Decent smoke detector? - Page 1
Forum section: electronics / general

author: Rachie5272
author_rank: Regular Contributor
timestamp: November 19, 2013, 07:47:31 pm
content: For years, I've been plagued with terrible smoke detectors. False alarms and random chirping occur far too frequently. There are no discernible environmental conditions causing these things. No steam, humidity changes, dust, or cooking fumes. I've replaced everything several times, too. I've tried photodetector based and radiation based. I've tried AC hardwired, and the kind with battery backup as well. I installed a power filter to make sure transients weren't the problem. I've come to only one conclusion: they're all rubbish.Cracking them open, they're all based on the same design. An unisolated mains power supply, and a single chip for reading the sensor and driving the piezo. If there's a battery, it's a 9 V. Everything is clearly built down to the lowest cost point. You'd think after a couple decades manufacturers would have made some improvements, especially in the user interface. There's no visual indication of a low battery--only a chirp every few minutes. In a house with several of these and an open room design, locating the problematic unit is very difficult. The backup batteries die as quickly as the battery only units anyway.Is there anything I can do? Are there any decent smoke detectors on the market? How about commercial units? I can't take the persistent false alarms anymore.

author: Stonent
author_rank: Super Contributor
timestamp: November 19, 2013, 07:57:22 pm
content: They typically only chirp when the battery is low. They question is, how much are you willing to spend for it. The last smoke detector I took apart had an Americium sample inside an ion chamber and a 14 pin dip chip by Motorola that was a special part designed for smoke detectors according to the data sheet. Then several resistors, ceramic caps, 2 or 3 transistors, a LED and a piezo element. I got it for 2 dollars unopened at a second hand store. But it retails for about 7 to 9 dollars new.

author: JoeyP
author_rank: Frequent Contributor
timestamp: November 19, 2013, 08:23:31 pm
content: I've become convinced that insects cause a lot of smoke detector issues. In my house, I had about 8 or 9 (out of 20+ - ridiculous overkill) "go bad" over the past few years. The symptom was always the same: Start chirping like a new battery was needed. Replace battery. Within a few days chirping again. Tried different brands and models with the same result.Recently I decided to try using compressed air to blow the dust out of the sensor to see if that might help. It did! I've done this to two units so far, and both seem to be fixed. The first time I did it, I'm sure I saw something the size of a small insect blown out of the sensor. I worried that what came out might have been part of the sensor itself, so tested with real smoke to be sure it still worked.If you do use compressed air, I think you should always do a function test with real smoke after to be sure you didn't damage the sensor.

author: Rachie5272
author_rank: Regular Contributor
timestamp: November 19, 2013, 11:10:27 pm
content: I know the battery isn't the problem, as they read over 9.2 V when it starts chirping.I've tried both a vacuum and compressed air. No dust or insects come out, and they continue to have problems. I opened one unit which was giving consistent false alarms, and didn't see any dust at all. Everything look perfectly clean.I wouldn't mind paying upwards of $50 each for smoke detectors if I could be assured they would actually perform as desired.

author: Circuitous
author_rank: Unknown
timestamp: November 19, 2013, 11:30:19 pm
content: I haven't bought a regular smoke detector in ages. Mine are all industrial types, hardwired to the security system. But, some of these same manufacturers make some units that are AC powered as well. Some of the better manufacturers that I've seen are:GentexEdwardsInterlogix-EslI usually get stuff from ADI (adilink.com), but there should be lots of suppliers.

author: GeoffS
author_rank: Unknown
timestamp: November 20, 2013, 12:34:45 am
content: The smoke alarms in my house were recently replaced to meet new legislation (must be hard wired or have a 10 year battery life)The new units are Quell which have a none replaceable, lithium battery. So far, no false alarms, only warnings of burning toast.One nice feature is a smoke 'snooze' button which, when pushed, stops the sound for a few minutes, the led continues to flash. About $50 each.

author: free_electron
author_rank: Super Contributor
timestamp: November 20, 2013, 12:38:31 am
content: The new one from the company that makes that Nest thermostat are pretty cool

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 20, 2013, 03:28:32 pm
content: What about the ones designed for commercial fire alarm systems?

