Introduction: How to Make a RFID Pet Food Access Control System

Picture of How to Make a RFID Pet Food Access Control System
In this instructable I will explain how to make a simple RFID pet food access control system. This system uses a stand-alone RFID system that can be purchased either pre-assembled or in kit form if you desire to do the soldering yourself, and also wish to save a few dollars in the process.

The reason I made this was out of pure necessity. I have two dogs, and when my vet placed one of them on a special diet I needed some way to ensure they ate their own food... and only their own food. Since they are open-bowl fed and I'm gone part of the day, I decided to look for a product that would do what I needed. This meant I wouldn't have to spend a great deal of time trying to re-train them and still give them the freedom to eat whenever they chose. This is where my frustrations begun...


Frustrated with the situation, I decided to roll my own. This first version does the job, but I would eventually like to make the antenna extend around the entire perimeter of the bowl. If anyone has experience with RFID technology, I would appreciate any feedback that would assist in modifying the antenna into that configuration.

***** UPDATE *****
Anthony Targa, holder of patent #5570655 contacted me. Apparently he DID manufacture the device and it was featured in numerous Veterinary publications. Because of this, I fully retract my "patent troll" statement. I simply wish Anthony's device was produced on a larger scale so more people could have access to it.

Step 1: Materials and Tools

Picture of Materials and Tools


  • SK02 - 125 kHz Proximity Key Fob
    • The smallest quantity sold is a 10 pack. I asked QKits if they would substitute the access cards that come with the kit for the key fobs, and they did... I'm not sure if this was a "one off" case, but it doesn't hurt to ask. If they won't do this for you try contacting AVEA, the mfgr of the kit and see if you can purchase from them.

  • Project box
    • The dimensions of the box I used are 13cm x 7cm and was purchased at a local electronics dealer, but you can also buy them at Radio Shack.
    • The KL042 circuit board can be cut down to a min. size of 9cm x 5.7cm, so make sure your box is at least this size PLUS the dimension of your adaptaplug and buzzers.

  • Annoying buzzer(s)
    • Also available at Radio Shack

  • Wire or L-Bracket
    • Used to secure the box to the food bowl. I bent one side of an l-bracket to make a hook shape.


  • Dremel
    • In case you decide to resize the circuit board.

  • Hot glue gun

  • Drill
    • For adding the sound and adaptaplug holes. You can also use your Dremel if you have the bits.

  • Soldering gun & solder
    • If you buy the unassembled version of the kit.

Step 2: Assembly

Picture of Assembly

There isn't much to this step. If you purchased the unassembled version of the kit, consult the diagram that's included with the kit and put it together.

Then, have a look at the pictures below to put it all together.

Before you close the box, program the RFID key fobs via the DIP switches. Consult the manual that comes with the kit for this.

You need to program the RFID key fobs that DO NOT have access to the bowl. This way, when the pet who DOES have access to the bowl tries to eat nothing will happen... but when a pet who DOES NOT have access to the bowl, a successful read will occur and the buzzers will sound.

Step 3: Attachment and Positioning

Picture of Attachment and Positioning

I used the modified l-bracket I mentioned in step 1 to attach the box to to the bowl. Of course, you can do whatever you want.

Then I cut a slit in the charcoal colored mat and ran the power cord underneath for safety reasons.

All that's left to do is position the box so the key fob hovers over the box while the dog eats!

I hope this helps other pet owners who are in my situation. Please feel free to comment and suggest modifications.


Mexicoman (author)2007-09-14

Ummm... Not as a complaint, but you and others that use acronyms might define them in parentheses so those of us who are unfamiliar with that particular condensed term might also follow. Such as: Building a ULDB (Ultra Light Displacement Boat) is easy when you have a good instructable.

SteveW67 (author)Mexicoman2015-10-28

Wireless Whiskers is a very sophisticated patented RFID feeder in high volume production with many unique capabilities:

aqwiz (author)Mexicoman2009-08-20

Mex: Most acronyms are easily identifiable by cutting and pasting them into google. No offense meant, but to have every acronym spelled out would defeat the purpose of using acronyms, of which RFID in particular is a hugely widespread acronym, and only takes 3 seconds to find out what it is.

finton (author)aqwiz2012-10-01

aqwiz, I think Mex is probably suggesting you only do that for the first time the acronym appears, thereafter just write the acronym. I'm currently reading a book where the author eventually lets us into what the acronym stands for, if ever - very frustrating! For those of us who have missed some of the hugely widespread acronyms,  the words "Radio Frequency Identification" in parentheses the first time the acronym appears, would allow us to get on with enjoying an Instructable without having to stop to check out what the heck RFID stands for.
Took me 7 seconds...  ; ]

CuteLunchLady (author)2011-07-29

Totally groking this idea - I've two cats - one of which like to steal the other's food, and knock the water dish about. I'm going to put both food/water bowls in a separate box for each cat - and make both lids openable via the RFID tag on their respective cat's collar. This should stop our big boy from knocking the food and water dish about, as I can make the boxes with plenty of weight - and he quite literally can't access his step-sister's food.

