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.
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.
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 firstname.lastname@example.org