From 8cbe75f0047732c865f58e2f847a5ffafe066e71 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Sat, 20 Dec 2025 11:25:26 +0800 Subject: Change projects to poc and blog to log. --- _site/poc/my-first-pcb/index.html | 120 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 _site/poc/my-first-pcb/index.html (limited to '_site/poc/my-first-pcb/index.html') diff --git a/_site/poc/my-first-pcb/index.html b/_site/poc/my-first-pcb/index.html new file mode 100644 index 0000000..55dc58d --- /dev/null +++ b/_site/poc/my-first-pcb/index.html @@ -0,0 +1,120 @@ + + + + + My first PCB + + + + + My first PCB + + + + + + + + + + + + + +
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MY FIRST PCB

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14 JULY 2025
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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.

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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.

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+ Design (front) +

Footprint (front)

+ 		+ PCB (front) +

PCB (front)

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+ Design (back) +

Footprint (back)

+ 		+ PCB (back) +

PCB (back)

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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.

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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.

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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.

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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.

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

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by W. D. Sadeep Madurange

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© ASCIIMX - 2025

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+ + + + -- cgit v1.2.3