
Coin Card Teardown - monkeypod
http://www.bitsofcents.com/post/124593977646/coin-card-teardown
======
joshstrange
I had the beta and a final Coin and neither one were reliable enough to to
trust. You HAVE to carry backup cards which more or less defeats the purpose.
Then there is the slightly embarrassing, extremely annoying "Your card didn't
work/Do you have another card this one isn't swiping". I've stopped carrying
my coin altogether because if you have the cards you might as well use the
real ones (I tried for 7+ months to use coin first).

~~~
markbnj
They probably didn't have the ability to test it on nearly enough readers,
given that there are literally thousands. They may also be running into some
timing issues based on how people swipe. Those are things you sometimes just
can't work out barring wide scale testing and adoption.

~~~
Someone1234
Right. But file this away in the "not my problem" draw. You can make all the
excuses you want, but this is ultimately up to them to resolve, not for the
consumer to deal with.

------
ceequof

      The specs aren’t listed on the FDK site but the safety 
      data sheet shows it is a 3V battery although amperage is 
      unclear.
    

All lithium-ion batteries have a nominal voltage of 3.7V, like how all
alkaline batteries have a nominal voltage of 1.5V. It's just how the chemistry
works.

( _Actual_ voltage can vary quite a bit, depending on where you are in the
discharge curve:
[http://i.stack.imgur.com/UkodS.gif](http://i.stack.imgur.com/UkodS.gif))

And to be somewhat needlessly pedantic: you want "amp-hours" there, not
"amperage". Amp-hours is the unit of capacity, amps is how much current is
being drawn at that very moment. In the automotive metaphor, amp-hours (or
watt-hours) is how big the gas tank is, while amperage is engine horsepower.

~~~
Dylan16807
Lithium is not lithium ion.

Single-use lithium batteries are made in a variety of voltages. This chemistry
is in fact three volts.

~~~
ceequof
Whoops, guess I'm wrong.

------
stephengillie
_What Coin has managed to do in such a thin package is really impressive. It’s
a shame they weren’t able to do it more reliably._

It's a really cool idea. I actually wonder what the technological hurdle was
that held them back - mechanical (reliably magnetizing the coils, easy-to-
break components due to narrow size), software (programming issues), or QA
(reliable SoCs, reliable builds, reliable solders)?

~~~
pjc50
I suspect flexing the PCB caused the usual problems of hairline cracks in
solder joints, resulting in intermittent faults.

~~~
thaumaturgy
If that's true, I wonder if something like a paper circuit would work? e.g.,
[http://www.instructables.com/id/Paperduino-20-with-
Circuit-S...](http://www.instructables.com/id/Paperduino-20-with-Circuit-
Scribe/)

~~~
pjc50
Flexible substrates are not a problem - the industrial solution is polyimide
(Kapton) or just really thin FR4. The problem is inflexible components. As
soon as you bend a curved surface attached to a small flat rectangle (IC), it
pulls at the joins.

You might get better results with bare die+wirebonding, then encapsulating
with slightly flexible epoxy. That would allow the bondwires to flex and take
up the bending. Doesn't help with the discrete components or the battery.

------
ngoel36
I was so damn excited to use my Coin - the idea was brilliant. I tried to so
hard to use it, but with a 30%+ failure rate, it became completely useless.
Simply not worth the embarrassing "Sir, your card didn't work" or "Is this
real?". And if I have to carry backups anyways, what's the point?

