Spring 2016 RoFi: PCB Layout

Christopher Andelin (Project Manager)

Mario Ramirez (Systems Engineer)

Qui Du (Manufacturing Engineer)

Andrew Laqui (Electronics and Controls Engineer)

Henry Ruff (Electronics and Controls Engineer)

Table of Contents

PCB Layout

Qui Du (Manufacturing Engineer)

Once I received the PCB schematic from the Electronics and Controls Engineers, I create the PCB layout.

First, I clicked on the Generate/Switch to board button at the top left corner of the schematic window. Then I clicked Yes on the Warning window to confirm that we will create a PCB layout from the schematic. The below window will appear:

Figure 1: Generate/Switch to Board

Adjust PCB Board Size

I designed the PCB board the same size as the Arduino Mega (101.6 X 53.33mm) to allow the user to interchange the PCB with the Arduino Mega in RoFi’s head. To adjust the PCB board size, first I turned grid on by clicking the Grid button → changing the Unit to mm → selecting On at Display → and then by clicking Ok. Then I clicked on the top right corner of the white rectangular and adjusted the until shape until it reached 101.6mm X 53.33mm.

Figure 2: Turn on Grid Display and change unit length

Figure 3: Adjust the size of PCB board

Visualize and Understand PCB Design

Figure 4: System Block Diagram with Arduino Mega

Since our level one requirement requires that we not use the Arduino Mega; we installed the ATmega1280 chip onto our PCB board. We still need to adjust the pin mapping from the ATmega2560 board to the ATmega1280 chip on the system block diagram. More information can be found at, https://www.arduino.cc/en/Hacking/PinMapping2560.

Component placement

The power trace takes up a lot of space on our PCB, therefore, it is better to isolate the power supply with other components. In my design, I placed the power trace on the top border of the PCB board.

I began placing the ATmega chip, Bluetooth, USB chip, Accelerometer/Gyroscope onto the board and placed all the supporting components around them. Then I used smash features to smash and delete unimportant names on the PCB layout.

Figure 5: PCB Component Placement

Make a Ground Plane and Copper Pours

Apply polygon on top layer.

Figure 6: Draw Polygon on Top Layer

Next click the Ratsnest button to view the ground plane.

Figure 7: Top Layer Ratsnest Results

Apply Polygon in bottom layer.

Figure 8: Polygon Applied to Bottom Layer

Click Ratsnest button.

Figure 9: Bottom Layer Ratsnest Results

Draw a Wire Signal

Determine a current width trace

According to our power report found here, https://www.arxterra.com/spring-2016-rofi-preliminary-project-plan/ each servo can draw up to 1.896A.

Figure 10: Current Draw

Since we plan to order our PCB board from www.4pcb.com, I used the trace width calculator from their website to determine the trace width of each wire.

Note: The thickness of the trace cannot be adjusted in Eagle CAD. We can order the trace thickness when we send the PCB layout to the PCB fabrication house. In our PCB layout, we ordered a 2 oz/ft^2 thickness.