TDCS questions

edited August 2016 in Community
I have just got a TDCS device from Ebay while I wait for the parts to arrive to build my own better one.  The one I got came with some kind of silver cloth electrodes and not sponges.  I haven't found my meter yet to make sure it really is only 2 mA like the seller claims but I have no reason to think that part is wrong.

It didn't come with any kind of instructions.  I tried the electrodes dry since they were listed as wet/dry electrodes.  Dry there was no feeling at all.  Then I mixed up 1/4 teaspoon of salt in a cup of water and used that to wet the electrodes.  That made a difference and I got the flash of light and the prickly sensation.  It soon became "painful" and I was afraid to keep it running.

I then tried it with plain water and that was a bad idea.  Not only did the shocks sting, it even made my arm twitch when turning it on or off.  The kit also came with smaller electrodes which I haven't tried and an ear clip.  I did try the ear clip for a couple seconds and it was very painful.

So, did I somehow get a bad device or am I doing something wrong?  I intend to build my own that is adjustable and hoped to use the electrodes from the bought one but I'm not sure the electrodes are not the problem.



  • Could you upload a picture or a link to the product. I can't tell if you bought a cheap knockoff ( most probable by what you are writing, they should all come with instructions  ) or simply using badly. 
  • I didn't want to advertise but this is the one I bought.

    Here's what the description says in case the link doesn't work.

    We offer a complete, DIY tdcs kit with a regulated 2 milliamps or 2/1,000 (+/- 10%) of an amp, power supply cord.
    Kit updated on 03/21/16 to include material to make electrode placement cap.
    The kit includes:

    1 regulated, 2mA Power Supply
    2 two inch Long Lasting, Wet/Dry, Silver Cloth foam backed Electrodes
    1 one inch Long Lasting, Silver Cloth electrode
    1 ear clip electrode
    1 splitter wire
    1 Cap-Kit (3m of Cord and 16 snaps. Cap must be cut to size and assembled)
    1 storage bag

    I can't access the actual circuit but there is very little to this thing.  A battery and a switch with some wire is all I can see but I assume there is a current regulator and probably a resistor hidden inside.

    Except for the ear clip and when I tried plain water, it was a tolerable pain but I don't want to end up burning holes in my head by ignoring the pain.

    Like I said, I have parts ordered (coming from China) to build my own and I intend to have some way of controlling the amount of current so it doesn't have to be all or nothing.  Maybe 2mA is too much for the size of electrodes included in the kit?  I didn't even try the smaller 1 inch electrodes.
  • Yeah , It is a knockoff, just throw it away. Well you can keep the head band. The electrodes look really cheap , and the sponges are wrong the have to distribute the electric charge in a area and not in just in the center. Maybe ask back the money or , leave a 1 star review.  

    2mA is the max all Tdcs go. The Charge should distribute it self, that is the reason the sponges are used. I would recommend the 3*3 or the 2*2. Keep in mind that how much of the electricity will end up in your brain also depends on the water you put and  the sponges. 

    I always felt a light stinging on the area like small nails of cats, or needles. Annoying not painful. But keep in mind they can irritate the skin. If I don't recall bad there is a possibility of electric burn. 

  • Thanks.  I just tried it again and it wasn't as bad.  I moved the cathode (negative) electrode from my left bicep further up more to my shoulder but I don't know if that made any difference.  The anode (positive) was above my right eye on my forehead.

    I used the same salt solution I had been using so the only difference was where I placed the cathode unless my battery is getting weaker.  I did still have some tingling but not as bad as before and got a flash of light when I turned it on and again when I turned it off.

    The metal parts of the electrodes worried me and I tried covering the metal before with no difference.  Unless you purposely push the electrodes down in the center, the metal doesn't appear to touch the skin but maybe it was.

    I haven't risk using it more than 5 minutes at a time yet but haven't seen any real noticeable benefits.  I did try looking at some magic eye pictures right after using it and I was able to see all of them fairly quickly.  I've never been very good at seeing those pictures before but I'm not ready to credit it to the TDCS.

    I'll try to get some sponges and make my own electrodes and I still intend to build my own better version but got this one because it was pretty much ready to use.  It could take me a while to build my own depending on how many bells and whistles I decide to include.

