This is a galvanic electrolysis epilator. U/abbxrdy designed and built it and her writeup is [link]. I built one too and this is my writeup.

This machine is obsolete technology. It uses galvanic electrolysis, in which DC current flowing through the body creates lye in the hair follicle, and the lye destroys the tissue. Modern electrolysis machines use "blend," in which the DC current is combined with AC current, which heats the probe, so the tissue is destroyed both by the lye and by the heat. Blend electrolysis is much faster (one or a few seconds per hair). But this machine does work, if slowly, and I've permanently removed hair with it. I don't think it's great, and it hasn't seemed to work on my face (it takes multiple minutes of exposure to get each hair out and then the hair came back). But hey, what can you do?

I'm putting this out there not because it works great or is particularly useful, but because when I searched for plans for an electrolysis machine, this was the only one I found. It was designed and posted on Reddit by u/Abbxrdy a few years ago and the description was pretty skeletal. I tried to get in touch with her but never heard back. Since I was able to replicate her design and have it work, I thought it was my responsibility to post it with a more detailed description of how to put it together.

The total cost of this machine was somewhere around $300-400, including the soldering station I bought, but not including some of the switches and hardware, which I already had.


TECHNICAL DESCRIPTION

Here's a description of how the circuit works, starting at the top left of the schematic and moving down. There's a power supply, which is three 9v batteries in series, and then an on/off switch. Then the power goes to the LM317 adjustable voltage regulator, controlled by a knob (RV1). The output of that goes to three places: the probe circuit, the voltmeter that tells you what voltage you're set to, and the L7805 fixed voltage regulator, which puts out 5v for the control circuits. Then from there the 5v power goes to a lot of different things. I put a wire to one of the buses on my board and had a power bus, because so many of the components need a 5v power source. First there's a light that's on whenever the machine is on (I used a green LED). Then there's the 555, which is the timer. When pin 2 of the 555 is connected to ground (by the user pushing the pedal switch), it starts the timer; the length of the time is determined by the values of RV2 and C4, and for the duration, it puts out a constant signal from pin 3. That signal goes through some opamps (operational amplifiers), and I don't fully understand why. Abbxrdy drew three separate opamps to make the schematic easier to read, but she used the LM324, which has 14 pins and can do four operations at once, so she only had the one chip on the board. That's why one is labeled with pins 1, 2, and 3, one with pins 5, 6, and 7, and one with pins 8, 9, and 10. One of the opamps only goes to a light that's on whenever the probe circuit is energized (I used a blue LED). The other goes to a transistor, then a knob (the current adjustment knob), then another opamp, and finally to a transistor that acts as a potentiometer in the probe circuit. I think all those operations are to make the resistance of that transistor, which directly controls the current of the probe circuit, be the right values, and have the right relationship with the resistance of the knob you use to change it. (I.e. you could just have the probe circuit go through a knob, but it might put out way too much current, or not enough, or the knob might only adjust it by 0.2mA or something.) The voltmeter is in parallel with the circuit it's measuring, and the ammeter is in series in the circuit it's measuring. There's a test switch (on mine labeled "test mode/go mode"), and in test mode it completes the circuit that would normally go through the body. In other words, it cuts out the electrode and probe and makes a complete circuit, so you can see a reading on the ammeter.

I'm also including the DC circuit textbook I used to understand the basics of wiring. I learned how to read a schematic from this: https://learn.sparkfun.com/tutorials/how-to-read-a-schematic/all#schematic-symbols-part-1 To learn more about the integrated circuits in the design, you can search for their names (like the LM317) and the word "datasheet" to find the manufacturer's description of what they do and how to use them.

If I make another one of these, I'd like to redo the design with the option to use a pedal potentiometer, like a sewing machine pedal, as the current control. This way you wouldn't use the timer; with the pedal at rest there would be no current, and you would increase the current by stepping on the pedal. I think that would make it easier where I want to slowly turn up the current, especially in places where I'm using both hands to place the probe.


ASSEMBLY

I built the circuit board while holding it in a wood clamp. At first I tried to place all the components on the board and then solder them, but it turned out to be much easier to place and solder them one by one. I was afraid I'd somehow paint myself into a corner, but as long as you leave room between the components, you can make the connections with jumper wires. I used a perforated prototyping board and 22 gauge solid copper wire. The soldering iron I used was the Circuit Specialists brand 60-watt soldering station (part number #STATION60 in their catalog).

