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diff --git a/_archive/my-first-pcb.md b/_archive/my-first-pcb.md deleted file mode 100644 index 7750f20..0000000 --- a/_archive/my-first-pcb.md +++ /dev/null @@ -1,64 +0,0 @@ ---- -title: My first PCB -date: 2025-07-14 -author: Wickramage Don Sadeep Madurange -layout: post ---- - -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. - -<table style="border: none; width: 100%"> - <tr style="border: none;"> - <td style="border: none; width: 49.5%; vertical-align: top; text-align: center;"> - <img src="front_design.jpeg" alt="Design (front)" style="width: 100%"> - <p>Footprint (front)</p> - </td> - <td style="border: none; vertical-align: top; text-align: center;"> - <img src="front.jpeg" alt="PCB (front)" style="width: 100%"> - <p>PCB (front)</p> - </td> - </tr> - <tr style="border: none;"> - <td style="border: none; width: 49.5%; vertical-align: top; text-align: center;"> - <img src="back_design.jpeg" alt="Design (back)" style="width: 100%"> - <p>Footprint (back)</p> - </td> - <td style="border: none; vertical-align: top; text-align: center;"> - <img src="back.jpeg" alt="PCB (back)" style="width: 100%"> - <p>PCB (back)</p> - </td> - </tr> -</table> - -The PCBs have two layers. A copper region serves as the ground plane. The 0.3 -mm wide 1 oz/ft<sup>2</sup> copper traces can carry up to 500 mA (the tracks -connecting the power source and the linear regulators have a width of 0.5 mm). -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 13.8 mA (3.3 V) and 4.6 mA -(5 V) respectively, as long as they are connected to the power supply. - -Although the circuit didn't draw more than 200 mA without a load, the servo -under load could draw up to 600 mA. I'm sailing too close to the wind with 0.3 -mm copper traces. Instead, 0.4 mm wide 2 oz/ft<sup>2</sup> 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_back.zip), [gerber_front.zip](gerber_front.zip), - [source.tar.gz](source.tar.gz) |