422 replies to this topic

[ATA]

hi I'm ATA from brmlab
I will try to answer your questions

First of all on the page is only small part of info i did not have time to finish it (many other projects )
I did not expect that it will be of such interest .

I am not good in electronics. What for does he use current regulator? His scheme is not understandable as well as how he made the electrodes. Did he attach sponges to the foil cut from beer can? Also I do not understand why he adds a test lamp to the scheme. The new battery will work for some time and he can later measure the current with a digital multimeter or by attaching the lamp from an old pocket lantern.
Also it is strange that he attached electrodes to the piece of cloth. If they are not detachable from it, he cannot use electrodes on other areas of head where the distance between electrodes is larger or smaller. He presents only one way of application of electrodes to head. Are there any other ways? Who has already tried tDCS? Any experiences?
IS it possible to use nickel-magnesium rechargeable battery instead of the alkaline one?

my knowledge of electronic is only very base . I try to built tdcs simplest way from available material.Simlest in not safest but for the purpose it is sufficient.

current regulator- because the resistence of brain+skin is very variable , if not regulated curent will change quickly

Electrodes - this part is not wiriten yet , i still try to find better way to built it.
The electrodes taht i uset is brusehed beercan foil (it has nonconductive layer tat must by brushed away) stitched between 2 layers of sponge like ths http://aao.cz/foto/71049.jpg

The diode is only for test battery ,circut not need it (there were lot of space in the box tahat i fill it)
Pres the buton is fastest than finding multimeter, lamp from lanthern is for higer current.

Electrodes is on plastic and there is detachable , conection is made from this http://www.broz-brac...ct_280_1855.jpg

distance, areas
I made it for my head, position is fixed - for one user/head only.
Fixed position is for safety reasons to avod problems like changet polariry , wrong place of stimulation ..
čkal I get it that every stand by their head

battery - you can use use nickel-magnesium rechargeable battery instead there is no problem

[ATA]

Which voltage should be used? The scheme mentioned here shows some resistors and a current regulator? Don't resisters low down the voltage? I thought that the voltage should be 9 volts and 1 ma strength.

Most important is the current ( current density on electrodes) volts are not so important.
Thre must by enough volts to overcome the resitence of head. For 1mA and this type of electrodes is 9Vsource best choice. Some comercial device use about 80V becouse they use electrodes they have much higher resitence.

I followed the link and found this concerning the scheme in question:

"I frankly don't know how much current you will get. The resistance between OUT and ADJ is way out of specifications. I've never tried going that far beyond the specifications.

The box on the left is an excerpt from the datasheet.

While R1 = ~1.25/Ireq; they omitted that 10mA <= Ireq <= 1.5A, so 0.8333 Ohms <= R1 <= 125 Ohms. They are using 1251 Ohms, or more than 10 times the maximum allowed."

According to this post the scheme should give 10 mA and not 1 mA!

yes it is true that in datasheet is this limit. But in practice it works well it seems that regulations work to 0.7 mA (higher resistors take no effect).
Im not sure wht type of LM317 i use i thing tahat was LM317T.

Safety: If something go wrong in a control circuit and regulation not work, the current true the head still not exeted 9mA because the resistance does not drop below 1K (head resitence ).
It way below tissue damage .

[ATA]

Where am I going wrong in my calculations below?

Take a voltmeter and set it on resistance (Ohms), put salty water on your fingers, and then hold the tips of the two probes in the wet finger tips of each hand.

What do you read?

When I do this experiment, my meter reads a resistance of about one hundred thousand (100,000) ohms +/- 100%.
That seems to be a typical resistance across any two points on the human body.

So if you want to create a current across two points on your body, then you can use Ohms Law to find out how much voltage to use:

V(volts) = I(amps) * R(ohms)

R = 100,000 ohms
I = 2 milliamps = 0.002 amps (according to my reading of the tDCS literature)

Solving:

V = 100,000 * 0.002 = 200 volts

(Better check my math)

So a 9 volt battery is not going to cut it.
You need the approximate voltage you get by sticking your fingers into house wall sockets, except as DC not AC.
Ohms Law says a 9 volt battery would produce only 9/100,000 = 0.00009 amps = 0.09 milliamps = 90 microamps
That is lower than the typical tDCS 2 milliamps by a factor of 2/0.09 = 22.22x

Looks like you will need a lot bigger battery!

Perhaps this higher voltage required explains why the the research systems are so expensive.
You want to be pretty careful when dealing with hundreds of volts and human bodies.
I guess electric chair makers found out long ago that they could not get by with battery power.

