ENGR 361 2020 Fall

Lab 1 Power Supply
Nic Theobald
nstheobald@fortlewis.edu

Power Supply Design

Introduction

This Lab covers the design of a 3.3V and 5V power supply capable of supplying 1A and 3A. Eagle PCB and an online Gerber viewer were used to design and verify the power supply.  The PCB was ordered online and  the SMD components were soldered on.

Materials

Materials
Computer	1
Eagle PCB	1
Your Brain	1
Some Patience	1
SMD Components	many

Abbreviated Methods

All of the components for the 3.3V 3A and 5V 3A were made from custom libraries (Figure 1, 2, 3, 4, 5). All of the components were first laid out in the schematic. All of the parts in the uppermost circuit came with Eagle PCB, but all of the ones in the lower circuit were made during this lab (Figure 1). New components were created through the use of custom libraries. All components were organized on the board before auto routing and the copper pour (Figure 2). Auto routing was performed and the copper pour was completed on top and bottom layers (Figure 3, 4). The board and schematic were checked through the use of DRC and ERC checks; the files were also imported into an online Gerber viewer which helped recognize any mistakes (Figure 5, 6). The SMD components were then soldered to the PCB and the board was tested.

Results

All of the components for the 3.3V 3A and 5V 3A circuits were made from custom libraries.

Figure 1: Electrolytic capacitor library.

Figure 2: Voltage regulator library.

Figure 3: Inductor library.

Figure 4: Schottky diode library.

Figure 5: Power switch library.

All of the components were first laid out in the schematic

Figure 1: Schematic for power Supply

All components were organized on the board before auto routing and copper pour.

Figure 2: Board before auto routing and copper pour.

Auto routing was performed and the copper pour was completed on top and bottom layers.

Figure 3: Top layer copper pour.

Figure 4: Bottom layer copper pour.

ERC and DRC checks were performed before export.

The 8 approved errors were from unvalued headers…

The Gerber files were imported into a viewer and drill and silk screen were confirmed.

Figure 5: Drill and silkscreen.

Figure 6: Overview of important details.

The SMD components were soldered to the PCB and the board was tested.

Figure 7: The PCB before soldering.

Figure 8: Testing 3.3V 3A.

Figure 9: Testing 5V 3A.

Figure 10: Testing 3.3V 1A.

Figure 11: Testing 5V 1A.

Figure 12: The PCB inside a 3D printed case with a 3 position switch.

Discussion:

Eagle PCB was used in the design of a power supply circuit. The circuit was designed to output 3.3V and 5V with 1A or 3A. The PCB was ordered online and the SMD components were solder on. Initially, the board was tested but didn't operate correctly. It was found that the 5V 3A circuit was not grounded. A small amount of solder mask was scrapped off, exposing the grounded copper layer. The ground tab of the voltage regulator was then soldered to the exposed copper and the power supply worked as intended.