iFixit: AirTag teardown

> It's hilarious to a certain extent that they built the thing smaller than all the competition and bulk it up with a wad of leather anyhow.

That's essentially how I feel when I see the "Our thinnest iPhone ever" slide knowing that 95% of iPhone owners put it in a bulky case. That said, that's not unique to Apple and the phone is at least usable without a case.

The Tile is much more compact than the kitted out AirTag. Shame that Apple had to pander to the twin gods of accessories margin and fashion.

Apple’s unique ethos is technology as a means for creative expression. That’s why they’ve excelled in font rendering, colour accuracy, sound fidelity, and input-lag.

I think this value came from Steve Jobs, and I hope they never lose it because it imbues Apple with real human spirit. They’re more than just another profit-seeking company.

Is the magnet strong enough to stick the tag to ferromagnetic metals?

I’ll go out on a limb here and guess that their guiding principle with this was as it is with every other portable device they have now - make it as small as practically possible and let people extend it if and how they want[1] to.

Saves a little bit of material, makes manufacturing a little less complicated, and makes the accessory ecosystem a whole lot more appealing.

1. I don’t carry a keychain, for example, but I’ll slip one in each of my bags.

Beside the size it's probably a tradeoff on mechanical integrity: a keyring can introduce immense mechanical stress. On my last tag the small loophole just broke away after a year on a key that was not used daily or in harsh environments. With the AirTag you can just replace a $2 third party accessory. Apple didn't have to engineer a very durable (maybe milled?) loophole, which would have increased cost.

I think it has as many non-loophole uses as loophole uses, so I can see why they chose to cut down on bulk there. I put one in my wallet and one in a small internal pocket in my bag, neither are actually attached.

I can't remember the last time I actually lost my bag or my wallet, but these are definitely pretty fun.

Are the iPhones always tracking and reporting? Or are they just watching passively for the devices reported lost and only reporting the location to Apple of your own AirTags. The latter seems far more sensible. The battery cost of this is fairly trivial. Your phone is already capturing its location and reporting for FindMy. The incremental cost of attaching the AirTag’s location is minimal. To monitor BLE for a bunch of addresses is also minimal cost that’s typically predominantly done within the BT chip to avoid waking the SoC. At first glance there are some details that are unclear here in terms of how they scale this. For example, at Apple scale, the total size of lost AirTags is quite large, larger than what you can typically offload to a BLE chip. Similarly, the privacy protection features mean that BLE addresses rotate so just passively scanning wouldn’t be sufficient. My bet though is that that’s the work that was done - offloading all of this to the BLE chip in ways that are friendly to the HW capabilities. It’s also entirely possible they worked with their BT supplier to add the necessary low-level hooks to make that perform well and preserve privacy.

The AirTag transmits every 2 seconds. The iPhone should scan every 2 minutes for 2 seconds in order to capture the AirTag. BLE scanning costs about ~20mW. So the average power consumption is 20mW * (2sec / 120sec) = 0.3mW.

Over an entire day, it's 7mWh. The iPhone 12 battery is 10000mWh.

Conclusion: it's neglibile.

I would say those AirTags will be with the iPhones of their respective owners. Mine report as “With you” so perhaps they don’t advertise themselves in this state. The phone will be frequently updating its own location to Find My anyway so no extra power draw.

However if you’re walking by a set of left luggage lockers or through some similar environment where lots of AirTags not with their owner then there would indeed be some overhead. If you work in baggage handling in an airport would probably be telling. This all depends on the frequency which the AirTag reports itself and the frequency where your iPhone listens out. I suspect the impact would be negligible considering the power draw of the U1 in the AirTag is of order the power draw that the phone must commit.

At first glance, I'd say the resource consumption is actually going to be basically negligible. The Bluetooth and GPS radios would probably be on anyway, and the packets flow through the air anyway, so just making a note of the IDs you see, batching them, and sending that every hour or so, is not going to be very heavy.

The ifixit folks are really good at getting people invested in understanding what’s going on inside our gadgets. A little bit of humour like this is especially fun.