wip: Unix desktop.

author: Sadeep Madurange <sadeep@asciimx.com> 2025-11-02 15:12:54 +0800
committer: Sadeep Madurange <sadeep@asciimx.com> 2025-11-02 15:12:54 +0800
commit: 3b63c5139ca9a34fa79bc2eb132ecfd71897dc7e (patch)
tree: a2f060fb2deb2bfd3f541f46e6a842fac5f9c752 /_site/projects/my-first-pcb
parent: eb6497e805627137e15bf30d3ec46fb510103f56 (diff)
download: www-3b63c5139ca9a34fa79bc2eb132ecfd71897dc7e.tar.gz
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+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>My first PCB</title>
+
+    <head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>My first PCB</title>
+  <link rel="stylesheet" href="/assets/css/main.css">
+  <link rel="stylesheet" href="/assets/css/skeleton.css">
+</head>
+
+
+
+  </head>
+  <body>
+
+    <div class="container">
+  <ul id="navlist" class="left">
+    
+    <li >
+      <a href="/" class="link-decor-none">hme</a>
+    </li>
+    <li >
+      <a href="/archive/" class="link-decor-none">blg</a>
+    </li>
+    <li class="active">
+      <a href="/projects/" class="link-decor-none">poc</a>
+    </li>
+    <li >
+      <a href="/about/" class="link-decor-none">abt</a>
+    </li>
+    <li><a href="/feed.xml" class="link-decor-none">rss</a></li>
+  </ul>
+</div>
+
+
+
+    <main>
+      <div class="container">
+        <h2 class="center" id="title">MY FIRST PCB</h2>
+        <h6 class="center">14 JULY 2025</h5>
+        <br>
+        <div class="twocol justify"><p>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.</p>
+
+<p>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.</p>
+
+<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>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>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.</p>
+
+<p>Files: <a href="gerber_back.zip">gerber_back.zip</a>, <a href="gerber_front.zip">gerber_front.zip</a>,
+       <a href="source.tar.gz">source.tar.gz</a></p>
+</div>
+        <p class="post-author right">by Wickramage Don Sadeep Madurange</p>
+      </div>
+    </main>
+
+  </body>
+</html>
diff --git a/_site/projects/my-first-pcb/source.tar.gz b/_site/projects/my-first-pcb/source.tar.gz
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author	Sadeep Madurange <sadeep@asciimx.com>	2025-11-02 15:12:54 +0800
committer	Sadeep Madurange <sadeep@asciimx.com>	2025-11-02 15:12:54 +0800
commit	3b63c5139ca9a34fa79bc2eb132ecfd71897dc7e (patch)
tree	a2f060fb2deb2bfd3f541f46e6a842fac5f9c752 /_site/projects/my-first-pcb
parent	eb6497e805627137e15bf30d3ec46fb510103f56 (diff)
download	www-3b63c5139ca9a34fa79bc2eb132ecfd71897dc7e.tar.gz