The Motor Driver
The motor driver has a lot more components to it than the Analog Reader. But don't worry, it's still pretty straightforward to solder, and it's a great opportunity to practice your soldering skills on a more complex board!
Components and placement
For this board, you'll need:
| ID | Component | Description | Quantity |
|---|---|---|---|
| 1 | 5-pin JST-PH Connector | Connector towards the Main Board | 1 |
| 2 | 2-pin JST-PH Connector | Connector towards the Main Board | 1 |
| 3 | 3-pin JST-PH Connector | Connector towards the Paw Board | 4 |
| 4 | 0805 220Ω Resistor | Short-circuit protection resistors | 14 |
| 5 | 0805 2.2kΩ Resistor | Pull-up resistors for I2C bus | 2 |
| 6 | 0805 100nF Capacitor | Decoupling capacitor for the ICs | 2 |
| 7 | 0805 200kΩ Resistor | Level-shifter resistor | 1 |
| 8 | SSOP-8 PCA9306 Chip | 3.3V to 5V I2C level-shifter chip | 1 |
| 9 | TSSOP-28 PCA9685 Chip | PWM Motor Controller chip | 1 |
While placing the components, make sure that:
- The JST-PH & XT30 connectors are oriented correctly, with the connector centered inside the silkscreen markings on the PCB.
- The PCA9685 chip is placed in the correct orientation, with the little notch on the chip towards the right (where the 5-pin JST-PH connector is).
- The PCA9306 chip is placed in the correct orientation, with the little notch on the chip towards the bottom (where the brain icon is on the silkscreen).
Soldering the PCB
The SMD Components
All the components should be soldered following the Soldering Guide.
As for the Analog Reader board, make sure to apply the proper amount of solder paste to the pads for the PCA9685 and PCA9306 chips.
The JST-PH Connectors
Place all the JST-PH connectors on the PCB, and flip the board over to solder the pins. This way, you can ensure that the connectors are properly aligned and flush with the PCB.
If you have some solder flux, apply it to the pins before soldering to improve the quality of the joints. Use a fine-tipped soldering iron and be careful not to apply too much heat, as the connectors can be sensitive to overheating.
For each connector, solder one pin first to hold it in place, then check the alignment and adjust if necessary before soldering the remaining pins.
Final inspection
After soldering all the components, inspect the PCB carefully to ensure that all joints are solid and there are no solder bridges or cold joints. Use a magnifying glass if necessary to check for any issues.
If you have a multimeter, you can also check for continuity between the pins of the connectors and the corresponding pads on the PCB to ensure that everything is properly connected.
Everything is looking good? Great! It's now time for the final boss!