The Pathfinder Circuit

The circuit will enable the following systems/functions:

  • PyPortal as the central brain, display, and touch screen. This can be reprogrammed over the USB data port, and can be reset with illuminated external momentary button.
  • Battery and PowerBoost converter for power and external USB port for charging. The power switch connects to the PowerBoost.
  • 3.7W amplifier and speaker with volume knob.
  • NeoPixel full-color LED for eyeball lighting.

The circuit diagram above shows how all of these parts are connected. Follow that diagram closely and build the circuit on the Perma-Proto board.

You'll see in the photos below that we'll use interconnect cables for some of the parts to make assembly into the 3D printed model easier. While it takes more work than simply soldering long wires directly to the proto board and the PyPortal, the added flexibility can be a lifesaver when trying to fit buttons and switches through their mounting holes!

Amplifier

Tie the power and ground rails of the PermaProto board together.

Mount the audio amplifier to the board as shown and then add the JST connector breakout board so the two center pins are connected to the L- and L+ of the amp board. To prevent shorting these to R- and SDWN you can cut the traces on the proto board the would join these and don't solder the outer pins of the breakout board to the proto board.

Power Rails

From the bottom of the proto board, jump the 5V and G columns where the PowerBoost will connect to the power rails.

Use a bare JST PH 2-pin connector to connect the toggle switch to the En and GND pins of the PowerBoost as shown. This will be used to turn Pathfinder on and off.

Power and Sound Connections

You can then plug in the USB power cable, the amplifier input from the PyPortal, the enable switch cable, the speaker, and the battery as shown here.

Note: ignore the DIY USB plug soldered to the PowerBoost here, we'll simply plug one end into the PowerBoost USB-B and the other to the panel mount adapter later.

PyPortal Connections

The PyPortal audio out runs to the L+ and L- inputs on the amplifier, you can see the small JST cable plugged in here.

Note: ignore the DIY USB cable plugged into the PyPortal here -- we'll leave that port free for programming and run the power over JST instead.

Reset Button

To access the reset button from the outside of the robot, solder two leads to the left two SMD pads of the programming connector as shown here. Polarity doesn't matter as this is used to short the reset pin to ground.

You can use a female socketed JST cable as shown here to make the connect to the button easier later when feeding it through Pathfinder's torso.

Knobs and Switches

Solder a two conductor interconnect cable to the power enable switch and plug it into the JST socket that extends the PowerBoost En/GND pins.

Solder an interconnect cable to the potentiometer as shown in the circuit diagram, and in order to plug it between the speaker output of the PyPortal and the left channel input of the amplifier.

Connect the speaker to the screw terminals of the amplifier's left output channel as shown.

Final Wiring

Here we can see the final wiring and the circuit powered on (we'll still need to program it before testing).

Power runs from the PermaProto board rails to one of the three-pin JST connectors on the side of the PyPortal (this leaves the USB port free for programming).

The other three-pin JST port on the PyPortal is used to send power and data to Pathfinder's eyeball NeoPixel LED as seen here.

Next, we'll prep Pathfinder's PyPortal for coding!

This guide was first published on Jun 24, 2020. It was last updated on Jun 24, 2020.
This page (Build the Pathfinder PyPortal Circuit) was last updated on Sep 30, 2020.