Thank you for the wonderful idea! I'm sure this is the solution to the issue at our house.

Pader (author)2010-12-01

Aas an alternative for a brush (which may be difficult to clean), a carousel of some sort or even an Archimedian screw in a tube. Obviously, they both will require some sort of timing.

mdelzo (author)2010-08-02

is there a way that this device could be battery operated?

berdellmc (author)2010-04-26

 There is another option for people who need to keep certain pets away from either food or cat litter. Check out They offer a product that will work for cats or small dogs. It's new, so I imagine at some point they'll offer larger ones as well. My roommate uses two of them. One to keep his dog out of the cats' food, and the other to keep the same dog out of the cats' litter. It's a bit spendy $150, but he said the $300 he paid for both has saved his sanity, and his dog hasn't been sick from eating cat feces and cat poop since he started using them. These units work with magnetic door openers, but I've ordered one from them special to use with an rfid door since my cat needs to eat different food from his, so my cat has a different access than his cats, and they can't eat my cat's food. I'm paying a bit more to get the rfid model $210, but I see what it's done for my roommate, and it's well worth it in my opinion. They also look pretty classy. check it out.

James (pseudo-geek) (author)2007-09-13

why not replace the buzzer with a recording of "the mosquito sound"?....this is VERY annoying to people AND dogs and sometimes even painful.

most people over 25 cant hear it anyway, its so high-pitched, so it wouldn't bother you, just the dogs (or your kids if you have any lol)

hehe, nice one. Do you know where I could buy one of these online?

Audacity can be used to generate a tone of the appropriate pitch.

Unless the sound is extremely intense, humans cannot usually hear sounds over 20,000 Hz. For comparison, the whistle created by an old CRT television screen is around 16,000 Hz.

Remember that your sampling rate must be at least twice the highest frequency in your sound. For example, if your rate is 44,100 samples per second, sounds with frequencies over 22,050 Hz will either be cut off or replaced with a lower-pitched sound (aliasing).

do a google search for "the mosquito sound " I looked it up and couldnt find one to download :(

finfan7 (author)2009-01-03

How hard do you think it would be to use one of these as a car ignition?

ElvisLives (author)2008-12-18

I think another avenue for creating one of these is to use a kit I found on eBay that is designed for controlling an electronic door lock. The kit cost $32.00 including shipping. It requires a 12v power supply and provides Normally Open and Normally Closed 12v outputs that are activated by a key fob. The controller has two antennas. The kit comes with 5 key fobs. The eBay seller is "kawalock," but please note that I have NOT received my kit yet and do NOT vouch for this seller. The kit looks promising though!

zetareticuli (author)2008-11-13

buy a petporte and hack it? :) just a thought.

katerlyn (author)2008-10-31

This reminds me that I have a pet electric dog door i had to take out because the collar device stopped working for one dog, I had bought tons of batteries for these collar devices, does anyone need the batteries? Batteries bought in quantity for the other pet door are: i have at least 18 batteries with 2016 expriration, duracell: DL2430B. Does anyone know what other devices use this battery? i hope i'm not overstepping any rules. Also, I bought a staywell infra red door and do not use the collar devices, never got them returned, i have 3 with batteries, never used, for use with 861 infra red dog doors. BTW I LOVE my two solopetdoors.

frogspasm (author)2008-01-17

I so came up with this idea! Then did a patent search and found out someone already had...bummer, there went my millions. I seriously need to make a pair of these for my cats. One is on a diet, and the other should be able to eat whenever she wants. I'd have to make one bowl that closes any time the diet cat gets near it, and another that opens for him on a timed schedule. Thanks for the inspiration!

ranandrada (author)2008-01-10

Can you please give me the circuit diagram of this project and the program if possible? I really need to have this information. Please help. thank you

cynvision (author)2007-09-14

This RFID collar tags sure would work better than the infrared cat doors I presently have. I was planning on using a couple of pet doors to control access to some rooms I wanted to keep selected cats out of but I have found some cross-over between the colors of the infrared tags. The yellow tag is activating the blue keyed door. Plus you have to keep loading them with watch-sized batteries. Yuck! But like the dog bowl antenna, the cat door would need a little bit greater reach for the antenna. Would the stock antenna cover the lower, inner curve of the pet door so when the pet approaches the dangling tag touches the perimeter and the door unlocks?

