Cat Feeder Unreminder: Concept

Ok, this is a project I talked about way back on Episode 237 of the MacroFab Engineering Podcast.

Its a small electronic device that makes sure you don’t overfeed your cat by feeding more often then needed. Low power consumption with no need of changing batteries or external power sources. Solar power? Basically a resettable egg timer that doesn’t need batteries cause if the batteries die then you won’t be reminded to feed the cat!

User interface should be simple. One button to reset the timer, then a LED that lights up when you are ok to feed the beasties and another LED that lets you know the system is working correctly. Maybe one led that is turned on when its not time to feed and then turns off when time to feed. Pressing the button resets and turns the LED back on? Verifying the circuit is still powered? Prevents hungry cats at least.

Simple BOM so far:

  • AEM10941
    • This is a Solar Energy Harvesting IC
  • DSF505Q6R0JBG
    • Super Caps
    • 5F Capacitance!
  • Solar Panel  AM-1816CA
    • 84µA at peak power
    • This is specced at 200lx
  • LTC2956
    • Low power, configurable timer

Napkin math on power requirements. The LTC2956 draws 0.8μA. LED at 40uA. Total draw when Cat Feed Indicator is on is 40.8μA.

5F x (4.5V-3.6V) / 0.0000608 = 74,013 seconds -> 20 and a half hours!

So we have enough power from the fully charged Super Cap to run everything for almost a day. That is good. Should bump up the capacitance just to get a full day.

Github repo for the project.