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| author | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-13 22:40:06 +0800 |
|---|---|---|
| committer | Sadeep Madurange <sadeep@asciimx.com> | 2026-01-14 11:02:47 +0800 |
| commit | 8be504601aeb9005b4e227fb2529d12672ea697e (patch) | |
| tree | 4deed91f1d9cd912045a8028615e3cac70ef2c3f /_log/fpm-door-lock-lp.md | |
| parent | 1fc1dbcb34bfb0a7f99bbc068edff93ae97c4662 (diff) | |
| download | www-8be504601aeb9005b4e227fb2529d12672ea697e.tar.gz | |
Tighten prose.
Diffstat (limited to '_log/fpm-door-lock-lp.md')
| -rw-r--r-- | _log/fpm-door-lock-lp.md | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/_log/fpm-door-lock-lp.md b/_log/fpm-door-lock-lp.md index aed991e..b846797 100644 --- a/_log/fpm-door-lock-lp.md +++ b/_log/fpm-door-lock-lp.md @@ -6,9 +6,10 @@ project: true thumbnail: thumb_sm.jpg --- -Second iteration of the [RF 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 [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. <video style="max-width:100%;" controls="" poster="pcb.jpg"> <source src="video.mp4" type="video/mp4"> @@ -42,8 +43,8 @@ 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 RFM--noise -isn't a big concern. Buck's pin breakout not great--wouldn't fit commercial dev -boards. +isn't a big concern. Buck's pin breakout not great--wouldn'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. @@ -52,7 +53,9 @@ 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. -Total power savings: 99.9% (30.6mA → 2.9μA). Verdict: Fixed. +Total power savings: 99.9% (30.6mA → 2.9μA). + +Verdict: Fixed. Commit: <a href="https://git.asciimx.com/fpm-door-lock/commit/?id=75290945b2fd84b3bc108fd46419ee478eaac3ca" |