mlarsen (author)cynvision2007-09-24

The read range is only about 1"-2"... and the direction of the key fob as compared to the reader antenna is also a big factor. For example, if the key fob and reader antenna are parallel you will get the maximum range of about 2". BUT, if the key fob and reader antenna are perpendicular to each other (this is the normal way the key fob would dangle from the collar of your pet) you will get a shorter read range.

e1mer (author)2007-09-21

I got my kit today, but they ignored my request for the fobs to replace the cards. I guess I have to buy a bag of 10 just to get 3. Before I do, has anyone bought a 10 pack and want to sell me half?

mlarsen (author)e1mer2007-09-24

I've seen 125khz RFID key fobs on eBay before. Try checking there...

You could also contact AVEA, the maker of the RFID reader and see what they could do for you. Maybe ask if the key fobs on eBay would work or if you could buy individual ones from them.

Let me know how it turns out!

sniffydogs (author)2007-09-13

I have Bloodhounds. This wouldn't work, even with an air raid siren. You really shouldn't "free feed". This usually leads to obesity in dogs. You should offer the dogs food twice daily. If they don't eat it in 10 minutes, pick it up.

mlarsen (author)sniffydogs2007-09-14

I’ve tried to quit the open bowl feeding and do as you said in the past without success. Just as your Bloodhounds are stubborn when it comes to sound, my mutts are stubborn when it comes to breaking them of their habits. I’ve tried everything, numerous times, and they still will not eat right away when food is placed into their bowl. I do agree with what you are saying. I’m all about proper and correct training, but unfortunately this isn’t a perfect world and sometimes things just don’t work out as planned. Hence the creation of this device :-) I guess this begs the warning: DO NOT use this device in an attempt to simply alleviate yourself from proper feeding duties. ONLY use it as a last resort.

sniffydogs (author)mlarsen2007-09-14

No dog will starve to death with food available. If they are leaving food in their dish, you are probably overfeeding. Pet obesity is a huge problem in America. They will eat when they get hungry enough.

gallatea (author)sniffydogs2007-09-14

Totally not true.. My sister-in-law has a bichon frise that is only about a year old. She rarely eats all her food when she gets food. She grazes. SIL said she can leave a big bowl out for 4 days before she finishes it. Scary. The dog's ribs are palpable - she's totally underweight. So "free feeding" does NOT always make your dog obese. If the dog doesn't eat it all in 10 min. that doesn't mean it's not hungry. It may mean it hates its food's flavor or has a health problem - and I'd not advise to starve it and take the food away to 'fix' the problem.

jridley (author)gallatea2007-09-18

As with humans, if the dog is getting enough activity, it'll stay in shape. Our dog free feeds, but she also spends a large part of the day outside running around, chasing wildlife and running alongside cars on our residential street (she's contained within an invisible fence and can't get within 60 feet of the road; she drag races cars that go down the street). One trick is to not feed a food that they find irresistable. Our vet recommended Science Diet, but the dog camped over the bowl and ate a ton. We find that Diamond has exactly the same nutritional values, but the dog eats only what she needs. We've switched her to Lamb & Rice which she loves, but at 8 years old she's developed eating habits so that unless we were feeding her chopped bacon she wouldn't overeat anyway.

sniffydogs (author)gallatea2007-09-14

Yeah, that's why all the furballs have rotten teeth and are picky eaters. People keep pandering to them and create picky eating dogs.

ehem. free-feeding only does that to SOME dogs. I have 2 mini-pins that I free feed and their not fat, all the dogs I've ever had (about 7) have been free-fed and never got fat. as for your bloodhounds, do a Google search for "the mosquito sound", that should annoy them plenty heheheh.

clipless (author)sniffydogs2007-09-14

Take the food away after 10 minutes? That sounds kind of harsh. My dog is half-bloodhound, and I put food in his bowl in the morning and evening. Sometimes he eats right away, other times he might wait up to an hour, and he’s far from obese.

sniffydogs (author)clipless2007-09-14

I rescue Bloodhounds. Most are very other dog food aggressive. We have to feed them separately. If you only have one dog, go for it. Most hound breeds in general will eat until they blow up.

