Spot Welder Device with Capacitive Discharge

Overview

This spot welder contains a very large capacitor that is charged to a precise voltage then discharges through the material to produce a controlled cut.

Explanation

There are 5 key segments that make up the design including discharge electrode, controller/supervisor board, discharge controller, energy storage device, and power/charging/drive supplies. The controller can be disregarded for simple discharge-cutting. This is done by connecting the audio capacitor directly to a high-current rectified DC supply and using a switch or signal source along with MOSFETs/drivers to turn the discharge ON/OFF or control the duty cycle and frequency. If the electrode gets stuck, the rectifiers may blow or smoke the transformer when using high-current charging supply, so it is better to leave out the ability to switch the output under no circumstances.

If the voltage gets too high, a discharge MOSFET can be used which eliminates the long wait for capacitor to discharge when setting to a lower voltage. A potentiometer is used to preset the voltage and the code checks to see if the measured voltage is less than the preset voltage. The microcontroller will act like a proxy between the tactile switch and the MOSFETs.