Prototype 6

photo of board

photo of when opened up

Bill of materials



See also Circuit 9.1





  1. Cut the "3.3V" solder jumper on the Arduino to enable it being powered by a battery
  2. Solder on both of the straight 15-pin headers to the Arduino
  3. Solder on all the parts of the PCB
  4. Attach battery clips (doesn't need to be soldered) and battery
  5. If you use the pin sockets, you can just plug in the Arduino now. See the "Arduino micruUSB socket here" inscription for how to rotate the Arduino.
    • Otherwise, do a test run and check
      1. Whether the circuit produces 5V on V+ and 2.5V on Vref,
      2. Whether it can power the Arduino (connect GND, and V+ to Arduino's "3.3V" pin) and still produce 5V and 2.5V
      3. Ideally, run GNURadio or PsyLink UI to establish a bluetooth connection to see if it's working
    • Once all tests work, solder on the Arduino. Again, see the "Arduino micruUSB socket here" inscription for how to rotate the Arduino.
  6. Attach Velcro to the PCB on the mounting holes on the corners (you may need to remove battery clips to reach the holes) with needle and threat

In the end, it should look like this:

soldered board


  1. At minimum, sew a 10cm long cylinder that fits tightly around the middle of your forearm
  2. Add whatever features you like, e.g.:
    • wrappable cover for the electronics
    • velcro straps to tighten it to various arm widths


  1. Attach the female snap button to the fabric
    • One of them (the ground electrode) should ideally be placed at the Ulna or Radius bone and should stay on the bone (if possible) as you twist the wrist
    • The others can go whereever you want. You may need to test nice spots that work with your body. I recommend the area around the Flexor Digitorus Superficialis in the middle of your forearm, since most other muscles provide signals that are redundant to the IMU signals (gyroscope/accelerometer)
  2. Hammer together the two parts of the male snap button, but not completely, leaving a little space for some wire
  3. Attach Cable
    1. Take one jumper cable (female-to-any)
    2. Only the female end is used
    3. Cut off the other end at desired length
    4. Remove 4-5cm of insulation at the cut end
    5. Add 1.5cm of shrink-on tube onto the wire (don't burn yet)
    6. Wrap the exposed wire around the ridge between the two parts of the male snap button
    7. Twist the male snap button to tighten the wire (don't overdo it, we don't want it to break)
    8. Hammer the male snap button tight
    9. Pull the shrink-on tube towards the electrode and burn it
  4. Repeat this 9 times. Each cable should be just long enough to reach the target electrode on the fabric.
  5. Plug the ground electrode into one of the Vref pins of the board, and the other electrodes into the A0-A7 pins

If you require more detailed assembly instructions or further information, please contact the author.