The wiring for the new electronics going into the bear is fairly straightforward. Make sure you have assembled the Adafruit DC and Stepper Motor Hat first.
USB Cable Modification Option
To power the motors, you are going to use 5V directly from the USB Power Bank. While it could be powered from the Pi, the output isn't as high and the motors are noisy which may be heard through the speakers.
For the more compact build option, you will shorten the wiring with the following procedure.
USB Cable Adapter Option
For the easier build option, you can create a little adapter for the USB cable. This method is less compact, but non-destructive.
Install the jumper wires in the female DC power adapter. It's a good idea to use different colors so it's easier to tell which side is positive and which side is negative.
Foot Button Connection
You will want to connect the other half of the JST SM connection pair to the Motor HAT. If you are soldering the white wires directly to the HAT, you should have already prepared them in the Modifying the Bear step.
MAX98357 I2S Amplifier
Because the project is using a 3W amplifier with a 0.25W or 0.5W speaker, it's a good idea to reduce the gain as much as possible because too much can actually heat the speaker coil to the point of melting the speaker cone. This can be accomplished by connecting a 100K resistor between Gain and Vin.
Prepare a 4-inch wire by cutting and stripping it. You can just use one of the jumper wires with both ends cut off if you don't have extra wire. You will also need a 100K resistor and the MAX98357 with only the terminal soldered on. Optionally, you could just solder the speaker directly to the MAX98357 instead of using the terminal.
Next, take the resistor and fold the leads down at a 90 degree angle so that they are parallel to each other.
About 5mm further down from the resistor, add a 90 degree bend in the leads keeping them parallel. Cut one side of the resistor so that the cut side touches the underside of the Vin wire and the remaining lead can be soldered to Gain pin.
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