Daily Archives: January 29, 2009

DIY Automatic Cat Feeder

So, our cat Mohinder is a growing boy.  He wants to eat constantly.  It’s not actually constant eating of course, but he always seems to be hungry when we want to sleep.  Madeline has become patient with our sleeping/feeding schedule but Mo is terribly persistent about eating whenever he is hungry.  Typically, he will jump up on the bed and carefully grab a bit of Emily’s hair in his mouth and gently pull it.  It’s not meanness and it doesn’t hurt, but it is annoying to be sure.  Of course, I have no hair so he can’t wake me in the same way.  On the few occasions he has picked on me, he gently nips on my nose.

Electronic parts for the automatic cat feeder

As you can imagine, that has gotten pretty old so I started to tinkering.  I am going to post some ideas that I am fooling with and will show the finished product at a later date.  The basic idea I am working with is to have a digital alarm clock trigger some electronics to open a stripped down computer cd-rom tray.  I think the mechanism on a computer cd-rom is pretty nice and will work perfectly as a gate to let the cat food fall from a hopper into the cat bowl.  I started by salvaging an old cd-rom from the junk bin at the office.  I stripped all of the electronics out of it (basically, I just pulled off anything that wasn’t the mechanical stuff that opens the tray.  With a little experimentation using a 9-volt battery, I was able to find the motor that drove the gears to open the drawer.

The cd-rom motor to open the automatic cat feeder

I bought a new alarm clock to trigger the electronics to trigger the motor that opens the cd-rom.  I opened the alarm clock and found the wires that connect to the speaker for the alarm.  A quick hole in the sidewall of the clock allowed me to pass the wires from a 9-volt connector to the wires that used to connect to the speaker.  I closed the clock back up and was able to measure the current in the 9-volt connector when the alarm was (silently) going off. In other words, when the alarm goes off and would normally sound the alarm, it now send an electrical pulse out through my 9-volt connector which runs outside of the clock.

The alarm clock to trigger the automatic cat feeder

My plan is to have the power from the intercepted alarm signal drive a relay which allows a larger current to pass through it and a transistor.  The relay and transistor work as a basic switch to send power to the cd-rom motor.  I wired this all up last night and all of this stuff works just fine.  I am sort of experimenting now with how to get the drawer to actually deliver the catfood.  My plan is to have the drawer push open a slide or else be the slide that opens the hopper of food.  The real challenge is to figure out how to make all of this stuff cat-proof.  Mo is persistent and has a lot of free time and has gotten in to the most unusual things. Anyhow, these pics are an overview of the project, meant solely to both confuse and amaze.  I’ll post the actual schematic and the finished product another day when I get it all figured out.  Anyone have any thoughts about cat proofing stuff?