~~~
BrentOzar
I like it because it got me down from several cards (debit, credit card A,
credit card B, business card, business debit card) to two (debit card, Coin).
The debit card is my backup to Coin.

~~~
ngoel36
I formerly did the same, but it became insufficient.

There are at least 4 cards that I need working at all times: (1) Debit card,
as you mentioned, to be able to withdraw cash in a pinch, (2) Chase Sapphire
Preferred - card with no FX fee, (3) Corporate Amex for charges I don't want
to take on personally, (4) Starwood (SPG) card to amass a non-negligible
amount of points on hotel stays. And maybe a 5th on which I'm trying to spend
a large amount on quickly (for example - I might be planning to put $1500 on a
random card with a big signup bonus, and it might be critical for me to get
points I need for an upcoming reservation)

I of course have all of these loaded into my Coin, but each has failed enough
times (forcing me to use the debit) that I started carrying the others as
backup. Then I found myself carrying 5 cards....plus the Coin. And if Coin is
targeted to users like me (who carry multiple credit cards, optimizing for
different uses)....then what's the point?

------
yrral
Fcc photos of the coin pcb here [1]

I think that the coils that drive the magstripe are only activated when the
buttons to the left or right of the stripes are depressed (e.g. by the process
of swiping).

Also, I believe coin only transmits track 2 [2]. Why it looks like there's 2
coils is curious to me as well.

[1]
[https://fccid.io/document.php?id=2397353](https://fccid.io/document.php?id=2397353)

[2] [https://support.onlycoin.com/hc/en-
us/articles/204263414-Coi...](https://support.onlycoin.com/hc/en-
us/articles/204263414-Coin-Compatibility)

Some merchants require your full name (also known as Track 1 card data) as a
part of the transaction process. Coin does not transmit Track 1 data and may
be rejected at the point of payment.

~~~
joezydeco
It seems like a logical thing to do, especially when you're trying to a) save
power and b) time the speed of the coil's "stripes" to make the reader think
it's seeing a physical card. It's probably also the source of a lot of
rejected swipes.

Conductive rubber pads and/or membrane switches are always a bad thing.
Necessary for this design, but they'll always fail you in the end.

------
treycopeland
I received my Coin about 2 months ago. I was excited to test it out after
preordering almost 2 years in advance. The concept of having all my cards on
one central card was a great idea. But having it not work at some locations
was rather embarrassing and frustrating. I have decided the Coin was a fail
and I will not carry it anymore. But, Coin, keep innovating. You tried.

~~~
lvs
It sounds like just another startup hardware offering with a spotty launch.
But I've always been confused about the perceived "embarrassment" of a card
not working at the point of a transaction. This seems to be a common marketing
trope in payments, but I don't know what it comes from. It's a piece of
technology, and tech often doesn't work quite right. Sometimes my phone
restarts itself. What's the big deal?

~~~
rio517
I have been super broke and unable to pay bills at two points in my life -
just out of college and trying to find a job after the dot-come bust, and
again when my startup failed. During those bad times, I'd lose track of my
finances and a few times couldn't pay for my groceries.

I can't describe in words how much I felt like a total, utter failure. All the
fears I had about how I was going to pay my bills that month, the pressure
from family to pay them back for money borrowed, the pressure from roommates
to come up with rent - all came bubbling up in those moments.

After all, I was the first kid in my family to go to college. I was the smart
one who was supposed to have his shit together, but there I was - totally
broke. It creates a fear that is not rational and hasn't gone away (at least
for me).

About a year ago, I forgot my bank card at TJ's and only had $20 bucks on me.
I was embarrassed in ways I can't describe. I was cold sweating to the point I
was soaking my shirt. I had to leave everything except for some essentials I
needed for that night. One of the cashiers lent me $5 to help me pay for my
groceries (I paid him back). I feel weird that I accepted the $5, but I wasn't
thinking rationally. I wanted to scream "no, really, I have my shit together
now." I kept telling myself that this is not a big deal... chill out... But I
just couldn't calm myself down. It was like poverty PTSD.

Even though I now have paid off all my debt, school loans and have a healthy
nest egg, I still have these fears. Whenever my card won't go through on the
first try or I type in the wrong pin number, my heart jumps.

It's entirely irrational.

~~~
Domenic_S
I can relate to your feeling, and this ONE WEIRD TRICK will greatly increase
your positive feelings: get a credit card with no fees that you pay off every
month. Once I got my Amex, I never again wondered if that swipe would go
through -- it just does, every time. That of course comes with its own set of
problems (ahem, budgeting).

