Going back to electronic after a 20 years break

 Small   youtube video  of the replacement control board. There's a tiny bug where the rotary encoder button sometimes stops working, apart from that it works  really fine. It is safer than the original one thanks to the LEDs/behaviour of the unit : The state by default is "Off" and the unit can be safely manipulated. When it  is armed , the green LED is On. You can switch between Off and Armed easily. The red light is a good indicator of a blown mosfet. If the red LED is on without contact => mostfets are blown. Similarily if the LED does not get lit when contact is made there is an issue. How do we simply do a pulse of the right duration  ? We program the PWM to have a total period of 100 ms and set the duty ratio to the pulse duration. 5 ms becomes 5% duty ratio. We then stop the PWM after 75 ms. Since we have 25 ms to stop it, so it's not an issue to gurarantee it will be stopped in time. That enables us to have accurate, hardware driven pulse w...

 First tests are ok, a couple of pictures of the replacement control board for the cheap spot welder The board just plugs in the original power part of the spot welder. The casing is a temporary one for testing purpose. The project on   GitHub

  This is the prototype board for the Cheap Spot Welder control board. It is a drop-in replacement for the original control board. It is based on a STM32F1 / bluepill board with a SSD1306 Oled screen, a rotary encoder, and a buzzer salvaged from an old 3D printer board. What does it bring ? Not much, it's cheap to make (<10$), it's opensource, it is easy to tune / change and it's massive overkill :) On the othe hand, a bluepill board is very cheap ~ 2$, so no point in trying to make something with a smaller MCU. It even runs freeRTOS. This is very much work in progress, all the building blocks are there, just need to do the magic sauce to glue all of them together.

 /!\ May contain errors! Kicad file  link

 This is revision BL101 2K Schematic of the control board, it may contain errors ! ( V2 , couple of errors fixed) NB : See next post for a more complete schematic