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Fire alarm audio detection, using FFTs and Go

github.com

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Re: Fire alarm audio detection, using FFTs and Go

#11

Post by wongarsu »

ashleyn wrote: post #4
beefnugs wrote: post #3

Just solder a wire in there somewhere. Even if you knew absolutely nothing about electronics, 50 trial and error solder points sounds like less work.

These projects exist because modding life-critical safety equipment is usually not the best idea. You invalidate the testing originally put into the product, and it may fail when you most need it.

Then put up two fire alarms, one unmodified and one where you replace the speaker with an Arduino that does whatever you want with the signal. They only cost $10 a piece. Or I guess buy one with wifi or zigbee connectivity, but then you don't have a project anymore.

Re: Fire alarm audio detection, using FFTs and Go

#12

Post by gosub100 »

beefnugs wrote: post #3

Just solder a wire in there somewhere. Even if you knew absolutely nothing about electronics, 50 trial and error solder points sounds like less work.

Then what? Run 50-200 feet of wire back to an Arduino? Or buy an Arduino and provision it for every smoke detector in the house? How do you power them? Another wall wart?

If audio fingerprinting can identify Miley Cyrus in background noise in a crowded bar, certainly it can identify the symmetrical piercing monotone of an alarm.

Re: Fire alarm audio detection, using FFTs and Go

#13

Post by morpheuskafka »

ashleyn wrote: post #4
beefnugs wrote: post #3

Just solder a wire in there somewhere. Even if you knew absolutely nothing about electronics, 50 trial and error solder points sounds like less work.

These projects exist because modding life-critical safety equipment is usually not the best idea. You invalidate the testing originally put into the product, and it may fail when you most need it.

Yeah, everything that touches them needs to be UL listed. Commercial alarm panels have approved relay modules that can be used to output to various unregulated devices without affecting the electronics inside the panel for this reason. They also use cellular now and have to use a special modem that is UL-listed to connect.

Re: Fire alarm audio detection, using FFTs and Go

#14

Post by KeplerBoy »

a-dub wrote: post #7

bandpass filtering in the time domain seems like it may be more efficient for this use case to me. if i'm reading the code correctly, it seems it's computing a 512 point window and fft on every non-overlapping window. i guess it depends on what vector/matrix instructions are being used in the underlying implementations.

I'm also curious about the power draw of continuously executing FFTs on a rpi.

Seems like the kind of task where one could easily burn 10 watts, if the wrong FFT Implementation is chosen. You'd absolutely want to do this in DSP hardware.

Re: Fire alarm audio detection, using FFTs and Go

#17

Post by asdefghyk »

Is there sample audio of the fire alarm, when it is activated? Is this alarms to US standards ? It seems so, It seems different countries have some different requirements for this audio sound? ...... There is also commercial fire alarms and residential smoke alarms. which in my country have different signals ( if my recollection is corrct )

Re: Fire alarm audio detection, using FFTs and Go

#18

Post by pdubouilh »

asdefghyk wrote: post #17

Is there sample audio of the fire alarm, when it is activated? Is this alarms to US standards ? It seems so, It seems different countries have some different requirements for this audio sound? ...... There is also commercial fire alarms and residential smoke alarms. which in my country have different signals ( if my recollection is corrct )

There's an audio file in the repo to simulate an alarm (works for 3 different models bought in Germany, they all sound the same). You can pass the target frequency, beep-length and audio threshold as parameters in the CLI (you can estimate these params with audacity).

Re: Fire alarm audio detection, using FFTs and Go

#19

Post by pdubouilh »

KeplerBoy wrote: post #14
a-dub wrote: post #7

bandpass filtering in the time domain seems like it may be more efficient for this use case to me. if i'm reading the code correctly, it seems it's computing a 512 point window and fft on every non-overlapping window. i guess it depends on what vector/matrix instructions are being used in the underlying implementations.

I'm also curious about the power draw of continuously executing FFTs on a rpi. Seems like the kind of task where one could easily burn 10 watts, if the wrong FFT Implementation is chosen. You'd absolutely want to do this in DSP hardware.

yeah using a DSP for this definitely makes more sense - but I'm lacking experience in the field. Same goes for using a discrete band-pass filter. This project is more of an attempt at "how can I build something in 2 hours that works reliably" !

For reference, it eats ~25% of the available CPU resources on my rpi zero 2w - which draws a maximum of 350mA, so this implementation definitely draws less than 1 watt.

Re: Fire alarm audio detection, using FFTs and Go

#20

Post by Spivak »

beefnugs wrote: post #3

Just solder a wire in there somewhere. Even if you knew absolutely nothing about electronics, 50 trial and error solder points sounds like less work.

Agreed, I have no idea what the sibling comments are on about with safety. A binary sensor reading the wire going to the speaker isn't some magic modification that invalidates the safety and you can get teeny tiny sensors with zigbee off the shelf.
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