Project: A DIY tDCS Device

Discussion in 'Electronics Resources' started by Halsey, Jun 12, 2018.

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  1. Halsey

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    Mar 4, 2018
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    Mods note:
    No video channel promotion.
     
  2. ScottWang

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    Aug 23, 2012
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    Is this project design or build by yourself?
    (if not then we will move it to other properly forum.)

    If you want to share your project to the members, please check How to post a project to the collection first and add some more documents, circuits, pictures, when you complete the contents and pass the approved and then we will move it to The Completed Projects Collection forum (there are many projects that they can be your reference), thank you.
     
  3. Halsey

    Thread Starter Member

    Mar 4, 2018
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    Yes, I did build this and it is my design. The schematics are shown in the beginning of the video. This video is composed of pictures and each step of construction, though some changes are using a 50k Potentiometer instead of a 5K and using a DC jack and cable instead of wires simply exiting the case, making it more modular.
     
  4. Raymond Genovese

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    Mar 5, 2016
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    I watched your video for your transcranial direct current stimulation (tDCS) device. Can you please comment on how you incorporated safety measures in your design?
     
  5. -live wire-

    Active Member

    Dec 22, 2017
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    Why would you not just create a real constant current supply to get rid of the fine tuning with analog stuff? You could easily do so with a buck/boost converter that is designed to supply constant current. I assume the goal is to stimulate a brain with a controlled constant current. I do not see anything in there to limit the current. If their brains are less restive, you may end up applying a dangerous current.

    I do not understand this. Why are you making your own medical device for something that is so vital? Shouldn't you at least not cut corners here and make a real design? There are plenty of other great electronics projects you can make where you are not jeopardizing people's health and safety. Additionally, after doing some research, it only appears to be helpful for a few neurological disorders, but useless or even harmful for healthy people and people with other disorders. Are you aware of that?
     
  6. Halsey

    Thread Starter Member

    Mar 4, 2018
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    Let's clear a few things up, this is not a medical device and is not regulated in anyway whatsoever. This is actually an improvement for DIY devices with thousands of people using these devices, mostly DIY devices are used without reports of any injury except maybe some skin irritation, even the commercial ones usually do not include a way to measure the milliamps of have a readout, so you don't really know what you're getting. Reading one article does not mean you are informed. This device has a lot of potential and there is much interest in this field. The lm334 chip is designed to regulate current which is included in the circuit.

    The potentiometer is there to simply ramp the current manually, once the resistance is reduced, the lm334 reaches its target milliamps.

    You can not get a damaging amount of current from 18 volts, there is a current regulator in the design as well as a digital readout. The skin has far too much resistance for 18 volts to ever be a serious threat of injury.

    For instance DARPA uses this device with an electrode placement so that people learning to navigate and identify enemy targets with drones require less training time to do so with this device. However, then people think this electrode position help you learn faster, but this is not the case, it may well help to learn faster, but only for visual spatial memory specific to that task. So, it can have a beneficial effect in even healthy people, but if you don't have a strong grasp of the underlying neural circuitry involved in some cognitive task, you will likely end up not doing anything in particular. Like if someone thinks the DARPA montage is for learning in general and thinks it will help them learn math faster.
     
    Last edited by a moderator: Jun 15, 2018
  7. -live wire-

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    Dec 22, 2017
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    I thought it was being directly applied to the brain, or dura mater or something. Or at least to the skull with a highly conductive gel. Your internals can have a resistance of only a few hundred ohms. So at 18V, with 1k total resistance, you may have up to 18 mA! They have shown that these levels of current lead to severe brain damage. Regardless of the safety of the design, I do not trust a hobbyist to make medical devices. Do you want a chip that could easily fail between your brain and a voltage source like that? And it is a warning sign when there is so much linear/analog stuff. It shows a lack of fundamental understanding of more advanced principles.

    I could not find a datasheet for that chip. Even then, a chip and some potentiometers is not enough. And it should not be so manual.
     