Calculation is fine but mesurment is wrong.
Mesured resitence it highly depens of type of electrode (material) and its size , in my electrodes it was 2-6kO.
This means without regulation currnet 1,5 - 4,5mA

[Nootr]

Ata, we are happy to meet you here on this forum! The project is really interesting and your experience is invaluable!
Do you continue to do direct current stimulation every week? Do you have positive results? Have you taken any nootropics and how can you compare direct current stimulation with chemical nootropics as to their effect?

Also I do not understand why you placed the beercan foil between two sponges coz you actually need one sponge only on one side of the foil - that side that will be contacting the head.

Have you used other routes of application of electrodes to the head and with which consequences?

Can you recommend any online shops where I can buy the radio units for the device? The only one in my town is closed.

[ATA]

Do you continue to do direct current stimulation every week?
No i used it mainly for for headaches several times a month.
To improve cognitive functions i prefer use warious mental techniqes its is safer and i can achieve the stronger effect. I use tDCS if i lazy to use techniqes the effect is very similar.

Do you have positive results?
yes, better concentration ,more "mental energy",better vision..

Have you taken any nootropics and how can you compare direct current stimulation with chemical nootropics as to their effect?
Few years back i take DLPA (dextrolevophenylananine) nad piracetam + B comlex . improve the learning and mood before exams ,sometimes i used with warious binaural beats like hemi-sync or BWgen

Also I do not understand why you placed the beercan foil between two sponges coz you actually need one sponge only on one side of the foil - that side that will be contacting the head.
It better held together , and design

Have you used other routes of application of electrodes to the head and with which consequences?
yes but its too little bach of test to draw any conclusions. in one test in temporal (mastoid behaind the ears) i notices significant encerase of endorphines

I not recommend application in other parts of brain that DLPFC is reguired differnt shape and current density of electrodes ,kowledge of neuroanathomy..


Can you recommend any online shops where I can buy the radio units for the device? The only one in my town is closed.
I buy it in local shop or pull up from old PC monitor.

[ATA]

some notes about tdcs:
*my notes

Electrodes used for tDCS generally consist of a metal or conductive-rubber electrodes enclosed in a perforated sponge pocket which is saturated with an electrolytes (fluid with salt). Another possibility is the use of rubber electrode with conductive gel. Prolonged passage of direct current current across metallic electrode (where electrons from the stimulator are converted to ions carried through the body⁸) can produce undesired electrochemical products such as pH changes. The sponge pocket may act to physically separate, and thus buffer, the skin from electrochemical changes.
*rubber electrodes has to much resistence to work with 9V (about 20kO)
*material dont use Cu, Fe, Ni ,Cr (allergy or dangerous electrochemical products)

Inspect the skin for any pre-exiting irritation, cuts, or lesions - avoid stimulating over damaged skin

After finding the site of stimulation and skin preparation you should place one of the elastic or rubber head straps around the head circumference. The elastic head strap should be placed under the inion as to avoid movement during stimulation. The elastic straps should be made of non-conducting material (or they will function as electrodes) and non-absorbent material (to avoid the straps absorbing fluid from the sponges).
*hydrophobic plastic foam
*find right one ,confortable ,minimum sweating

Each side of the sponges should be soaked with saline solution. For a 35 cm² sponge, approximately 6 mL of solution per side may suffice (total of 12 mL per sponge). Be careful not to over soak the sponge (not excessively wet- there should be no water leaking; but also not dry as to have a good electrode contact). Avoid fluid leaking across the subject. You can use a syringe to add more solution if needed.
There is evidence that electrolyte solutions with lower NaCl concentrations(15 mM) are perceived as more comfortable during tDCS than those solutions with higher NaCl concentrations (220 mM)^11,12. Since the ionic strength of deionised water is much less than that of all NaCl solutions, there is a significantly larger voltage required to carry current across the electrode and through the skin compared to NaCl solutions. Thus, it is recommended the use of solutions with moderate NaCl concentration, in the range 15 mM to 140 mM, as tDCS at these concentrations is more likely to be perceived as comfortable, requires moderately lower voltage while still allowing good conduction of current.¹¹ The use of gels (adapted from applications such as EEG) has also been considered – a main limitation is the increased hassle of set-up clean-up following stimulation, without proven benefit regarding outcome when using perforated sponge electrodes.
*glass of salty water put electrodes in - out and sueze squeeze out excess liquid

"Anode" always indicated the relative positive terminal where positive current flows intro the body, while "Cathode" indicates the relative negative terminal where the positive current then exits the body.

