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diff --git a/_site/log/fpm-door-lock-lp/index.html b/_site/log/fpm-door-lock-lp/index.html new file mode 100644 index 0000000..76715d7 --- /dev/null +++ b/_site/log/fpm-door-lock-lp/index.html @@ -0,0 +1,115 @@ +<!DOCTYPE html> +<html> + <head> + <meta charset="utf-8"> + <title>Fingerprint door lock (LP)</title> + + <head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <title>Fingerprint door lock (LP)</title> + <link rel="stylesheet" href="/assets/css/main.css"> + <link rel="stylesheet" href="/assets/css/skeleton.css"> +</head> + + + + </head> + <body> + + <div id="nav-container" class="container"> + <ul id="navlist" class="left"> + + <li > + <a href="/" class="link-decor-none">hme</a> + </li> + <li class="active"> + <a href="/log/" class="link-decor-none">log</a> + </li> + <li > + <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"> + <div class="container-2"> + <h2 class="center" id="title">FINGERPRINT DOOR LOCK (LP)</h2> + <h6 class="center">18 AUGUST 2025</h5> + <br> + <div class="twocol justify"><p>Second iteration of the <a href="../fpm-door-lock-rf">RF door lock</a>. Old version worked +but drew too much quiescent current. Sensor and servo pulled 13.8mA and 4.6mA +idle. Linear regulators were a disaster. Battery didn’t last 24 hours.</p> + +<video style="max-width:100%;" controls="" poster="pcb.jpg"> + <source src="video.mp4" type="video/mp4" /> +</video> + +<p>Redesigned the PCB completely. Tossed the RF modules and the second MCU. +Connected R503 sensor directly to the ATmega328P. Sensor now mounts on door +exterior, servo attaches to interior knob, MCU stays on the back to prevent +tampering.</p> + +<table style="border: none; width: 100%"> + <tr style="border: none;"> + <td style="border: none; width: 49.9%; background-color: transparent; text-align: center;"> + <img src="breadboard.jpg" alt="PCB" style="width: 100%" /> + </td> + <td style="border: none; background-color: transparent; text-align: center;"> + <img src="pcb1.jpg" alt="Design" style="width: 100%" /> + </td> + </tr> + <tr style="border: none;"> + <td colspan="2" style="border: none; background-color: transparent; text-align: center;"> + <img src="footprint.png" alt="PCB footprint" style="width: 100%" /> + </td> + </tr> +</table> + +<p>PCB specs: 2-layer, 1oz copper, 0.3mm traces (1mm for power and servo). Ground +plane on bottom layer.</p> + +<p>Solved idle power draw with MOSFETs. 2N7000 and NDP6020P cut power to sensor +and servo before deep sleep. Through-hole MOSFETs that switch at 3.3V are +getting harder to find. NDP6020P already obsolete.</p> + +<p>Replaced linear regulators with MP1584EN DC-DC buck converters. No RF, noise +isn’t a big concern. Buck’s pin breakout not great–wouldn’t fit most +commercial dev boards.</p> + +<p>Squeezed more power savings from the MCU by running it at 3.3V/8MHz. Combined +with buck converters: 56% total power savings.</p> + +<p>Wake sequence: MCU activates sensor MOSFET, unlocks sensor over UART, scans and +matches fingerprint. Match triggers blue LED, servo MOSFET, PWM signal to +unlock. No match triggers red LED. MOSFETs off, back to sleep.</p> + +<p>Total power savings: 99.9% (30.6mA → 2.9μA). Verdict: Fixed.</p> + +<p>Commit: +<a href="https://git.asciimx.com/fpm-door-lock/commit/?id=75290945b2fd84b3bc108fd46419ee478eaac3ca">7529094</a> +| Gerber: <a href="gerber.zip">gerber.zip</a></p> +</div> + <p class="post-author right">by W. D. Sadeep Madurange</p> + </div> + </div> + </main> + + <div class="footer"> + <div class="container"> + <div class="twelve columns right container-2"> + <p id="footer-text">© ASCIIMX - 2025</p> + </div> + </div> +</div> + + + </body> +</html> |