Introduction: Evil Kitty Low Food Warning Device for Human Servants

Picture of Evil Kitty Low Food Warning Device for Human Servants

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.

Step 1: Site Inspection

Picture of 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

Picture of Supplies

I bought most stuff from Radio Shack.

Step 3: Assembly

Picture of 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

Picture of 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.


HeidiSN (author)2015-07-11

I think it is cool!

Jbabu3120 (author)2014-04-08

Would be cool if you replaced the LED with a piezo buzzer. These you can get from RadioShack for about $3 USD.

ahallock-1 (author)2011-03-12

And what happens when the batteries die and you didn't notice? :P

n8man (author)2008-07-22

! think you forgot the evil kitty high pitched beeping noise that forces you to refill it.

ReCreate (author)n8man2009-04-22

yes it could be done with a 555 and a speaker(get the 555 to go on and of fast enough to make a noise in the speaker)

Dream Dragon (author)ReCreate2009-10-15

or one of those annoying musical greetings cards.  They have a"pull" switch already built in.

but then, my cat would have ripped the bottom corner of the food bag open.

"Please explain why I should waste my time with that silly littlefeeder thing when there's a whole sack of cat food just here that I caneat whenever I want?"

trailleadr (author)Dream Dragon2010-09-13

That's a very assertive cat!

ReCreate (author)Dream Dragon2009-10-15

Yeah they do.

Wyle_E (author)2008-09-09

You didn't mention a ballast resistor for the LED. If you used a 'constant current' LED, you don't need one, but a typical red LED has a forward drop of 1.8 volts, and will overheat on 3 volts unless you put a resistor in series. There is a small range of overvoltage in which the LED gets just hot enough to limit the current, but doesn't burn out, Yours seems to be operating in that range. The ballast resistor value is easy to calculate if you know the operating current of your LED. Radio Shack LEDs have this on the back of the package. To get the resistance, subtract the LED forward voltage from the supply voltage and divide the result by the LED current. In this case, assuming 15 milliamps for the operating current, (3.0 - 1.8) / 0.015 = 80 ohms. The nearest standard value is 82 ohms, close enough. My cats usually inform me that their food dispenser is empty by jumping into my lap and stomping on a part of my anatomy that is not adapted to such treatment.

haruspex (author)Wyle_E2009-10-15

For a fun and in-depth look at which LEDs need resistors, check out:
Some thoughts on throwies by Evil Mad Scientist Laboratories.

knexfan9182 (author)Wyle_E2008-09-10

ohh mine bites me :(

Brad_Smith (author)Wyle_E2008-09-09

Thanks for the technical info. The radio shack people were my consultants but may have missed selling me a resistor. My light seems to last quite a while but also seems to use up the batteries faster than it should. I will look into improving this by getting a resistor. Back to the shack...

Kosmos (author)2008-04-03

Do you think this could be adapted to work on a 2 litre water bottle....

my 3 feline overlordessess get very mad when their water bottle empties and I have a disability which prevents me from bending down far enough to check the water level.

if the only part of the project that goes inside the container is a piece of fishing line and a ball, then there should be no electrocution risk. I'd just need a ball that acts as a float? right?? but then it might not be heavy enough to trigger the switch?

Any ideas ? My HRF's are hard to please (HRF = Her/His Royal Furriness)

Great Idea by the way :)

Brad_Smith (author)Kosmos2008-04-03

I guess you have one of those bases where a bottle is held upside down and it dispenses into a bowl. Making any kind of hold in the bottle would upset the air pressure that holds the water back and would let it all out. Maybe something like a floating object that you could stuff inside the bottle. You could then look for this colored floating object instead of trying to identify what level is the clear water. In your case the small opening of a 2-liter bottle presents a challenge. One idea could be a dozen or so small colored floating balls. The would spreadout over the surface of the water level. If you used just the right amout they could form a single layer the diameter of the bottle. This would be easier to see. Maybe someone out there can suggest another idea. One concern about this is mold/bacteria growing on the components that come in contact with the water. I used fishing line instead of string and clean it regularly. I also throughly washed the golf ball. You may want to keep this in mind when planning your solution. Good luck.

