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PIC Controlled Spot Welder schematic
This circuit pulses half cycles of AC current into the primary of a
transformer which has had its secondary removed and replaced with a few,
really thick turns. The PIC controls an opto coupled triac which
then triggers a power triac connected between the primary AC power and the
transformer primary. With the keypad, custom heat cycles can be
programmed and then with the press of the "fire" button (Or foot switch)
applied to the work piece: ((h x 8.33ms) + (r x 8.33ms)) x p.
The time unit is 8.33ms because all timing is based on the line frequency
x 2. h=heating, r=resting, p=pulses. I have melted tungsten
rods in half with no problem with this unit. Releasing the "fire"
button in the middle of a heat cycle terminates the cycle. The
firmware was done in PIC ASM, and only far enough to do the job it was
built for (Welding tabs onto batteries). The plan was to be able to
enter in and save complex profiles etc. I suggest the
APT1211 optocoupler and
Q2008L4 alternistor to
drive the transformer primary and provide PIC to mains isolation.
Gerber Data /
Firmware |