  8. Halsey

    Thread Starter Member

    Mar 4, 2018
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    lm334: http://bfy.tw/Ic0G
    tDCS is not regulated as a medical device, therefore it is not considered a medical device.
    The chip will only output a max of 10mA, if it fails the circuit no longer works.
    "So at 18V, with 1k total resistance, you may have up to 18 mA! They have shown that these levels of current lead to severe brain damage." - I would really like a link to this study/article.

    Also to give you some perspective, electric convulsive therapy which is done with a medical device delivers 800mA for a 6 second period to the brain, unlike my device this does cause brain damage.
     
    Last edited by a moderator: Jun 15, 2018
  9. -live wire-

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    Dec 22, 2017
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    Here is one of many sources saying that when the skin is pierced, the resistance can be under 1kOhm, and that nervous/muscle tissue is the most conductive.
    https://van.physics.illinois.edu/qa/listing.php?id=6793

    That is insane! But according to this source, it is much less current when done properly and it requires anesthesia. This shows that real medical treatments administered by real doctors are much less likely to lead to those issues than less reliable devices.

    I do not have the link but it showed that equivalent levels of current cause brain leasons in rats.
     
    Last edited by a moderator: Jun 15, 2018
  10. Halsey

    Thread Starter Member

    Mar 4, 2018
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    It is fact that electroconvulsive shock treatments cause brain damage, I know a few people, one of which no longer knows their left from right and can not read at the level they used to. These are considered things to weigh against the therapy vs the potential to remediate the illness, but brain damage occurring from that intervention is not disputed anymore. I have never heard, of all the studies and enthusiasts anyone acquiring brain damage. I remember a wikipedia article mentioning rats, but you have to convert the metrics they used. In this device 2mA over a 2"x2" electrode is roughly .039mA/cm^2 of current density, which is about what they use in studies give or take. Some studies have used up to 5mA total current with a similar surface area. There is a pretty wide safety margin for these current levels. I've seen people mess up with a bad setup(not my device), they quickly feel a sensation of pain and shut off the device. If it did exceed 5mA it would become uncomfortable due to skin irritation and they would shut off the device, this is the worst case scenario.

    I believe it was in A/M^2 for the rats. Here: Studies have been completed to determine the current density at which overt brain damage occurs in rats. It was found that in cathodal stimulation, a current density of 142.9 A/m2 delivering a charge density of 52400 C/m2 or higher caused a brain lesion in the rat. This is over two orders of magnitude from what is currently being used.
    An order of magnitude is an approximate measure of the size of a number, equal to the logarithm (base 10) rounded to a whole number. For example, the order of magnitude of 1500 is 3, because 1500 = 1.5 × 103. So, if I'm using protocol, I would need roughly 1000 times the current density to cause damage which two 9 volts can never do. The device is limited to 10mA.

    The chip is limited to 10mA of current regardless of condition of the skin. There is also a link on the video page to an article which discusses the protocols for use, skin prep etc.
     
    Last edited by a moderator: Jun 15, 2018
  11. wayneh

    Expert

    Sep 9, 2010
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    FWIW, here's a similar project.
    https://forum.allaboutcircuits.com/threads/micro-current-electrical-stimulation-device.126578/

    Mine limits current to no more than ~600µA, like the more expensive commercial devices. Of course it may be less than that if the impedance of the patient's body is too high.

    I disagree strongly that 18V cannot deliver a 'damaging' current. Here's why: I was extremely skeptical of this whole concept at first and, after reading more about it and learning that it's legitimate, for some reason I decided to connect a 9V battery directly to my opposite ear lobes. I initially felt nothing and wondered how this could possibly do any good. After a few minutes though, there was a massive and profound effect. It was not unpleasant, just odd. I stopped as soon as I realized something was happening and that there was a lag. I was concerned that the feeling would continue to intensify. Thankfully the feelings passed after a while. I would never want to have a longer treatment at a higher voltage. Maybe it would not produce lasting damage, but I'm not eager to be the guinea pig to find out.
     
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  12. -live wire-

    Active Member

    Dec 22, 2017
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    10mA still seems like a lot. Across the heart it could easily be fatal. But is it drastically different for the brain? How sure are you?
     
