[chbot] CovidCard implementation - how expensive should it be to manufacture 1M of them?

[Charles Manning]

The Silabs parts use a bit less power and there are some with a very
interesting "wake on RF" mode which can extend the life of a CR2032 to
something life 5 years.

However the "wake on RF" needs pretty high RF levels to trigger.

The actual manufacturing cost per se can be low, but the engineering cost
and logistics of trying to roll out , say, 3 million units in less than a
year precludes many of the cheaper options (eg. the sub-$ micros used in
the tags).

I still think the easiest way to achieve the basic goal is to use a phone
app that sends and listens for BLE beacons. This might mean you need to
charge your phone twice as often. For the 10% of adults that don't have
cell phones it would be cheaper to buy them $50 phones than it would be to
develop a CV card.

That could all be rolled out in less than 3 months.


On Mon, Aug 31, 2020 at 10:11 AM hamster <hamster at snap.net.nz> wrote:

> Fully agree.
>
> TX => COTS parts can do this.
>
> Contact Storage => mildly challenging. You you would timestamp every
> minute (for 1440 timestamps per day, 5760 bytes per day), and keep a least
> recently seen table of 127 entries, keeping recurring contacts to one
> bytes, and new contacts to once byte + ID.
>
> RX => Well, there's the crux.
>
> All of the low power RX parts I've looked at consume somewhere between
> 10mA -> 25mA when active, and with approximation 720 hrs in a month it
> starts requiring batteries with many AHrs of battery capacity - a coin cell
> is ~250mAhr,, only enough for 10 to 20hrs of RX per coin cell.
>
> Mike
>
> On 30.08.2020 22:37, Stephen Irons wrote:
>
> These are the technical challenges that I see:
>
>    - Clever transmit/receive protocol to ensure that every card manages
>    to capture the contact data for every other card in its vicinity in a busy
>    location
>    - Battery life, due to receive power consumption, because the receiver
>    must be always-on
>    - Battery life, because it must be powered by a coin cell if it is
>    credit-card sized
>    - Data storage, because it must provide enough storage for the people
>    who make many contacts during a day, not only the average person
>
> I have no idea how you can coordinate transmission and reception between
> nodes in continuously changing, overlapping clusters of 10s of nodes, such
> as would happen in a shopping mall. Mall-trackers work because they don't
> actually care if they only identify a small fraction of the actual people
> there. The CovidCard, on the other hand, should collect all.
>
> I did some power-consumption estimates for a client:
>
>    - A transmit-only BLE beacon will operate for a year or two on a
>    CR2032 cell, transmitting for about 4 ms every 1.5 s, giving an average
>    transmit current of about 4 uA. This is based on the measured power
>    consumption of a real implementation using a TI CC26xx part, with cell
>    capacity from the Panasonic CR2032 datasheet.
>    - (Wikipedia has a description of BLE beacons.)
>    - Receive will kill the battery, drawing about 5--6 mA continuously
>    (datasheet).
>
> Data storage might be an issue, especially for people in a customer-facing
> job (eg. the guy who sprays goop on your hands when you enter the
> supermarket)
>
>    - Assume that a busy person makes 1 contact per minute for his 8-hour
>    working day, for a total of 480 contacts per day, or 14400 contacts over 30
>    days.
>    - Assume you store a 64-bit ID (BLE MAC or other unique ID) and a
>    32-bit for a timestamp, you need to store 12 bytes per contact.
>    - This gives a total of 173 kbytes to store this data.
>    - That TI part has 128 K of flash; there might be other parts with
>    more flash.
>    - Alternatively, those SPI flashes give unlimited storage, but they
>    add to the cost.
>
> That TI part has enough grunt to do the BLE stuff and to run some
> application stuff -- it is pretty simple. I don't think you would need a
> separate processor.
>
> That TI part on a PCB with a CR2032 in a key-ring housing costs a few
> dollars in 10K quantities. A credit-card form-factor would be much the
> same. A separate flash chip will add a bit more.
>
> Personally, I think the 300-person trial in Rotorua is much too small.
> Contacts between CovidCards will be rare, and it will not test operation in
> crowded malls, restaurants, and other busy locations.
>
> Stephen Irons
>
>
> _______________________________________________
> Chchrobotics mailing list Chchrobotics at lists.ourshack.com
> https://lists.ourshack.com/mailman/listinfo/chchrobotics
> Mail Archives: http://lists.ourshack.com/pipermail/chchrobotics/
> Meetings usually 3rd Monday each month. See http://kiwibots.org for
> venue, directions and dates.
> When replying, please edit your Subject line to reflect new subjects.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ourshack.com/pipermail/chchrobotics/attachments/20200831/81c2bb69/attachment-0001.html>