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

[bobhill]

What he meant was that the circuit in the picture above replaces also the transformer. The component on the right side is a transformer. If you look at the high-pass of my schematic you can see that I left this part out in the high-pass block because it comes after the high-pass.

Oh, I get it, thanks.

EDIT: I do actually get it now and the rest of my prior message was wrong.

[mantrid]

In terms of winding ratio if it doesnt work we just need to resolder the 0.6W connection to 1W or 2W instead and try if that provides the desired power.

The power which is transferred through the transformer depends inductive component of the input impedance which is approximately equal to output impedance divided by winding ratio in square. Output impedance is resistance between electrodes plus (DC) resistance of the output winding.

In order to optimally tailor the components (output power also depends on series resistor ...), the output impedance and the required output power would have to be known. But I never measured this numbers. Maybe I will do that in future.

Spoiler: show

Due to electrochemical effects there is always a voltage between the electrodes. That's why both values have to be measured in action with AC. Rough estimation for the output power is 1W

I tried out the Reichelt transformer with winding ratio 1:10 and the Digikey transformer with winding ratio 1:25 (see the links in the earlier posts for part numbers). The only difference I could detect is that the Digikey transformer was weaker which may also be a result of the high DC resistance of the output winding.

So at least the range of 1:10 to 1:25 is usable.

[alexfayer]

If I calculated correctly the transformer lolol2 mentioned from Conrad has a winding ratio of 1:61 in the configuration I posted(4ohm and 0.625W) and 1:42 with 4ohm and 1.25W. To achieve a 1:15 ratio we would need to select 8ohm and 5W.
Datasheet of this transformer:

datenblatt-516104-elma-tt-iz-1892-impedanz-4-16-primaerspannung-100-v-inhalt-1-st.pdf

(94.82 KiB) Downloaded 488 times

Is this correct?

Looking at the 1:10 transformer you posted from Reichelt I wish I never ordered the one from Conrad.

Thanks for the help so far mantrid. When I understand all of this I can create a noob guide on how to build a safe device for everyone. Then more people will be able to build and enjoy unfiltered estim devices.

[alexfayer]

@ZeeWW The way I have it planned the clips will be for no use because I will connect the components directly with one single wire. When you connect components you cannot use clips so over all this will make it simpler.
I don't think I explained that well but it will make sense when you see the final result.

Do not just bend wire together so there is a connection. It could come loose or have a weak connection and when that happens you don't want any electrodes on your body. The most important thing will always be safety.

[mantrid]

If I calculated correctly the transformer lolol2 mentioned from Conrad has a winding ratio of 1:61 in the configuration I posted(4ohm and 0.625W) and 1:42 with 4ohm and 1.25W. To achieve a 1:15 ratio we would need to select 8ohm and 5W.
Datasheet of this transformer:
datenblatt-516104-elma-tt-iz-1892-impedanz-4-16-primaerspannung-100-v-inhalt-1-st.pdf


Is this correct?

Correct. You get this values if you use the winding numbers in line 4.3 of datasheet. Winding assignment is guessed correctly (datasheet keeps that in secret), because the ratios (r) i get from the power (P) and impedance (X_s) ratings neglecting the loss are very similar: 63, 45 and 16 (formula is r=100V/sqrt(X_s*P) )

According to the ratings the transformer is quite efficient at a frequency which is kept in secret too. But from the user comments on the products page one learns, that this transformer works well for audio frequencies ...

Looking at the 1:10 transformer you posted from Reichelt I wish I never ordered the one from Conrad.

I think the transformer from Conrad isn't bad. It's just a little bit unhandy and the documentation is obscure.

@alexfayer can I make a request that when you do write a noob guide, and that would be awesome, can you please limit the amount of soldering used? I have taken on to using the Wago 221 clips as Lolo2 uses and the are fantastic, easy to use and reduces soldering.

The components I use cannot be connected safely with such clips and you probably don't want to repair it during Esim session.

Another option are crimp contacts. But soldering is IMHO easier.

For private purposes, use the good old SN60PB40 solder with flux core. Unless you eat it all characteristics are better than that of typical lead free solder.

It should also be mentioned that stainless steel can be soldered easily with the right flux (DIY electrodes).

[Dust]

Maybe I will finally try to build a device for myself with this guide. It is especially convenient that all the parts are from a german retailer :). Altough the longer I wait, the more I get confused by the new posts....

Coming from a 2B: is there any advantage to use the suggested input / output ports over a simple AUX input / output? Since all my electrodes and PC use AUX I would have to use adapters anyway...

