For my final project in Circuit Design and Prototyping, I plan to make a customized muscle sensor (EMG) for my thesis MASK, and the idea is to use the data as a measurement of mask wearer’s nervousness, and try to cope with it with MASK (virtually and hopefully also physically).

Research

• Tutorials: DIY EEG Circuit, DIY EMG Circuit
• Documents: 1(general introduction ppt), 2(detailed paper), 3(a chapter of a book)
• Products: Sparkfun, Backyard Brains(1, 2, 3[2 channels!])

Breadboarding

This is the first attempt to breadboard the muscle sensor, based on the design of the one on Sparkfun and also the tutorials on instructables. Because I don’t have the component, e.g. instrumentation amp, specific resistors, there are a lot of hacky moves, and I need sticker patch electrodes, 9v batteries*2, and components to know if it’s working or not :/

 <– originally thinking to hook up two power supplies, but because it requires one’s positive connecting to another’s negative, I think I should ask Eric first to see if it’s safe to do that instead of using two batteries

Next steps

1. Order components (Should I order both surface mount(for final) and through hole(for testing)?)
2. Combine and adjust SpikeShield 2-Channel SpikerBox’ schematics, so having two inputs for microcontroller (using ATTINY)
3. Design the shape and arrangement of the circuit to fit on the mask
4. Qs to answer
   • What’s the power supply strategy to integrate microcontroller on the same board, with 9V for sensors and 3~5V for microcontroller?
   • …

Getting excited :DDD Lots of work and to be continued!

And the midterm presentation!

3/6

2nd try – SUCCEEDED!

1. Still couldn’t find 100 ohm resistor, so I tested with breadboard first and decided to use 68 ohm resistor.
2. Extended 1/64 short wire
3. Replaced some 1/64 with 1/32 to speed up milling

3/5

1st try – FAILED!

1. When wiring 1/64 route for milling in Eagle, I made them too short underneath resistor and LEDs thus made circuits inseparate
2. Wrong wiring to block the resistor to ground O_O 
3. Couldn’t find 100 resistor and used 220 resistor –> too much!
4. So now it rest on my Failure Wall 

Reference: instructables<3

I. Breadboarding

II. Eagle

Based on the tutorial of instructables, after calculation, with 9V input and yellow LEDs, I use 3 for 4 series, so total 12 LEDs, and the resistor connected to transistor will be 2.2k Ohm, and the one connected to emitter will be 22 Ohm.

The most challenging part is routing on the board. How to have an efficient route map without overlapping? Here I did a dangerous move, having a route under the electret mic, between its positive and negative hole. Don’t know if it’s doable or not.

[ UPDATED ] It’s ok to route under the mic, but should be careful not touching the pad –> adjust the width of the route to be thinner!

2/19 update, all LEDs lit up 😀

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Took so much time!! The issue is that the solder paste got cold so fast, and put it on top of the mug warmer would make it dry fast too! T_T

The circle part is the only LED didn’t light up because I put too less solder paste. Will try it again tomorrow 😀