Conversation

foone🏳️‍⚧️
@Foone
why do smoke alarms never fail at 2pm why is it always 5am on a fucking sunday
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foone🏳️‍⚧️
@Foone
here's the business end. this weird maze is designed to let air in but not light, then the light in the top left is designed to not be visible to the sensor at the bottom. but if there's particulates in the air, they'll glow when the LED is on, and the sensor will see them
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foone🏳️‍⚧️
@Foone
they gooped over the top of the IC so I can't easily read it, but I can make out the Microchip logo and PIC16?F so yeah it's a PIC microcontroller of some sort.
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foone🏳️‍⚧️
@Foone
so like if it's a PIC16(L)F1615/9, then it's an 8-bit microcontroller with 8 kilowords of program memory, 1024 bytes of RAM. it uses between 8 and 32 µA while running, and in sleep mode it can drop to 50 nA. So, perfect for a device that's gotta run for 10 years on one battery
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foone🏳️‍⚧️
@Foone
it's got a fun feature where you can reclock the processor without needing an external oscillator. it can run at anywhere between 16 MHZ to 31 kHZ
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foone🏳️‍⚧️
@Foone
although they clearly decided they needed their own oscillator. I wonder if they're running it even slower than 31 kHz?
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foone🏳️‍⚧️
@Foone
The Beepy Boy module is an EAST EFM-290EDFW. That's a Piezo beeper, 105 dB at 30cm, producing a 3200 Hz tone.
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foone🏳️‍⚧️
@Foone
although since they're probably not driving it at 4.5V (the battery is 3V and I don't see any voltage regulators), it won't reach the full volume.
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foone🏳️‍⚧️
@Foone
this thing is spec'd for 2-7 volts with a corresponding voltage curve. I don't want to be in the same state as someone testing a 7v one
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foone🏳️‍⚧️
@Foone
Replacement purchased. Turns out it goes off when you install it (to test), so I guess I'll wait for everyone to wake up first. Although if I install it now, they'll definitely be awake!
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foone🏳️‍⚧️
@Foone
The battery reads 2.8v so it's fine. Something else must have failed. Bugs in the optical sensor, maybe?
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