[alexfayer]

I don't think there is much difference. That's why I bought a 3.5mm port. Also it is possible to put both connectors into the housing. So you can still switch between them if wanted.
My orders should arrive on the weekend so I can finally start building it, test it and write an how to build guide.

[BamaSwitch]

Hey guys,

I'm a newbie but love stimming so far. I have a 2B but its limitations are frustrating. It did help me learn that I really wanted to try a more versatile unit.

I can do basic wiring and soldering but don't know anything about electronics. Can someone help me source the correct items from a US location? I'm having trouble making sure what I find will actually work as a substitute.

I keep trying to reactivate my smartstim account but can never seem to get registered properly. Anyone with contacts there would be helpful too. :)

[cl13a]

Hey guys,

I'm a newbie but love stimming so far. I have a 2B but its limitations are frustrating. It did help me learn that I really wanted to try a more versatile unit.

I can do basic wiring and soldering but don't know anything about electronics. Can someone help me source the correct items from a US location? I'm having trouble making sure what I find will actually work as a substitute.

I keep trying to reactivate my smartstim account but can never seem to get registered properly. Anyone with contacts there would be helpful too. :)

viewtopic.php?f=12&t=23322&p=288189#p288189
I made a build list based on the MidiStim from smartstim, all the parts there can be shipped to the US (eBay listings). And the Parts Express version is $43.12 (it should work but I will say that as of this post nobody has tested those components before).

[BamaSwitch]

[/quote]
viewtopic.php?f=12&t=23322&p=288189#p288189
I made a build list based on the MidiStim from smartstim, all the parts there can be shipped to the US (eBay listings). And the Parts Express version is $43.12 (it should work but I will say that as of this post nobody has tested those components before).
[/quote]

Thanks! I posted a couple of questions in the thread you linked.

[mantrid]

I can do basic wiring and soldering but don't know anything about electronics. Can someone help me source the correct items from a US location? I'm having trouble making sure what I find will actually work as a substitute.

I already posted Digikey part numbers for the output circuit in the past:

• Transformer: 237-1146-ND
• Capacitor: 493-17272-ND
• TVS-Diode: 1.5KE15CALFCT-ND (plenty alternatives, search for 1.5KE15CA)
• Resistor 10Ohm/2W: A138253CT-ND (plenty alternatives)
• Resistor 5.1Ohm/2W: A138346CT-ND (plenty alternatives)
• Banana jacks and plugs
• Heat shrink tubings for isolation

Circuit diagram and pictures of the output circuit are there, review of the Digikey variant is there (if it is to weak, this can be compensated using a lower resistor value).

Also see the other posts and links in this thread.

Readily boxed amplifiers (with balance knob) can be purchased from Ebay or Amazon (search terms: amplifer MA-180)

P.S.: The circuit in the other thread is IMHO unsafe. AFAIR this thread is the 4th thread here on Milovana in which I wrote about that topic and I do not plan to discuss it a 5th time in parallel.

[bobhill]

P.S.: The circuit in the other thread is IMHO unsafe. AFAIR this thread is the 4th thread here on Milovana in which I wrote about that topic and I do not plan to discuss it a 5th time in parallel.

Yes - it's very confusing to have the multiple threads running. I saw that @alexfayer had completed a build of the unit in this thread and was very pleased with the result. I'm hoping that he completes the tutorial of his build when he has time (in this thread).

[Dust]

I finally ordered all the parts over the week and wanted to build it all together but there are two parts I am not sure about.
First: How am I supposed to attach the heat sink to the amp? Just put it on the back with the clamp (but that seems to need a lot of force and I am afraid to break something)? Or should I put some thermal paste somewhere?

The second thing is more important I guess. I can't seem to figur out what connector is + and - on the AC port. I tried looking through the documentation of the product but that did not help to much. From the pictures I would guess that the one in the middle is - and the one on the left (with middle upwards facing) is +. Is this correct?

I already drilled all the holes in my case. Only the soldering is left to do :) (and could end in a complete disaster)

Btw is there a recommended test sequence for those DIY builds? I unfortunately don't have a multimeter or something similar but I can imagine that there are safer first things to do than attaching it right away to the genitals.

[lolol2]

1) Yes it's just clamped on the amp part, maybe stretch the clamp a bit, but it need to sit tight on.
I added some thermal paste but I guess this isn't necessary.

2) Please get a multimeter before you start.
Then plug in the power supply and just measure the voltage with the multimeter, you will only have one scenario where it will be +12V, when you swap the connectors you will get -12V. The third connector will not have any voltage as long the power supply is plugged in, this pin is designed when you have a setup with a power supply + an internal battery.

[Dust]

Then I guess it will take a bit more time until I finish the build^^.