| Laser Pointer


Introduction:

This project is a simple laser pointer that is powered by an 18650 lithium ion battery. It takes between 3-4.5V in and gives a 5V output which is connected to a small 5V laser pointer.

This tutorial is split into multiple sections: Introduction (this one), Schematic, PCB Design, and the final product. You can navigate to any of these sections through the links above.

Parts:

For this project, I used:

- (1) PAM2421
- (1) 30KΩ resistor
- (1) 10KΩ resistor
- (1) 51KΩ resistor
- (1) 150Ω resistor

- (2) 10µF capacitors
- (1) 1µF capacitor
- (1) 47pF capacitor
- (1) 2.2nF capacitor
- (1) 10nF capacitor

- (1) 6.8µH inductor

- (1) 5V+ 100mA+ diode
- (1) 20mA LED

- (1) 18650 lithium-ion battery

Schematic:

For this project, I decided to use the PAM2421 from Diodes Incorporated. This IC is a boost converter that takes a 2.7-5.5V input and outputs up to a 24V output. In this case, I have programmed it to output around 5V, as the laser pointer I am using is rated for 5V.

For the most part, I followed the typical application schematic located in the PAM2421's datasheet, but removed the large 470µF capacitors on the input and output. I did this because the capacitors did not affect the finished product in a noticeable way, and the capacitors themselves would dramatically increase the size of the PCB for the finished laser pointer.

Laser Pointer schematic

PCB Design:

While designing the PCB, I decided to go with a layout that was long and narrow, and I don't remember exactly why. I positioned the IC in the center of the PCB, with the supplementary components surrounding the IC. My goal was to keep the components as close to one another as I felt comfortable with, but I was not as skilled with soldering or PCB design, so the parts are spaced out more than they need to be, and the pad sizes are slightly larger than they need to be.

The green plane across the PCB is a ground plane that covers the entire bottom of the PCB. All vias that lead there connect ground to different components on the PCB.

Laser Pointer PCB design Laser Pointer PCB render

Final Product:

After soldering all of the components on the PCB, I realized the flaws of my PCB design. The PCB is very long, and that makes it hard to implement as a final product with a small form factor. If I were to make this PCB again, I would place components on both sides of the PCB in order to compress the size to a point where it can be placed in a small container. For now, I have placed the PCB, an ON/OFF switch, the 18650 lithium-ion battery holder, and even a small voltmeter LED panel to measure the battery voltage on a small piece of acryllic. It is comfortable to hold, even if it is large, and works perfectly.

Laser Pointer final product