Magic Ring v2 is available!

glad to be here. :nerd_face:

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The new packaging is awesome!

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Any plans to make a magic ring in the future with a gen 4 chip or any other chips that accept 7 byte UIDs?

Possibly… would be a very expensive ring… chips are hard to get and very expensive and ring batch production would require hefty minimums or very high small batch production costs… like $500 per ring?

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You could roll-your-own

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Ahhh, yeah that would be a bit too expensive. That makes sense though, thank you!

I am thinking about laying it into a leather watch band actually as I don’t have a printer!

Do either of you guys have any suggestions for resources on antenna placement/ length/ coil diameter/ separation for non EEs? Or any tips you’ve picked up along the way?

There are a number of approaches you could try, but you need some info first.
I gave my ultimate magic cards away, so I cant measure the chip resonance capacitor
This will probably be 17pf or 50pf

If you scan your card with TagInfo, it MAY populate that info ( It doesn’t measure it, but it think it is in the manufacturer info )

Is your watch band leather or similar? i.e. does it have a hollow centre or centre that can be hollowed to hold the chip and antenna?
How do you plan on attaching it? do you have a plan?

There are some off the shelf antenna options you could grab and experiment with like these

wich are similar to the size and shape you will need for a watch band.

You could do something like this

as you will also find antennas in small circles
Just go to your Chinese wholesaler of choice and type in 13.56MHz antenna.
You’ll want something 15mm or smaller diameter to just drop in and seal up.

Is your watch a smart watch? there may be some issues to consider, but easily mitigated.

Because ideally you want you antenna inductances close, the above antennas may not match.
You could try it and see how you go, or you could try your own by adjusting the wire thickness.

BUT The other route you could take is a little less off the shelf and more maker space.
It’s probably a better option because you know the inductance matches

Disolve the card in Acetone or similar
desolder the antenna from the chip (to make the antenna easier to work with)
Photocopy your watch band and use that as a template to lay the antenna turns ( wound thinner and shorter than the actual strap) lay your antenna out and work out how you are going to attach it ( actually do THAT before winding )

You could do a hybrid
Get yourself the Hornady watch band, pop out the chip from that
Wind your cards antenna around a ~12mm guide
Solder the chip to the ends
Test range
Drop it into the band
Fill with epoxy or cap it off/ plug it up.

If I wasn’t clear, do worry too much about the shape, It is not as important.
You will likely go for a tightly wound Rectangle, Oval or Circle which will all be fine for what you want to achieve.
I would just add, whatever shape you choose, The bigger the better

Hopefully that gets you started on the right track.
Sorry this was rushed and probably disjointed.

Feel free to ask more questions if you need

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Thank you so much for the advice, that’s extremely helpful!

I did pick up a Hornady watch band clip and a couple of the cuid 7 byte 1k fobs, I’m hoping the coil in those will be close enough in diameter that I will be able to pop it in without much issue for a short term solution.

For the long term I ordered a cheap leather band so I can lay the tag in between the layers, it is an Apple Watch but I’m hoping getting it out about 100° off from the actual watch will minimize selection issues. I currently have an mf ultralight c transit card as my default card on the watch and it has not tried to interface with either this or my last apartment’s readers as far as I have noticed.

I ordered a couple gen 4 cards from lab401 and my plan is to do the acetone thing and reshape the antenna to lay flat in the watch band, good to know that the shape shouldn’t matter too much! Thanks again, I’ll let you guys know how both projects go!

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Is anyone able to test setting the SAK value on the ring for me? Looking to get this for a friend, but I’m wanting to make sure that the SAK value can support having a different value from bit #6 in Block 0, as their building’s fob system uses that as an anti-duplication check.

Most Gen1a tags I’ve seen will either have a SAK:

  • that’s not modifiable (e.g. they are always “08” regardless of Block 0 values), or
  • will follow the Block 0 SAK bit (e.g. it’ll be “99” if Block 0 is “xxxxxxxxxx99xxxxxxxxxxxxxxxxxxxx”)

Can you let me know if the SAK value can be changed, and if so, can it be changed independently from Block 0?

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It appears to be a known issue with some possible solutions:

@Equipter seems to know about it :classic_smile:

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Yes, this is the behaviour that I’m observing (“Wake up” SAK value is different from the “Vanity” SAK value), though if I’m reading it correctly, I don’t see any solutions in the link would apply to the Gen1a tag on the ring (just solutions for emulators and Gen4), hence my questions about how the ring handles SAK values.

Just need to know if a) the Wake up SAK is changeable or burned in, and b) if it’s changeable, is it changeable independently or will it follow the Vanity value in Block 0?

It sounds like it follows the block 0 value

Sorry, I feel like I’m missing something again. What in the linked article makes you think that the specific Gen1a chip in the ring follows block 0? As I mentioned in the first post, I’ve seen Gen1a tags with Wake Up SAK values that are burned in and unchangeable (i.e. they don’t follow Block 0), so what is making you think that the ring is not using one of those chips?