As I built the board, every time I needed a wire to go from the board to something else, like one of the knobs, I soldered one end of the wire to the board and left the other end dangling. I marked bands around the dangling end with a marker--one band on the first dangler, two on the next, etc. On a piece of paper, I'd write something like "1 power switch...2 volume knob wiper...3 volume knob left pin." Then when I was done with the board, I soldered all the danglers, in order, to the pins of one side of a 15 pin D-sub connector. From the other side of the connector, I ran a wire to each of the other things (the power switch, the volume knob, etc.), using the paper to know which pin went where. (Notice that the arrangement of pins on the D-sub connector will be mirrored. The pins are numbered with tiny numbers but I didn't see that at first.) This way, I could make the whole board, then wire everything on the faceplate, then connect them together. I could also take the board all the way off to fix problems.

The things that needed to plug in and out are the pedal (trigger switch), the electrodes, and the probe. The pedal I bought came with an internal ("male") 1/4" audio jack on it, so I used a panel mount 1/4" external audio jack to connect to it. The jack I got had six pins, and I plugged the pedal in and used a meter to find two the had continuity when I pressed the pedal, but not when I didn't press the pedal, and put the wires to those two. For the electrodes and probe, which each have one wire going to them, I used some kind of XLR-looking connector I had, but anything will do. I couldn't find any good-looking panel mount connectors on the internet; if I had to do it again I'd probably use a D-sub. Make sure not to reverse the polarity of the probe and electrode, or it won't work! If you test the wires with a meter, the electrode should be positive and the probe should be negative.

The faceplate of the machine, which has the meters and knobs and switches and lights, I made out of a piece of a square plastic cat litter bucket. It was the ideal thickness. Then I used a jigsaw to cut out a square hole in a wooden board (a 1x10 or something) and screwed the faceplate to the board to cover the hole. I used a step drill bit to make the holes in the faceplate; I liked that I could get a clean hole by turning it by hand for the last step. For the two panel meters I had to cut rectangular holes in the plastic. I used a vibrating multitool, but you could also use a knife, it would just take a lot longer. I seem to remember the jigsaw not working because the plastic was too flexible.

Ideally you'd mount the circuit board with long tiny wood screws through the mounting holes, going through spacers. But I didn't have any screws that were small enough and long enough, so I put a machine screw through each of the four mounting holes, then through a spacer, then through a wider mounting plate (in this case a cigar box lid, but you could use more bucket plastic), then put a nut on the end to tighten it. Then I screwed the mounting plate to the back of the board. Hardware stores usually sell those nylon spacers. Maybe not like home depot, but a hardware store that has lots of little drawers probably has those.

The machine has a voltmeter and an ammeter to show you the voltage and current you're using at the probe. In some professional electrolysis videos I watched, people mentioned watching an analog ammeter for small drops and peaks and getting some kind of information about what they were doing from that. But I had a lot of trouble finding an analog ammeter that would measure small enough amperages, and I've never seen small drops or peaks, so I think a digital ammeter (which is what the original used) would be better.

I used TENS electrodes, and their connector is basically a 2mm hole. You can buy "TENS leads" with a 2mm pin to fit in the hole, but I used a piece of 12 gauge solid copper wire, the kind you find in house wiring. It fits tight in the hole. I cut about an inch of it and used a butt connector to attach it to the wire coming from the machine.

For the probes, I did what the original builder did, which was to buy a single "female" D-sub connector and solder it to the end of the probe wire. F shank electrolysis probes fit tight in it. I made a stylet by cutting a pencil to be two or three inches long, then splitting it in half longways, laying the wire against the flat part, and shrinking 10mm shrink tube around it. I like this stylet because I can put a pen cap over the probe, so I don't have to take the probe out every time I want to set it down.

There are a few errors and unclear spots in the schematic. The right pin of RV1 looks like it connects to U1, but it shouldn't be connected to anything. The wiper of RV1, pin 1 of U1, and R1 should connect to each other.

The maximum time of the timer is the ohms of RV2 times the farads of C4. In the schematic that comes to 5.5 seconds, which is too short. I ended up using a 10,000uF capacitor instead of a 1,000uF capacitor, but it sometimes acts a little weird when you turn the knob while it's on. I think the ideal fix would be to use a 50k potentiometer for RV2 instead of a 5k.

Finally, one of the transistors was drawn correctly with regard to what the collector, base, and emitter were supposed to be connected to, but the numbering of the pins didn't match how the pins were on the component I had in my hand. She had the base numbered as 2, or whatever, but it was actually a different pin. So on the transistors, make sure to look at the datasheet that comes with that transistor and figure out which pin is which, instead of relying on the numbers. In the symbol, the emitter is the one with the arrow (even if it's facing out), the base is the one on the left side that's perpendicular to the thick vertical line, and the collector is the remaining one.

