer if this were built in an actual enclosure, with a grounded transformer.
It’s not really that dangerous, but no safer than the conventional method.
Oh no, mains switches are so dangerous. I better replace them on every device ever.
Don’t talk to me about safety and not have fusing or a switch on the mains before they get into the triac. Safety in devices like these are multi-staged. Plugged in? Switched on? Settings checked?
I used a foot actuated spot welder for years and the extra bit you needed to press the pedal to engage the current was that final safety step. The timer is a nice touch.
Thank for the video, but i am not gonna making something like this at home, i mean it’s little dangerous
You better replace mains switches on every device ever. I thinks It’s really that dangerous.
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