Smoke detector design

Anyway...

You know how obnoxious smoke detectors are? When you're sleeping and they suddenly start beeping every 10 minutes because the battery is low?

What about designing them with tri-color LED's instead, so they flash green if the battery is ok, yellow when it starts getting low, and red when it needs replacing? And the alarm wouldn't sound unless there was actual smoke detected.

That's the point

I would imagine those who never change the battery would also never check the led's. The makers of the devices also will not add a single component unless competition calls for it. Have you noticed when checking the flashing led that somehow it knows and waits for about 5 mins before flashing ??

Rheilly P

Flashing a LED eats up the battery. My solution was fit the detectors with Lithium-Manganese PP3 cells. They are expensive - 11.49 euro from Farnell (order code 299390) but offer a 10 year shelf life.

Newark sell much the same thing cheaper - $10.64

The beeping is just as irritating, but it doesn't happen as often.

This reminds me of a townhouse I had once. I kept hearing a cricket chirp every once in a while, while I worked at the computer. It drove me a little crazy - I was ready to take some paneling off the walls to get that annoying critter.

Then my sister-in-law suggested I check the smoke detector battery, which of course saved me a lot of trouble. That miserable thing sounded so much like a cricket. Except that it only chirped only once, every so often.

I believe folks have sometimes created "electronic crickets" to drive others mad with. Park one under the sofa or chair in the living room. If it only chirped once every 20 minutes or so, it might take a while for the offended to find them.

Warren.

Get the plugin kind, or the ones with 20 year batteries.

Or replace the batteries every January 1st.

"Libertarian Lilly"

And before anyone mentions the deaf, smoke alarms are no use to them at all.

BTW:

I strongly suspect that beeping with a low battery is a LEGAL requirement for smoke alarms.

.... Phil

The plug-in kind still have batteries that go bad at 3:00AM. Been there, many times.

Fall back. That works if you know where they all are. The first year in the AL house had a few nights with interrupted sleep, looking for the damned things.

...or a dog.

Right.

What's annoying about them, and cheap piezos in general, is that you can't tell where the sound is coming from.

Smoke detectors do tend to come with "heavy duty" (ie, cheap) zinc-carbon batteries. Replace them with premium alkalines first thing.

So, does the human hearing system have the hooks to distinguish between sources and echoes, based on the dispersive nature of reflections or something? Does a single-frequency beep defeat that system?

That would be a great science project: see of wideband sources are easier to directionalize than narrowband ones. Chirps, anyone?

Birds must care about this, too.

Reminds me of my dalmation, "Domino".

One night, somehow, a cricket got lodged way inside the door jamb. The cricket would chirp and Domino would bark, causing the cricket to stop. Then the cycle would repeat in an endless loop.

Domino was the dumbest dog I've ever owned. I got no sleep whatsoever.

I have been listening to one, outside in my little camper. Started before winter. Peeped all winter, slower and weaker. Now on cooler days no peep, just on warmer days. About 10 months now. I'm going to miss It.

Greg

What's really annoying are those backup alarms, yo can't tell where its coming from. Please use square waves.

Greg

many

The human hearing system has two mechanisms for locating direction - one for low-frequency signals (below 800Hz) which dpends on sensing the phase difference across the head, and one for high frequency signals (above 1.6kHz) which depends on amplitude differences across the head.

Naturally, smoke alarm beeps and modern telelephone ringing tones are normally placed between 800Hz and 1.6kHz, so we can't work out which one is beeping or ringing.

It's been done

And bats.

And to hell with the 6% or so of men whose color blindness makes it impossible to distinguish the green from the red from the yellow?

Sure, bring it on. Who needs us anyway?

(I hate those so-called "tri-color" LEDs -- "try-color" would be a better name. Use different colors of twinkie lights if it floats your boat, but if you encode critical information in the colors, figure that you're alienating about 3% of your customers right off the bat).

Pull the battery before it's guts escapes & ruins the detector.

Dalmations are nice dogs but they never seem to bright!

That's odd. They share with human the incapacity to get rid of uric acid. Like humans they lack the gene that converts uric acid to allantoin and with them - like us - high meat consumption is associated with gout, hypertension and kidney.

Isaac Asimov pointed out that there's a weak but significant positive correllation between human uric acid level and IQ, which may be why the defect hasn't been eliminated from our gene pool.

Your observation suggests that this doesn't seem to work for Dalmations.