URL: https://github.com/hmbusch/PCB-Designs
From time to time I sit down and design some circuitry that can be used for multiple purposes, a component if you will. The designs for these PCBs are stored in this project (or at least those I feel confident to share).
I started out developing a basic two button remote that I could use together with Home Assistant. I expected the design to go through various iterations as I try different functionality, so instead of designing several completely different iterations, I created a sort of universal motherboard. It breaks out almost all pins as header (+3.3V, signal, GND), offers an I2C connector and some onboard LEDs. It is powered by a 18650 LiPo battery and uses one of these cheap TP4056 charging/protection boards. For the 3.3V supply, I added a connector for a 3.3V buck/boost converter from Pololu, as I have a couple of them lying around. They are quite expensive these days, I know that and wouldn't use them if I didn't already have them.
I designed these schematics about 10 years ago. They are provided "as is", the files have not been maintained or updated.
This design features a small PCB with an 74HC595 shift register at it's heart. Multiple modules of these can be connected together to form a shift register cascade. The register connects to an ULN2803A Darlington Array sink driver whose outputs are available as a 9 port screw header (8 ports + VCC connector). As should be obvious from the design, this module can only be used for sink switching, as it requires fewer and more common parts than a similar design for source switching.
Contains libraries for use with Cadsoft Eagle. These libraries contain parts and packages I added myself for components that are not contained in the stock libraries.
The Pixel is a small board that puts three 5mm LEDs in series with a SMD resistor to create a larger light source than a single LED. The Pixel is supposed to be powered by 12 Volts and outfitted with three high brightness LEDs. The pixel is a good alternative to power LEDs in terms of price, power consumption and temperature management.