Introduction

The DX10 is a low-cost battery-powered spot-welder. It comes with a couple of electrodes, a length of metal strip (for use as battery tabs), a small piece of abrasive paper (for reshaping the electrodes as they wear out, or for removing oxide), a USB C cable, and a nice cloth case that feels water-resistant (it might not be!).

In use, you place the metal strip onto the desired surface, and then apply the electrodes at two points on the strip. Once the DX10 detects the resistance has dropped to a level, then current is applied and heat is generated due to metal resistance, and welds are formed.

This blog post just contains some teardown photos of the DX10, because I wanted to see the internals, and I didn’t find the information on the Internet. The unit is available on AliExpress or Amazon (costs more there!). The particular seller I used was called 'Learning education store' on AliExpress.

Note: There is a risk of a battery short when removing the internals from the enclosure. It’s not recommended to disassemble this unit unless you're an engineer and are aware of the risk. It will also probably invalidate any warranty, since a couple of the screws are not removable.

 Screenshot: AliExpress

How does it work?

The way it works, is that the items (say two flat strips of metal) to be welded are placed together, and then two electrodes are placed one on each side, or on one side. Current is passed through the electrodes and the items being welded, and the resistance of the items, results in heat being generated. In theory you can control the heat by adjusting the current, the amount of time of the current pulse (or pulses), and the actual resistance of the items being welded (the pressure of the electrodes will also make a difference to that; a good contact is required so that the items are heated and not the copper electrodes).

In practice the DX10 technically doesn’t have directly adjustable current; other parameters are adjusted. It may be as simplistic as a configurable burst of current, or there may be pulses, to pre-heat the weld location. I don’t know what algorithm the DX10 implements; I have not used it yet!

Internals

It’s actually not easy to unscrew the DX10, because a couple of the screws are deliberately mashed by the manufacturer! I had to take a dremel to them and cut a notch in the head of the screws. A possible Dremel-less approach would be to unscrew the rear of the unit (which has unmashed screws) and pull out the unit from that end; there are a couple of side metal rods that would need to be removed, and the battery has a foam pad stuck to one side which makes it harder to pull from that end, but it could be feasible.

The unit is quite well built. There are a couple of slabs of LiPo cells, in parallel, attached to a circuit board that fits into guides inside the enclosure. The unit is rated to be 10.6AH, which I have no reason to disbelieve yet (the battery size is substantial).

There is a nice, very readable two-color OLED screen. The unit makes beeps during some operations such as power-on/off, and it’s of good volume. The main connector looks like EC5. It’s good that it is a standard connector, so that new electrode cables can be attached if desired.

With the OLED display removed, it can be seen that there is a Nuvoton 8051-based microcontroller present. The MOSFETs are HYG011N04 and there are six of them (three on either side).

The two cells are directly connected to the PCB, due to the very high current requirement. There is a DW01-A battery IC on the board (on the left side in the photo below), however you can’t rely on that for complete safety; there will still be a risk with such high current through the MOSFETS. Personally I would detach the electrode cables from the unit when not in use, to prevent an accidental short in case a MOSFET has failed.
There were a couple of other things of note. Firstly, the soldered battery contacts are just millimetres away from the conductive metal enclosure (it isn’t significantly anodised). I didn’t feel comfortable with that, in case the enclosure ever gets dented. The solution was to apply an insulator (I used Kapton tape) to the exposed metal. I covered most of the exposed metal, because if you slide out the board and battery from the case, there is a risk of a short. Also, any tool like a screwdriver or tweezers or metal pen on a desk could cause a short, so the tape provides a bit of protection against such situations.

Another thing was that there appear to be bronze-like metal rods soldered onto the PCB. I would like to replace them (or add) copper rods for further reducing the path resistance, but it’s risky working on a board with attached battery. I might attempt it if the spot welds are not good, but personally I wouldn’t advise it without taping up all the surroundings to protect against accidental shorts; it’s very high-risk. It will also need a lot of heat, so it needs a very powerful soldering iron.

The underside of the board doesn’t contain much beyond the MOSFETs. There is an optoisolator, and a battery charging chip, and a bit of circuitry using a SOT23-6 chip labelled AL274 (I don’t know what this is). I expected to see a bit more circuitry, perhaps an op amp, to determine the contact resistance before the unit fires a current pulse. Perhaps it is mainly done in the microcontroller chip.

Summary

Personally, I thought the unit was well built, although it does benefit from a bit of tape to provide a bit more protection from dents etc. The unit should be stored such that dents do not occur, and such that the front panel buttons cannot accidentally be held down to power on the unit. I might also add some heatshrink sleeving on the sides of the electrode ends, in case there are any accidental slip-ups; the electrodes should not be directly shorted when operating.

Thanks for reading!