The advance of electronic technology has beenĀ closely followed byĀ the medical community over the past 200 years. Cutting edge electronics are used in medical imaging solutions to provide ever greater bandwidth andĀ resolution in applications such as MRI machines, and research to interface with the human nervousĀ system continues at a breakneck pace. The cost of this technology – particuarly in research and development –Ā is incredibly high. Combine this with the high price of the regulatory approvals necessary for devices which deal in terms of life and death, and you’ll find that evenĀ basic medical technology is prohibitively expensive. Just ask any diabetic.Ā On the face of things,Ā there’s a moral dilemma. Humanity has developed technologiesĀ that can improve quality of life. Yet, due to our own rules and regulations, we cannot afford to readily distribute them.
One example of this is that despite the positive results from many transcranial electrical stimulation (TCS) studies,Ā the devicesĀ used are prohibitively expensive, as are treatment regimens for patients.Ā Realising this, [quicksilv3rflash]Ā decided to develop a homebrew, open source transcranial electrical stimualtion device, and publishedĀ it on Instructables.Ā Yes, that’s the world we’re now living in.
It’s important to publish a warning here: Experimenting with this sort of equipment can easily kill you, fry your brain, or have any number of other awful results. If you don’tĀ have a rock solid understanding of the principles behind seperate grounds, or your soldering is just a little sloppy, you don’t want to go anywhere near this. In particular, this device cannotĀ be powered safely by a wall-wart.
To be honest, we find it difficult to trust any medical device manufactured out of modules sourced from eBay. But as a learning excercise, there is serious value here. Such a project requires mastery of analog design to avoid dangerous currents being passed to the body. The instructions also highlight the importance of rigorously testing the device beforeĀ ever connecting it to a human body.
The equipment is based aroundĀ an Arduino Nano receiving commands from a computer overĀ serial, fed by an application written in Python & PyGame. To think, this writer thought he was being bold when he used it to control a remote control car! The Arduino NanoĀ interprets this data and outputs it over SPI to a DAC which outputs a signalĀ which is then amplified and fed to theĀ human brainĀ courtesy of op-amps, boost converters and sponge electrodes.Ā The output of the device is limited to +/-2.1mA by design, in accordance withĀ suggested limits for TCS use.
It should be noted, [quicksilv3rflash] has been experimenting with homebuilt TCS devices for several years now, and has lived to tell the tale. It’s impressive to see a full suite of homebrew, opensource tools being developed in this field. [quicksilv3rflash] reports to have not sufferedĀ injuries from the device, and severalĀ devicesĀ have been shipped to redditors. We’ve only found minimal reportsĀ on people receiving these, but nothing on anyoneĀ actually using the hardware as intended. If you’ve used one, get in touch in the comments.
It goes without saying – this sort of experimentation is dangerous and the stakes for getting it wrong are ludicrously high. We’ve seen before what happens when medical devices malfunction – things get real ugly, real fast. But hackers will be hackers and if you were wondering if it was possible to build a TCS deviceĀ for under $100 in parts from eBay, well, yes. Yes it is.