FireAngel smoke alarm stupid engineering - Page 1
Forum section: electronics / general

author: bd139
author_rank: Super Contributor
timestamp: November 17, 2019, 02:20:06 pm
content: So I woke up this morning with a reminder to check my smoke alarm. It was 100% dead! This is a FireAngel SI-610 apparently good for 10 years. It has lasted just under 2 so far.Took it to bits to work out why as this is one of the new sealed ones without replaceable batteries. Checked batteries expecting them to be dead. Nope all good.Well I found the issue and it's a fucking stupid bit of engineering. The entire thing has a reed switch which enables or disables it based on whether or not it is attached to the base. The base however the magnet had fallen out of and fell out onto the floor when I took it down. I found it in the shoe cupboard. I looked at the plastic and it's actually flexible as hell and doesn't hold the thing in properly so just a tap on the base will knock the magnet flying. So the entire smoke alarm actually operating properly is based on a flimsy bit of plastic hook that doesn't work properlyI've replaced these units with two Ei Electronics units which are relatively old style ionisation units. Also dirt cheap as there's no fancy shit.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 17, 2019, 02:41:28 pm
content: So it would be tested and working but if it fell down or got knocked down and there was a carbon monoxide leak and that didn't go off it maybe too late.I don't think the FireAngel ST-622T one I have has that mechanism as they are just plastic mounting holes in the back and the screen is always on.

author: bd139
author_rank: Super Contributor
timestamp: November 17, 2019, 02:47:56 pm
content: In this case I think it was because the button gets whacked regularly on it due to burning toast etc. It probably worked its way out. Definitely not suitable for a domestic situation. Also it appears that it rotates on the frame very easily so it's possible for the magnet to actually be misaligned with respect to the reed switch. Also I notice the reed switch was just glued on and was quite loose.So to fix the issue of having batteries that go flat, they made it more complicated by putting lithium batteries and a reed switch in it that fuck up earlier than the batteries would have done. Stinks of design by committee.Also it came from Amazon and they are refusing to refund / return. I've just cancelled Prime. That usually kicks them into dealing with it

author: MrMobodies
author_rank: Super Contributor
timestamp: November 17, 2019, 03:47:23 pm
content: Amazon at their prime when it comes to returns like that but I like the name Fire Angel.When there is a fire and it doesn't work you might even meet one.

author: amyk
author_rank: Super Contributor
timestamp: November 17, 2019, 07:39:18 pm
content: A smoke alarm that doesn't work unless it's perfectly mounted, even if it has batteries? That's certainly stupid. A simple on-off switch would be far better, since they clearly wanted the unit to be switchable on/off. (If they only wanted it to be turned on once, a pull-tab over a battery terminal would be appropriate.)

author: bd139
author_rank: Super Contributor
timestamp: November 17, 2019, 08:02:05 pm
content: Yeah exactly that.Pull tab would make more sense.

author: floobydust
author_rank: Super Contributor
timestamp: November 17, 2019, 08:41:22 pm
content: Contact the manufacturer and let them know of the problem, and whoever the approvals agency is.They will open a file and investigation. In North America, they issue a product recall overanything that causes it to not detect smoke.FireAngelSI-610• "Independently certified to BS EN 14604:2005 by the Loss Prevention Certification Board (LPCB) Certificate No. 651d/02"I've done it before, as smoke detectors get imported from china now and have fake approvals and parts that do not last.I had one the mains capacitive dropper started smoldering and false triggering the smoke alarm.Most of the board was half baked due to heat. But UL and the manufacturer swept it under the rug, as technically it didn't fail to detect smoke.

author: mnementh
author_rank: Super Contributor
timestamp: November 18, 2019, 12:50:26 am
content: seems to me the least assache solution is to assemble the stupid thing to the base & put a dot on the detector with a Sharpie through the magnet hole; use that to locate and epoxy the magnet to the detector.Then rehang it and fucking get on with your life.mnemAlternately, just burn the house down and use that as an excuse to move to Canada.

author: bd139
author_rank: Super Contributor
timestamp: November 18, 2019, 07:52:06 am
content: I think the best solution turns out to be either to jump the reed switch or buy a cheaper unit without this turd in it. I did the latter

author: tggzzz
author_rank: Super Contributor
timestamp: November 18, 2019, 08:40:08 am
content: Am I the only person thattestsfire alarms by holding smouldering paper near them?Having said that, without my deafaid in I wouldn't hear one anyway

author: bd139
author_rank: Super Contributor
timestamp: November 18, 2019, 09:07:14 am
content: No you're not the only one although I suspect very few people bother. I test mine properly as well. I take some plastic wrap off some bread, stick it on a fork and set fire to it.

author: forrestc
author_rank: Unknown
timestamp: November 18, 2019, 09:34:46 am
content: I actually have an aerosol can of smoke tester spray. Yes, it's a real product, made by several vendors. One can lasts almost forever for residential use.It's particularly nice since it squirts the "smoke" far enough away that I can test ceiling mounted units without climbing on anything.A bonus is that it doesn't require creating a fire risk. It also dissipates quickly and doesn't smell up the house.

author: mnementh
author_rank: Super Contributor
timestamp: November 18, 2019, 04:49:59 pm
content: Yes, but do you KNOW the detector is actually any good at detecting SMOKE...?mnemconfidence is low...

