wallet watch? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: March 17, 2025, 07:29:18 am
content: If you want a watch to put in your wallet like a credit card does such a thing exist with todays advanced technololgy ?I had a casio organizer kinda like that but it was way too fat and also eons agoSpec would be ~1mm thick. For people that wanna know the time by opening their wallet.

author: Swake
author_rank: Frequent Contributor
timestamp: March 17, 2025, 09:57:49 am
content: There used to be credit card sized calculators, some of them had a clock. About 2mm thick.I also recall bank cards with an integrated second factor authenticator in this format.This Ferrari watch is 1.75mm thick. Just a tad too expensive for me.

author: Haenk
author_rank: Super Contributor
timestamp: March 17, 2025, 01:53:51 pm
content: 1mm thickness is close to impossible - you need display, quartz, battery to fit in there, plus some sheets on bottom/top.Seiko and Casio made credit card sized clocks in the 80s, but those were about 3mm thick.Maybe invent some transparent film calculator with printed electronics, printed solar cells, printed OLED and foil supercap. That would be great.

author: squadchannel
author_rank: Frequent Contributor
timestamp: March 17, 2025, 03:18:33 pm
content: definitely possible.one-time key card for my bank account, it is e-paper and only about .8mm tickness.interesting project. I might try to make it.

author: coppercone2
author_rank: Super Contributor
timestamp: March 17, 2025, 10:46:30 pm
content: how do you do the crystal. it might need a special low profile crystal designThe display, battery.. I think its doable. The PCB can be something like the back cover being a aluminum thats anodized and then patterned into "ceramic' pcb. But the crystal is too bigit would need metal covers for top and bottom to be a good watchsay 1.5mmhttps://www.sitime.com/support/resource-library/datasheets/sit1533-datasheetthe crystal is still a bit fat. it might need just 'plastic filling' instead of a metal bodyhack that crystal to the card you have and it might work?What I was thinking though is to make a ECL display on top of a anodized aluminum card. In principle anodized aluminum is the same as ceramic substrate just finicky. Nasa experimented with this PCB material because the thermal performance is monstrous, there is no bond layer. So despite being not copper, there is no glue, you just have traces on top of anodization (which I think can be low temp thick film or just electroless + electro copper). This means if you solder a part on it, it only goes through the anodization layer and then directly into the aluminum. electrochemlumescence is the thing in the apollo guidance displays, thick film put on alumina.of course the problem is ECL is high voltage. LCD solves this problem I think

author: Bud
author_rank: Super Contributor
timestamp: March 17, 2025, 11:09:03 pm
content: I've seen credit card sized calculators, cards generating music melodies, crads with 7-segment displays, cards with fingerprint readers. And that was back to earlier 2000-s. They were working prototypes for winning the customer.

author: coppercone2
author_rank: Super Contributor
timestamp: March 17, 2025, 11:23:58 pm
content: They had a very thin solar calculator but this needs to have a crystal, which will set it apart from gimicks. . Since the battery sucks, maybe a capacitor button to turn the display on too? Or a solar switch, so when you open your wallet, the light turns the display on. And if you take it out of your wallet it could even have a big thin film solar panel on it that charges it!I wonder how much R&D on this thing would cost lolI think its nice that it would be a watch gadget that is not pompous because you won't be opening your wallet to show people on the street. Or is it extra bad because it gives people an excuse to open a wallet with 5kUSD and have platinum cards fall out on the floor infront of you? be sure to cushion your expensive wallet watch with at least 50 of these worthless paper dampers.

author: squadchannel
author_rank: Frequent Contributor
timestamp: March 18, 2025, 03:04:52 am
content: concept...JLCs $2 flex pcb(0.11t)onuc : BGA/QFN package STM32L4battery : NGK ET382704P-H (0.45t)xtal : CM9V-T1A-32.768KHZ (0.5t)display : GDEW029I6FD e-paper display (~0.2t?)switch : metal dome switch?(~0.6t?)and some 0402/0201 resistors and caps (~0.5t?)~0.8mm total thicknesshollowed out PP sheet as a frame structure, and laminating pouchingyep!

author: coppercone2
author_rank: Super Contributor
timestamp: March 18, 2025, 03:20:01 am
content: But it would need a battery manager / charger / port too if its going to be a realistic clockHow does that micro processor compare to those tiny-gecko processors that were discussed here a while back on power usage?I guess you could have a keychain assembly that plugs into USBC that clips over the card to charge it but it leaves something to be desiredThose thin film solar panels that they are saying they might try to put on cars one day would be ideal to charge it on the backCould you have exposed pads on the side that a USB-C cable slips over.. I think you can use that cable with only one half?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: March 18, 2025, 08:05:04 am
content: Quote from: squadchannel on March 18, 2025, 03:04:52 amOk start, but it might need a better frequency source ?A standard watch benefits from the users controlled temperature most of time, but a wallet is less fortunate.Perhaps SiT1811 Ultra Low Power, Low-Jitter, 32.768 kHz Oscillator ?