[John Miller] has the perfect response next time he complains about an ache or pain and one of his friends says, “You should listen to your body!” As you can see in the video below, he already does. Using two 9V batteries and some instrumentation amplifiers, [John] built an electromyography (EMG) rig.
If you haven’t heard of EMG, think of EEG or EKG, but for muscles instead of your brain or your heart. The LT1167 amplifier is well-suited for this application and even has a data sheet showing how to create an EMG circuit. [John] also used some more garden-variety op amps and the ubiquitous LM386N chip for audio amplification.
This isn’t the first EMG rig we’ve seen, but [John] does a nice job of explaining why such a special amplifier is used and how it works. He also provides a lot of pointers to more detailed information, including a paper that covers the safety aspects of hooking yourself — or anyone — up to electronics.
The op amps require a dual polarity power supply, so the project uses two 9V batteries. Not only is this handy, but it eliminates any concerns about the device that connects to you getting power from the wall.
Why do you want to listen to muscles? Maybe just to do it, which is a perfectly good excuse around here. However, it is possible to use the signals to control devices like prosthetic limbs, cursors, and more. You can even move someone else’s arm with the right equipment.
We’ve covered an open source muscle interface as part of our Hackaday prizes. Our own [Bil Herd] has even used himself as a guinea pig.
Another thing to add to my to-do list.
Why? Scoliosis. Curved spine causes muscles to grow at different rates, and stretch much differently. In the people I know, this results in very painful muscle spasms. So painful that 24/7/365 fentanyl patches have been used to control it because the dose of muscle relaxant required to stop an existing cramp was high enough to knock them out. So relaxants just get used to reduce frequency. But people build tolerance to opioid medication, so one longer term solution is “facet nerve ablation”. Literally burning (or freezing; RF heat, alcohol, or cryo fluid could be used) a nerve near the spine that only exists to warn your body that you have broken a vertebra. Those nerves get confused by the malformations, and are debilitating when a muscle cramp hits.
There are problems after ablation, though, too. Imagine a muscle cramp on one half of your spine; how that would cause certain movements to be difficult or unsteady. Now imagine not feeling that cramp because feeling it would leave you crying from the pain. Knowing that the muscle is cramping after nerve ablation could possibly prevent falls, could be used to tell the person to use their TENS unit; or maybe trigger a TENS unit on the same sensors. And could track the spasms so the person and their doctors aren’t surprised by things that can no longer be felt.
If the author is listening, why use MyoWave sensor pads instead of the cheaper and ubiquitous RedDot? Is there some difference in composition, or some other reason?
Hi Quin! John (author) here. I only linked to the MyoWave sensor pads because I was lazy and didn’t find a cheaper deal on Amazon! The RedDot electrodes would definitely work and are the better choice. I’ve updated the link on my Instructable. Let me know if you find a better deal on electrodes somewhere else!
Nothing like the needle tests.
Ususaly hurt like heck. But not always.
Then a few days later?
Those bruises that slowly drift to the top of your skin.
Interesting oder that the colors show up.
Kind of an icky yellow spot that slowly gets darker.
Sort of like a “blunt trauma”(?)bruise, color scheme in reverse.
Can get some really odd looks from people as they wonder what the heck you’ve been doing to yourself!
…sometimes the rare head nod of anther person who’s been there.
All, please consider adding an [Instructables Warning] to this link. Viewing it on my mobile device (Chrome, with adblock) spawned multiple popups, at least one of which caused the phone to vibrate continuously(!) and hijacked the back button. I would not voluntarily follow an Instructables link again.
*Al (thanks autocorrect)
You don’t read the URL before actually ‘clicking’ links?
He said he’s on a smartphone/tablet, and no smartphone I’ve ever owned has displayed the link address after you click the hyperlink, it just navigates straight to the page.
You hold on the link, and info/title text shows up.
Are you sure you don’t have something infecting your browser/phone either by accident or on purpose? I can look at instructable pages on both of my devices with no ill effects. And that includes my work phone with no ad blocker and not rooted. That’s an iPhone, but my Android (which is rooted and blocks most ads) doesn’t have any problem either.
Pretty sure the device is not infested; I use it daily and very rarely get sketchy popups; this is the first ‘vibrate ad’. It’s possible it’s just an isolated rogue advertiser made its way into their supply chain, but I recall aggressive ad practices on that site in the past. Sidenote, any site whose ads make techs knowledgeable folks ask “do you have a virus?” as their first question might deserve a warning :) Just sayin’.
I am surprised anything linear with a lot of gain dis not burst out in oscillation being built on a solderless board like that. Interesting project none the less.
Thanks for writing this up, Hackaday! I’m glad you liked the project. If you’re interested in some more applications of EMGs, check out my EMG MIDI device: https://www.instructables.com/id/Make-Muscle-MIDI-Music/
At least the two 9V batteries will die long before you do; unless you want to hear to your own (ahem) suicide :-(