author: jebcom
author_rank: Regular Contributor
timestamp: November 21, 2013, 04:28:38 am
content: I suggest getting some photoelectric smoke detectors.I'm guessing you currently have ionization smoke detectors. In these detectors, the radioactive americium causes a very tiny current, perhaps in the picoamp range, to flow through the ionization chamber. Smoke particles disrupt the ionization current flow, resulting in a slight drop in the current. The controller chip has to detect this change and trigger an alarm when appropriate. The problem is, other things, like humidity, might also cause the detector to alarm. So if you have certain locations in your house that tend to get the false alarms, try changing those locations to photoelectric.A photoelectric smoke detector uses a baffled photo chamber that allows air to pass through but blocks light. The controller chip pulses an infrared LED. A PIN photodiode positioned out of direct view of the LED is sampled at the time of the IR pulse so that it can detect the IR light scattering off of the smoke particles. If the photodiode current is high enough for a certain number of consecutive pulses, the detector should go into alarm.Specialized chips are available, originally developed by Motorola, for each type of detector, to handle the sensor, alarm, and low battery functions.The biggest advantage of photoelectric detectors is that they tend to go into alarm much sooner than ionization alarms in the presence of smoldering toxic smoke that frequently indicates the start of a fire in the furnishings of modern homes. Some advocates are claiming that photoelectric detectors can save lives while ionization detectors may alarm too late. Photoelectric detectors may also be less susceptible to some types of false alarms.Note that ionization detectors may go into alarm sooner with raging fires.I suggest doing as I have done in my house, and that is to use both types. I use dual detectors, with both types of sensors, in sleeping areas, and a mix of photoelectric and ionization in the rest of the house. Also, I put a smoke detector in each bedroom. If the bedroom door is closed and a fire starts inside the room, a smoke detector in the hallway probably won't sound until it's too late.Other smoke detector tips:Definitely test the alarms frequently. Many of the alarms use piezoelectric horns which may be constructed with non-soldered pressure contacts to the piezo element. Under some conditions, these contacts may be subject to corrosion, and this could render the unit silent. Replace it immediately if this happens.Wired-in AC (mains) powered smoke detectors may be interconnected throughout the house, so that all alarms will sound if any one goes into alarm. This can make it more difficult to find the alarming unit.Wired-in detectors may be prone to alarming from bad connections. For example, if wire nuts are installed carelessly and the power makes and breaks, you may get alarms on each power-up. In this case, either get an electrician to fix it, or change to battery-powered alarms.If your alarms use replaceable batteries, set a ritual time to change them each year. We change ours when we put up the Christmas decorations, because when I was a kid I remember hearing about a lot of house fires starting in Christmas trees. Note that if you wait until the alarm chirps to change the battery, by this point you will have a reduced time that the unit can be in alarm before the battery dies.Smoke detectors should meet certain safety standards to help assure that they have a good chance of properly detecting fires. These standards cover sensitivity, airflow directionality for detecting smoke, audibility of the alarm, and other characteristics. While this testing is probably far from perfect, it is some measure to help assure you that the product is reasonably well designed. I would avoid any product that has not been approved by the testing organization for your country or region.Remember that the purpose of these products is to save lives, so don't skimp on quality for a couple of dollars, pounds, Euros, crowns, or whatever. If I think the $20 product is better than the $10 product, I spend the $20.

author: tsmith35
author_rank: Frequent Contributor
timestamp: November 21, 2013, 04:55:55 am
content: Quote from: jebcom on November 21, 2013, 04:28:38 amHaving set old Christmas trees alight (outside) while I was younger, I can tell you that once a Christmas tree catches fire, the house is very likely going to burn down. It's incredible how quickly the trees burn. I don't have real Christmas trees in the house anymore for that very reason.

author: Rachie5272
author_rank: Regular Contributor
timestamp: November 21, 2013, 06:40:34 am
content: That was a nice post jebcom, but did you read anything I initially wrote? I've tried photoelectric. They're just as flaky as amerecium-241 based. The detectors aren't in humid areas, and they act up in the dead of night, when the air hasn't been disturbed for hours. The AC wires are solidly connected, the batteries always test well over 9 volts, and I don't buy cheap ones.All consumer models I've been able to find are built to the lowest price point, and it shows. It's not just false alarms, but nonsensical things like half chirps, sounding an alarm for one second then stopping, or crying low battery at 9.5 volts. Everyone gives the same old advice, trying to shift the blame to the user, but it doesn't solve anything.It's not just bad luck. Take a look on amazon, and you'll find even the top rated smoke detectors have plenty of malfunction complaints. And since they're all wired together, the probability of false alarms goes up with each additional unit.Industrial units would be great. I'd love to have some notification of which detector triggered the alarm, but I only have the standard three conductor parallel wiring. I can easily convert it to low voltage, but I can't get independent data lines from each unit.

author: codeboy2k
author_rank: Super Contributor
timestamp: November 21, 2013, 08:07:58 am
content: Quote from: free_electron on November 20, 2013, 12:38:31 amI'm still skeptical.. it's too polite. Has it been certified and /or tested in a closed room with smoldering couches like in those consumer reports and/or fire safety videos? I don't know enough about it to be sure. Also, there is some benefit to having a smoke detector that is as simple as possible--there is less to fail.The one great thing about the Nest Protect smoke alarm is that it will tell your iPhone that your house is burning to the ground while you are at work, so at least you won't be surprised when you get home .

