Help with Smart Pet Feeder project involving RFID


I’m currently working on a Smart Pet Feeder project that uses a Raspberry Pi and RFID reader to allow access to a pet wearing a RFID collar. Once the pet approaches the food bowl, the lid will open automatically for them if they are wearing the RFID collar.

I have read the article on the PiicoDev RFID module, which uses a Raspberry Pi, but the reading distance is only 25mm. Considering that a pet will be wearing the RFID tag, I believe I need a longer range (15-20cm I guess) for this to work.

I have zero experience with RFID technology, so I’d be grateful if someone could give me any assistance.

Thank you

Hi BenHur
There is a bit more in this than what may be obvious. Firstly the reader has to transmit enough power to operate the electronics in the card. As the card has no battery the operating power must be derived from the RF energy received from the reader. Most of these card reader type of devices require the card to touch or be very close to the reader to work.

If the system you saw is quoted at 25mm increasing this to 200mm is not a linear progression of power increase. As with any RF system doubling the distance requires an increase in power by 4 or 6db for the same signal strength or in other words an increase of 18db or 64 times the original power.

Someone might know of such a system but personally I have not come across it. Road Toll readers operate the same way but with a large transmitter and I would think a large antenna system built into the gantry structure. Probably a bit beyond the home handyman I think

But you never know these days so don’t give up. Maybe a motion detector system or similar might be considered but you would lose the individual ID but there may be a work around for that too.
Cheers Bob

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Hey Ben,
Welcome to the forums!

Electronic pet dog doors use an RFID system already, so it would be feasible to get this working for you, unfortunately this isn’t something our RFID reader excels at due to it being a NFC (13.56MHz) reader and not a Low Frequency RFID (125KHz) reader.

The typical ranges for these different types of tags is as follows:
High Frequency/NFC: typically 4cm
Low Frequency: 10-30cm or if using a more powerful reader up to 1m.

The basis of range with these tags is providing enough power at range to wake up the chip in the tag, this can be done by using a larger passive tag type and/or using a larger coil supplying the power from the reader.

Another alternative is using a UHF RFID tag and reader (the type used in garages to automate doors opening when you pull up) as they tend to have longer ranges than the standard HF and LF RFID tags.

Hope this gives you a little more information on available options and ask away with any info that you may need to get this project put together.



Hi Ben,

Just to add to Blayden’s recommendation, we do actually have 125KHz readers and tags in our store!

The kit SparkFun makes is based around a module that just outputs the ID of the tag over serial, so anything that can accept data over serial will work well! I’d suggest a Pico, but the choice of host is up to you.

Let me know what you think about that idea

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Long range RFID is available. But I think this will be expensive: Long Range RFID - Nedap Identification Systems

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Hey Rooppoor,

It looks like thats an active/semi-active RFID tag which would be a great way of extending ranges of RFID. Although I am not sure how it is triggered to activate the output from the chip itself as at those ranges (15M) that takes a bit of current and I cant see a button battery being capable of supplying that for extended periods of time.

Would be interesting to know if there are any active tags available for use in a hobbyist capacity, I haven’t seen anything around but haven’t yet had a proper look for it.


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Here I can see a simple pet feeder: Pet Feeder Controlled Via WiFi - ESP8266 - Share Project - PCBWay

Pet detection system is not included in this. I think, the most accurate method will be to use image processing. You can proceed with an ESP32 and ESP32 CAM or a Raspberry Pi Zero+Raspberry Pi Zero Camera. I think rather than looking for a long range RFID, you can just train your model to detect a cat/dog. Core electronics has many similar type of blog tutorials.Here is one: Object and Animal Recognition With Raspberry Pi and OpenCV - Tutorial Australia