I recently got interested in TDCS again.  I got my old Ebay 2 mA device out and it seemed to work the same way I remembered.  It gave me a stimulating feeling somewhat similar to caffeine when the positive electrode was above my left eye (or on my left temple) and the negative was on the opposite arm.  The problem was the electrodes that came with the device were not the sponge type so I had to add my own sponges and the wires are real thin so they broke and needed to be repaired. The snaps on the electrodes also rusted.

I built another homemade device with a full 2 mA which worked like my old Ebay one but I still had the poor homemade sponge electrodes.

I finally broke down and got the APEX type A TDCS that has an analog meter and is adjustable up to 4 mA.  The design of this device is very nice and the sponge electrodes are the best I have seen. The sponge case is a soft silicone and it has some kind of conductive rubber behind the sponges instead of any kind of metal.  The adjustable current combined with the meter makes it easy to ramp up or down the power to keep the stinging sensation to a minimum and the 18 volts (2 nine volt batteries) allows the electrodes to be a lot further away from each other and still work.  Instead of placing the negative on my upper arm, I can place it on the back of my hand if I want.

The biggest problem with the APEX device (and other commercial devices) is the high cost.  

I redesigned my old schematic to add in a potentiometer and meter and increased the maximum power to about 4 mA.  I wouldn’t recommend skipping the potentiometer if going over 2 mA. The meter could be eliminated but it helps to know that the electrodes are making good contact.  The LED power indicator is nice but I left it out of the test device I built and I also skipped the switch just because I didn’t have one and I just unhook the power to shut it off.  Without the LED light, just removing the electrodes should shut it off but I like to either have a switch or remove the battery to make sure it doesn’t waste the battery when not being used. I couldn't really tell much difference between 9 volts and 18 volts besides possibly allowing the electrodes to be further apart but I calculated the changes to use different voltages without blowing out the LED. I don't know if lower than 9 volts would work.

I know that 2 mA was (and might still be) considered the maximum “safe” current but I like having the extra power especially if trying to place the electrodes in positions with hair.  The potentiometer allows lower current settings so it doesn’t need to be used at full power. Use your own judgement if you build this circuit or try higher than 2 mA current. The sponge electrodes and the saltwater electrolyte are an important part of this device. If anyone is interested, I can describe what I have used on homemade devices.


  • I just noticed that the bottom connection on the schematic should have been on the center pin of the potentiometer. It should be almost a short circuit when turned all the way clockwise so check which outside pin to use if you want clockwise to give more current.

    With the parts I used, the minimum current is about 0.5 mA and the maximum is just over 3.5 mA and not the 4 mA I designed it for. It might be the cheap, Chinese potentiometer I used but it still works pretty good.
  • Do you ever user amperage above 2mA, and what is the perceived difference?

    Any longer term effects?

    Also: Why do you need more amps if you have hair in between?! Shouldn't voltage the only problem, since all resistance are in series?
    Or does the hair make a short circuit directly to the arm ...? :)

  • Yes, I have been using over 2mA since I got the APEX device. The added current seems to give a quicker effect meaning less time is needed.

    The extra voltage helps mainly if you want to place the electrodes further apart. At 9 volts, placing one electrode on my head and one on my hand didn't even get up to one mA. At 18 volts, I can get the full 4mA or can adjust the current with the potentiometer down to whatever level is comfortable. Many times the current needs to be ramped up slowly to keep the pain (and possible burning) to a minimum. By slowly increasing the current, the stinging sensation is eliminated.

    The extra voltage and current does allow the electrodes to conduct through hair better. The sponges need to be wet with the saline solution enough that the hair is also wet in order for it to conduct the electricity.

    I personally like the 4mA better than the 2mA. The physical effects are more noticeable at the higher current. Electrode placement has a lot to do with the effects and some effects MIGHT be placebo but, with the positive electrode on my left temple and the negative electrode on the back of my right hand, I get a flash of light when the device is turned on and off or even when the current is adjusted. It also gives a kind of metalic taste in my mouth. Not real strong but definitely noticeable. If both electrodes are on my head, the metalic taste doesn't seem to be there or at least not very noticeable.

    I get a stimulating effect kind of like caffeine with the positive on my left temple and the negative on my right hand (or on my right temple) and can focus my thoughts better. It might be at least partially a plecebo effect but the effects have been the same every time I use it.

    I used it at least a couple times a day when I first got the more powerful device mostly just playing with it and trying out different electrode positions. I keep going back to the same one since it gives me the effects I wanted. I now skip a day every once in a while and mainly only use it before I get up in the morning and/or before I go to sleep. It did make it a little harder to go to sleep at first but not a problem anymore. It does seem to make me dream a lot more since I started using it.
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