author: amyk
author_rank: Super Contributor
timestamp: November 21, 2013, 12:30:22 pm
content: Quote from: Rachie5272 on November 21, 2013, 06:40:34 amThat sounds like there is something odd about your environment that's causing all this; high levels of stray EMI or RF? Any high-impedance nodes in the circuit could build up enough charge to cause the alarm to trigger.Some images of the high-impedance connection on one:http://imgur.com/a/GRGeWDatasheet:http://www.allegromicro.com/~/media/Files/Datasheets/A5364-Datasheet.ashxNotice the 1pA input current.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 21, 2013, 02:17:53 pm
content: Rachie5272, Just wanted to say that your experience with smoke detectors is similar to mine.I have 6 within my house only one is working usefully.1 (disabled by me) mains wired photoelectric maybe a year or two old with a rechargeable lithium battery, does the low voltage beep at random intervals, often the middle of the night. PSA lifesaver. It cost $70 dollars.1 (no battery) non mains wired, working ok but goes through the batteries.1 (working sort of) mains wired photoelectric maybe 5 years old, never causes any trouble but it will only alarm if I light a large bit of newspaper underneath it. Whereas the others only require a thin strip of burning paper. PDL.1 (broken switch) mains wired photoelectric maybe 5 years old, my wife killed it by continually hitting the hush button too hard with a broom handle. PDL.1 (disabled by me) mains wired photoelectric maybe 5 years old, does the low voltage beep at random intervals even with fresh batteries. PDL.1 (working well) ionisation must be more than twelve years old goes of appropriately if toast is burnt etc.Maybe the PDL ones were a bad design.Choice magazine (Australia) recommended some a couple of years ago, one was Kidde and one was maybe First Alert.I think they were dual sensors. Anyway I could not buy them in Australia, either at the manufacturers local office or any of the listed distributors or where Choice said they got them from (K and D), or from Amazon for legal reasons.If anyone can recommend some available now in Australia let me know.

author: belasajgo
author_rank: Contributor
timestamp: November 21, 2013, 08:56:48 pm
content: I ordered a few smoke and fire detectors a few months ago from Germany. I wanted to install smoke detectors in each of my rooms, but had the same concerns already mentioned in the other posts. So I searched on the internet for discussions and reviews on forums about smoke detectors.What I was looking for:- good build quality- reliable detection in case of smoke- no false alarms- long product life- if possible with long-life battery- no need for periodic maintenanceBefore I decided which smoke detectors to buy, I spent almost two months only with the research, which detectors to buy...And here are the detectors I bought:- For the rooms we don't use much (dry air / no steam) I bought basic optical detectors, from EI-Electronics model Ei650. They have built-in lithium batteries, which should last 10 years, the detectors have 5 years warranty.http://www.eielectronics.com/images/pdf/Ei605TY_131010.pdf- For the rooms we use often (possibility to have some steam in the air from the steam iron and other appliances) I bought "bi-sensor" detectors, which have an optical sensor and also a temperature sensor, to reduce the number of possible false alarms in case the room fills up with steam... The dual-sensor detectors are from Abus model RM20 and from Pyrexx model PX-1 (both are identical in construction). They have built-in lithium batteries, which should last 10 / 12 years, and the Pyrexx detectors have 12 years warranty (the Abus detectors have only 2 years warranty, but the detectors are identical).http://www.abus.com/eng/Security-at-Home/Fire-protection/Smoke-alarms/RM20-Lihttp://www.pyrexx.com/en/technologies/px-1/px-1- For the kitchen (probably often dense steam in the air) I bought a heat detector, which has only a temperature sensor, to exclude false alarms generated by the steam. The heat detector is also from EI-Electronics model Ei603TYC. It has also a built-in lithium battery, which should last 10 years, the detector has 5 years warranty.http://www.eielectronics.com/images/pdf/Ei603TYC_131010.pdfIn my opinion, the smoke and fire detectors I bought are very good from the perspective of product quality, reliability and product lifetime. The price / performance ratio is also very good, if you take in account that the smoke detectors have a long lasting battery (>10 years). The only point where I am not sure, is the long product life; from the electronic point of view the batteries will probably last 10 years, but I think that the optical sensors won't last that long, because dust will accumulate with time in the detection chamber, and even if the smoke detectors have an intelligent dust-compensation feature that adjusts the sensitivity, at some time the detection chamber will be full of dust causing false alarms. But I think the detectors should work fine at least 7 years (depending from the amount of dust in the air), so the price is good, if compared to cheaper models (from the same manufacturers) with 9V batteries what you have to change every 2 years...