    I'm not going to send it back and I haven't left feedback or wrote a review yet.  I knew it wasn't a high end model and assume it is probably homemade by the seller.  I have no problem leaving negative feedback if it is deserved but I still hope the problems were something I did and not a defect in the product.  I don't intend to try the ear clip again though.  I probably won't even try the smaller one.
  • Keep in mind that just because you have a little electricity going in your skin doesn't mean it is reaching your brain. Tdcs is prone to the Placebo effect and it is very easy to feel small changes in the beginning that can trick you. 
  • I think my experience with the magic eye pictures was probably a placebo.  Something must have made a difference though because I couldn't even bring out the hidden pictures and then they started popping out as soon as I looked at them.  Whatever caused it, it's gone again.  Even knowing what and where it is I can't see them anymore without looking at them for a long time.  Sometimes not even then.

    I still can't credit it to the TDCS.  As far as I can tell, I wasn't even stimulating a visual part of the brain.  I thought I was doing the DARPA accelerated learning montage but, now that I look at it again, I had the placement wrong.  I think I was at FP2 instead of F10 with the anode and the cathode on my left arm.  Looks like that should have been for improved attention.



    Anode: Orbital PFC (FP1) or (FP2)

    Cathode: Opposite Shoulder

    Study Results: Improving Attention 

    Other Uses: Working Memory Improvement, Complex memory span and ADHD 

    Notes: Some
    individuals have shown an increase in selective attention. Selective
    attention and memory appears to be improved through the use of this

    Maybe the selective attention helped with seeing the hidden pictures or maybe it was all placebo.  I only used the TDCS for about 5 minutes before looking at the pictures.

    After experimenting a little more, I think the electrodes are the problem.  They dry too fast and then it becomes painful again.  Too bad because the electrodes were a big reason I bought the kit instead of waiting to build my own.

  •  I'm afraid that 5 min is just to small. I have always seen experiment run for minimum 20 minutes. 
  • Looking at the tDCs papers I have a feeling that rather than electricity running through the body it's actually the electric field affecting the extra membrane ions around the neurons in the brain cortex resulting in an increase / decrease of membrane potential and increased / decreased ease of said neurons firing, but I'm no physicist.

    Anyway, there should be some tinkling sensation but not burning at least. Also, mind that everyone's brain / skull is slightly different so effects might not be exactly the same (I feel more focused with the F10 rather than feel like learning more, and for some reason my brain speed according to brainhq increased after a F10 montage. No idea why).
  • The seller responded to my questions on ebay and suggested putting sponges between the electrodes and my skin.  He also pointed me to a website with the saline solution recipe that uses both salt and baking soda.  Basically what I was using with the addition of baking soda.

    I tried that on the included electrodes (no sponges yet) and it seemed about the same.  Worked fine until the electrodes started drying and then it became painful again.

    I know 5 minutes is not enough time but that is all the longer I have been able to use the device before it starts hurting too bad.  The light stinging I can handle but it starts to be more of an actual shock as the electrodes dry.  Enough to make my arm twitch from the shocks.

    I'll eventually find my meter and check this to make sure it really is only putting out 2mA.  I'll get some sponges and try that but really should have just waited and built my own device.  At least then I would only have myself to blame if it didn't work the way I hoped.
  • edited August 2016
    I cut up some sponges and put them (wet with the saline solution the seller recommended) between the electrodes and my skin. That made a big difference.  I still wouldn't call it a pleasant sensation but no longer painful and I could leave them on longer.

    I checked out the magic eye pictures right after using the TDCS again and I could see them all again.  Many of them popped out as soon as I looked at them.  I was using the DARPA accelerated learning montage.  Probably just a coincidence or that Placebo effect but it is an easy test to repeat especially since it normally takes me a while to see those pictures if I can even see them at all.

    My meter needs a new battery so I still haven't checked to make sure this device is only putting out 2mA.  Likely it is just the electrodes that were causing me trouble.

    EDIT:  I still had a tingling sensation while it was on and got the flash of light and a slight arm twitch when first turned on and when it was shut off.  A little metallic taste also but not real noticeable.
  • Um... The arm twitch might mean that you stimulated the motor cortex by accident. Flash of light can be... well, more likely the optic nerve / radiation I think.

