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

[strommann]

Hi phoopha,
I followed the original plan and no, no changes were made;-). I ordered all parts at Conrads in Germany simply following lolol2s links. After I had problems with the stiffness and diameter of the cable from the list I changed to a slightly thinner and more flexible one. I found it quite useful to have some of the little Wago clips with three and five openings you can see in lolos2s pictures. In childhood my father, an electrical engineer, got deeply disappointed when he tried to explain Ohms law to me. So I have little to no knowledge in this field and the ongoing discussion further down the thread at some point was too technical for me. As you might have noticed already English is not my mother tongue. This combined with the technical jargon of some posts brought me to further sticking with lolols plan. Yesterday I used the box for several hours and yes, it feels great. imho it feels definetely way better than a 2B and in terms of signal even better than the ET312 although it lacks of course any builtin modes and a ramp function. I still haven't closed the box. Maybe it would be more save to use a small cooling fan with the box although I didn't notice any serious heating so far. After turning the knobs around aprox a third I reach my pain limit.
hope that helps, strommann

[Fantasiawizard]

Hi everybody

I'm building my stim box with the instructions in this thread but ran into confusion and need a little help.

I planned to use these https://secure.reichelt.com/fi/en/nf-tr ... tml?&nbc=1Reichelt transformers mentioned earlier, but I don't know which pins to connect to amp side and which to trodes.

Here's the specs for the transformers https://cdn-reichelt.de/documents/daten ... 00/NFU.pdf and https://cdn-reichelt.de/documents/daten ... 1-500A.pdf

And which resistors should be used with these, before or after transformer?

Thanks

[JakofClubs]

Fantasiawizard, you might want to ask mantrid, as I believe those are the transformers he recommended. Generally, you are trying to boost the voltage (step-up) so you hook them up the opposite way from a typical AC mains to lower voltage (step-down).

The resistors should go between the amplifier and the transformer, as in the image here: viewtopic.php?f=12&t=23322

[Fantasiawizard]

Thanks JacofClubs

Stepping up or down with the transformers was the information what I was looking for.

I tried the Reichelt transformers both ways in my test set up but got nothing out of the electrodes. I have small LT700 transformers from my first Stimbox diy build and I tested the set up with those and know that everything else works fine.

I have better transformers coming from Reichelt. I think the ones I tried first are not suitable for this. If someone had success with those I'm happy be proven wrong.

I built the high pass resistors like mantrid suggested. Seems to work ok for me.


The actual box is in testing mode as you can well see

[mantrid]

I planned to use these https://secure.reichelt.com/fi/en/nf-tr ... tml?&nbc=1Reichelt transformers mentioned earlier, but I don't know which pins to connect to amp side and which to trodes.

The winding with the smaller DC resistance is connected to the amplifier. I always measure it, but on the Reichelt transformer the two pins on the labelled side are connected to amp.

And which resistors should be used with these, before or after transformer?

According to the spreadsheet I posted here in the past they should not be to large, otherwise the signal is to weak and clipping occurs (U_A should be less than about 7V at desired load (R_L and I_S)).

With 1 or 2 Ohm resisters (0.6W resistors are sufficient) or even no resistor you should have enough power. Capacitor should be 100µF in that case.

[Fantasiawizard]

I planned to use these https://secure.reichelt.com/fi/en/nf-tr ... tml?&nbc=1Reichelt transformers mentioned earlier, but I don't know which pins to connect to amp side and which to trodes.

The winding with the smaller DC resistance is connected to the amplifier. I always measure it, but on the Reichelt transformer the two pins on the labelled side are connected to amp.

I tried these transformers without resistors and got nothing out of electrodes. In my opinion they just don't work for this. Better to stick with the ones already known to be suitable.

[NEGEV]

I think the plans are really nice but the last time it did anything with electricity was in the 10th grade. So I dont know the meaning of ohm, transistor.. Is there some tutorial series or something similar you would recommend to beginn learning the basics? So that a beginner would be able to learn the basiscs and after that could feel safe and confident building the device because he actually knows what he is doing (understands the parts and knows how to read the schematics).

[GH-Hoss]

I read through this entire thread twice. After seeing strommann’s comment about how it compared to his 2B and 312, I decided should have a go. I’m pretty good with DIY and even if I’m not great at soldering it seemed doable. I started checking the specs on the components at Conrad in order to find similar products in the US. This is where I gave up because after a couple hours searching Digi-Key it became clear that I didn’t know enough about electronics to ensure I would be ordering the equivalent parts. Conrad doesn’t ship to the US unfortunately.

If anyone in the US has managed to source parts for a successful build, could you share your shopping list possibly with links? Thanks!

[JakofClubs]

If anyone in the US has managed to source parts for a successful build, could you share your shopping list possibly with links? Thanks!

This thread has a simple build and links to US parts.

viewtopic.php?f=12&t=23322

[GH-Hoss]

If anyone in the US has managed to source parts for a successful build, could you share your shopping list possibly with links? Thanks!

This thread has a simple build and links to US parts.

viewtopic.php?f=12&t=23322

Thanks. I've been looking at that build also. I'll check it out again and see how it goes.

[19Hellothere83]

I just wanted to show off my device - build it identical to the schematics in the first post. Had some problems fitting everything in the box ... for now only tested it on my leg ... it feels completly different than all other commercal devices i own.
I am somehow scared of connecting it to my junk
Will try it with a tease next week probably

[19Hellothere83]

I am now trying to work on some addition to the box. What I am missing is an information of the input signal.
As I connect it to my devices via jack I cannot hear if there is any sound going in ... I can only eventually feel it.
If there is a long pause on the audio file I will feel nothing and think that the signal may be to low, turn the potentiometer up more and then the signal starts up ... and that hurts.

I am planning to connect a bargraph to each channel - left and right - of the pre-amplifier - I have an old circuit I used on my old guitar amplifier using an LM3915. This way I can keep the potentiometer down and see if there is any input signal on the preamplifier.

Attached an example of bargraph

Let me know if anybody has done this before and if this is a good idea. Im oper to suggestions.

[Rooktus]

I am not sure how would bargraph help you. I think you will see bargraph changing and pain almost at the same time. What would help you is some kind of current limiting circuit. With this circuit you can limit max current, so you cant go over your pain threshold no matter the gain.

PS. I think design is way off. You have very big components designed for way too high power. For example resistors, transformators and amplifier are made for 20+ W.

[19Hellothere83]

I am not sure how would bargraph help you. I think you will see bargraph changing and pain almost at the same time. What would help you is some kind of current limiting circuit. With this circuit you can limit max current, so you cant go over your pain threshold no matter the gain.

PS. I think design is way off. You have very big components designed for way too high power. For example resistors, transformators and amplifier are made for 20+ W.

The picture is for reference.
The bargraph is connected to the input signal wich is not powerful.
It helps as i can see if there is an inputsinal before turning up the Potentiometer and actually feeling pain. Also if i set the bargraph to the right level i know approximateoy the input powerofthe signal.

[19Hellothere83]

I am not sure how would bargraph help you. I think you will see bargraph changing and pain almost at the same time. What would help you is some kind of current limiting circuit. With this circuit you can limit max current, so you cant go over your pain threshold no matter the gain.

PS. I think design is way off. You have very big components designed for way too high power. For example resistors, transformators and amplifier are made for 20+ W.

However I also were thingking of a way to set a max output power ... Something like a varistor peak limiter or a z- diode ... But that would be a fixed limitation ... Nice would be something adjustable ....