My first PCB

MY FIRST PCB

14 JULY 2025

-
-

In 2023, I started tinkering with DIY electronics as a hobby. Until now, I’ve -been using development boards like the Arduino Uno and ESP-32-WROOM so that I -can focus on the software. Recently, I decided to step outside of my comfort -zone and design a PCB from scratch for a door lock I’m working on.

- -

The lock comprises two subsystems: a fingerprint sensor in front of the door -and a servo connected to the physical lock behind the door. The fingerprint -sensor authenticates the person and signals the servo behind the door to unlock -the door over an encrypted RF channel.

- - - - - - - - - - -

- - Footprint (front) -	- - PCB (front) -
- - Footprint (back) -	- - PCB (back) -

- -

The PCBs have two layers. A copper region serves as the ground plane. The 0.3mm -wide 1oz/ft² copper traces can carry up to 500mA (the tracks -connecting the power source and the linear regulators have a width of 0.5mm). -Both subsystems were functional. I was able to control the servo reliably using -the fingerprint sensor.

- -

The designs aren’t without flaws, however. The main shortcoming of the circuits -is that they draw significant amounts of quiescent currents despite employing -sleep modes. The linear regulators were a poor choice as they dissipate too -much heat. The fingerprint sensor and the servo draw 13.8mA (3.3V) and 4.6mA -(5V) respectively, as long as they are connected to the power supply.

- -

Although the circuit didn’t draw more than 200mA without a load, the servo -under load could draw up to 600mA. I’m sailing too close to the wind with 0.3mm -copper traces. Instead, 0.4mm wide 2oz/ft² traces would have been -safer.

- -

I’m working on improving the design to reduce idle current consumption and -extend the battery life. Despite its deficiencies, this was my first PCB -design, and I’m glad that it worked as well as it did. Custom PCB design marks -an important milestone in my DIY electronics journey.

- -

Files: gerber_back.zip, gerber_front.zip, - source.tar.gz

by W. D. Sadeep Madurange