    Time to brush up the neuroanatomy. :P
  • So, the flash of light could also be caused by a stimulation of the optic nerves. The optic nerves pass pretty close to the area you're stimulating, I believe.
  • Update.  I have been using the TDCS machine for a couple weeks now although not every day.  There still seems to be some benefit to my mood and I intend to continue using it.  Some of the caffeine like effects have gotten less.  Mainly the caffeine like "shakes" have gone away so either I am getting used to the effect or, more likely, that part was just a placebo.  If I use it before going to sleep, it makes it a little harder to lay down but, once I do, it doesn't seem to keep me awake but then neither did caffeine.  I have been dreaming a lot more but the memory of them vanishes as soon as I awaken. 

    The arm twitching stopped when I moved the electrode higher on my arm so I assume I was just hitting a muscle before.  The flash of light is still there and I use it to insure the device is actually working.  I turn it off and back on during the session just to make sure it is still making good contact.  The sponges have pretty much eliminated any painful stinging or shocking sensation so the electrodes that came with the kit must have been the problem there.

    I haven't been experimenting with different electrode placements but probably will once I do some more research.  The Anode on F10 and Cathode on my upper right arm seem to make a difference in my mood and my ability to focus on one thing at a time instead of my normal many thoughts all at once.

    It could still just be a placebo but, so long as it keeps working, it doesn't really matter why.
  • Have you done anything to try and enduce a placebo effect? Maybe have some one else control the power on/off?
  • @Meanderpaul

    I haven't thought of that.  It would be difficult with the device I have right now since I can tell by the flash of light when it is turned on or turned off.

    I might try to incorporate the ability to randomly have a sham session if I build a nicer model and incorporate an Arduino to control it.  That way I could program it to still give the visual indications that it is working but cut it out for all but the beginning and end.  I do want to have a way to step up or down the current on my own version if/when I build it.

    I have considered reversing the electrodes to see if it gives a noticeable different effect.  I'm not sure how good of an idea that is but would be interesting to test.  Probably best to try it when I won't be around other people just in case.  I've seen how I can get.

    Maybe I'll give it a shot before I go to sleep instead of first thing in the morning.  Might give another section of my brain a chance to come out and play.
  • O.K. I tried reversing the electrodes and the effect was much different.  Instead of it giving me more energy or making it easier to focus, it seemed to cause my thoughts to wonder and I couldn't stay focused on any one thing.  Every little sound caused me to loose focus.  It also made me more tired but it was not easy to fall asleep. My short term memory was also effected badly.

    I finally fell asleep but woke back up after several hours and still didn't feel right.  I switched the electrodes back the way I originally had them and used the device for another half hour while watching TV.  Almost immediately, I started to feel better and my focus returned.

    I'm starting to think it is not just a placebo and this TDCS thing actually does work.  A 9 volt battery is pretty cheap medication.
  • An adjustable tDCS could be turned down to zero without the noticeable flash. I have both, adjustable and fixed 2mA, and I don't see a flash when I lower the current. This could give you the test you're looking for. I do see it when I switch on or off and I get the metallic taste.
    I haven't tried connecting an Arduino to a tDCS but I worry that if the PWM output was used (analogWrite) that it would wreak havoc. Then again, it shouldn't hurt even if it's disorienting. There are other options of course but the simplest might not be the best here.
  • I haven't worked out exactly how I would interface the Arduino to the TDCS but I was thinking of using the digital outputs to switch between a few different currents and still use the 9 volt battery to power the TDCS.

    Now that I think about it, the same battery could probably power the Arduino too.  I'm not sure how much power it would draw though since I want to include an LCD display, some lights, and probably some "bells and whistles".

    I want the Arduino to have a countdown timer and display the current although I wasn't figuring on it being an actual meter but just an indicator.  The sham feature could be displayed at the very end to let you know if you got the real thing or if it was a sham session.  That way, you could still watch the display until the very end and not know if it was really on or not.  I would like the option to turn that random feature off completely but, to avoid using another switch, I suppose the Arduino sketch could just be changed and reloaded if that feature was wanted. 

