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Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]
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Refrigerator:
Finished the wire speed controller, I had some 555's laying around somewhere but couldn't find them.
No big deal because i found a neat little LM393 PWM controller schematic on google and made the speed controller with that.
Drew the traces with a permanent marker and etched the board, soldered everything on top because i couldn't be bothered to mirror the layout on the other side and drill the holes.
I put dots around the circuit with my marker, those dots are there in case i ever wanted to experiment with feedback so that i'd have pads to solder to.
Planned to use a TO-220 MOSFET but the only ones i had were IRF640 and IRF614, which would get way too hot, so i bodged in a NTD70N03R that i pulled from a dell motherboard.
My PWM is tuned to 30kHz and the MOSFET stays ice cold.
For my wire feed i'm using a VW windshield wiper motor, which seems to have some good torque so the open loop speed control might not be as bad as i had anticipated.
strawberry:
is it posible to use TL494 as PWM controller
more detailed info for TL494:http://www.ti.com/lit/an/slva001e/slva001e.pdf
mikerj:

--- Quote from: Refrigerator on July 02, 2019, 05:35:44 pm ---For my wire feed i'm using a VW windshield wiper motor, which seems to have some good torque so the open loop speed control might not be as bad as i had anticipated.

--- End quote ---

That going to be a very heavy duty wire feed, but it's a nice choice for an easily found/cheap part to repurpose.  Getting/making suitable rollers and assembling then in an accurate, mechanically rigid assembly is key to a decent wire feed, and typically is where all the cheap MIG welders have problems (flexible plastic rubbish held together with self tapping screws).
Refrigerator:

--- Quote from: strawberry on July 02, 2019, 06:07:20 pm ---is it posible to use TL494 as PWM controller
more detailed info for TL494:http://www.ti.com/lit/an/slva001e/slva001e.pdf

--- End quote ---

Yeah i saw that but the LM393 circuit is much simpler.


--- Quote from: mikerj on July 02, 2019, 06:59:45 pm ---
--- Quote from: Refrigerator on July 02, 2019, 05:35:44 pm ---For my wire feed i'm using a VW windshield wiper motor, which seems to have some good torque so the open loop speed control might not be as bad as i had anticipated.

--- End quote ---

That going to be a very heavy duty wire feed, but it's a nice choice for an easily found/cheap part to repurpose.  Getting/making suitable rollers and assembling then in an accurate, mechanically rigid assembly is key to a decent wire feed, and typically is where all the cheap MIG welders have problems (flexible plastic rubbish held together with self tapping screws).

--- End quote ---

While i was looking up wire feed mechanisms on the internet i found quite a few that use a 24V windshield wiper motors in them.
The roller problem was sorted with the help of a cheap skateboard bearing that i welded shut to keep it from spinning, this one will be mounted to the windshield wiper motor and will function as the drive roller.
One problem that i came into though is that the bearing is so cheap that the races are not even hard, my dull file bites pretty well into it.
I might try quench hardening to see if it helps because as i assume a soft metal drive roller won't last long.

tautech:

--- Quote from: Refrigerator on July 02, 2019, 08:27:55 pm ---While i was looking up wire feed mechanisms on the internet i found quite a few that use a 24V windshield wiper motors in them.
--- End quote ---
Yes because the 24V wiper motor is a good match for MIG welding voltages and simple speed control circuits are needed as the motor is only energised when the handpiece trigger is pulled.

--- Quote from: Refrigerator on July 02, 2019, 08:27:55 pm ---One problem that i came into though is that the bearing is so cheap that the races are not even hard, my dull file bites pretty well into it.

--- End quote ---
More likely you annealed the hardening from it by welding it.
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