Just to see how easily it could be done, I built a couple of tDCS units for about $30 each using common parts. The meters were purchased from EBay for about $7 each and all the remaining components came from a local Radio Shack, including the case, voltage regulator, resistors, etc. The tDCS units feature a potentiometer to make it possible to adjust current for treatment specifics or pad variations.
(Two tDCS units built in about 3 hours for well less than $100)
(This view show the small circuit board with its voltage regulator, fixed resistor, 5k potentiometer, etc.)
I used the circuit that appears at http://brmlab.cz/project/brain_hacking/tdcs and other tDCS related web sites. I changed the circuit by eliminating the LED indicator light and switch and adding a 3 mA meter and variable resistor. I found that a fixed 150 Ohm resistor in series with a 5 k Ohm potentiometer seems to work best.
CAUTION: There is concern on the web that the LM317 regulator used in the brmlab.cz design may not be “stable” at low current levels. Some have suggested that the LM334 is a better, safer, regulator choice. The “GoFlow” design uses the LM334. UPDATE: I have updated my tDCS devices to use the LM334 design. See one of my later posts or http://www.flowstateengaded.com for examples.
(From brmlab.cz)
Before attempting to build your own tDCS device, please read, read, read, about tDCS and look at my web site and others for safety precautions.
Question or comment? Email me at brent@speakwisdom.com
SpeakWisdom 
hello i wanted to find out where did you buy the LM334 variable Voltage Regulator i’ve been looking online
I bought mine on EBay. You can get several for $10 including shipping.
Brent
thank you very much every since i first heard about the tDCS device and its benefits i have wanted to build my own
Very nice design. Is there a step-by-step guide anywhere that would show how to build a device like this, for someone with no experience in building electronics? I would really like to build a simple but elegant device like yours rather than spend $300 on an iontophoresis unit.
Hi Kevin,
I’m not aware of a step-by-step guide for building a tDCS device. Perhaps a friend or associate with electronics experience could help you?
Brent
I’ve been surfing online more than 2 hours today, yet I never found any interesting article like yours. It’s
pretty worth enough for me. In my opinion, if all site owners and bloggers
made good content as you did, the web will be much more useful than ever before.
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I couldn’t refrain from commenting. Exceptionally well written!|
Thanks
Will you sell one to me?
Sorry, I don’t sell tDCS equipment.
Brent
OK, this is what I get for not doing the minimal research before asking a question.
http://www.ehow.com/how_5887749_wire-potentiometer-variable-resistor.html
Can you confirm that this is what you were doing, jumping terminals 2 and 1 to use it as a variable resistor input to the LM334?
Thanks!
If you are referring to the schematic, it’s just the way the drawing tool made it look. Pin 1 goes to + on the battery, pin 2 to pin 2 on the pot, and pin 3 goes to the point where the 470 and 15 meet. Hope that helps.
Brent
Ah, I was actually referring to the pot itself. Looking at the newer schematic on you site, I think it all makes sense. Pot terminals 1 and 2 get wired together (wired as a variable resistor), 2 goes to the LM334, and 3 goes to the 15 ohm resistor. The wiring for the LM334 itself seems fairly obvious.
That leaves one last thing I want to verify before going off to build. I feel a silly asking this, but is the LED you have for verifying battery function going the wrong way in the schematic? And do you have a value for the LED’s resistor? It seems we don’t have Radio Shack in Japan so I’m trying to match your design as closely as possible without the pair.
Thanks again!
Yes – thank you for catching that. I have flipped the LED in the diagram.
The RS device is a combination resistor and LED. Most designs I’ve seen use a 4k or 5k resistor in series with an LED.
Brent
Thanks for finally writing about >tDCS – Building Research
tDCS Units | SpeakWisdom <Loved it!