Also note that I sometimes used two resistors in series to add up to get the resistance value I needed. On the schematic, she wrote the total resistance as if it was one resistor, for simplicity. In my parts list you can see which resistors I bought to add together.

The digital voltmeter I used had to have its own power supply. I used a fourth 9v battery, going through the power switch, which was a double-pole single-throw switch, so it could turn on both circuits. But if I did it again, I'd have used a separate switch for the voltmeter, because it runs down the battery fairly quickly and I don't usually want it to be on. I usually just stick with the same voltage.

My parts list includes where I got everything. Most of the components I needed I ordered from circuitspecialists.com. For a few things they didn't have, I used sparkfun.com. I could probably have gotten almost all of what I needed from digikey.com, but their selection was too overwhelming. Depending on who manufactures the integrated circuits you buy, they might have different names; for example, the timer is sometimes called LM555 and sometimes NE555. I was able to guess what was the same without too much trouble. The LM317 is an adjustable voltage regulator, the L7805 is a 5v fixed voltage regulator, the 2N4403 is a basic PNP transistor, and the PN2222A is a basic NPN transistor.

The only electrolysis supplier I found that sells to the public is Texas Electrolysis Supply. But it doesn't seem to matter, because the probes always come in packs of 50, and they always cost $33 a pack, no matter where I saw them being sold.

Ballet brand probes come in sizes 2 through 6, written as F2-F6 and K2-K6. The letter is the shape of the shank, and it has to match the stylet that holds it; this machine fits F shank probes. The number is the diameter in thousands of an inch. Ballet says to use 2 for "fine, shallow hairs on hands and feet and women's upper lip, 3 or 4 for chests, forearms, and lower legs, and 5 and 6 are for armpits, pubic hair, thighs, and beard hair."

Some electrolysis probes are "insulated," which I think means that all but the tip of the probe is coated in heat insulation. My research suggested that that's only relevant if you're using thermolysis (AC electrolysis), so I didn't use insulated probes. There are gold probes for people whose skin is sensitive to other metals, but, for reference, I can't wear stainless steel jewelry, and I haven't had any problems from the stainless steel probes I use.


OPERATION

I put an electrode on my skin near where I'm working, then insert a probe into a hair follicle and press the pedal switch with my foot, which starts a timer that delivers current through the probe for a specified amount of time. The voltage and amperage at the probe are adjustable from 5-30 volts and from 0-2mA, and they're displayed on two panel meters. I usually use about 15 volts and about .7 or .8 mA. Then I take the probe out and pull the hair with tweezers. It should slide out with no, or almost no, resistance.

As regards what size needle to use, "choosing a needle that matches or exceeds the diameter of the hair to be treated will result in the best electrolysis treatment....When you use a thin needle, lye is initially produced in a more concentrated area, so pain may be greater. However, when you use a thicker diameter needle, since the needle has more surface area, the DC current will be distributed over a larger area. And that means that the treatment should be less painful."
http://synopticproducts.com/2018/05/17/needle-size-and-electrolysis/

It also helps to have good tweezers. Bad tweezers can be improved by sanding the grabbing surfaces with 300 or 400 grit sandpaper--gently grab the sandpaper with the tweezers and pull it through. I would guess it's better to move the sandpaper perpendicular to the direction in which the tweezers are going to pull, so that any microscopic "teeth" grab hold of the hairs like the teeth on pliers, but I don't have any evidence that it matters. With some coarser sandpaper and/or a file, you can customize the shape of the tweezers a lot!

Electrolysis is hard and I see why people get trained to do it. It's hard to get the probe in the right place, and I have to go by how it feels in the skin it's going into. I tried it on a friend and I couldn't get it to work. I didn't know if the probe was in the follicle or just stuck into the skin off to the side. It helps me to turn the current on before the probe is all the way in, that way it stays in the follicle a little better, I think.

I have a few tips. The pros sometimes bend their probes to make a more comfortable angle, so their wrists aren't always bent around. To get a sense of how deep the hairs go, grab one as close to the skin as possible and pull it out, then hold it up next to the probe and use it as a guage.

Love the youtube channel Electrology Now (https://www.youtube.com/channel/UCAxzAWBSrxvWhgLeL4nhS_w) also see this insertion video: https://ballettechglobal.com/ballet-video/

Good luck if you try to build this.