vault backup: 2026-07-11 16:48:59

Projects/Servo Latches.md

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+---
+active: false
+tags:
+  - project
+created: 2025-05-30
+completed: 2025-06-21
+---
+## Goal
+
+Create door latches that use servos with more torque so that the latch will open under side pressure.
+
+- Must be able to open with side force of up to 30 Pa (kg/m2)
+- Must be able to lock automatically on closing
+- Must support access port to unlock manually from outside of otherwise sealed box 
+- Must only use power when unlocking
+- Must be quiet in operation, no more than 20 dB
+- Must be not cost more than $25 per lock
+- Duty cycle of 20 opens/closes per day
+- Must be made from readily available parts (just in time delivery)
+- Can be level, edge or PWM triggered with a 5VDC signal
+- Power can be supplied separately up to 24VDC
+- Must be no more than 100mm x 50mm x 50mm in size
+- Latch throw must be at least 10mm
+## Tasks
+
+- [x] Order servos ➕ 2025-05-30 ✅ 2025-05-30
+- [x] Order springs ➕ 2025-05-30 ✅ 2025-05-30
+- [x] Create a circuit to test the latch using PWM pins on the RPi ➕ 2025-05-30 ✅ 2025-06-03
+- [x] Test that the servo can open under side pressure ➕ 2025-05-30 ✅ 2025-06-03
+- [-] Create `SoftPwm` class and use it to drive the servo ➕ 2025-06-04 ❌ 2025-06-18
+- [-] Design a housing for the latch that the servo can attach too ➕ 2025-05-30 ❌ 2025-06-18
+## References
+
+- [MG-90S Micro Servo Datasheet](https://www.electronicoscaldas.com/datasheet/MG90S_Tower-Pro.pdf)
+