  13. Halsey

    Thread Starter Member

    Mar 4, 2018
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    10mA would probably cause skin irritation and pain, so if someone intentionally set the device to this, they would not do it for very long. The answer to your question is in what you just quoted. You would need roughly 1000 times the current density to match the damage they observed in rat brains. The heart has one job which is to beat and even a short duration of it not doing so can cause unconsciousness. There is a small area of the heart that has the job to send out this electrical signal to make the heart beat, the heart is setup this way and the heart moves whereas the brain does not. I think when it is referenced of mA being able to stop the heart, they are talking about the current directly across the heart. I did read one study where they used tDCS with one electrode on the head and one on the the inner thigh, which began to cause heart abnormalities so they had to stop and I can't recall if the particular subject had a pre-existing heart condition. I don't remember the current they used. I think this was a bad idea on their part and it may have been a much older study. There is risk involved in everything, some people bring hairdryers into the shower with them, this does not mean that the devices are inherently unsafe. I have concluded the risk is minimal and there have been no studies to my knowledge that it is dangerous or harmful or a mechanism whereby it would be. Some neurologists were skeptical that such low currents would do anything to the brain at all. However, I can say I do not know for sure, but they experimented with this in the 60's for a bit and did not go anywhere with it. Now that there is access to neuro-imaging and the wealth of data that came with it in understanding brain circuits it has regained interest. If I thought there was a risk of injury with this device I would have never made the tutorial and I believe that it is pretty safe.
     
  14. Halsey

    Thread Starter Member

    Mar 4, 2018
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    So this is an Alternating Transcranial Stimulation Device? Are you familiar with Ardruino? Could this be done with that device fairly simply? I just briefly skimmed it and will have time to look over it more thoroughly later, looks interesting.
     
  15. -live wire-

    Active Member

    Dec 22, 2017
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    I know that the heart and brain are different but I imagine interfering with certain parts could still be harmful. And why take a chance? The best possible outcome is a slight improvement, but if you do it wrong you may regret it for the rest of your life.
     
  16. -live wire-

    Active Member

    Dec 22, 2017
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    Arduino is not meant to supply real power. Maybe a few 10s of milliamps to some LEDs (or a brain;)), but that's it. And it operates on 5V. However, you can use transistors to control the power delivered from something much more powerful. If you want to get started programing arduino, it's simple, easy, and cost effective. Just download their software onto your computer, get a cable, and get an arduino to program.

    If you want to get started, you can get a kit, or get only the stuff you need for your project. Here is an arduino with the USB cable, for just $5. If you even just have some LEDs, resistors, and pushbuttons, you can make some pretty cool stuff.
    https://www.ebay.com/itm/USB-Nano-V...uino-W-Cable/121899176682?hash=item1c61c1d2ea

    Here is a good kit. It will allow you to learn the basics and make more advanced projects.
    https://www.amazon.com/Elegoo-EL-KI...05207&sr=8-1-spons&keywords=arduino+kit&psc=1

    I also made a ton of interesting automation/robotics projects with a 10 pack of servos. You do need an external power supply for more powerful stuff. You can google "arduino projects", "arduino 101", and "arduino projects for beginners". You could also ask us any questions you have. But maybe start another thread for that.

    Regarding their use in this situation, a microcontroller based solution would allow you to easily integrate a screen and more precise control, as well as many more features. But it really depends on what exactly you want here.
     
  17. Halsey

    Thread Starter Member

    Mar 4, 2018
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  18. wayneh

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    I’m sure you could go wild with all sorts of timings and waveforms if you bring a microprocessor into it. I just don’t feel like climbing the learning curve.
     
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  19. ScottWang

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    Aug 23, 2012
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    The project post on The complete Project Collections forum is not just showing your results, the purpose is for the members can be copy it, reduplicate your project, when they need it and could copy it, so that's why we asked you to provide some more details, and thank you for your cooperation.

    If you wish this thread move to The Completed Project Collections forum, please recheck my posted on #2 and follow the guidance and click the "Report" button.
     
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