Purewrist prepaid payment card in USA

@PaulT I have so many questions. Is there a fourth “selector” chip that handles connecting/disconnecting the inactive chips from the antenna?

How do you know it works if you have all the parasitic elements from a breadboard?

Yes an RF switch matrix.

When I say breadboard that’s generalist, not necessarily the plastic multipin things but RF specific stuff. Which can simply be a copper ground plane and everything mounted ‘dead bug’ style. Prototype to final layout will always bring changes but as long as these things are known then they can be compensated for. Working at HF but with very short lead/trace lengths is advantageous when it comes to mitigating strays.

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Will it ever be able to fit in an implant form factor?

Yes, the main limit is the RFID devices to be honest. Depends what package/dies are available.

Very interesting. Let me know if you want any assistance. My primary focus is PCB Design and MCUs, but I’m becoming an accidental RF engineer working on RFID and other projects.


Hobby RFID things are a bit on hold at the moment as real work stuff has been getting in the way.

I got a read with my Purewrist PAY on that Verifone MX 915 terminal that was giving me trouble. The issue is that some of the terminals have a huge metal clamp holding them, and others have a proper armature screwed into the back center.



I was able to get a read no problem on the unit on an armature by placing the implant horizontally against the black area above the LCD. I still haven’t been able to find the sweet spot on the ones with the clamp. I think the large body of metal is affecting the field shape

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Would you suggest chip toward finger?

I have the antenna end towards the fingers for mine, but with my external testing it didn’t make a difference which side of the reader you approached it from.

Think I’ll get back on track with this, any reason I shouldn’t?

Nope. Everything seems to be in order. I’ve had no issues with the implant, the company, or their interface, and 80% of the readers I’ve tried work fine first try

Was filling out a feedback form and wanted to share this gem:


Hahaha, it has become a part of you? Hehe :grin:

Not to drag this out again, but shouldn’t the question be “How would you feel when you will no longer use your Purewrist after daily use with it?” It will expire after all :slight_smile: Or is the replacement date already in your agenda?

The comment was more a joke on the feedback form to confuse the reviewer. I hold no allegiance to this payment implant, it’s a tool just like my others. Even if it does last for 3 years, I’ll almost certainly have it removed before then. I semi-regularly switch out obsolete implants for newer ones. Thus is the nature of “upgrades”. Even someone with a prosthetic leg has them tuned up and switched out regularly.

The Apex is about to become available at the beginning of next year, so I’ll likely be able to use that for payment before this one expires. If not I’ll just switch out for another (probably better) payment solution, when the time comes


Holy crap! Okay, I didn’t realize. I had assumed you were okay with switching out every 3 years because you had to, but I didn’t realize you actually opened yourself up on a regular basis for upgrading.

We really are different: the less I breach my skin the better I feel :slight_smile: Although I might consider doing it more often if the logistics to do so out here in the sticks weren’t so complicated: the only installer I’d trust with scalpel work is 400 miles from my place, so it’s not like I can decide to implant something on a whim, sadly.

With a crucial difference: there’s no blood or stitches involved - if the prosthetist knows what he’s doing anyway. And you can DIY.

Yeah, that’s the truth. I’m truly lucky because of my location that I have a trustworthy body mod artist about 40 minutes away. It’s so much more difficult to get the installs done in most places. I wish there was more we could do to connect people with qualified artists or doctors, but it’s inherently word of mouth because of the varied regulations on this grey market.

Still waiting for my purewrist to get verified because of my stupid 1/2 address… Overall giving me a bit of pause about stuffing something into my body that I might be dependent on third party support channels and their vendors decisions for… But we’ll see how i feel when I get verified.

That’s really unfortunate. I understand your hesitation. If you want more direct assistance you could email ari@purewrist.com

Someone is starting to see how I see things :slight_smile:

Having said that, if you want a payment implant, you ain’t gonna escape it, by the very nature of the application.

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