Place one sponge electrode below the elastic head strap. Ensure that excessive fluid is not ejected from the sponge unto the scalp during this process as this will spread current flow across the scalp and deplete the sponge of fluid.

The path from one device terminal, through one electrode, across the body, through the second electrode, and back to the second device terminal forms a circuit – the total resistance of which (sum of the electrodes and body resistance) can be measured. If the overall resistance is abnormally high, this may indicate improper electrode set-up. If your device measure resistance - this would be recommended – the indication field should display appropriate electrode contact. Ideally, one should aim to have the impedance under 5k Ohms. Some devices indicate the voltage across the path rather than resistance - in this case resistance can be calculated simply using ohms law (Resistance = Indicate Voltage / Current applied). Many devices continue to provide an indication of resistance during the course of stimulation, which provides a useful way to detect a potentially hazardous situation (such as a drying electrode). In some cases, device will automatically terminate stimulation or reduce stimulation intensity if resistance increases beyond a certain threshold.
* in my electrodes 2-6kO

to be continued...

[ATA]

At the beginning of stimulation, the majority of subjects will perceive a slight itching sensation, which then fades in most cases. Similarly, rapid changes of the stimulating circuit immediately might induce peripheral nerve firing. The subject can notice it as brief retinal phosphenes with electrodes near the eyes. These effects can be largely avoided by ramping the current up and down at the beginning and end of treatment. This might also prevent the dizziness or vertigo occasionally reported when current is suddenly increased or decreased.
* dizziness or vertigo - cranil vestibular stimulation CVS (electrodes close to ears)
*phosphenes on start and end of simulation - my device dont use ramping

It is reported that repeated daily tDCS causes clinically significant skin irritation under the electrodes in some patients⁷. There is evidence of tDCS induced lesions according to skin integrity. For instance, it has been shown extensive redness and brown crusty intracutaneous changes with irregular round shapes due to tDC stimulation at an intensity of 2 mA for a period of 2 weeks including five sessions each week²⁵. If tDCS is strongly indicated or has to be conducted, it is possible to take into consideration to stimulate with a lower intensity such as 0.5- 1.0 mA, but it is not guaranteed that this will prevent skin irritations or lesions. Thus, the condition of the skin under the electrodes should be inspected before and after tDCS⁷.

[ATA]

some photos of tDCS http://orlin.rajce.idnes.cz/tdcs

[Krell]

some photos of tDCS http://orlin.rajce.idnes.cz/tdcs

Interesting pictures! New uses for duct tape.

It looks like this system uses 4 nine volt batteries, or about 36 volts maximum.

By Ohms law, if the maximum output is 2 milliamps, then the total resistance of the skin and
electronics in series is R=V/I=36/.002=18,000 Ohms.

This is less than the 100,000 Ohms resistance that I measure when I put salt water on my fingers
and hold the probes on my digital volt/ohm meter. Perhaps the professional pads that the pictures
show have even less resistance than my probes/fingers because they are larger area, and their fluid is
more conductive? I see that eBay has lots of similar pads for sale.

It is possible to build a circuit that ramps the current up and down smoothly rather
than just on/off, if that causes less problems. But we need to know what rate of ramping up
and down is recommended. 0.1 second?, 1 second? 10 seconds? 100 seconds?

[ATA]

Hi
In this version i used 2x9V battery and 4 current settings (1 1,5 2 2,5mA) (*in reality little more i dont have resistors of precise value)

The resistence of electrodes + head is about 2-6kO max load of device in max current is about 7,5kO (17V - LM317 takes some voltage for self)

pads is homemade - its ony brusehed foil from bearcan between sponges

salty watter is pretty conductive

i dou no waht type you see in ebay but the must be correct size and resisten this a little poroblem electrodes fo TENS will didnt work .

for me is flash in turn on no problem ,ramping is because sham study

if you they use ramping use 10sec maybe little more (or look to smome study how much)

[Krell]

Hi
In this version i used 2x9V battery and 4 current settings (1 1,5 2 2,5mA) (*in reality little more i dont have resistors of precise value)

The resistence of electrodes + head is about 2-6kO max load of device in max current is about 7,5kO (17V - LM317 takes some voltage for self)

pads is homemade - its ony brusehed foil from bearcan between sponges

salty watter is pretty conductive

i dou no waht type you see in ebay but the must be correct size and resisten this a little poroblem electrodes fo TENS will didnt work .

for me is flash in turn on no problem ,ramping is because sham study

if you they use ramping use 10sec maybe little more (or look to smome study how much)

Thanks again for all the help!

