Horrible mistakes – Wrong parts order

This week I finished the board design for the muscle sensor, after trying several layouts.

( old ones )


Here’s the fake final look.

And I use OtherMill to mill the board, because the Roland can’t do the curvy routes.

And here’s the result whoo!


And then when I was happily ready to solder the parts on, I found out that what I ordered for the 150K, and 80.6K resistors were way too small!! Their type are 0402 instead of 0603! What was I thinking?! So tiny omg *_*


After being down for a while, I ordered parts from DigiKey again and refueled my life with hope.

And, I also found out that I have surface mount 1N1418 diodes when I was examining my parts ( so many mistakes ooops ), so I changed the schematics again! Replacing the through hole diodes with the surface mount ones, creating curvy dimension, and a making a hole for hanging, possibly.


Muscle Sensor MASK version

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).



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!

Roland & Surface mount soldering


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



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 mistake_1
  3. Couldn’t find 100 resistor and used 220 resistor –> too much!
  4. So now it rest on my Failure Wall 

sound to light analog circuit!

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!

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