Older industrial equipment is often a great option if you’re on a budget, and you might even be able to add some premium features yourself. [Brett] from [Theoretically Practical] has done with his old MIG welder, adding premium control features with the help of an Arduino.
The main features [Brett] were after is pre-flow, post-flow, and a spot welding timer. Pre-flow starts the flow of shielding gas a moment before energizing the filler wire, while post-flow keeps the gas going after the weld is complete. This reduces the chances of oxygen contaminating the welds. A spot welding timer automatically limits welding time, enabling consistent and repeatable spot welds.
The Miller S-22A wire feeder can have these features, but it requires an expensive and difficult to find control unit. All it does is time the activation of the relays that control the gas flow, power, and wire feeder, so [Brett] decided to use an Arduino instead. The welders control circuit runs at 24V, so an optoisolator receives the trigger signal, and relays are used for outputs. Potentiometers were added to the original control panel, and all the wiring was neatly fitted behind it. The upgrade worked perfectly and allowed [Brett] to increase the quality of his welds. See the video after the break for the full details.