The Paw PCB
Let's continue the soldering process with the Paw PCB. This board does contain a few SMD components, which will be the perfect opportunity to apply the soldering techniques we talked about.
Components and placement
For this board, you'll need:
| ID | Component | Description | Quantity |
|---|---|---|---|
| 1 | 4-pin JST-XH Connector | Connector for the servomotors | 6 |
| 2 | 2-pin JST-PH Connector | Connector for the feet contact switches | 2 |
| 3 | 3-pin JST-PH Connector | Connector towards the motor controller | 2 |
| 4 | 4-pin JST-PH Connector | Connector towards the analog reader | 2 |
| 5 | 0805 4.7kΩ Resistor | Pull-up resistor for Feet Contact Switch | 2 |
| 6 | SOT-23 3.3V LDO | Voltage regulator for Feet Contact Switch | 1 |
| 7 | 14 AWG Wire - XX cm | VCC wire for motor power supply | 1 |
| 8 | 14 AWG Wire - XX cm | GND wire for motor power supply | 1 |
While placing the components, make sure that:
- The JST-PH connectors are oriented correctly, with the connector centered inside the silkscreen markings on the PCB.
- The VCC and GND wires are soldered to the correct pads.
Soldering the PCB
The SMD Components
This board contains a couple of SMD components. Don't worry, they aren't too small and you can easily solder them using the techniques we covered in the Soldering Guide.
Little reminder : Resistors are not polarized, so they can be placed in either direction.
For the voltage regulator, since it has only 3 pins, it's pretty easy to identify the correct orientation by matching the pins and the pads on the PCB.
The Connectors
Place all the 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.
The Wires
Finally, solder the wires for the motor power supply. Make sure to solder the VCC wire is connected to the bottom pad, and the GND wire is connected to the top pad.
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.
A TNY-360 uses two of these Paw PCBs, one for the front legs, and one for the back legs. So make sure to repeat the process for the second board as well!
You've done that? Perfect! Let's make the next PCB!