X3Cliff (author)2007-09-12

Is the antenna a fixed length, or can you make it longer? If it can be a bit longer, do you think the antenna can be attached in a ring around the top of the bowl to set off the alarm from all angles? Nice work.

mlarsen (author)X3Cliff2007-09-12

Thanks :-) Actually, in the second sentence of the last paragraph in the intro I mention exactly what you say. At the current time I don't have the proper tools to create an antenna that would sit atop the rim of the bowl. I've tried... trust me, I've tried... but figuring out how many loops of fine wire I need in proportion to the size of the rim is a daunting task. Ideally, what I need is a formula that would let me plug in the diameter of wire along with the radius of the desired antenna (same as bowl) and would return the number of loops needed for said antenna... Any ideas?

KD7WHQ (author)mlarsen2007-09-13

At that frequency, a resonant antenna would be infeasably long, and all provided are a serious compromise. You might try 40 turns of #32, or really any magnet wire at the diameter you need. Finer is better for lots of turns, as it will bulk up. Go for 60 turns if you really feel ambitious. Draw a circle on a bit of wood with a compass at the diameter you want, tap brads at 1/2" spacing around on the line, and start winding. To secure the coil, you could brush/spray with polyurethane, or wrap with electrical tape. Personally, for testing, I'd flip tape at intervals around the loop. Hope this helps, and great idea there ;)

mlarsen (author)KD7WHQ2007-09-14

Wow, so do you think I could get away with 60 turns using #32 wire for a 9" diameter antenna? That would be about 45' of wire, which isn't too bad.

KD7WHQ (author)mlarsen2007-09-14

It should. Likely, it would outdo the stock antenna. Remove turns if you need to shorten the range. Add if you need more. A quarter wave antenna at that frequency would be 1,872 feet long, but even 20' would work for a short distance.

mlarsen (author)KD7WHQ2007-09-15

:-( No go. I made an antenna by looping #30 wire 60 times in a 9" diameter, but it didn't work. Are you saying I would need 1,872' for a 9" diameter antenna?

KD7WHQ (author)mlarsen2007-09-15

That would be a quarter wave.. Just for grins, try it with the coil vertical. Could be the cross polaraization is killing the signal. Real antenna design wouldn't be simple..

e1mer (author)mlarsen2007-09-13

It's been a while, but I think the length of the antenna is supposed to be 1/4 the wavelength. I can't find it in my books any more. Sigh. I wasn't able to figure out the frequency of your detector, but assuming it's in the 130kzc range for passive tags, then you're looking at about 1800 feet for a quarter wavelength antenna. I think you can wrap any diameter as long as the total length of the wire is about that long. Seems like you could apply electrical tape (sticky side out) on a bike wheel between the spokes, wind thin copper wire on a partially inflated tire, then cut the tape at the tire/rim on one side of the wheel, use the short end tobind the antenna loops, repeated all the way around, then deflate the tire to remove the coil with long flaps of tape, and finally wrap the tape to make it look neater. Hmmm, seems like a lot of work if I am wrong. :)

mlarsen (author)e1mer2007-09-14

The bike wheel idea is genius! I'm using 125kHz tags.

fungus amungus (author)2007-09-05

Nice, I was thinking of a way to make a light that turns on when my cat is near the back door and wants to get in. This looks perfect.

mlarsen (author)fungus amungus2007-09-14

Have a look at the book "RFID Toys" by Amal Graafstra. Chapter 7 shows how you can make a RFID dog door that might do exactly what you want...

oh yeah I saw that book in B&N;, it looks awesome, I totally recommend it.

fungus amungus (author)mlarsen2007-09-14

Sweet link! Thanks

Andrew546 (author)2007-09-02

Has just the buzzer been sufficient to discourage the other dogs? When I first saw this, I thought you were going to rig up some kind of remotely operated lid.

mlarsen (author)Andrew5462007-09-02

Amazingly (and honestly) its proven to be more than enough. The first few times they tripped the buzzer I scolded them, so now they associate that with being a "naughty dog." I have to be careful playing that sound on my computer (via the movie) because my dog Mazie (the one in the picture) will lay down and sulk because she thought she did something wrong, lol.

btop (author)mlarsen2007-09-12

I thought that as well andrew, or you might have used a solenoid to open a hatch and let out some food. good job.

mlarsen (author)btop2007-09-12

I'd like to add an automated food dispenser to this eventually.

I pondered long and hard (well, maybe a few hours and a trip to PetCo to examine an automatic feeder they have for sale) to figure out how to do this. The feeder I looked at used a rotating plastic brush, like so:

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Using hard plastic bristles, the food would pass thru when the brush turned and stay put when stopped. And, since the bristles were hard but flexible, no food would jam the machine (potentially releasing all the food). This is the method I think I will use in the future...

SacTownSue (author)mlarsen2007-09-14

I wonder how it would work to rig something similar to an old fashion gum ball machine.

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