I really love my 12-lead ECG machine I got for £10. It prints using thermal paper, and has an audio output that I put into the laptop mic input. It's not dangerous at all so you shouldn't be afraid. Sticky electrodes can be had for very little on ebay.
Happy to help others with their experiments.
I've been working on a side project (https://octopusmetrics.com) that allows you to connect these devices to your computer to record, visualize and analyze your EEG data in the browser. I think it's great that there are people out there thinking about how to do this more cheaply as it'll bring _real_ EEG devices into the price range where it'll be more available to hobbyists.
For example with an EEG sensor you can do neurofeedback training to improve attention, which has been shown to help with ADHD and even epilepsy, among other things. For this purpose, the Neurosky Mindwave Mobile with its low price tag and bluetooth interface is certainly a better choice than any homegrown amplifier.
For EMG, besides controlling something, feedback training is also possible. For example when EMG sensors are attached to your shoulder muscles you can teach yourself to actually relax them. The computer can then alert you to unconscious tension building up, during typing for example.
I don't know if ECG (I think that's the correct English spelling) has been shown to be useful in biofeedback, but the trainability of heartrate is well known.
Here is a much older article from 2003; it begins with a dire warning.
> This device requires you to strap electrodes across your chest. This is inherently dangerous. Both because of the pain caused by sticky tape pulling hairs out of a person's body and also because even small currents can kill. Do not attempt this experiment unless you fully understand the potential problems with this device.
Here is another article from 2007; again, it begins with a dire warning.
> Before I continue to explain what I did, I would like to WARN you! 500mA (miliAmps) on 220V will completely destroy your nervous system (so run it from battery supply), check everything twice and you are responsible for it on you own.
In this article from 2013, there is a rather extensive back/forth paragraph ;P.
> If you’re worried about electrical shock, or unsure of your ability to make a safe device, don’t attempt to build an ECG machine. For an ECG to work, you have to make good electrical contact with your skin near your heart, and some people feel this is potentially dangerous. Actually, some people like to argue about how dangerous it actually is, as seen on Hack-A-Day comments and my previous post comments. Some people have suggested the danger is negligible and pointed-out that it’s similar to inserting ear-bud headphones into your ears. Others have suggested that it’s dangerous and pointed-out that milliamps can kill a person. Others contest that pulses of current are far more dangerous than a continuous applied current. Realists speculate that virtually no current would be delivered by this circuit if it is wired properly. Rational, cautionary people worried about it reduce risk of accidental current by applying bidirectional diodes at the level of the chest leads, which short any current (above 0.7V) similar to that shown here. Electrically-savvy folks would design an optically decoupled solution. Intelligent folks who abstain from arguing on the internet would probably consult the datasheets regarding ECG input protection. In all cases, don’t attach electrical devices to your body unless you are confident in their safety. As a catch-all, I present the ECG circuit for educational purposes only, and state that it may not be safe and should not be replicated There, will that cover me in court in case someone tapes wires to their chest and plugs them in the wall socket?
ECG can cause safety issues if there is a significant current across the sensor leads, but even that is unlikely unless the completely wrong resister values used and the person hypothetically has a heart condition.
Disclaimer: I'm not a physician, neurosurgeon or lawyer. I did however design and repair EEG systems.
Most hobbyist designs, like the one in this article, do not have such protection. Indeed, for this particular circuit, a simple static discharge, as might happen when you're applying the electrodes after walking over carpet, can fry the input amplifier, connecting it to the power rails. ESD (and, indeed, defibrillation -- which is about a thousand times more energy than ESD) protection would be present and required in any medical biopotential amplifier, even unrelated to the single-point protection described above.
If the ESD failure happens to short out to power rails, your current will be your power rails divided by your electrode impedance. This distribution is described in EC11/EC13 (although electrode technology has improved since the days when those tests were done, so impedance is even lower). Even with the ancient electrodes in EC11/EC13, you would get unsafe currents some of the time. With modern electrodes, you would get unsafe currents much of the time.
I've seen dozens of circuits for home EEG/ECG/EMG. Almost all of them, including this one, are a deathtrap. They will work okay most of the time. At some point, someone's going to kill themselves.
Disclaimer: I am not a physician, but I've designed ECG circuits all the way through safe, successful human trials.
Most of the "danger" comes from poor isolation. The skin resistance is too high for EEG to cause major problems. I realize the actual standards have requirements that are detailed and somewhat strict.
The difference is that ECG has sensors that can directly put current through the path to the heart so the risk is higher if there is a worse-case ESD latchup. 5mA is enough to stop a heart in certain conditions.
EEG isn't ECG or EMG and have different characteristics even though they seem vaguely similar.
PS. My contact info is in my profile.
With electrodes, the current can be /much/ greater than touching metal wires with a finger. Single-digit kilo ohms is typical. The big ECG paddles are tens of ohms, probably.
Another way to think about it -- have you ever felt even a 24v battery? No. Now You know that 9v tingling on your tongue? That's saliva and a tiny contact area. Now think of a large patch of engineered electrolyte can do.
That alone is a massive problem - how do you know? Most people only discover things like this when things start going wrong. And if you make things go wrong, then you risk doing even more damage. I've never had any of the tests done professionally, but I imagine there is a certain amount of assessment that takes place before the tests are even conducted.
It has some background as well as an example circuit with a discussion of safety and isolation issues which is a bit more in-depth than the posted article.
For the posted schematic: at least put some current limiting resistors on the electrode leads.
Free ECG software: http://www.neozap.com/freeECG.htm
Neuralfeedback training: http://vimeo.com/69318799
DIY EEG/EMG can be used for alot of interesting applications though, if you want to play around with "mind controlling" things ;)
Generally though it does rather seem that there is going to be an increase in the amount of data that patients bring to clinic; what may appear to be little more than silly iPhone apps today might well become the important monitor tools of tomorrow. My guess is that this will create opportunities for online analysis startups to perform data triage an initial review, turning the data into something more valuable.
Edit: To be clear, there will be no actual barfing or slurping involved.
I'm a bit hopeful it will go on sale in some other country soon that doesn't require a prescription and I can have one shipped to me.
It's nice to see DIY moving from blinking lights to really useful and serious areas.
I've had a few EEGs and there was never any on the chest. Proper placement would seem to be an issue.
I guess you've never had a polysomnography. There are electrodes placed on the scalp, chest and leg.
I hope it it makes the difference between the infrastructure it has taken to build to get care within our reach and the less infrastructure available / needed in different corners of the world.
Things didn't end up the way they are by accident. The current situation is the result of decades of medical devices and interventions killing people because of faulty design. It's not unlike the situation with the FAA and airlines.