MIG welder wire feeder using step motor. Provides precision control of speed. In-place replacement for PWM controlled DC motor. Also added 2-1 mode to help weld thin sheet metal (autobody work). Two seconds welding then one second wire retrive. Then two seconds welding and so on.

Board schematics.

Upgraded MIG welder.

Removed DC motor and two gears.

Stepper motor from Amazon: two for $7.50. Shinano Kenshi STP-42D201-37 Bipolar Stepper Motor, 12V, 18" Lead Wires, 1.8 Step Angle, 1.65" Dia x 1.49" D

Stepper motor model.

Motor adapter plate made from old PCB.

Made hole in reductor to fit stepper motor gear.

Mounted stepper motor. Bottom left screw allows for gear fit adjustment.