The order of the PCB of Power Module 4 has arrived, and so all the parts for Prototype 8 are finally here :) After some assembly (and crimping of some rainbow-colored connectors that look a little neater than those stray black wires from previous photos), this is the final picture:
And another picture:
A sample of the signal is this, using an INA128 with a gain of x228 and electrodes near the flexor digitorum superficialis:
The baseline is the midly noisy line around a value of 0.3 and shows the state of rest.
The spikes and "spindles" (periods of higher amplitude) occured when I performed various movements, like extending the arm, snapping the fingers, or twisting the wrist.
Bugs in the BP4
The Power Module 4 is not perfect though:
- The solder jumper J8, that activates the central Screw 5, overlaps with the battery clip, resulting in a short circuit with the battery's ground, unless I put some isolation tape over the jumper... Need to move the jumper further away.
- The power switch (SW1) is too close to the Screw 2, so the switch I wanted to use didn't actually fit, and I had to fall back to one that points off to the side, and looks a little awkward.
- I also wish that the analog pins were closer to the power pins, so that I can bundle up the wires, resulting in what would appear like one single connector, rather than two, per Electrode Module 3. Although this may lead to EM interference between the wires, reducing the quality of the signal, so maybe it's actually better this way.