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benkrasnow / BiteSensor

Mechanical CAD for in-mouth bite sensor with potentiometer output
MIT License
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Possible alternative to using mechanical potentiometer #1

Open victornpb opened 3 years ago

victornpb commented 3 years ago

The entire time I was watching the video I was thinking about using a LDR as a instrument interface to simulate the analog pot.

LDR_analog_read

Potentiometer like resistor divider: RockNControl_3Pole_Schematic http://www.thetonegod.com/tech/rockncontrol/rock.html

This would give you a lot of possibilites in how you can sense, like a hall effect sensor it the first thing that comes to mind for linear actuation, or even an analog opto-sensor.

You should be able to make a wireless mouth piece, using a micro controller with a builtin 2.4 radio with a ADC powered by a button cell.

benkrasnow commented 3 years ago

Victor, that's a really good idea! Thanks so much for posting this. It looks like there are some CdS cells on digikey that barely get down to a few hundred ohms, so it would be possible to make a galvanically isolated pot, and control it with another circuit. Really cool.

royvandam commented 3 years ago

Hi Ben, I was about to open another ticket when I came across the one from Victor, so I am just going to add to the discussion :)

You may or may not have considered this, but I think there is actually a way to use your original pressure based mouthpiece of which i suspect is far superior in ergonomics to the one with the build in potentiometer.

The way this would work is to use a digital pressure sensor[1] and digital potentiometer in combination with a microcontroller. The uC continuously measures the pressure and sets the wiper position of the potentiometer digitally. Which removes most of the mechanical complexity in the project and it would even allow for some signal processing like linearisation or other special effects by for example detecting patterns in bit pressure.

[1] https://sps.honeywell.com/us/en/products/sensing-and-iot/sensors/pressure-sensors/board-mount-pressure-sensors/basic-abp-series

mouthpaddle

victornpb commented 3 years ago

The sensing part I was thinking more about something like this:

https://img.filipeflop.com/files/download/Datasheet_QRE1113.pdf https://www.sparkfun.com/products/9453

The breakout board can be easily sourced from SparkFun or eBay. You could probably make it tiny by trimming the breakout board or making a custom PCB, or maybe gluing the bare STM component to the mouth piece body.

I don't know if the dynamic range would be useful for the desired distance/range of motion, but it seems like a promising choice, and you could try tweaking the led voltage, and the reflection surface color and material in order to get the best dynamic range.

There's even a possibility to make a fully analog solution, if the signal conditioning happens to fall in the sweet spot. Of course with a microcontroller is always more flexible when dealing with DSP.