Our two evil kitties get really mad when their food runs out. They have gentle ways to remind us of our failings (rotten cream-sucking cats). To prevent such 'reminders' I made a device to indicate when the food level starts to run low.
We have a cat food dispenser that stores the food vertically in a silo type tower with an opening at the bottom where the food spills out into a small dish. We keep this tower in a closet on the floor under a shelf. The light in the closet does not illuminate the tower enough to see the food level. This device lights up when the food level runs low.
The device is mounted at the top of the tower. Inside the tower, a golf ball attached to the device with a piece of string monitors the food level.
When the ball lowers to what the kitties refer to as dangerously low food level (anything but full), the string goes taught causing a light to indicate the food level is unacceptably low. When a human servant (i.e. me or my wife) see the light we know we must obey the kitty rulers and refill the food tower immediately.
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Step 1: Site Inspection
We cannot see if the food level is low due to the shelf blocking the closet light. I know what you are thinking, just move the food tower somewhere else or install another light to illuminate this are under the shelf. If only it was that simple. We offered this solution to the kitty committee and both ideas were rejected. Anyway, its more fun trying to work something out - excuse to publish instructable. Picture shows closet with food tower in center.
Step 2: Supplies
I bought most stuff from Radio Shack.
Step 3: Assembly
This is the fun part. Assembly consists of using super-velcro to attach battery pack to project box and switch to battery pack inside project box. Then I connected wires to LED light. Drill holes in project box - one for LED light and another to allow string to exit bottom.
This was the first time I used a soldering iron. Really pretty fun but obviously something I could use some pointers on - sloppy soldering all over.
Step 4: Food Tower in Action
Here is the food tower all assembled. I did some testing by pulling food out of the bottom like cats eating to see if the golf ball would be strong (heavy) enough to trigger the light.
Just a few small tweaks and it works great. I found that adjusting the length of fishing line from the golf ball to the light allows an early or later warning. Once the kitties agreed with the line length it was put into action.