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Using headphones/headphone jack for input to magnet implant
I have a few smart phones that are basically good but have broken screens that I've been looking for a project to work on with. I was having a hard time imagining the output from the phone to the magnet when I realized that the headphone jack is the perfect thing, assuming it can produce enough juice to be noticeable. I haven't found anything that has the range of sensitivity with these magnets, and mine is too new to test. Is that something that's out there? Would using the transducers from a set of ear buds work?
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Also, is there any reason I couldn't use an analog sensor and then just amplify the output? Would that input be too difficult to understand?
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Good questions and good job thinking of ways to use an old phone. Smart phones are potentially great platforms for some kinds of projects. Unfortunately the wattage ("juice") from a headphone jack won't be enough by itself. "Invisible Headphones" [LINK] have a portable amplifier and a coil all ready to go out of the box. Cheap audio amplifiers, [LINK] may do the trick if you connect them to a coil of wire. Those may give you a usable output.
Hooking directly to an analog sensor won't work most of the time. Practically never. There are two problems. Most sensors can't supply enough wattage to drive an electromagnet we could sense. The second problem is that the output wouldn't be a signal we could recognize. The easiest thing to feel is a pulsating field because it's constantly changing so it VIBRATES our magnets. Many analog sensors don't change frequency and the ones that do are a frequency we can't appreciate. Most of the times putting a $2 Arduino between a sensor and a coil will do the trick.
Bad news: it's not plug and play.
Good new: it's not hard to learn if you're willing.
Even better news: there is probably already a project out there similar to whatever you want to do.
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"The second problem is that the output wouldn't be a signal we could recognize."
This is my main question. If you amplify it, which is easy, then could you alter it analogly to be more comprehensible? Could there be a learning curb on that sort of thing?Do you know if there's any hard numbers on sensitivity of finger magnets? -
Amplifying most signals still won't produce usable output. It's like a matter of language, if you don't understand French then someone SHOUTING in French won't do any more good than speaking normally.I don't remember the exact hard numbers for fingers but I think we can sense 20Hz or 60Hz better than other frequencies. As far as computers and electronic sensors are concerned this is slow and they will operate at a higher frequency if the output a waveform. Orders of magnitude higher. And that's only the tiny slice of sensors which output a frequency.Fortunately, generating a frequency in this neighborhood is easy for computers and microcontrollers. What do you have in mind? What do you want to sense?
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I wanted to start with a heart rate monitor. Ultimately I'd like to figure out what could be most useful to me as a street medic at protests.
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I see where you’re coming from. Now I’m intrigued. Personally, I rarely find a person’s pulse on the first try and usually just end up jabbing his or her neck for a few moments. When I do find it I second guess and wonder if I’m just feeling my own pulse. Also, street medic sounds BA. Next time lead with that!
You probably already know there are plenty of sensors which can detect a pulse just by touching skin. This would be great if you had to take a pulse from someone who’s covered in blood and you don’t want to put your hand there. That type of signal COULD be amplified. It won’t be a very good signal mind you unless you add more components like a Schottky transistor, op-amp or a microcontroller to activate an electromagnet digitally. The difference is that you will feel a CLICK instead of a slow build-up which may be too subtle. Honestly, unless someone tries this it won’t be clear if the conversion is necessary.
Now, you don’t gain anything by using a finger magnet as your feedback device other than only cyborgs or people holding magnets can use the device. And the first version will look rickety so maybe not a good thing to find in your pocket at a protest. At least it’s not a clock, eh?
Anyhoo, I have one of those amps and a pulse sensor at my apartment so I’ll see if I can whip something up tonight. In my left hand is a Haworth magnet and an m31. I also have “invisible headphones” so maybe I can try those out too. Like I said, this first version will look rickety.
Can you tell me how you expect to USE the device? Do you want to simply place some mysterious black box on your patients and know their heartrates? Walk us through a scenario.
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I was hoping to have it in a glove form factor, not a box, so I would just have it with me and not worry about pulling it out or about weirding people out *too* much. Honestly, a pulse finder would be plenty, but I'll have to do some research on exactly how those would work.In regards to a practical scenario, I'd like to have easy access to the heart rate/pulse just through a glove and then a thermometer separate. The biggest issues at protests are dehydration, heat exhaustion, and hypothermia. If there's a situation where there's blood all over then I expect that it's beyond my skill level at this point, but these days that's certainly a possibility. In that case it would be very helpful for triage.This would all work a lot better with an invisible headphone. Is that in the tragus?How much training have you done with the magnets? I know with things like color and pitch you can train yourself to differentiate a lot more than you'd expect. It seems like that should be true with this as well.Sorry if I'm full of questions and not a lot of answers, I'm chomping at the bit to heal up and start testing this thing.
