handicraft work

spot welding #3

Today the last blog about my self-made spot welding machine. The ordered parts from china arrived these days and i could assemble the whole machine.

two connectors and the new frontpanel

With the additional parts it becomes very tight in the old housing. But some time later all holes and the frontpanel cutout were made and the parts mounted.

safety feature: upper left a resettable 10A fuse, on the left a bimetallic switch
The 9V auxiliary transformer is mounted under the circuit board
the new front: for the display unit the right distance bolts are missig…

All i had to do now was to connect the electrodes to the plugs and equip the foot switch with a hollow plug. Afterwards the first battery packs could be welded, equipped with a battery management system and packed in heat shrinkable tubing.

foot switch and electrodes
battery packs, made from old laptop cells
before i assembled the packs i checked the cells with a imax b6 balance charger
handicraft work

spot welding #2

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.

zero crossing detector schematic
perfect edge at the zero crossing

Perfect! With the triac circuit below i am now able to dim a light bulb or some other resistive load.

triac circuit
Arduino, zero crossing detector and triac circuit
dimm to 25%

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.

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.

First welding points
3S2P Battery Pack with 3D printed spacer

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.

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…