    I'll have to draw some stuff out on paper and see what it would take to do what I want.  I'm having trouble visualizing how I can change out resistors (to vary the current) without having a very brief period of no current as they switch.

    If there is an interest here, I will try to post some more thoughts and some drawings as I work it out.  If not, I am still willing to share the final design but it could take me a while.  I don't really NEED to build my own but I have a feeling I could come up with something better than I could afford to buy premade if such a thing even exists.
  • This is the circuit schematic I am starting from for my design.  It's not my own design. 


    Obviously, I will need to make some changes because I am only using 9 volts instead of 12 but it looks similar to what I am trying to achieve.  Some of my calculations don't match what this schematic shows.  The switched resistors are approximate and probably close enough.  The one they call 0.5mA is (by my calculations) 0.84625mA but, since it is the lowest one, it should be fine.  I don't know how they calculated the LED resistor.  For 9 volts, I'm only figuring a 390 ohm for that one.  Maybe the (high efficiency) LEDs are different than the standard (junk box) one I plan to use.  I figured 20mA to run the LED.

    I already bought the LM334Z current regulator but I'm hoping to get all the remaining parts from my junk box.

    I'll bet my design doesn't include that safety fuse.  $$$

    As far as controlling the switches using the Arduino, relays might work but I don't have any of them in my junk box.  I need to do some studying but I'm thinking there should be a way to use transistors as the switches.
  • edited August 2016
    Sorry.  Double post again.
  • Not to intrude in electronics not my field but is better to lower the safety fuse on the Anode at 2mA , because that is the limit to protect the skin from burns .keep in mind that I know of no Tdcs ever goes over 2mA. 
  • @kuroro86

    Same problem with that size fuse.  Real expensive.
  • I'm one step closer to actually building my own TDCS machine.  I got the Arduino board to blink an LED using a transistor as a switch to control a separate power source.  I'm still not sure my idea will work, using the transistor to switch resistor values, but I could at least turn the device on and off.  In fact, I might just modify the one I bought to be controlled by the Arduino and not even bother with the variable current.  I don't know for sure if the transistor will cause the resistor values to need changed. 

    The wires broke on the one I bought which gave me an excuse to see what it was made of.  It is pretty much a stripped down version of what I am looking to build except it uses surface mount parts and is one set current rating.  I kind of want some form of display (maybe just simple LED's) and a timer to automatically turn off after a set time.

    Considering this could be built without using a microprocessor at all if it just used manual switches, I wonder if there is even any benefit to changing the current settings during a session.  The flash of light I get from turning the power on or off is not really a problem.  Sometimes I will turn it off and back on while using it just to get that flash of light as an indicator that the electrodes are still making good contact.

    Using the Arduino, it should be possible to change the time and the current any way I want.  I don't know if there is any benefit other than less discomfort to the lower current or if just going full power the whole time gives the best results.

    Is this worth doing or is a much simpler, manually controlled TDCS device just as good? 

    Would a slow pulsing (Low, Medium, High, Medium...) pattern have a different effect than the constant current I have been using?  Might it be better?

  • In my experience , longer time give longer results. Even at lower Amp. But I'm afraid it is different for every brain. You will have to experiment. 
  • Well, I haven't figured out how to hook it to the Arduino yet but I built my own breadboard TDCS machine.

    I used the schematic posted above and found a couple resistors close enough.  I got one 33 ohm resistor that should give me around 2 mA of current.  I then found another resistor that was only 25 ohms.  Combining that one with the 33 ohm resistor in series should give me 58 ohms which should bring the current down to between 1.0 and 1.5 mA.

    I didn't wire up anything permanent yet but a simple switch to short out the 25 ohm resistor (or just moving the wires on this test circuit) would bring it back to full power.  No idea how to do that with the Arduino without a relay.  Keep in mind that the 25 ohm resistor shouldn't be used alone.  I didn't do the calculations but that would give over the safe 2 mA limit.