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Who would you be testing? If you’re reaching out to take someone’s pulse they shouldn’t be any less worried about a glove with electronics than a small plastic box. Would it be more convenient to carry a fingertip pulse/oximeter. Those are like $12-20 so practically disposable. [LINK]
I mentioned the invisible headphones as an amplifier, not because I wanted to use sound. 1-2Hz would not be audible anyhow.
I haven’t done formal training with my magnet but when I pass my hand over something where I expect a field and I don’t feel one I realize it. Like seeing a room where one of several lightbulbs has burned out. For your training you could simulate a particular heart rate, 80bpm, and get used to the rate. From there you could estimate the difference and say, “This heart rate is (significantly) faster/slower than 80bpm.” But you won’t be able to tap a person on the shoulder and know their heart rate in a moment.
Most likely the inexpensive heart rate sensors from eBay will be prone to noise and only fluctuate a tiny bit. A microcontroller can detect these changes but if I’m right an implanted magnet would not move noticeably. -
My goal is to have a glove with a small form factor, something that doesn't look bulky and computery, for lack of a better word. It would have to be relatively small on the hands so you could get nitrile gloves over it, which is necessary for safety reasons. I've got a pair of neoprene gloves that would work well I think, just sew some of the components in.As for what's most practical, I don't think that there are very many things that currently are more practical to use an implanted magnet for. I want to do this with an implant, that's the core point to it, seeing if I can. I'll worry about practicality after that.
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The pulse sensors I'm thinking of need to see skin. They can probably be behind a clear layer but they need visible skin to work. Same with the fingertip sensors I mentioned earlier.If you need a new sanitary surface before touching a new patient it would need a clear layer like Saran Wrap each time. All of a sudden it is not very convenient.
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The goal would be to have the glove small enough to fir a nitrile glove over it. You have to do that anyway when you might have contact with a bodily fluid. If you can keep the part that covers the hand relatively small then it would be easy to get the gloves on and off.
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Size isn't what concerns me yet. The sensors need to see skin and nitrile isn't clear so those cheap sensors won't work.My other thought would be a stethoscope and microphone which could work through a flexible layer. The problem I see now is that you have to aim for a spot where a stethoscope is normally used. If you can take a pulse from the neck with a stethoscope then you're golden but if you start reaching for people's chest with your double-gloved hands people are going to be more apprehensive than if you actually had a stethoscope.In your case would it be so bad to touch everyone with the same device? You're testing for afflictions cause by environment, not microorganisms. Plus you could take their pulse from the arm. It would still be less harmful than using the door handle in a bathroom.In case it wasn't clear, I don't have medical training.
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I would be hesitant to touch an unknown person like that simply because you don't know if they have some kinda sickness that could be passed from contact. But I am also in the same boat as no medical training aside from first responder. I also mean with no gloves when I say touch some one.
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Last night I pulled out the $1 pulse sensor and an analog meter. It worked. Sort of. I had to move the IR LED and phototransistor all over before I got a reasonable reading. When it was shipped the emitter and receiver were arranged to clip around an earlobe so the light would shine through the skin and land on the receiver. After I rearranged them I could make it work by pressing them to flat skin like a fingertip or my leg.As I feared the readings were minor blips on the needle, which was why I used an analog meter. Depending on where I placed the sensor I might get readings anywhere between zero and my supply voltage. This means that simply amplifying the signal won't get anywhere, something intelligent has to interpret the signal and recognize those blips. That code wouldn't be bad but it's another piece of the build.As we've already discussed this type of sensor needs to see skin. Are clear nitrile gloves a thing? A quick search of Amazon says no.Stethoscope/microphone/amplifier/electromagnet could still work but are stethoscopes for heart sensing limited to use on the chest? I don't have one handy so I can't check.
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This sensor needs a clear IR view of the skin. You need a nitrile glove that's transparent for that slice of the spectrum, which may exist. (coca-cola is transparent to IR, but opaque to our eyes) It's not always easy to tell.
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After some looking around it seems like the Adafruit Flora platform is probably the best fit. It's specifically made for wearables and has a slim form factor as well as a good number of sensors available. The circuits can be sewn with conductive thread and it works with at least one of the heartbeat/oximeter sensors I found.The gloves aren't a big problem. There's no nitrile but there is latex and vinyl both available in clear. Obviously their effect on IR would have to be tested but it seems reasonable to expect one of those gloves to work.Of course, this means I'm back at an arduino based unit, which I should have expected. I'm also going to try setting up just a sound sensor and seeing what I can do with that in analog.
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Honestly everything you want would work better in a handheld medical unit, like the ones from star trek.
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I just got home from a boat show, I was going to say something when my account was approved but I completely forgot it other than does anyone know where there are any M36 magnets that are in stock?
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There are already hand held units that do all of this, maybe not all in one, but they definitely exist. The downside to those is that they're easy to drop in frantic situations or when being pushed around by a crowd. Both of which are rather common in at protests while running as a medic.And of course there's the fact that I just want to do it this way. I don't think we can really tell how well it will work until the prototype is put together and we get a medic or two to test it in simulated situations.
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