This advanced controller is used by many people and has a unique reduced inrush current circuit that prevents main fuse blow up.

The advantages of the spotwelder

  • Completely ready for use and tested
  • Reduced inrush current prevents main fuse blow up
  • Menu controlled operation with TFT display
  • High power alternistor triac max. 270A
  • Can also be used as a reflow oven controller in the future, see here.
  • Single board that fits into a standard Hammond Electronics enclosure

You can use it for:

Dual pulse spotwelder controller  in Hammond case
Dual pulse spotwelder controller in Hammond case
Dual pulse battery tab spotwelder controller
Dual pulse battery tab spotwelder controller

Zero crossing detector prevents main fuse blow up

There are many spot welder controllers for sale from China. These are pretty good and cheap, but they do not have a zero crossing detector as this controller. A zero crossing detector is necessary for reducing the weld transformer inrush current, to prevent the mains fuse blow up.

History

I have developed the D.I.Y spot welder because I needed a special spot welder for the building of my Maxun One solar bike. It turned out that the spot welder is being built by many people worldwide. Because the electronics was not so easy to build, I have made a controller for sale. When I started building in 2015, there were no other controllers on the market, but now there are many for sale in China too. But I hope you buy my controller, it has extra options...

DIY battery tab spot welder with controller
DIY battery tab spot welder with controller

FOR SALE: spot welder parts

How to order

To order, use my Shop, You can pay with PayPal too.

Complete spot welder controller €34,95

You get what you see here:

Spotwelder timer bs
Arduino-spotwelder-controller


All you need further are the microwave oven transformer and all the other mechanical parts and cabling.

Front panel for the Hammond Electronics enclosure with self tapping screws €12,50

Front panel with self tapping screws

Electrode holder radiator earth clamp set €7,95

This makes the mounting of the welding electrodes very easy. Size 20mm x 20mm x 12mm

Clamp

Welding electrode set €4,95
Pure red copper, length 45mm, diameter 6mm. 
It is important that the electrodes are made of the right material, not all types of copper are suitable. Note that there are special copper alloys for spot welding, such as Class 2 Chromium Copper 18200 or Chromium Zirconium Copper 18150, but these are just needed for example at car production. My welding electrodes don't stick to nickel tabs. You only need one set of electrodes in your life, because the wear is negligible, unless you have to weld thousands of batteries. You have to shape the electrodes yourself with a bench grinder.

Weldpin

Menu controlled operation with TFT display

The big advantage of this spot-welder timer is that the control is menu-driven and therefore very simple. A manual is actually unnecessary.

Wiring and mounting

No connectors are required because only screw terminal blocks are used.
Note: the in and output connectors are for AC voltage and there is no + or -.

Spot welding pulse timer controller wiring
Spot welding pulse timer controller wiring

  • MAINS: 110VAC to 240VAC input
  • OUT: output to the welding transformer
  • Footswitch (optinionally)
  • J6: rotary encoder (not yet implemented)

Weld times

The time-table has a logarithmic distribution. The distance between the steps is 20% to 30%:
0, 10, 20, 30, 40, 50, 60, 80, 100, 120, 150, 200, 250, 300, 400, 500, 600, 800, 1000ms.

The welding times are different for 60Hz mains: 8.3, 16.7, 25.0, 33.3, 41.7, 50.0, 66.7ms etc. But because these are not round numbers, the fictional weld times for 50Hz are still used for 60Hz. So at 60Hz, a welding time of 1s is actually 830ms.

  • Pre-weld time: 0ms to 1000ms 
  • Weld pause time: 0ms to 1000ms
  • Weld time: 0ms to 1000ms

To protect the microwave oven transformer, the maximum welding time is 1s. For longer welding times, use the continuous mode.

Here are some oscilloscope images of the measured weld current:

Weld current for weld time 10ms
Weld current for weld time 10ms
Weld current for weld time 20ms
Weld current for weld time 20ms
Weld current for weld time 30ms
Weld current for weld time 30ms

Interval time

We also have to take into account the minimum interval time between successive welds. The welding transformer and the alternistor need some time to cool down. When we weld batteries manually, the electrodes must be accurately moved from one weld to another each time, this ensures sufficient interval time.

Settings for nickel plated steel strips of 0.15mm thickness

Most used are nickel plated steel strips with a thickness of 0.15 mm, these can be welded the best. You may have to experiment with the weld times and the electrode force, but start with these values:

  • Weld electrode force 0.4kg (4N)
  • Pre-weld time 50ms
  • Pause 500ms
  • Weld pulse time 100ms (50 to 250ms)
  • Electrode tip diameter 1.5mm
  • Electrode outer distance 5mm

Controlling high-power spot-welding machines

High power spotwelder controller
High power spotwelder controller

The controller can also be used for professional, high-power spot-welding machines. Here, longer welding times are common, up to 3s. The alternistor heatsink may get too hot when using very long welding times with short intervals. In case of doubt, check the temperature of the heatsink after the voltage has been removed

Built-in power supply

The controller contains a mains power supply and works on all mains voltages worldwide from 110V to 240VAC, 50 and 60Hz. You only need an extra microwave transformer. 

