[Tutorial] Building your own DIY E-Stim Stereo Device

[Stéropès]

A forum is not the best place for such a knowledge collection. After a while these information are lost because its almost impossible to dig them out. That's also the reason why the same topics are discussed over and over again.

The right place would be a Wiki. Unfortunately neither Milovana or nor similar sites (e.g. EroScripts or SexScripts) have one.

In fact, I had the idea to capitalize the result in a wiki and or a git.
To have on one side a design with schematics, components sizing and reasons for these choices and on the other side a guide with several components assortments according to suppliers / countries.

The topic is rather to discuss the basics, to have a place to exchange ideas without everyone having to create another account somewhere else and have to take over a new tool. I thought it was more practical to start from scratch.

Then, the evolution proposals and the versioning of the designs can be done on the wiki / git.

In any case, do not do as for the Smartsim Tronics where the forum has disappeared and we just have pdf that hangs out on the web which we do not know the version, the reason for the design choices and which does not evolve anymore.

I don't see purpose a fuse would play, because when you short these boxes for reasonable amount of time (i.e. <30 sec) there should be no damage done to box, so fuse would not prevent any damage, but it would end your session when you have to replace it.

This was just an example because the issue was raised earlier in the thread.
I'm not saying it's relevant or that it should be discussed here.

Anyway, I don't want to make this topic drift off topic.
I will create a new one to explain in more detail how I see things and what I already have at hand. If people are interested in it, that's fine, if not, it's not a big deal.

[Electro]

The purpose of the parallel resistor is to make the device act more like a current controlled device, as opposed to a voltage controlled device. I have not tested this but reportedly this improves the sensations.

No, that's the purpose of the series resistor. The parallel resistor was originally implemented for amplifiers that couldn't handle an open circuit, this is deprecated for amplifiers with the tpa3116/tpa3116d2 amp chips because they don't need it and it's the reason it has no longer been recommended for quite some time.

[f12345u]

I'm in progress building my box with the TPA3116D2 Dual Channel and the 70v transformer from Parts-Express. I had it all together and was doing continuity checks. I'd been doing segmented checks while building, all good. Well, I was just checking the power input side of the device and had a short from vcc to ground. Disconnected all wires from the board and it still had a short from the VCC to GND pins in the screw post. It would slowly ramp from open to 2-3-4ohms then reset. No clue what's wrong with the board I got. I noticed the heatsink was a bit crooked, I figure the chip under it is the short because the rest of the board/solder joints look clean. Just ordered a new board instead of trying to mess with it.

With all that said, I kind of just jumped into the deep end with Estim and have no clue what I'm doing besides basic safety stuff. I'd like to understand the considerations especially when dealing with a diy device. I found StimAddicts massive google drive for estim stuff. How would I play a video/estim file I have found and downloaded on milovana? I use script player for my other toys, is that the recommended player for estim?

I know all this info is spread throughout this thread, but honestly, re-reading it multiple times to find what I'm looking for has been quite a pain.
If someone would be so kind to leave a bullet point list of things/order of operations for checking and testing the unit before safely using it, I would appreciate it greatly. Obviously continuity checking, then plugging in the power supply and hopefully getting a blue led lit up, then what? Do I need to adjust the onboard(on the TPA3116D2) pots? What do I set the max output to when each channel is fully turned up? The schematic I am following only has 1 pot per channel, no master volume. Do I need to create a dummy load. Is this all of the safety checks I need to do before using the device?

[f12345u]

The purpose of the parallel resistor is to make the device act more like a current controlled device, as opposed to a voltage controlled device. I have not tested this but reportedly this improves the sensations.

No, that's the purpose of the series resistor. The parallel resistor was originally implemented for amplifiers that couldn't handle an open circuit, this is deprecated for amplifiers with the tpa3116/tpa3116d2 amp chips because they don't need it and it's the reason it has no longer been recommended for quite some time.

Am I reading correctly that the 22ohm paralell resistor in some of these wiring diagrams within the thread is redundant if I am using a tpa3116 amp board?

[edger477]

Am I reading correctly that the 22ohm paralell resistor in some of these wiring diagrams within the thread is redundant if I am using a tpa3116 amp board?

Yes. With majotiry of transformers it just wastes electricity since app works fine without it.

I use script player for my other toys, is that the recommended player for estim?

Yes, configure estim audio device in settings, and it will automatically load mp3 file with same name as current video file and play it in sync to that device.

Is this all of the safety checks I need to do before using the device?

I had led indicators of output on my box, but you could also start with low volume, i.e. pots on amp at 25% and start playing sound from pc at low volume too (depending on your sound card output impedance matching/voltage, high volume might overload/clip at the amplifier input opamp), and measure output of one of channels with AC voltmeter. They are designed for 60Hz so it might show less volts when you play 600Hz signal, but you should see few volts. Then you can try connecting 2 sticky pads to i.e. your upper leg and test if output feels pleasurable.

[f12345u]

I have an issue somewhere I think. Box powers on with new board, but the left channel voltage goes up with the right Pot and the left pot isnt doing anything on either channel. I think my pots are wired wrong.

