FOC-Stim: a new approach to DIY stim hardware.

[rob1112]

diglet releases all code and hardware designs as open source, and you talk about gatekeeping? It's a shame that you don't understand how to use this stuff, but this is a hobbyist environment, and diglet is having dialog about his creations and sharing that openly with the community. To compare this to the smartstim guy is ridiculous.

It might feel the same to you, because you feel excluded, but it would be the same if you tried to understand anything that you don't have knowledge of. I'm afraid it is not gatekeeping, but ignorance that you are frustrated with.

[boundupone]

I was on SmartStim back in the day. Their level of gatekeeping was a whole different thing. They wouldn't even allow links to mp3's or other sites because of "copyright concerns".

Yeah I was there too... Mentioning that site in this context made me smile for real because that strawman is so ridiculous.

I had run in's with the owner too. made lots of threats and I have never had anyone get so aggressive and unreasonable so quick. of course didn't want him to die, but he massively held back stim. the resource of the site is missed, but we are in a much better place now.

[lorada]

Would anyone be willing to post a step-step build of their FOC unit? It would be great if they could.

Thanks.

I second that. This tech sounds absolutely fantastic. I understand that this might just not be intended to be built by someone like me and if so, carry on gents, but I honestly don't feel like the layman has enough information to work with given the risks involved with these kinds of devices. The BOMs I've seen are a little confusing and while diagrams mean everything to most people in this thread, I have no clue how to actually put one of these together only from looking at that or a few pictures of the finished product.

I put few pics of how I made mine (along with cad files for 3d printed case and bom of all that I used to make them) to the fork of the repo https://github.com/edger477/FOC-Stim/tree/master/case

I looked at your repo. Nice, efficient, compact. But what is that big capacitor in the most recent picture? You mention it in the BOM, but I'm confused as to what it's for, and exactly how it's wired in.

[edger477]

But what is that big capacitor

I added that since I powered it with usb-c pd trigger, and did not want to risk having session interrupted if my powerbank doesn't have stable enough voltage. This is just plain electrolytic capacitor wired to 12v input, - to -, + to +

[lorada]

But what is that big capacitor

I added that since I powered it with usb-c pd trigger, and did not want to risk having session interrupted if my powerbank doesn't have stable enough voltage. This is just plain electrolytic capacitor wired to 12v input, - to -, + to +

Thanks for explaining. So, no benefit adding that to an AC powered build.

[lorada]

But what is that big capacitor

I added that since I powered it with usb-c pd trigger, and did not want to risk having session interrupted if my powerbank doesn't have stable enough voltage. This is just plain electrolytic capacitor wired to 12v input, - to -, + to +

Thanks for explaining. So, no benefit adding that to an AC powered build.

Before I submit my parts order, would you mind telling me more about your output? I am used to my stereostim box, which has four banana plug outputs.

Thanks.

[edger477]

Before I submit my parts order, would you mind telling me more about your output? I am used to my stereostim box, which has four banana plug outputs.

Thanks.

Mine too, but this box is miniature so I went for 3.5 jack (since it has 3 terminals anyway). Keep in mind to not plug/unplug cables while it is running (to avoid shorting outputs), I just made dedicated cables from 3.5 to connect my existing electrodes (using 2mm banana plugs)

[lorada]

Before I submit my parts order, would you mind telling me more about your output? I am used to my stereostim box, which has four banana plug outputs.

Thanks.

Mine too, but this box is miniature so I went for 3.5 jack (since it has 3 terminals anyway). Keep in mind to not plug/unplug cables while it is running (to avoid shorting outputs), I just made dedicated cables from 3.5 to connect my existing electrodes (using 2mm banana plugs)

I like that idea. Can you describe how you made your cables?

[edger477]

I like that idea. Can you describe how you made your cables?

Yes.

I used these plugs: https://www.amazon.de/-/en/gp/product/B08LYKZGT6/

I stripped one wire from this 4-wire cable, used about 30cm (red common, green left, blue right for no particular reason except to have several that are same so I have spares), screwed them to the terminals of plugs above: https://www.amazon.de/-/en/gp/product/B01HY42R2S/

On the other side of these cables I soldered banana plugs.

I use 2mm banana plugs (like these https://www.amazon.de/-/en/gp/product/B07GNQZ6Y1/ and these https://www.amazon.de/Colours-Gold-Plat ... B07NL7DXV5) that fit well into any sticky pads and I use female version on my diy electrodes so they are all consistent. I have 2mm female to 4mm male banana plug adapter cables to connect things like e-stim systems electrodes that have 4mm plugs. Previously I used 4mm banana for all but these were kinda clumsy, I switched to 2mm and thinner wires because they are less distracting for me.

And, since my cables are about 30cm, I got these extensions to box, you can have them in different colors if you use multiple boxes https://www.amazon.de/-/en/gp/product/B0CFZX77ZM

[darthjj]

I'm primarily a Linux user and a full time Linux admin, but I bought a used $200 Dell Precision Windows PC off Ebay for estim because I don't feel like fighting it and not everything I want to play with has a Linux version. I recommend taking the path of least resistance in things like this. Do yourself a favor and get a Windows PC if you don't want to mess with your work Mac.