I see lots of inexpensive (~ $0.10) ECG electrodes for sale on eBay, etc and some are as large as 20 cm2 and they all seem to have an AgCl gel coating.

Do you think a large ECG electrode would work for tDCS?

Edited by Krell, 28 February 2012 - 04:39 PM.

[ATA]

Using AgCl elctrodes is posible but whole thing is more complicated tahan you think.
Using these electrodes will be almost impossible with device without voltage multiplyer ,these electrodes and gels have much higher resistence than saline soaked.

more info:
http://bme.ccny.cuny...ctrodes2010.pdf

My opinion is that for the DIY device is best choice saline soaked electrode

Ag/cl, rubber.. would be better suitable for HD-tDCS and more complicaded device

Edited by ATA, 28 February 2012 - 07:53 PM.

[Krell]

Using AgCl elctrodes is posible but whole thing is more complicated tahan you think.
Using these electrodes will be almost impossible with device without voltage multiplyer ,these electrodes and gels have much higher resistence than saline soaked.

more info:
http://bme.ccny.cuny...ctrodes2010.pdf

My opinion is that for the DIY device is best choice saline soaked electrode

Ag/cl, rubber.. would be better suitable for HD-tDCS and more complicaded device

Thanks for the very interesting but very complex article!

Some interesting points I got from a quick reading

1. these folks are trying to make a very small electrode: ~100mm2 = 1cm2
Comment: That suggests to me that commercial ECG electrodes with much bigger area might work for DYI.

2. different makes of AgCl gel have very different conductivities: 10 to 1 differences
Comment: That suggests to me that commercial ECG electrodes are not all the same, even if their area is
similar.

3. they mention a 10 second ramp rate
Comment: That gives us a DYI design criteria for building a current source with ramp up and down.

4. they say that the body conductivity drops by about 1/10 after current is first applied.
Comment: That may explain why I get 100,000 ohms between my two hands with a DVM, and
how it could go down to a more reasonable 5-10k ohms when current is applied.

5. AgCl seems to be the preferred professional gel salt since they did not try any others.
Comment: I am not sure how the conductivity of AgCl solutions compare to NaCl solutions.
AgCl gel seems to be in all ECG electrodes.

6. Their system went up to 67 volts and that seems to be a common professional system voltage.
Comment: If we want to use battery power for DYI, then 2 nine volt batteries would be more reasonable,
so we need electrodes with better conductivity and larger area than the paper's mini electrodes.

I need to read the paper again several times to absorb more of its important information!

[ATA]

1. these folks are trying to make a very small electrode: ~100mm2 = 1cm2
Comment: That suggests to me that commercial ECG electrodes with much bigger area might work for DYI.
HD-tdcs use electrode aray and usage is little complicated than normlal tdcs ,next thing is gel on ekg electrode may not be suitable
i dount recomant this for starters is need more knowledge

2. different makes of AgCl gel have very different conductivities: 10 to 1 differences
Comment: That suggests to me that commercial ECG electrodes are not all the same, even if their area is
similar.
yes not only resistence but also electrochemicla products


3. they mention a 10 second ramp rate
Comment: That gives us a DYI design criteria for building a current source with ramp up and down.

not necessary its for the limiting sense of itching in start of stimulation - to perform sham (placebo) studies


4. they say that the body conductivity drops by about 1/10 after current is first applied.
Comment: That may explain why I get 100,000 ohms between my two hands with a DVM, and
how it could go down to a more reasonable 5-10k ohms when current is applied.
its more complicated than that

5. AgCl seems to be the preferred professional gel salt since they did not try any others.
Comment: I am not sure how the conductivity of AgCl solutions compare to NaCl solutions.
AgCl gel seems to be in all ECG electrodes.
Mainly becouse they need to mesure signal without noise -its primary for measuring not stimulation

6. Their system went up to 67 volts and that seems to be a common professional system voltage.
Comment: If we want to use battery power for DYI, then 2 nine volt batteries would be more reasonable,
so we need electrodes with better conductivity and larger area than the paper's mini electrodes.
tdcs and hd-tdcs is diferent thing of HD-tdcs definytly needs more voltage thats devices use voltage multiplyer

[ATA]

tDCS and Dual N-Back game
My state is far from ideal i tired and take antyhystaminics (cause sleapines) and i have some other porblems.
This my first encounter with DNB i use D2B for this test , becouse that main part is could be learning curve.
I measure some subjective values too.
tDCS anodal 1mA DLPCF start in time 168 ,end 200

effect of tdcs is very little but i precive litle more focus, in end of stimulation something go wrong and my body start produce more stress i dount no what coused it(tdcs or other intrenal or extrenal factor)
best resuts was after tDCS.

not much to show in graff effect is too little and all is may be only learning curve but data is data nad i not pick only good locking one like some "reserchers"

[Ben]

Hi ATA,

Thanks a lot for coming here and posting this. I'm following the thread with a lot of interest.

