Need tiny bit of assistance.

Ah!! Why indeed.... I don't want to run the motor directly from the transformer as the rectified voltage was 34Vdc and as the motor only takes a meager 0.7A that doesn't drop it enough... The LM338 is set to 20V which drives the motor slightly slower than normal then I feed the bridge with a PWM from a pic12f1840... This in turn reads the "speed" pot .. There is also a direction, but I don't need that and keep it at 5vdc.

It is working exactly as I wanted.... The other reason for the LM338 is the 5v reg only allows 28v input max so it needed dropping anyway..

Like I said, the LM338 isn't even getting warm anymore so the flyback diode on the ADJ pin must have been needed..

Nigel Goodwin said:

There's been plenty of scrap printers full of steppers over the years

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Don't think one of those single stack can motors that are in most printers is what I would choose. The price of NEMA 23 motors is so small that is the way to go.

So much advice after you have it working as you want it to.

I like watch my son welding... As I said I cannot weld properly as I have a lazy eye and I tend to drift. Anywho Watching a full weld and the amps sit at 90~100a for a complete turn of the tube.... I really wish I could weld as smoothly... Good job we're not all the same... I just provide the facility.

At first I was worried that at 1 rev per 10 seconds would be too slow for any motor + no torque left, But I was happy to see it running... Even at that low speed ( and it'll go slower ) I couldn't stop the spindle... Glad to see the hbridge didn't even get warm at all...

Ian Rogers said:

I like watch my son welding... As I said I cannot weld properly as I have a lazy eye and I tend to drift. Anywho Watching a full weld and the amps sit at 90~100a for a complete turn of the tube.... I really wish I could weld as smoothly... Good job we're not all the same... I just provide the facility.

At first I was worried that at 1 rev per 10 seconds would be too slow for any motor + no torque left, But I was happy to see it running... Even at that low speed ( and it'll go slower ) I couldn't stop the spindle... Glad to see the hbridge didn't even get warm at all...

Click to expand...

It's a decent sized motor, and it's geared down nicely, so should have lot's of torque.

How about a video of your son welding using it?.

Got a picture.. Video is useless as the welding glare spoils the vid.. We left the motor loose like that so we could swing it out of mesh while we swapped tubes

Next is a real one... Now the concept works. I will have a lazered frame and nylon fittings, and a proper disengage mechanism.

Do you tack weld them first or do you have another way to hold them in place?

Mike.

There is a middle spindle so the top locates around center... We just tighten the end clamp the weld.. If you watch the video you can see a tube ( plated yellow for another job) and you can see the tube is centered and the end bracket locates on the center part. the bit is right at the end at around 22 seconds...