The Power PCB
We'll continue the soldering process with the Power PCB, which handles a lot of currents so it's important to solder it properly to ensure good electrical connections!
Components and placement
For this board, you'll need:
| ID | Component | Description | Quantity |
|---|---|---|---|
| 1 | 4-pin JST-PH Connector | Connector for the I2C bus | 1 |
| 2 | 2-pin JST-PH Connector | Connector for the 12.6V power | 1 |
| 3 | XT30 Female Connector | Connector for the battery input | 1 |
| 4 | 0805 100nF Capacitor | Decoupling capacitor for the INA219 | 1 |
| 5 | SOIC-8 INA219 Chip | Current and Voltage Sensor | 1 |
| 6 | 2512 2mΩ Resistor | Current Sensing Resistor | 1 |
| 7 | 14 AWG Wire - XX cm | GND wire for robot power supply | 1 |
| 8 | 14 AWG Wire - XX cm | VCC wire for robot power supply | 1 |
While placing the components, make sure that:
- The JST-PH & XT30 connectors are oriented correctly and on the opposite side, with the connector centered inside the silkscreen markings on the PCB.
- The INA219 chip is placed in the correct orientation, with the little notch on the chip towards the bottom (where the XT30 connector is).
Soldering the PCB
The SMD Components
As for the other boards, follow the Soldering Guide to solder the SMD components on the board, starting with the capacitor, then the resistor, and finally the INA219 chip.
The Current Sensing Resistor is going to have a lot of current flowing through it, so make sure to apply enough solder to create a solid joint and ensure good conductivity (to reduce resistance, and thus, heat).
The JST-PH Connectors
Place the two 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.
The XT30 Connector
The XT30 connector is going to be the most challenging component to solder on this board, as it has large pads that require a lot of heat and solder to create a solid joint.
Make sure to apply a good amount of solder flux to the pads before placing the connector, as this will help the solder flow better and create a stronger joint.
Use a hot soldering iron with a high wattage (at least 60W) and a large tip to apply heat to the pads while feeding solder to create a solid joint. Don't hesitate to apply a lot of heat and solder to ensure a good connection, but be careful not to overheat the PCB or the connector, as this can cause damage.
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.
Looks good? Nice. Let's build the fun PCBs now!