handicraft work

spot welding #1

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.

high current transformator with the new windings

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 old remove aluminium windings….

The first try with a tasmota wifi plug and the commands:

pulseTime1 1
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.

try to remove the nickle band

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.

schematic figure

I found this example in the web ( https://www.aeq-web.com/230v-ac-arduino-dimmer-pahsenanschnitt/ , 04.06.2020 ) and because all parts are available in my small laboratory i could build the zero cross detection.

Zero-cross detection schematic
the zero-cross detection on a circuit board
checking the circuit with the oscilloscope – good enough?

But that was it for now because i don’t have the other parts in stock…

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