    I tried it out a short time just to make sure it was working and noticed that, with the capacitor across the output, the flashes of light don't show up.  In the short time I tried it, there wasn't even much feeling at all to tell it was on.  I think an LED power indicator is a good idea especially if it no longer produces that flash of light.  My purchased TDCS device just has a switch.  I got used to those flashes and might leave the capacitor out just to keep them but it also stopped the sharper pin prick sensations when first turned on or shut off.

    For such a simple device, I'm still having a hard time believing the effects it seems to be producing for me.  Not a REAL noticeable feeling but it does seem to make my mood a lot better and allow me to focus better.  When I reversed the electrodes, the effect was much different.  Kind of a foggy feeling and I couldn't keep my mind focused on any one thing for any length of time.  Not a very good feeling so I never repeated that experiment.

    Another time, I left the device on for almost 45 minutes using my normal electrode positioning.  At around 42 minutes, I started to fear "over charging" my brain and shut it off.  I was feeling very stimulated like having too much caffeine to drink.  It seems like 15-20 minutes is a good amount of time for me with the bought device.  I usually can feel some effects (other than the flash and the tingling) in 5 minutes but the longer time does seem to give longer lasting results.

    I have been using it almost daily but sometimes skip a day if I don't feel bad.  It is definitely doing some good for me but I still wonder if some of it is just a placebo.  I mean, can a 9 volt battery and a few electronic parts really change how your brain works?  It does seem to.
  • edited September 2016
    Well, it's a bit of a roundabout way of doing it, but you could use a MOSFET attached to the rset pin of the current regulator. and have your arduino output x volts to your output, and connect the gnd to the negative side of the battery-ish. Something like this(LINK), I believe. Have @thomasEgi check it before you try it. I don't wanna see a detonated arduino on account of my meddling. 

    The MOSFET acts as a voltage-controlled current source. Since it looks like the LM334z has the Rset pin using current to adjust its output, you can use the mosfet to fine-tune your output current. to basically anything between 0 and 2mA. Downside is, if your mosfet shorts closed, you might get a lot more than 2mA.

    Unless your arduino can output variable current. in which case,ditch the MOSFET, and wire the digital output straight to Rset. 
  • Thanks @TheGreyKnight.  I'll have to study up on how a MOSFET works and how the LM344Z current regulator works.  There could be a real easy way to make the Arduino control the current output using the programming instead of switching components like I have been trying.

    I'm kind of leaning towards forgetting about the Arduino and just keep everything manual.  A timer might be nice but I have just been going by feel lately.  When I feel like it has worked enough, I turn it off.  Sometimes 5 or 10 minutes is enough and other times I'll go a half hour or more.

    I've been doing some more research looking for electrode placement ideas to try and found an interesting diagram.


    Might help chose areas to stimulate.  I keep getting the left and right areas wrong.  What I was calling F10 before with the cathode on my right arm was actually F9 and sometimes FP1.  That's what I use most of the time but there might be something even better that I haven't tried yet.
  • edited September 2016
    I probably just need to find the right transistor but I have given up on that idea and ordered a few relay modules that are made for use with the Arduino.  At only 99 cents each with free shipping, it probably isn't much more expensive than using a transistor to switch resistors and should be much easier to figure out.

    One thing I discovered while researching how I could do this is that I can just use my two resistors in series to get a lower output power and, just by shorting one resistor out, it can switch to high power.

    I also just got a tens unit and noticed that it is very nice to have control over the power setting manually and not just by some set program.  The user can adjust the power setting anytime they want while the device changes the pulse rate and frequency according to set programs.  At first power level 1 felt strong but soon I could reach the high setting of 15 without pain and couldn't hardly feel level 1 at all. 

    I think a similar option should be included in the TDCS machine I want to build.  Only the user can tell if they want more power or if it needs turned down a little while.
  • Here's my latest schematic for a fairly simple TDCS machine with a high/low selector for the current.

    The switches could be normal, manual switches or (I hope) relays controlled by an Arduino.  I didn't add in the fuse from the schematic I copied the design from but you could easily include it if you want.

    This design comes with no warranty at all.  You're on your own if you build it but I put the drawing in the public domain so feel free to do whatever you want with it.
  • This is a question, not criticism.
    Why did you use two fixed resistors instead of a single variable resistor?

Sign In or Register to comment.