Breakout Board
The basic idea of a Breakout Board (BB) is to create a single board comprising all the circuitry that would be otherwise on a breadboard. In most cases, the BB is the final version of the circuitry of the breadboard, with decreased footprint and significantly reduced mess of wires. The BB also has a labelled collection of connectors for sensors, actuators and power supply.
The main reasons for using a BB for the Pi Car project are to eliminate the need for a breadboard and to have a voltage regulator to power the Raspberry Pi using the same power source (battery) as the sensors and actuators. The BB has a 2x20 header component that directly attaches to the GPIO pins of the Pi. This not only electrically connects the BB and the Pi, but also provides mechanical strength between the same.
The BB was designed on EAGLE 7.70 by Dr. Humberto Gonzalez. EAGLE is a free to use software. Using a student email account to create a EAGLE account will avail more benefits. The schematics for all the required connections was created first and is shown below:
The board was made using the schematic and looks like the following:
The top (red) layer is GND and the bottom (blue) layer is 5V. The two ‘mounting holes’ on the top left and top right are aligned with the Raspberry Pi mounting holes, and can be screwed in using spacers with a screw diameter of 2.5mm for additional mechanical strength.
The Eagle file ‘rpibout.brd’ (PiCar/hw/breakout_pcb/) was sent to OSH Park (https://oshpark.com/) for manufacturing. OSH Park manufactured three copies of the board.
Top view:
Bottom View:
Care must be taken while assembling (soldering) the components on the board. It is advised to start with the smallest components (surface mount capacitors, resistors and IC) and work towards the larger components (voltage regulator, through-hole capacitors, connectors, the 2x20 header and finally the LED array). The order list for all the components required to complete one breakout board is shown in the following table. All parts were purchased from Digikey. For more information about these parts, check the Bill of Materials. Note: The Molex Ultra-Fit 172310 connector has to be sanded on the sides to achieve a good fit.
| Part Name | # per Board | Part Number (Digikey) | Ideal Soldering Order |
|---|---|---|---|
| Capacitor 220uF | 2 | 399-6113-ND | 1 |
| Resistor 267Ohm | 1 | P267FCT-ND | 2 |
| Resistor 1.8KOhm | 4 | P1.80KFCT-ND | 3 |
| BSS138 Dual MOSFET | 1 | 568-8392-1-ND | 4 |
| PTR08060W Power Module | 1 | 296-22673-5-ND | 5 |
| Molex KK 6373, PCB Male, 3 pin, vertical | 2 | WM4201-ND | 6 |
| Molex KK 6373, PCB Male, 4 pin, vertical | 3 | WM4202-ND | 7 |
| Molex Ultra-Fit 172310, PCB Male, 2 pin, right angle | 3 | WM11586-ND | 8 |
| Capacitor 1uF | 3 | 399-8148-1-ND | 9 |
| 8x8 LED Matrix | 1 | 1528-1419-ND | 10 |
| 2x20 Pinhead 0.1 Female | 1 | S6104-ND | 11 |
Fully assembled, the breakout board will look like the following.
Top view:
Bottom view:
Use a multi-meter to ensure all the connections are well made. Additionally, use a power supply to ensure the voltage regulator is working as expected.
Start by selecting a component that needs a connector and select a contact crimp socket matching the wire's diameter (denoted in AWG). After cutting the wires to the length required, crimp the socket to the wire and ensure that it is secured firmly. Plug the crimped wires into the respective female connector while referring to the BB's EAGLE schematic to connect each wire in the correct order. A snapping sound will be heard when the wires and pushed in tightly. Again, test the tensile strength of the connection. Do this for all the components.
- Breakout Board designed and assembled by: Dr. Humberto Gonzalez
- Assisted by: Adith Jagadish Boloor
- Wiki page written by: Adith Jagadish Boloor