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

[edger477]

Don't worry about power rating of the supply being "too high"... it is just the maximum current the supply is able to provide... if the board is using 3w, then it will not draw more than 300mA.

[diglet]

Based on a couple days of experimenting, the estim feeling between the FOC-Stim and a DIY box is similar, but different in some pretty important ways. The FOC-Stim feels a lot smoother and cleaner. With the DIY box, if I move an electrode 1mm I can get a pretty big change in how it feels. With the FOC-Stim electrode placement is MUCH more forgiving and feels MUCH more consistent. With the FOC-Stim I never get little shocky or burny sensations like I do with the DIY box. I've also noticed you can move around a bit and the FOC-Stim seems to adjust to you. With the DIY box I was always afraid to move because I didn't know if I'd get a shock or loose the stim altogether. There is also something about the way FOC-Stim feels more like it's more directly connected to the nerves and muscles rather than how the DIY box feels like it's just on the skin. The FOC-Stim also feels a lot more separated between the channels. The DIY box can feel a little muddy in terms of separation, but the FOC-Stim never does. The separation is always very clean. This could be because it's pulse driven and the nerves aren't supposed to get as saturated with a pulse driven device, I don't know or really understand, I just know it feels better. I am definitely a convert to the FOC-Stim for playing funscripts.

FOC-Stim is not a pulse-based box, it output analogue waveforms just like stereostim. In fact, the waveform generation algorithm is a direct copy from the pulse-based audio generation in Restim. All the changes you feel are due to the current control and symmetric output stage.

When using sterostim I always had to change the calibration parameters every time to account for slight differences in electrode placement. But with FOC I can use the same settings every time and it feels mostly the same.

[lorada]

Just attempted my first build, and it didn't go well. I printed edger477's case, and it was too small to fit the ESC board. I must have screwed up the scaling somewhere.

I assembled everything via breadboard, and got the firmware built and updated. I was even getting data in teleplot, but I couldn't feel any output at all. I was trying to calibrate with the circle pattern in Restim, but I got no sensation through the electrodes.

Any tips on how to begin troubleshooting?

[edger477]

Just attempted my first build, and it didn't go well. I printed edger477's case, and it was too small to fit the ESC board. I must have screwed up the scaling somewhere.

the board is supposed to be inserted a bit sideways at middle, then snaps forward and down into place

[Pinco]

Hi, just started to work on this, I got the firmware built and updated.
It looks like it connects restim but the LEDs do nothing
Is there a way to check if the board is working without connecting coils, transformers, 12v power supply etc?

[diglet]

Hi, just started to work on this, I got the firmware built and updated.
It looks like it connects restim but the LEDs do nothing
Is there a way to check if the board is working without connecting coils, transformers, 12v power supply etc?

Not really, the software doesn't do much without connecting 12v.

Just attempted my first build, and it didn't go well. I printed edger477's case, and it was too small to fit the ESC board. I must have screwed up the scaling somewhere.

I assembled everything via breadboard, and got the firmware built and updated. I was even getting data in teleplot, but I couldn't feel any output at all. I was trying to calibrate with the circle pattern in Restim, but I got no sensation through the electrodes.

Any tips on how to begin troubleshooting?

Sorry for the delay I missed your comment.

You can try to short all the outputs and observe the values R_neutral/left/right in the console, this is the estimated resistance of the circuit. These should go down to 0.8 or 1.0 when you play a signal.

If you leave all outputs open, the estimated resistance should go to 15 (the maximum).

Make sure the pot isn't set to 0.

[icehash23]

Been getting current limit e-stops quite a bit - intermittently. Sometimes I'll go a whole session without, sometimes it's constant. Pretty similar electrode setups so I don't think that's the problem.

I noticed in teleplot, the right channel resistance (moaner, center) will slowly drop to 0.8 as the model takes effect, and that's the minimum resistance in the config. If I add a bit of series resistance (via my pan pot) then it can delay hitting the current limit for a while but then of course it's a different sensation/calibration.

Is there an easy way to tell if I have one of the boards with the current limit/temperature board design flaw I was reading about over at simplefoc? Edit: more threads here and here. Though we're not getting even close to those currents so that's not likely the issue either.

Could it be PSU-related, like if there's too much noise on the DC line? I will try another power supply, maybe this one is making bad connection. I'd expect a VBUS error if that was the issue, though...

[diglet]

Thanks for the feedback. I've been seeing more people hitting the current limits, I think I made the limits a bit too low for some electrode placement and/or bad boards.

I increased the current limit margin from 0.2A to 0.3A, reduced the minimum resistance from 0.8 to 0.7, and also expanded vbus and temperature limits. Let me know if you encounter more issues.

[lotionBob]

Ordered all the parts and slapped everything together on a breadboard.... works out of the box as advertised, wiggle and move all you want the sensation feels the same. Will have to play around with it because I hope I haven't seen 100% output or I might need guidance on which settings and frequencies to use.

[UFungus]

I finally finished assembling my box. Every step has been completed to the best of my knowledge, but I can't for the life of me, connect it to Restim. I see a message in teleplot saying 'V-BUS too low: 4.74', and after plugging in the 12V, I get 'V_BUS online. V_BUS 12.16 status: 3'. In the FOC-Stim tab, I can see the STM board, "Use teleplot" is ticked but I have no clue what to put in "teleplot prefix" or if I have to put anything in the first place.

I'm not sure if I messed something up when uploading the firmware or if it's something else. The instructions felt pretty vague to me, but to be fair, I don’t know much about electronics or programming...and it’s getting pretty late . I’d really appreciate it if someone could give me a hand with this.

[diglet]

I finally finished assembling my box. Every step has been completed to the best of my knowledge, but I can't for the life of me, connect it to Restim. I see a message in teleplot saying 'V-BUS too low: 4.74', and after plugging in the 12V, I get 'V_BUS online. V_BUS 12.16 status: 3'. In the FOC-Stim tab, I can see the STM board, "Use teleplot" is ticked but I have no clue what to put in "teleplot prefix" or if I have to put anything in the first place.

I'm not sure if I messed something up when uploading the firmware or if it's something else. The instructions felt pretty vague to me, but to be fair, I don’t know much about electronics or programming...and it’s getting pretty late . I’d really appreciate it if someone could give me a hand with this.

Teleplot prefix is useful if you have multiple boxes, leave it empty.

It sounds like you're connecting to the serial port in teleplot. Don't do that. Restim needs to connect to the serial port. Do you have FOC-stim selected in the device setup in Restim?

[UFungus]

It sounds like you're connecting to the serial port in teleplot. Don't do that. Restim needs to connect to the serial port.

That was enough for me to find the problem I was trying to connect to teleplot before connecting to Restim. Everything seems to be working now. Only thing left to do is to make new electrode leads and test things out. Thank you!

[nausea21]

Build mine, and works like a charm. Thank you diglet for the instructions and the great idea!

Just one question: Since many Estim-/Restim-Videos contain instructions like "common to head", "left to balls", "right to prostate" - on the board i have the outputs out1, out2 and out3 - is it possible to tell which is common, left or right?

[diglet]

The center output on the board is the neutral/common, and the one closest to the onboard potentiometer is the right.

[dr_bearcat]

3x capacitor

FG18X5R1E106MRT06 mouser
Many other options available. Must be ceramic, look for 4.7µH-10µH (10µH preferred), >25v

I guess here should be µF instead of µH ?