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

If you’ve shopped for an EID stick reader for sheep or cattle recently, you’ll know they’re not cheap. £400 at the budget end. £600–£1,000+ for the mainstream Shearwell, Tru-Test and Allflex 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 kit

We’re building a DIY EID reader kit at a fraction of the commercial price. You self-assemble — about an hour, no special skills, no soldering required. It reads HDX and FDX-B tags (the UK standard), pairs over Bluetooth to your phone or to a tablet, and works with the Tractr app or any other software that accepts a serial / HID keyboard input.

It’s not a Shearwell. If you’re running 2,000 ewes through a race in the rain, buy a Shearwell. But if you’re a smallholder, a new farmer or a researcher who just needs to read tag numbers reliably and cheaply, the kit is for you.

Join the EID kit waitlist →

Want to build one yourself?

We’ll publish the bill of materials and the firmware source separately. The kit is the easy route; the BOM is the curious route. If you want it, get in touch and we’ll send you what we have.