Minor improvements to LP lock to make it more like a journal entry.

1 files changed, 17 insertions, 17 deletions

diff --git a/_log/fpm-door-lock-lp.md b/_log/fpm-door-lock-lp.md
index b846797..10b452c 100644
--- a/_log/fpm-door-lock-lp.md
+++ b/_log/fpm-door-lock-lp.md
@@ -1,23 +1,23 @@
 ---
-title: Fingerprint door lock (LP)
+title: Redesigned fingerprint door lock for LP
 date: 2025-08-18
 layout: post
 project: true
 thumbnail: thumb_sm.jpg
 ---
 
-Second iteration of the [fingerprint door lock](../fpm-door-lock-rf). 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.
+Second iteration of the [lock](../fpm-door-lock-rf). The 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.
 
 <video style="max-width:100%;" controls="" poster="pcb.jpg">
   <source src="video.mp4" type="video/mp4">
 </video>
 
-Redesigned the PCB completely. Tossed RF modules and the second MCU. Connected
-R503 directly to the ATmega328P. Sensor now mounts on door exterior, servo
-attaches to interior knob, MCU stays on the back to prevent tampering.
+Redesigned the PCB completely. Tossed the RF modules and the second MCU.
+Connected the R503 sensor directly to the ATmega328P. Sensor now mounts on the
+door exterior, servo attaches to the interior knob, and the MCU stays on the
+back to prevent tampering.
 
 <table style="border: none; width: 100%">
   <tr style="border: none;">
@@ -36,18 +36,18 @@ attaches to interior knob, MCU stays on the back to prevent tampering.
 </table>
 
 PCB specs: 2-layer, 1oz copper, 0.3mm traces (1mm for power and servo). Ground
-plane on bottom layer.
+plane on the bottom layer.
 
-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. 
+Solved idle power draw with MOSFETs. 2N7000 and NDP6020P cut power to the
+sensor and the servo before deep sleep. Through-hole MOSFETs that switch at
+3.3V are getting harder to find. NDP6020P is already obsolete. 
 
-Replaced linear regulators with MP1584EN DC-DC buck converters. No RFM--noise
-isn't a big concern. Buck's pin breakout not great--wouldn't fit on commercial
-dev boards.
+Replaced linear regulators with MP1584EN DC-DC buck converters. No RFM—noise
+isn't a big concern anymore. Buck's pin breakout is not great—doesn't fit on
+commercial dev boards.
 
-Squeezed more power savings by underclocking MCU to 8MHz/3.3V. Combined
-with buck converters: 56% total power savings.
+Squeezed more power savings by underclocking the MCU to 8MHz/3.3V. Combined
+with buck converters, 56% total power savings.
 
 Wake sequence: MCU activates FPM MOSFET, unlocks FPM over UART, scans and
 matches fingerprint. Match triggers blue LED, servo MOSFET, PWM signal to