~~~
jldugger
Doesn't really solve OP's problem of forgetting their card, or my own of 'the
network is down.'

------
scoot
If the mag-stripe emulation is just a simple electromagnet, I'm curious how
they detected the position of the read-head in order to modulate the magnet
correctly to emulate the data that would otherwise be read at that point of a
traditional mag-stripe. Or is it more sophisticated still?

~~~
msandford
My guess is that this is why they have so many problems. I'd guess that
there's probably an accelerometer somewhere to give them an idea of what the
swipe velocity is, so they can know how fast to play everything back.

But ultimately the way they've chosen to do this seems to be very difficult,
especially if those are two very long single coils. It feels like it would be
much easier from the software side if they had made them addressable somehow
so that they could control every bit individually by either energizing or not
energizing a particular coil. Then you'd have eliminated the swipe speed
variable from the equation and a lot of complexity would drop right out.

Honestly looking at this teardown I'm surprised it works at all.

~~~
joezydeco
Doesn't seem to be any accelerometers anywhere. There _are_ two hidden
membrane switches to either side of the coils. The card is probably using the
press and release timing of that button as it travels through the reader to
guess at the speed of the physical card.

There are patents for dynamic magnetic stripes that have individual coils for
each bit. That is probably way too costly for this design, or perhaps too
expensive to license it.

------
mmosta
Pretty cool.

I'm interested in knowing which component failed? did the second card fail in
the same way? or was that remedied in the revision?

Did the display and button still work?

Hopefully the issue was with the coil, flex PCBs and displays are more or less
a solved problem, batteries not so much.

With the Nordic 51822 they're lined up well to roll out NFC after the mandated
phase out of mag-strip in the US (p.s how are they still a thing?).

It'll be interesting to see if they'll survive if a chip-and-pin foothold
overshadows NFC.

------
nadams
Was I the only one who canceled their pre-order after they asked for your
social security number?

~~~
jackreichert
I cancelled my preorder after I got the app and saw that silly tapping
security code.

I decided to try out Plastc after that. We'll see what that's like.

~~~
mildweed
After being burnt by Coin at $50, I'm not jumping at the chance to waste $150
with Plastc.

~~~
jackreichert
I hear you, I got my $50 refund, got some credit for finding a share link for
Plastc and felt $100 was worth it for my single attempt at using the tech.

------
Globz
This is the first time I am reading about this product but why mag stripe over
smart cards? isn't it less secure and deprecated technology? it seems very
useful but relying on mag stripe isn't the best move, no? Perhaps they
couldn't "switch cards" while using smart cards so mag stripe was the only
solution?

~~~
jackmaney
> isn't it less secure and deprecated technology?

Uhhhh...no? I've lived in the US my entire life, and while I've seen pin and
chip readers, I've never had a pin and chip card, never known anyone who has
ever had one, and never seen one used. Ever.

~~~
jordanthoms
That'll change very shortly, first of my US credit cards was just reissued
with a chip and you can expect that all of yours will be within the next year
or so.

Note that it is Chip and Signature though, not chip and pin.

~~~
jackmaney
My bank card expires in a couple of years, so we'll see if my next card is
chip and pin (or chip and signature). Hopefully, things will have changed by
then.

------
upofadown
>I was surprised by the number of test pads exposed on the Coin - all those
small metallic squares are programing points / test points. This suggests to
me that Coin is still going though some debugging since it’s rare to see so
many pads still exposed on a shipping product.

Perhaps their tester just couldn't probe the smaller pads/components. In
general, any shipping product these days is going to have a significant number
of test points, it is just that they are often not explicit.

------
tdicola
> It doesn’t look like there are many other products using the 51822

Actually the nRF51822 is starting to pop up in a lot of products, especially
those that use BLE. The BBC Micro Bit will be built around it:
[https://en.wikipedia.org/wiki/Micro_Bit](https://en.wikipedia.org/wiki/Micro_Bit)

~~~
mik3y
How's the toolchain support / dev environment for the Nordic parts these days?
I remember the "other" popular chips (TI CC2540 and friends) had a gross and
expensive requirement on "IAR Workbench".