I'm wondering, how're you measuring stress?

Regards.

[ATA]

it not scientific method it is only a subjective measurement by pendulum . I used it to view information from subconscious by micoromovement of hand . The body has a lot of internal sensors and is only question to get this information and some how view it.

or i use the scale by muscle stiffnes (tension) ,eye tierdnes, pain,focus ...

[Ben]

What about an HR monitor and some electrodes on your fingers (like a polygraph machine). Could send the output to your computer.

Edited by Ben, 01 March 2012 - 03:06 PM.

[ATA]

HR dount give my much info ,GSR (galvanic skin response) is usabe for stress measurment but i dount have it.

In lab i have EKG,EEG,pulse oxymetr but i dout get there for long time

i try once to measure dlpfc activation on eeg but there was a porblem with EMG noise from eyes nd facial muscles in gama band , in future i must prepare bettre protocol and filters

[Ben]

I'd be very interested to see the results using those measurements.

(Also, stand by for many emails. Your Czech hacker space thread has been linked to on boing boing.

[zeroskater6979]

if anyone ever gets their hands on a professional device let me know.

[Krell]

http://blog.makezine...ation-tdcs-kits

[zeroskater6979]

there's no link to the actual kit or any way to buy it. once they fix that i am all over that kit.

[hjmiii]

Anyone attempting to control the current digitally? I have an electrical problem, and I'm looking for some help.

I have prototype using an arduino, a digital pot, and a LM334 adjustable current source with 2 x 9v. For electrodes I'm using 6cm diameter ceramic EMS electrodes against saline soaked sponges.
The theory is with digital control I can do double blind trials by just varying the programming on the devices. This also gives the obvious advantages of changing the current and automating the time of delivery.

The problem I keep having is measuring the current being delivered as it's running. The method I was attempting was to run the output current (anode) through a small resistor load and measure voltage on both sides using the arduino analog to digital converters and a voltage divider. This brings the voltage down to the 0-5v range allowed by the arduino, and with a little math based on the known small resistor size I can calculate the current travelling across the circuit. After the standard resistor it outputs to the anode electrode. This works fine with normal breadboard circuits and static resistor loads, but as soon as I introduce saline soaked sponges or a human-sized load my ADCs start returning bogus values.

One thought I had was perhaps the layers of sponge and electrode are creating a capacitance, or perhaps the human load is just too high and the voltage is jumping up to where the voltage dividers are too small. Maybe it's just a limitation of the microcontroller. Anyone with some electrical insight would be appreciated.

[ATA]

http://blog.makezine...ation-tdcs-kits

its only a joke there no info and they use part of my image with electrode position , far i know resistor Lm 456 dount exist

[1thoughtMaze1]

i dont trust it, i dont trust any dyi devices or experiments, and i can't even interpret the data the guy posted, its complete nonsense. it's a shame there aren't any consumer versions that the public can buy. i think there have been enough studies demonstrating its safety and efficacy.

This company sells professional devices and had lots of studies posted

http://soterixmedica...ublications.php

Oh and let us know how it goes!

Edited by 1thoughtMaze1, 06 March 2012 - 12:15 PM.

[Nootr]

If i have flashes throughout the whole session of tdcs can i damage my neurons? If amperage changes from 0.5 -1.0 mA, i.e. not stable can I damage neurons?

[ATA]

i think no but i have very limited info about this
there is the technique claled pulsed tDCS using pulsing DC current , and CES using AC waveform or pulse in CES current about 0,5mA

better for safety be to avoid flashes - flashes during the sesion menas bad connections -) repair/improve it

[Ben]

Just wondering, if I wanted feedback on how much voltage / amperage was going through my brain, how would I do this? I'm thinking of building some sort of display that will show this. Could I just add wires to the pads where they connect with my head--a sort of feedback measure?

[ATA]

yes you can use digital multimeter to mesure when stimulating

measure current and try regulation (on 10kO trimmer) befere put it on the head !!!