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| author | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-08 22:28:37 +0800 |
|---|---|---|
| committer | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-08 22:28:37 +0800 |
| commit | e836c4b9e78cc3892cdebf8126cb650f1b91ed37 (patch) | |
| tree | 4e52155aef0105cc9b888a42b3e760455a2bcb36 /_log/fpm-door-lock-lp.md | |
| parent | 57ff09d2eefefa2462a2af0175e3e8164c7bc828 (diff) | |
| download | www-e836c4b9e78cc3892cdebf8126cb650f1b91ed37.tar.gz | |
Tighten prose.
Diffstat (limited to '_log/fpm-door-lock-lp.md')
| -rw-r--r-- | _log/fpm-door-lock-lp.md | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/_log/fpm-door-lock-lp.md b/_log/fpm-door-lock-lp.md index 1be2b76..d63131e 100644 --- a/_log/fpm-door-lock-lp.md +++ b/_log/fpm-door-lock-lp.md @@ -14,10 +14,9 @@ idle. Linear regulators were a disaster. Battery didn't last 24 hours. <source src="video.mp4" type="video/mp4"> </video> -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. +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. <table style="border: none; width: 100%"> <tr style="border: none;"> @@ -42,14 +41,14 @@ 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. -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. +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 commercial dev +boards. -Squeezed more power savings from the MCU by running it at 3.3V/8MHz. Combined +Squeezed more power savings by underclocking MCU to 8MHz/3.3V. Combined with buck converters: 56% total power savings. -Wake sequence: MCU activates sensor MOSFET, unlocks sensor over UART, scans and +Wake sequence: MCU activates FPM MOSFET, unlocks FPM 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. |