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what to do at end of life

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Dwight Elvey

Veteran Member
Joined
Jun 21, 2003
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4,995
Location
Santa Cruz
Here in California, we are required to have a CO detector in our house by law. These run for about 7 to 10 years, depending on the manufacture and then they are programmed to quit.
They give out a message on the LCD as End of Life or some such and start making annoying beeps.
Just curious, I open one up to see what makes them tick. It looks like they run on a 32Khz crystal and have a PIC16LF1933 processor. I assume these can be reprogrammed for other purposes ( I'm not sure what right now ). The CO sensor looks like a large can but that is the part that ages.
It has two switches, two leds, small LCD and a piezo speaker. There is a coil to make the oscilator for the piezo with a number of transistors, resistors and capacitors.
Now what could one do to give this uC a new life.
Dwight
 
Hey Dwight, what about adding "CO detectors: ..." to the beggining of the thread subject? ;-)

To say the least, the subject has scared me a bit at first...
 
As far as the PIC16LF1933, not much memory, not very fast. On the older CO detectors, the AtoD and DtoA chips can be moderatively interesting.. The MCU not so much.
 
Rip out the guts and leave it on the wall pretending to be functional?

Of course, I don't have any dependents to worry about, but as far as I'm concerned, I'll take asphyxiation over having to deal with the gorram nagging beepers. (See also: smoke alarms.)
 
Except that EOL doesn't mean End of Life, it means End of the Line, as in railroad track.

The trouble with modifying something like this is that the only real reason to have them is so your insurance isn't voided when you need it. And having a 12 year old detector is just as bad as having none.
 
I think he wants to just have fun seeing what the pic can do by itself,
He likely has another CO detector
 
Sorry about the tile ( no not really ). I just thought it was fun that the alarm has the PIC processor in it. I've not got a new one yet. It just gave out a couple days ago. It is a small slow processor but it is still something that could take a different project.
Any way, it got your attention.
I'm not sure how the detection part works. There is no A/D. It is just a bunch of discrete parts. It has twp areas marked WAX AREA-A and WAX AREA-B. They have a thin coat of what looks to be wax. I'm guessing these areas use the wax as insulation areas. My guess is that it charges up the CO cell and then waits to see how fast it discharges. Every thing is made with three lead transistors and there are two small 5 lead surface mount marked U2 and U4. The U4 one is covered in a thin layer of wax and hard to make out a label. U2 looks like a voltage regulator of some type. It is associated with the piezo and coil. One wonders if the piezo and coil may be used for a high voltage generator. It could be used at a high frequency for the high voltage and a low frequency for the low voltage?? Nah, it is just part of the sounder circuit.
Dwight
 
commodorejohn said:
Rip out the guts and leave it on the wall pretending to be functional?

Of course, I don't have any dependents to worry about, but as far as I'm concerned, I'll take asphyxiation over having to deal with the gorram nagging beepers. (See also: smoke alarms.)
Click to expand...

So let me get this straight, you are advocating that someone break state law, but in such a way as to make make people think they are protected by a CO sensor therefore putting them at greater risk due to a false sense of security. And on top of this you are saying you would rather die than have to deal with the occasional beeping of a CO or Smoke detector? Your risk vs gain calculator is seriously on the fritz my friend. Both of those types of sensors only beep when 1. They need new batteries, 2. The need to be replaced (once a decade I might add) or 3. When you are at risk of dying. I am ok with a few beeps every so often if there is even a small chance of my life being saved by such a beep.


Anyways, back to the subject at hand...

Dwight, sounds like the thing has it's share of useful parts, even if you can't re-use the micro-chip. Small LCDs can be used for a plethora of things, and I'll never say no to saleving an LED or switch. But that UC might be useful to drive a sensor or two and display the output to the LCD. A temperature and humidity sensor and you've got a useful device to monitor the environment around your old computers, don't think you'd need much speed or power to do that.
 
The MCU is very typical of low-end PICs. While I've programmed my share, I don't care for the left-handedness of addressing scheme on them nor the "you do everything through A". Even the low-end AVRs are easier to handle. PICs are cheap, which I guess is why they find their way into so many low-end devices.

As far as CO detector regulations go, we have those also in Oregon. We have a wood stove and the requirement is that a CO and smoke detector be no farther than 15' from any sleeping quarters. So we use the combination units and replace them every 10 years. They're AC line operated, with a backup lithium battery.
 
CO² detectors will also alarm in highly ionised air. This can happen in thunderstorms.

The problem I have with these devices is the government mandate.

I have a propane-burning furnace in my shop. So even though it's not required, I have a CO detector in there which incidentally is beeping right now for a dead battery. I have no idea where it actually is right now and don't care because I'm not going to run the furnace right now. So it's pretty annoying. But why do I have to have them in my house? If there's CO in my house, my house must already be on fire. But you know, it's just pocket change, so why don't I just give it to the CO detector lobby every seven years.

If only we could save just one child. Oh how much better it will be when every home has mandatory complete security camera coverage monitored by the local police and anti-crime department.
 
KC9UDX said:
If there's CO in my house, my house must already be on fire.
Click to expand...

How did you come to this conclusion?

Carbon monoxide is known as a silent killer. It's not often associated with house fires; exactly the opposite - it poisons people over a period of hours, whether they are awake or sleeping.
 
KC9UDX said:
CO² detectors will also alarm in highly ionised air. This can happen in thunderstorms.

The problem I have with these devices is the government mandate.
Click to expand...

When the govt mandates I have to marry someone of the same sex I'll have a problem. Alarms I don't have a problem with.

I have a propane-burning furnace in my shop.
Click to expand...

For melting wot? I'm in the early stages of building an resistance element furnace, I've done it in the past. It's easy, and much safer then gas, as long qs you're vigilant.

If only we could save just one child. Oh how much better it will be when every home has mandatory complete security camera coverage monitored by the local police and anti-crime department.
Click to expand...

The general idea is to save many lives, those that aren't capable of instituting safeguards and others. And pets. Really every life that's threatened. My mother quit smoking around the time I was born, yet died of lung cancer last year. Could radon have been the culprit?
 
Tobacco has been known to contain radionuclides, so it's hard to say.

Here's the bit with CO. If you have a gas furnace, water header or even a wood stove, a blockage or leak in the flue can quietly flood your house with monoxide. If awake, you'll maybe notice a slight headache or dizziness. If asleep, you'll never awaken.

That's why CO detectors are important--and that's why my state's fire code requires them to be installed near sleeping quarters. Kitchens, garages and workshops are specifically excluded.
 
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