Active NFC tag for wristband

[tapirtapir]

I’m a tech journalist and I’m doing a little feature on NFC. What I need is an NFC wristband that isn’t just passive.

What I’m after is an wristband that could be tapped to other NFC wristbands (the same models) to exchange some basic info (a line of text maybe) that could then be 'stored' (either using an NFC SoC with memory capacity / or additional memory) and then 'transferred' to a smartphone at a later time to be decoded.

I understand there may need to be a power cell for this, I was hoping a coin battery to keep costs / size to a minimum.

These wristbands would also, ideally, be able to tap against passive NFC stickers and tags to also receive and store info.

Is that possible? I hope that all makes sense?

[JL. Lebon]

Hello, 

This question has been tagged "ST25 Dynamic tags", but I think the dynamic tags is not what you need to do what you describe.

A Dynamic tag is a passive device that must be powered by an RF reader (i.e. a smartphone). Also, as defined by the NFC protocol, a tag (or dynamic tag) always never "speaks" first: it always answers to a reader's request.

What you need is a NFC reader IC. ST offers several NFC readers IC like the ST25R3916, ST25R3911 etc. Those readers can read passive NFC stickers, transmit data to other NFC tags, but can also act a tag (in cadr emulation mode). So it can definitely fulfil your needs.

Best regards.

[Ulysses HERNIOSUS · Accepted solution]

Hi,

a reader like ST25R3916B implementing both reader mode and tag mode could do this. But I have the feeling that this may not be realistic: Acting as a reader consumes considerable power and a button battery may deplete very soon. Also a wristband is rather slim, so also the antenna is expected to be small. Overall for sure a challenging project.

I am not aware of any our ST25R demos which could be (re-)used to prototype a wrist band.

Best Regards, Ulysses