Complete menu-driven spot welder control panel
Complete menu-driven spot welder control panel

With this controller, you can control the power of a spot welder. This is done by setting three timings: the pre-weld pulse, the weld pause and the welding time.

This spot-welder timer controller is a new complete and assembled version of the previous controller building kit. You can use it for a DIY spot welder made of a microwave oven transformer (MOT), for the Kende DN-100E welder and for the repairing of the Sunkko 788 welder. 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.

Spot welder control board with TFT display
Spot welder control board with TFT display

Because the electronics was not so easy to build; I have made a completely assembled and tested spotwelder controller board, which is for sale:

FOR SALE: spot welder parts

How to order

To order, contact me personally. Usually, everything is in stock, and you can pay with PayPal.

Complete spot welder controller €39,95

The controllers are fully tested by myself and are complete with the TFT display, small power supply and buttons. You get what you see here:

Arduino-spotwelder-controller
Arduino-spotwelder-controller
Complete with display, buttons and power supply
Complete with display, buttons and power supply

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

Radiator earth clamp set €7,95

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.

Weldpin

Shipping and handling costs €3.95 for all countries worldwide. 

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.

It is an old video of the D.I.Y. bare PCB version, it will be updated soon.

Wiring and mounting

No connectors are required, only screw terminal blocks are used.

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

  • MAINS: 110VAC to 240VAC input
  • OUT: output to the welding transformer
  • Footswitch

Optional:

  • 3.3V-out: optionally output
  • SEL: optionally external switch connection
  • UP: optionally external switch connection
  • DOWN: optionally external switch connection

Open-source software

There are no secrets, the advantage of this spot welder is that the software is open-source unlike other controllers.
Download the software at Github
Because the software is open source, it can be customized. If you have an idea how to improve it, please let me know. Then I will implement it and add to Github. You can read here how to update the software yourself with the Arduino IDE.

Hammond enclosure

The PCB fits exactly into the Hammond Electronics 1591XXSGY enclosure.

Hammond 1591XXSGY
Hammond 1591XXSGY

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. 

Center holes for drilling the front panel

The spot welder controller can be ordered with soldered switches or un-soldered switches. The version with unsoldered switches is for this handy invention: To make it easy to precisely drill the 6.5mm holes for the pushbuttons in a front panel, the PCB is equipped with 1mm centering holes in the middle of the 4 tactile switches.

Switch PCB footprint with center hole for drilling the front panel
Switch PCB footprint with center hole for drilling the front panel

  • First screw the PCB (without the tactile switches) on the back of the front plate.
  • Then drill 1.5mm or 2mm holes through the PCB and the front plate.
  • Now you can drill the four 6.5mm holes for the buttons easily and accurate.
  • The tactile switches can now be soldered.

Spotwelder controller front panel drawing
Spotwelder controller front panel drawing

Repairing the Sunkko 788 battery spot welder

The electronics of the Sunkko battery spot welder is not made well and often brakes-down. You san simply repair it: just replace the electronics by the Arduino spot welder controller. The PCB fits exactly into a the Sunkko 788 front panel, which makes repair easy. The outer tactile switches S3 and S6 are for the Sunkko 788 front panel.

Pictures are coming soon.

Sunkko 788 battery spot welder
Sunkko 788 battery spot welder

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 this controller you can greatly improve the weldings with the Kende DN-100E , see here how to do.

Kende DN 100E spot welder

Weld times

  • Pre-weld time: 0ms to 1000ms in steps of 50ms. 
  • Weld pause time: 0ms to 1000ms in steps of 50ms. 
  • Weld time: 0ms to 1000ms in steps of 50ms.

To protect the microwave transformer, the maximum welding time is 1s. For other welders, such as the Kende DN-100E, longer weld times may be allowed. Soon there will be a possibility to change the maximum welding time between 1s or 10s. For now, you can ask me for this and I will set the maximum welding time to 10s.

Microwave oven repair safety precautions

Working on a microwave oven is extremely dangerous. You will normally NOT survive the high voltage, the available power of more than 1000W is enough to kill you instantly like an electric chair. Please read this article first

Microwave-danger

Questions

If you have any questions, please post them on forum.arduino.cc.

Circuit description

Solid state relays with standard TRIACs will not work here, because the load is highly inductive. Standard TRIACs have turn-off problems with inductive loads, while SCRs always turn off at the negative half-cycle. Therefore, an antiparallel back to back connected thyristor control is used here. The RC snubber network R11 and C3 protects the circuit from voltage transient spikes. D1 and D2 are transient-voltage-suppression diode (TVS), without this diode the ATMEGA328 may be damaged by voltage spikes. The FTDI connector J4 is for re-programming. The ICSP connector is for burning the Arduino bootloader.

Note: the outer switches S3 and S6 are for the Sunkko 788 front panel.

Spot welding pulse timer control panel with TFT display circuit
Spot welding pulse timer control panel with TFT display circuit

Reducing the weld transformer inrush current

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 R5 and C6. The two internal clamping diodes of the ATMEGA328 limit the input voltage to 0 and 5V. 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 thyristor current

The maximum RMS on-state current for the BT151-800R is 12A. However, for short weld times we can take the non-repetitive peak on-state current, this is 50A for weld times below 0.5s. For a normal microwave oven transformers the thyristors are adequate oversized. Take stronger thyristors if you are using a large weld transformer. No heatsink is needed because the thyristors do not heat up.

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. 

To protect the microwave transformer, the maximum welding time is 1s. For other welders, such as the Kende DN-100E, longer weld times may be allowed. Soon there will be a possibility to change the maximum welding time between 1s or 10s. For now, you can ask me for this and I will set the maximum welding time to 10s.

 

 

Do you have any comments? Please let me know.
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