Build your own EID tag reader: parts, cost and setup

Update, November 2026: our reader is in prototype development and we’re concentrating on read range. We now expect a sealed, resin-encased reader rather than a self-assembly kit. Tractr itself (and its LIS movement reporting) is where our focus is; the reader will follow.

If you’ve shopped for an EID stick reader for sheep or cattle recently, you’ll know they’re not cheap: several hundred pounds at the budget end, and £1,000 or more for the mainstream options. For a smallholder with twenty ewes, that’s an absurd amount of money for something that reads a serial number off a tag.

So we asked: what’s actually inside one, and how cheap can a working reader be built?

What’s inside a commercial EID reader

A 134.2 kHz ISO 11784/11785 reader (the standard for UK livestock EID tags) has surprisingly few parts:

1. An RFID reader module — usually a chip from the EM4095 or TI RI-K2A family, with an antenna coil. This is the actual reading bit.
2. A microcontroller — to interpret the raw signal, decode HDX and FDX-B protocols, and format the tag ID.
3. A communication interface — Bluetooth (HID or Serial Port Profile), USB, or a screen.
4. A battery and charging circuit.
5. An enclosure — often the most expensive single part for low volumes.

That’s it. The chip set is well-documented, the protocols are open standards, and there are plenty of hobbyist projects on GitHub.

Why are commercial readers so expensive?

A few honest reasons and a few less-honest ones:

• Low volumes. The UK livestock market is small in tech terms. Tooling amortisation is real.
• Ruggedisation. A reader needs to survive being dropped in mud, sheep poo and the back of a truck. That costs money to certify.
• Calibration and certification. Some readers carry ISO compliance marks.
• Support and warranty. Real costs, especially in a niche industry.
• And, frankly, market position. When your competitors price at £600, there’s no commercial pressure to price at £200.

Our reader

We’re prototyping a low-cost reader that reads HDX and FDX-B tags (the UK standard) and pairs over Bluetooth with the Tractr app. The hard part at a low price is read range, so that’s what we’re working on now. We expect the finished reader to be sealed in resin rather than a kit you assemble.

It won’t replace a race-side reader for a 2,000-ewe flock. But if you’re a smallholder or a new farmer who just needs to read tag numbers reliably and cheaply, that’s who it’s for.

Where the reader is up to →

Want to build one yourself?

The parts above are all off the shelf and the protocols are open, so it’s a good hobby project. If you’re curious about what we’ve learned, get in touch.