- I want to create a wearable device that can track the contraction of each finger in realtime such that I can do some functions based on the gestures I make
- Because of that, I need a method that is quick and precise
- I imagine of placing 3 modules on each finger, each in the middle of each bone, allowing a wire to pass through it, though a pulley
- At the base of the hand, a spring is keeping the wire in tension, just enough to keep it straight
- When bending the finger, the total wire length retracted should be shorter, because each module is closer to each other
- I want to have this wire conductive, such that I can put a contact pad at the first module, and as the wire retracted changes length, the current will have to pass though more or less wire
- If the wire has enough resistance, I can convert the voltage read at the pad into the retracted length
- This solution is very quick because it's limited by the speed of reading the input voltage, since changes in contraction changes the voltage with the speed of light
- It's also very precise since the wire is homogeneous
- On top of that, since the wire can be passed through pulley at each module, it means that it can measure in multiple orientations, instead of a straight line, like a laser or ultrasonic would do
- I don't know where to get these wires from or how to make them. I see them online marketed as heat wires, but the issue is that the most resistive one is about 20ohms/m, so my cutout would have about 2 ohms in total
- The resistance is way too small, and for a straight finger, passing 3v3 though it would mean a current of 1.65 amps, and I want it to be in milliamps
- I can place a resistor with the wire in series, but it would greatly decrease the ability to read precise measurements, since the mapped range based on the voltage read would be over 100 times smaller
- Over 100 is not bad in a perfect world, but other interferences would make this range useless
- Where can I find wires with way bigger resistance, while being very small (this one with 20 ohms/m was 0.3mm in diameter)?
Consider studying what other people are doing, for example, using strain gauges instead of resistive wires:
Ready-to-wear strain sensing gloves for human motion sensing.
- I do not want to use gloves, since I want to design something more practical, that can be used daily, not just a gimmick project. I want to be able to do all my daily work without having to worry about them
- Since the modules towards the end of the fingers involves only a pulley, they are incredibly small in my design. I would 3D-print them
- I can't manufacture custom materials, it's too much of a challenge for me, and I don't have the equipment either
this seems way more involved than a glove... and moving pieces and small parts ... not sure how long that will last
another glove link
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What you have described so far seems completely impractical and unworkable in real life.
If you want to be taken seriously, drop the "speed of light" nonsense. The rate limiting steps in digital data collection are almost always analog to digital conversion and sensor communication.
And you are how experienced with programming?
Thanks everyone for you replies. Unfortunately, they are not too useful for me.. I do not want to make a glove, I wanted to pass a couple strings through 3D printed parts. I'm experienced enough with coding, and I can design custom circuits on PCBs too, though my question was hardware related, not software. On top of that, the glove examples do not follow the same direction as I intended, their accuracy and versatility are not supposed to reach such a high level as the design I have imagined, so even if I tried them, the results would've been unsatisfactory. I'm going to continue my search for wires that fits my needs..
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