Prototype 8

The order of the PCB of 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:

The Signal

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 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 . Although this may lead to EM interference between the wires, reducing the quality of the signal, so maybe it's actually better this way.

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• Newer post: Prototype 8 Demo Video
• Older post: INA155 Instrumentation Amplifier
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• Date: 2021-12-18
• Author: Roman