[f12345u]

Okay had 2 issues, my pots were swapped sides, and my 3DPT switch was bad.

Playing a 600Hz sine wave file, with laptop output set to 25 and youtube volume max, the board pots left as default.
Reading voltage on the right channel with the pot knob set to max I get 2.3Vac and on the left channel I get... 110volts ac. Can I please get exact expected results, voltage/current, both before the transformers (board out and post transformer out), safety limits, and more information on how to test this box, explained simply.

[f12345u]

So I used https://www.szynalski.com/tone-generator/ , 600hz, max volume on site, laptop output set to 25, adjusted the onboard pots till both channels read evenly at the output terminals on the board, which was 10.25 volts AC. I turned my 10k pots to max, put on triphase mode to rule out grounding issues, the right channel hot out from the 70v-0.62watt reads 5.63 consistent AC volts.
The left channel hot out from the 70v-0.62watt reads 241.6 consistent AC volts.

I double checked, both transformers are wired the exact same way according to https://i.imgur.com/wl1Riuu.png
I can only assume one of the transformers is damaged.

[edger477]

You could test transformers by swapping their connection to other channels.

It could also be that your 3.5mm cable is not making a good contact (often happens it starts to produce other channel when you move it).

The voltage of 240v is a bit wild (I saw 150 from my transformers) but this voltage goes waaay down once there is any load connected. If you have 1k Ohm resistor you could connect it to outputs to have realistic readout. Body resistance will be in range 600-1000 Ohms when you connect electrodes.

I don't understand why you put on triphase mode? Please show how you wired it. Can you make sure the right transformer has no proper output also when nothing is connected to it?

Since you are getting some output, it is very probable you wired it wrong, i.e. used wrong black wire or did not connect input properly.

[f12345u]

I've got it all apart now, can't find a single issue. Can't easily take a picture now but it's 100% wired exactly like this diagram, both are. It's no longer in triphase mode. https://i.imgur.com/wl1Riuu.png

one transformer reads 5ish volts, the other 230 volts. I do have a true RMS meter. I don't have anything except an led to pull any kind of load. I can try that.

[f12345u]

It lit the led and dropped it down to 38volts, but I shut if off before it burnt it out (smelled bad).
Interestingly the 5.4 volts from the other channel didnt light it.
I have swapped around the transformer+resistor to the opposite sides of the amp board, and the same set stay at 220+volts. What's weird is that the 3.9ohm resistor on the BAD transformer doesn't get hot at all, while the one on the other (5ish volt one) gets fucking crazy hot.

It's not the board or the cable. I tested all the leads for the transformer that is always at 220+ volts and they're all similarly very very high compared to the other transformer. I went ahead and bought 2 new transformers.

What is a normal ac voltage when doing this test without a load?

[f12345u]

I can also hear music that I play coming from my amp board on the 330 labeled components, very static like but distinctly the music I'm playing. Do I have another dead board?

[edger477]

330 are probably chokes and you hear coil whine. Does not mean the board is bad.

The fact that resistor doesn't get hot on one transformer means it does not pull any current. Check which wires is connected to, maybe there are 2 black wires and you connected wrong one.

Also if your resistors heat too much, you could try using 8Ohm taps on the amp side. If your bad transformer is on 4 now, check 8 Ohms, maybe that one is fine. You should measure resistance on both transformers inputs and compare.

[f12345u]

So I went out and bought 2 new transformers and wired them up. They're the Speco 70v transformers from the other diy device thread. I only have 1 channel hooked up right now, read 305volts. So like you said, put a 1k ohm resistor across the 0.25W and C pin and read out the voltage, was like 6.2 so I thought fuck it lets try it. Turned it all the way down with a 600hz sine wave playing at max volume, put 2 conductive rubber tube electrodes on my left thigh like an inch apart, slowly ramped the volume with the pot and instantly had the worst shock I've ever had. That shit woke me right tf up.

So now I'm lost. I'm 100% positive I had a bad transformer before, and now I think my board isn't good for this. This is the only thing in common with the last setup. I completely redid all the wiring and changed the pots etc.

This is the board. https://www.amazon.com/dp/B07KWZ9RQY?ps ... ct_details
The first picture is wrong, the one I have is the second picture with the screws in the heat sink.
Maybe it's the tl074 Op Amp. There's a guy in the reviews who mentions removing it, which I could do if I just new how to bypass it.

I can turn the onboard pot to just a sliver open and get it to max out at 8-10volts, but I think there's something wrong with my setup and I don't feel safe using it.

I'm confused why it wouldn't work though. It's outputting 11volts to the audio outputs on the board.

[diglet]

I'm confused how you can get a shock when slowly increasing the volume.

Are you sure the pots are wired correctly? i.e. when the pots turn, the volume at the output terminals increases slowly (L/R channel independently, no wiggling solder joints).

Are you sure there are no loose contacts before/after the transformer? Other wires from the transformer aren't touching?

Try a different audio cable or audio source (try a battery powered device, like your smartphone)

I have almost the same board (with screws, slightly different caps) from aliexpress and have no issues. Even ordered more boards to make a 4-channel box.