Motivation: I wanted to use battery powered Raspberry Pi camera to take once-a-day photos outdoors to create long term time-lapse videos. My particular application is to record ground cover plant growth this coming spring and summer.
Challenge: Design low current Raspberry Pi power control to ensure long battery life.
My Solution: I use a hacked alarm clock, Attiny85 circuit & Pimoroni OnOff shim to completely cut power to Raspberry Pi when not in use. While the Attiny85 and alarm clock continues running in standby mode, current draw is only 5 microAmps. Two AAA batteries power both Attiny and alarm clock, while a USB power bank powers the Pi.
Basic Operation: When to alarm clock goes off it wakes a sleeping Attiny circuit, which then signals Pimoroni OnOff shim to apply power from USB power bank to Raspberry Pi. The Pi executes a run-at-boot script (take a photograph). After sufficient time has passed (60 seconds in my application), the Attiny circuit again signals Pimoroni OnOff shim and then the Attiny enters sleep mode. Based on the signal from Attiny, the Pimoroni OnOff shim executes Pi shutdown command, and after Pi shutdown process completes, cuts power from USB power bank to Raspberry Pi.
Raspberry Pi Zero or Raspberry Pi Zero W (draws more power)
Raspberry PI Camera Module
Raspberry Pi Zero Case
Pimoroni ONOFF SHIM RASP PI POWER SWITCH, Digikey
Battery Operated Digital Alarm Clock Target
ATtiny85 8 DIP Digikey
(2) CAP ALUM 100UF Digikey
DS3231 RTC Module AliExpress
(2) 68 ohm resistor
Short (about 6 inches) micro USB cable
Clear Box Amac SKU#: 60120. 4″ x 4″ x 5-1/16″ h The Container Store
Kmashi 11200 mAh USB Power Bank # k-mp806 or similar
Double stick tape
Small self-tapping screw
(2) 1 X 8 pin female stacking headers – commonly sold a Arduino UNO stacking headers AliExpress
Perf or strip board about 1 1/4″ by 2″
5 1/2 by 5 /12 by 3/4 thick pine or plywood
1 1/4 PVC pipe about 15 ” long
1 1/4 PVC coupler
(2) short bungee cords about 10″ long
(4) 1/4″ dia. wooden dowel pins about 1″long
UltraDeck Natural Post Sleeve Cap Menards
Wire Cutters and Solder Iron
Arduino UNO or other way to program ATtiny85
Hook up wire and jumpers
Keyboard, mouse, HDMI monitor, USB port and Ethernet Hub , OTG cable
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