~~~
tdicola
Luckily GCC works great with it as it's an ARM Cortex M0. I use the GCC ARM
embedded toolchain here and haven't had issues: [https://launchpad.net/gcc-
arm-embedded](https://launchpad.net/gcc-arm-embedded) The only gotcha is that
you need to sign up with an account on Nordic's site to get access to their
SDK and libraries, however I'm pretty sure that's just a formality and it's
free to sign up (just can't distribute its firmware source, etc).

------
myth_buster
I'm curious to know whether given proliferation of the NFC alternatives
available now like Apple/Google Pay is there a problem that Coin Card
addresses which the former don't. Is paying in the restaurants one of those
use case or will we see table side point-of-payments in near future which
would make it obsolete.

~~~
fluidcruft
For what it's worth, all of my banks have already replaced my credit cards
with chip-and-pin capable ones in preparation for October's rebalancing of
fraud liability between merchants and banks. I can't imagine merchants will be
too keen to accept these Coin cards.

~~~
dboreham
Are you sure? I ask because the majority of US card issuers have opted to use
chip&signature, not chip&pin cards. In my wallet I only have one chip&pin card
(Well Fargo). The rest are chip&signature. Whether or not they send you a PIN
is a good indicator of which auth method the card supports.

~~~
fluidcruft
Hmm. Perhaps not... I hadn't heard of chip & signature until your comment. I
set the pin online during card activation, and hadn't thought about it
closely. So, it obviously must be chip & signature.

Anyway, that doesn't change that you can't clone the chip's contents. Perhaps
you could punch the chip out (like a sim) and array a few of them inside a
next-gen type of Coin card.

Chip & signature answers the "Amazon laughs at your chip&pin card" loophole I
had been sort of half puzzling over.

------
jtchang
I actually have the Nordic NRF51822 / NRF51 development board and it is super
fun to play with. I come from a web dev background so getting into hardware is
rough.

The toolchain for building firmware is crazy. It's kind of like in webdev we
dynamically generate css through sass and then put it through all these
different stages (minification/etc). Except this is all old school Makefiles.
Made me cringe a bit.

------
deegles
Does cloning your card to a Coin make you liable for fraudulent transactions?
I assume it would be against the ToS for most cards to allow cloning.

~~~
concerned_user
That is what signature is for, isn't it? If bank can't prove it is your
signature then it is a fraudulent transaction. Technically cashier/clerk
should not accept the transaction if signature doesn't match but I've rarely
seen them check it.

------
sciencesama
can we make eddystone beacon from this chip
[http://www.aliexpress.com/store/product/Bluetooth-4-0-BLE-
Bl...](http://www.aliexpress.com/store/product/Bluetooth-4-0-BLE-Bluetooth-
Low-Energy-CC2540-chip-Module-Iphone-4S/417006_819192101.html)

~~~
leybzon
feels like it should be possible Eddystone is just a message format Some
embedded coding skills will be needed thou

------
dimino
My Google Wallet card does the same thing this does.

------
jackmaney
I'm amazed that this idea actually caught on in the first place. "Wait, you
mean I can put every single source of (non-cash) money in a single card, for a
single point of failure? And if it breaks, I'm effectively penniless? WHERE
THE FUCK DO I SIGN UP?!"

~~~
concerned_user
Also imagine it gets stolen, good luck remembering all the cards you had in
there and banks you need to call. Payment gateway route, like paypal, gives
same convenience and less headaches.

------
dougb
Coin is an interesting idea, but I figured
[https://www.dynamicsinc.com/](https://www.dynamicsinc.com/) would sue the
pants off of them for patent infringement once they went to market. Dynamics
CEO is a former patent attorney.

dynamics seemed to have all the pieces in place to do the same thing.