MultiFunPlayer is the only e-stim related software that I wanted to use, but did not work on Linux. Well, and OpenFunscripter ran great on Fedora 39 but for some reason is borked on Fedora 41, both with Wayland and Xorg, but that is probably fixable. Never felt the need to dual boot to Win10, which I could in case of emergency.

[dymuffshthers]

Hi Digilet

big fan of the restim. I appreciate your work very much.

could you please tell me generic specs for the inductor and transformer.

e.g. 100Uh , 10A / Pri/Sec ratio - 1:15

the part of the world im from has plenty parts but not the brands you had named.


could you see if these are suitable at all

https://scionelectronics.com/product/20 ... -inductor/
or
https://scionelectronics.com/product/rl ... -original/

then
https://scionelectronics.com/product/12 ... e_vignette
or
https://scionelectronics.com/product/9v ... mer-local/



Cheers

40A is the maximum the hardware can deliver given sufficient cooling and very low resistance motor. I believe ST tested this hardware to 25A with forced air cooling, and the mosfets are rated for 160A pulsed. You will not see such high of a current in this application due to the internal resistance of the inductors and transformers.

Yesterday, I tested what would happen in the event of a software failure that would send the maximum voltage (12v) to the transformers. Over my test resistors (2 x 220ohm) which I placed on the output side of the box, I measured 180mA over 600µs after which the transformers saturated. This will deliver a nasty shock, for reference the strongest signal I tested in play is about 100mA over 300us. The large transformers used in most stereo units can deliver much larger shocks.


I don't want to sound too condescending wrt safety, but I just grabbed transformers some transformers off the shelf I had already tested to be adequate in size, ordered a kit of inductors/capacitors and started programming. The galvanic isolation the transformers offer made me comfortable enough to try it.

If you want additional analog protection, you can add a TVS diode to the input for additional protection against a failing power supply. Filter capacitors to block high or low frequencies are not needed in my opinion. I don't know what other hardware protections you can add, maybe a fuse on the input? Smaller transformers?


I don't know why combining foc + stereostim would behave differently than 2x stereostim or 2x foc. It may have something to do with the lack of a shared clock, but that should also be a problem with 2x foc since the pulse timing in foc is not super accurate. The audio algorithm in Restim has sample-accurate timings.

Can you use just 2 of the outputs on a FOC-stim? Not sure what kind of electrode configuration I could use with 2x triphase

The hardware supports it, but the code requires all 3 outputs to be connected to the same body. At some point, I will add some code to detect if one of the wires is broken/loose.

The capacitor specs are not critical. Any ceramic cap >12v and >=4.7uf, <= 20uf will work.

[diglet]

Are you sure mouser doesn't ship there?

These are the critical specs for the inductor:
Saturation current >1A, >1.5A if you can find it.
Inductance 200-470µH, 220µH preferred.
Best if you can find one that has a datasheet that lists a flat inductance-current curve.
Lower resistance is better, most options are in the 0.2 - 1ohm range which are all fine.
Most options with these specs are about 12.5mm * 10mm. On the website you linked I can only find 6*8mm which seems unlikely to have saturation current anywhere near 1A.

Critical specs for the transformer:
I think you need an audio transformer, not a 50hz line transformer.
Winding ratio around 1:10, higher winding ratio's are also fine.
Low secondary resistance (<1 ohm).
Don't overdo it on the size of the transformer. The specified transformer is only 1 inch wide, 25 grams. It doesn't pack enough punch to kill you even if you do something really stupid.

[bobsynol]

First of all thank you for the creation of the wonderful piece of hard- and software.

I also built a FOC stim and today I had some time to test it. If I turn the potentiometer to maximum and the funscript outputs 90-100%, the signal feels a bit weak? Kind of like if I have my stereo stim at 25% and use the same funscript with restim.

This is now related to restim i think, but has there been a change in how restim processes volume funscripts? In the configuration I had to change it from min 0 and max 1 to min 0 and max 10 to get 0-100% volume, otherwise it was at 0-10%.

[edger477]

First of all thank you for the creation of the wonderful piece of hard- and software.

I also built a FOC stim and today I had some time to test it. If I turn the potentiometer to maximum and the funscript outputs 90-100%, the signal feels a bit weak? Kind of like if I have my stereo stim at 25% and use the same funscript with restim.

This is now related to restim i think, but has there been a change in how restim processes volume funscripts? In the configuration I had to change it from min 0 and max 1 to min 0 and max 10 to get 0-100% volume, otherwise it was at 0-10%.

Have you found that new default for volume in volume tab is 10%?

[JakofClubs]

MultiFunPlayer is the only e-stim related software that I wanted to use, but did not work on Linux. Well, and OpenFunscripter ran great on Fedora 39 but for some reason is borked on Fedora 41, both with Wayland and Xorg, but that is probably fixable. Never felt the need to dual boot to Win10, which I could in case of emergency.

What I would like is to get my estim station running on a Raspberry Pi. I have Onwrikbaar's Dweeb running on a Libre Computer "Le Potato" RPi clone. Then that could be made into an image for a RPi and people who didn't want to mess with software could just burn that image on to a microSD card.

Self-awareness just kicked in. I just realized that I proposed making yet another Linux distro. Just what the world needs....
Maybe just ignore me until I'd had more coffee.