Standard Hammond enclosure

The PCB fits exactly into the Hammond Electronics 1591XXSGY enclosure. See the dimensions for drilling HERE.

Arduino spotwelder controller in Hammond case
Arduino spotwelder controller in Hammond case

Arduino spotwelder controller in a Hammond case
Arduino spotwelder controller in a Hammond case

The dimensions of the board are 101mm x 70mm. If you want you can cut the PCB just behind the buttons to 85mm x 70mm.

Front panel for Hammond Electronics enclosure 

I have front panels fabricated for the Hammond Electronics 1591XXSGY enclosure. The spacers for the (special) self-tapping screws from the original Hammond front panel are very weak, I have reinforced these:

Reinforced PCB spacers for the self-tapping screws
Reinforced PCB spacers for the self-tapping screws

Hammond Electronics enclosure front panels
Hammond Electronics enclosure front panels

Information for nerds

See this article for more details Info for nerds.

Spotwelders from other users

See the article HERE

Spotwelders from other usersMiroslav Kolinsky1

Repairing all Sunkko battery spot welders 788H 709A 709AD 737B

The electronics of the Sunkko battery spot welders are not made well and often brakes-down. You san simply repair it: just replace the electronics by the Arduino spot welder controller.

Sunkko 788H repair
Sunkko 788H repair
Sunkko 709A
Sunkko 709A
Sunkko 709AD
Sunkko 709AD
Sunkko 737B
Sunkko 737B

Note that it also happens that the transformer of the Sunkko has a short circuit. You can check that by connecting the transformer to the mains, if the main fuse blows, then the transformer is broken. In that case (also) the transformer have to be replaced, you can take a transformer from a microwave oven.

Kende DN-100E improvement

The Kende DN-100E does not have an electronic control of the welding time. Therefore it is hard to make high-quality weldings with a good repeatability. With the controller you can greatly improve the weldings with the Kende DN-100E , see here how to do.
Kende DN 100E spot welder

Microwave oven repair safety precautions

Working on a microwave oven is extremely dangerous. You will normally NOT survive the high voltage of 4000V, the available power of more than 1000W is enough to kill you instantly like an electric chair. Normal insulated tools are not safe, the high voltage may strike through it. Please read this article first

The microwave oven high-voltage is 5 times as dangerous as the overhead line of a train, see the video here:

Microwave oven repair safety precautions

Questions

There is a forum about the spotwelder controller (read 35000 times), see HERE. It contains answers to practically all questions.

Circuit description

See the Arduino universal AC power control board.

Zero crossing detector circuit

This circuit necessary for the reduction of the weld transformer inrush current, to prevent the mains fuse blow up. The current through the weld transformer, which is an inductive load, will lag behind the voltage by 90º. This is the reason that, to reduce the inrush current, the optimal switch-on time is not the zero point of the mains sinus but the top of the sinus. To be able to do this, the Arduino has to detect the mains zero crossings, this is done by U3. The delay time in the software "sinusMax_us" is 4583µs, this strange number is the average of 1/4 cycle of 50Hz and 60Hz. 

Phase
Inductive load phase shift

Setting the power of the welding current is done only with time control and not also with current value control. At some spot welder controllers, the current value can be set too, but because this works with phase control, this will increase the inrush current with the risk of blow up the main fuse. Weld-time setting has the same effect.

High voltage!

Warning

Pay attention: the PCB is directly connected to the mains, just the low voltage part is safe. Usage is at your own risk.

Maximum alternistor current

The maximum RMS on-state current for the T3050H-6I 30A. However, for short weld times we can take the non-repetitive peak on-state current which is 270A. For a normal microwave oven transformers the alternistor is adequate oversized. 

User guide

  • Use the up, down and select button for setting the parameters, see the video on YouTube.
  • The settings are stored in the EEPROM.
  • Press the weld button or the foot pedal to weld.

Continuous mode:

There is a possibility to weld as long as the weld button is pressed. To enable this mode, set the welding time to 0 (*note*), press and hold down the weld button simultaneously during power on for 1 second and than release the button. Now you can weld continuously without the timer. Take care: the transformer will be overheated easily, so use this feature only for testing or for measuring the weld current.

Rotary encoder

Instead of the menu buttons, a rotary encoder may be used. The hardware is implemented on the PCB, but the software still has to be made for this.

Do you have any comments about the website or problems with shopping? Please let me know.