Sometime in 2018 i created an I/O module with 8 (optocoupler isolated) inputs and 8 (mosfet) outputs. The controller is an arduino pro mini clone with an attached MCP2515 CAN-Bus controller. For the overall 16 in- and outputs i used a MCP23017. Thereby i used the SPI bus for the CAN controller and the I2C bus for the I/O expander. The can bus can be used for communication with the outside world.
Unfortunately, I have not yet found a useful application for the module – that can still happen… but overall it was a nice experience to design a whole module on my own.
The circuit boards are made in china and assembled by myself. If i would redesign the module i would probably put an ESP32 controller instead of the arduino on the controller board – wifi, bluetooth and can bus integrated and a bit more power.
When i wanted to continue with the zero cross detector and a triac i quickly realized that the zero crossing was not detected well enough. So i search in the net and found another circuit on https://www.dextrel.net/design-ideas-2/mains-zero-crossing-detector.html (08.06.2020). I altered the circuit a little bit (see schematic) and checked the signal with the oszilloscope.
Perfect! With the triac circuit below i am now able to dim a light bulb or some other resistive load.
The next step would be to design a printed circuit board – or to buy the almost same controller circuit board on aliexpress, with two poti, a stm microcontroller (STM8S003F3P6), a seven-segment display, a really powerfull triac (BTA100): The NY-D01 Board.
With the two potentiometer you can adjust the welding time in 20 ms steps (full sine wave) and the power between 30 and 99% (dimmer). An old 9 volt transformator, a foot switch and electrodes from ebay and i start welding the first lithium cells.
For the board is also a fitting frontpanel available which i have ordered on aliexpress (not yet delivered…). Connectors for the electrodes are also ordered.
To build and repair battery packs with lithium cells I want to build a spot welding machine. So I looked into my basement and found an old electrode welding tool. After disambling the machine this is the new main part of the spot welding machine, the high current transformator.
Because the transformator has about 48 volt no-load voltage and only about 100 ampere welding current i removed the secondary winding (made from aluminium). Then I winded up about 8 turns 16 mm² (about 2,5m – Thanks Rainer for the cable) on the transformator. The no-load voltage is now at about 6 volt – and the current should be much higher than before.
The first try with a tasmota wifi plug and the commands:
Backlog Delay 100; Power1 On
(0,1 second pulse time, then wait 10 Seconds before pulse the relay)
The electrodes are made from 2,5 mm² copper wire and two old clamps from an electrical cabinet. The testpiece is a laying around angle and a piece of nickle band.
Not so bad for the first try! The welding points are so strong that the nickle band around yielded.
Next step: the control circuit. To control the power of the welding machine i want to control the power of the transformator with a dimmer circuit and timer. The circuit should consists of an arduino nano, a display, two potentiometer (time and power), a zero cross detection and the triac circuit.