Sourcing T5577 chips for custom wearables

Hi all,

I working on making my own wearables but am struggling to find decent sized T5577 chips. I want to be able to fit it in a watch strap or even smaller and make my own fancy magic ring. Anyone know where to find appropriately small chips and antennas? The smallest I can find are the 25mm round tags online. Even if you have advice on how to approach just finding an appropriate antenna I am not beyond taking a chip from a card and soldering it into a small antenna.

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The last US based supplier I spoke with gave me a year lead time on the ATA5577C, so scavenging from cards might be the best approach with the current state of the supply chain.

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I would reccomend AliExpress, From experience I can tell you, the most difficult thing to find will be antennas.
The chips as @Fade0 suggested, salvaging chips from any of the T5577 products, MOST of the antennas you will find will be disc shaped.
However you may find a few of the EM40xx products with rectangular antennas.
Just attach the T5 to the EM antenna

Due to physics, you will find the 125kHz antennas will be either thin and large, or more Chode like (Short and fat)

Looking for a few for a project too …
How close can they be to a metal object without interfering?

It’s really more about orientation than proximity, if the metal is between the reader and the antenna you’ll experience interference but mere proximity alone shouldn’t really be an issue.

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Well … If you lay the tag on a big chunk of metal, you won’t be able to read it …

Well certainly, I guess I should back up here and ask you to expand a little on your question. Since the topic mentioned wearables and I didn’t realize you were not the OP, I assumed you meant proximity to something like a metal snap or a maybe a zipper or jewelry, not a block of steel :rofl:

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Thanks for the tip of the EM40xx, sounds like I have some ordering and antenna surgery to do.

Just get some and experiment I’d say. Not messed with LF yet but I have some HF chips. Can get reads on a 8mm ntag 213 about 2mm over 2mm silver. Will put a proper post together once I have done more work and have something to show for it.

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I’ve been messing with putting a tag in my watch for a while … It’s a stainless dive watch with a stainless band.
Inside the casing or behind the body I don’t read … Thinking about machining one of the link and embedding a tag there, but there is too much metal to get a read …
Next plan is to surface mount the take on one of the link … If I can find one the right size :sweat_smile:

For what it’s worth, I have a 25MM T5577 stuck with 3M behind my Pebble 2 watch emulating HID Prox, I found if I place the SIDE of the watch against the SIDE of the reader, it will work just fine, but this will obviously depend on the reader and how it was installed – can’t do this if it’s flush mounted.

Sorry, my typo


an example of some antennas

NZ$ 15.72 | 41*19mm 125KHz ID reader’s antenna Coil

It might be worth having a look at a teardown of an NFC ring. I would imagine that it might be possible to fit a similar sized chip and antenna in a watch band.

I actually did that exact thing. Sadly the LF antenna did not make it through the dissection.

I assume in both scenarios you’ll be ending up with metal between the tag and the reader, so it’s a no-go.

slightly oversimplified rule of thumb:

  • metal between reader and tag will “block” the radio field, forcing the field to bend around it. the closer you are on the other side the less of the field you get. So a larger antenna and more distance from the metallic body might help… or the loss of energy might still be too much.
  • metal behind the tag may “reflect” some of the radio field causing interference. tags must be shielded in a special way (i.e. not cheapy tags) to allow for that.
  • metal in direct contact with the tag might “sap/ground” some of the energy being harvested, rendering the tag starving.

So you want it placed:

  • with something non metallic between the tag and the metal
  • not surrounded by metal like a satellite dish effect
  • not having metal between the tag and the reader