bmlbytes (author)Brad_Smith2008-09-11

Yes, as brad said, any hole in the bottle would ruin it and make water overflow the little bowl below. One suggestion would be to point a laser through the 'flatter' parts of the bottle (not where the neck of the bottle is and not the handle. This would make the laser spread out when it is pointing through the water, when it is not pointing through the water, and is only pointing through plastic, it should make a better 'beam'. Point this 'beam' at a photo resister which is connected to a transister to close a circuit when the 'beam' hits the photo resister. I know it's complicated, but its the only thing i can think of right now.

ReCreate (author)bmlbytes2009-04-22

photo transistor,or photo cells(that is what it is called at radioshack)

bmlbytes (author)bmlbytes2008-09-11

Also, the laser should be near the bottom of the bottle (where it would be needed to be refilled) and not in one of the 'ribs' of the bottle

bmlbytes (author)bmlbytes2008-09-11

Here is a pic of my idea

Kosmos (author)bmlbytes2008-09-12

thanks for that :) partner is electronics engineer and could build that for me

u can puta peice of foam and the Low Food Warning Device

withnall (author)2009-03-26

Um, kitties kin jump upz! Just put the fud 'n water dispensers at your eye level and give them a few places to jump to get up. You can then see easily if they need filling and bonus-they exercise!!

rocksalt2342 (author)2008-09-11


deshane (author)2008-03-02

ingenious.. even if I can't spell it correctly! My kitty overlords (four of them share me in my small apartment) hate me for not doing this because KO #1 will get overweight again if I let them free-range on the food when I'm not around. I will have to hide this Instructable from them!

Brad_Smith (author)deshane2008-03-28

KO#1 - just love the abbreviation.

MoonDancerChick (author)2008-03-27

Great! We are lucky that our kittys just love us to death so we give them more food. I am sending this to my Mother in law, she has evil kitties that would love this device.

Do not mistake 'love' for demanding obedience. She should also obey the kitty over-lords.

kikkoman7347 (author)2008-01-27

Very good idea! While you still must serve the Evil Kittens, you can do so on your own terms. Way too "stick it to the man - er, Furballs!"

Brad_Smith (author)kikkoman73472008-03-28

I love your 'stick it to the man err furballs' wording. Too funny.

Brad_Smith (author)kikkoman73472008-01-27

We must obey the kitty-overlords

jongscx (author)2007-12-21

wow... those are expensive parts...

Doctor What (author)jongscx2007-12-21

Just rip apart old toys until you find the parts you need. Why pay 20 cents for a resistor when you can find a million of them in a barbie boom box??? I steal mine from my sister.

tyeo098 (author)Doctor What2007-12-21

Use a 99c buzzer instead, that way, youll hear it before you see it, and risk less of the... cat-piss beds

Brad_Smith (author)jongscx2007-12-21

I spoke with the kittys. They say nothing is too good for them. The official kitty orders are to spare no expense to keep them happy - well as happy as a cat can get. But seriously, cost of this project is less than compared to a few trips to the dry-cleaner with a comforter in hand. Thats what we were previously facing when the food ran out. Lemme tell you these are some angry vindictive cats! Also keep in mind I had plenty of left over materials to use on other projects so not all the expense was just for this one project. Plus I got my first soldering gun and a new tool is always welcome. Thanks for your comments.

Trinity (author)jongscx2007-12-21

then dont make it

jongscx (author)Trinity2007-12-21

It was more of a comment on how much Radio-hut price-jacks, but okay...

thomasedisonjr (author)2007-12-21

Brilliant! It could also be designed to activate some kind of a voice warning, like "FEED ME!".

Thanks for your comments. I did consider an audible alarm but realized the kittys eat at all hours. I would not want a buzzer going off at 3:AM even though I am a mere servant. Keep in mind, there is still food in the tower when the light turns on. It's primarily to get the humans attn to refill the food tower before it runs out.

GorillazMiko (author)2007-12-21

jongscx, it is pretty expensive, but its worth it.

mikesty (author)2007-12-20


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