author: station240
author_rank: Unknown
timestamp: November 19, 2019, 01:11:42 am
content: I was expecting FireAngel to be some slang term used by firefighters for human remains found after the fire.But no, it's a crappy smoke alarm where poor design and crappy choice of materials made it worthless.I would suggest a rename is in order, change to AngelOfFire, same train of thought as anything called AngelOfDeath.I wonder if the magnet used the same crappy brown glue that eats electronics ?

author: bd139
author_rank: Super Contributor
timestamp: November 19, 2019, 08:00:58 am
content: FireBastard is about right.I sent them an email. I expect a canned response.

author: tom66
author_rank: Super Contributor
timestamp: November 19, 2019, 10:07:02 am
content: Having worked on the design of smoke detectors FireAngel is not too bad, but they have a lot of reliability issues. They are making £10 detectors - you cannot expect too much for the money. The optical detectors are generally a lot better than the Ei ionising ones which are built to even lower price points.

author: tom66
author_rank: Super Contributor
timestamp: November 19, 2019, 10:09:08 am
content: Quote from: forrestc on November 18, 2019, 09:34:46 amYou do need to be careful with these cans. Always spray from several foot away. The moisture can condense inside the sensor which will cause an offset in the zero reading. This may either reflect itself as a false alarm, a fault condition or just a desensitised or oversensitive alarm. Usually it tends to slightly desensitise our alarms. On the test devices we have built, I have to recalibrate after more than 10 sprays - it seems the moisture doesn't dissipate quickly (it takes at least a day or so before they begin reading correctly again).The above applies only to optical detectors - I can't comment on ionising ones not having experience with them.

author: bd139
author_rank: Super Contributor
timestamp: November 19, 2019, 10:12:04 am
content: On optical vs ionisation, I have both for reference. The optical one has never gone off even when I've tried testing it and when my kitchen was actually on fire. I do not trust it.I suspect the optical ones mostly exist so they can be farmed out to non specialist bulk manufacturing as there are no radioactive components.

author: tom66
author_rank: Super Contributor
timestamp: November 19, 2019, 11:04:57 am
content: Optical alarms are better than ionising alarms for -most- applications. Optical alarms do not do well with smoldering fires, as the wafting smoke does not produce enough obscuration/scatter for long enough such that the alarm will actually reliably trigger. However, on almost every other test, they are superior. Therefore the general recommendation is to use optical or hybrid optical/ionisation sensors.It takes around 0.1dB/m of smoke to trigger an alarm. Obscuration of 3dB/m is half light attenuated transmitted per metre. 0.1dB/m doesn't sound like much but it's a lot once it reaches the sensor; the room has to be seriously smoky. Most detector designs don't trip below 0.05dB/m because the stability of the sensor (especially when you get people smashing into them and knocking them off the ceiling) over 10 years is hard to guarantee, and then dust and other things can set them off. Note most optical sensors work on a scatter principle instead of obscuration, as it tends to be easier to design and stabilise, but the behaviour is similar.The relevant standards are fairly strict about false alarms and alarming too soon, as they tend to be the detectors that get covered up or have their batteries removed. It is judged to be better to be slightly less sensitive than over-sensitive, as with a real fire the devices will still trip well even if they are 20% less sensitive, but they will not trip at all with the batteries removed.You aren't wrong about the ionising detectors being a pain, our consultant supplier for test tunnels doesn't like to deal with them because they invoke another tonne of paperwork regarding radiation and storage of components. But you can still buy cheap ones. In mass production they are cheaper to make. Optical sensors require discrete components in the smoke chamber, as well as a photodiode amplifier, usually some software to compensate for drift and the battery performance is a bit worse as the sensor is active and not passive.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 19, 2019, 02:25:29 pm
content: Seems to me that whole reed switch thing is over designed, if it's just to activate it after you buy it, some kind of pull tab that closes the battery contacts would be much simpler. The more complicated something is, the more likely it is to fail, and you don't want that with a fire alarm.

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 19, 2019, 03:11:31 pm
content: Quote from: tggzzz on November 18, 2019, 08:40:08 amMost manuals I've seen explicitly warn you not to do this.

author: jogri
author_rank: Frequent Contributor
timestamp: November 19, 2019, 04:24:51 pm
content: A local public broadcaster (SWR) here in germany ran a piece on those smoke alarms (model ST-630s), it seems like there is a major problem with their lifetime: Out of 70.000 smoke alarms (total, they didn't mention how many of those were from FireAngel) that were installed in one city a few hundred from that manufacturer failed each year (battery was low). They also interviewed a chimney sweeper who had to swap over half the units he installed because they failed after two years and FireAngel stopped providing free replacements for the faulty units.Here is a link to the video (it's in german and it doesn't have subtitles):

author: tggzzz
author_rank: Super Contributor
timestamp: November 19, 2019, 04:30:57 pm
content: Quote from: Mr. Scram on November 19, 2019, 03:11:31 pmDo they say why, and how to test them?

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 19, 2019, 04:51:07 pm
content: Quote from: tggzzz on November 19, 2019, 04:30:57 pmThey don't say why but I suspect it has to do with contaminating the sensor or offsetting the calibration. It's generally recommended to use the test button.

author: tom66
author_rank: Super Contributor
timestamp: November 19, 2019, 05:04:27 pm
content: And the test button doesn't test the sensor. Well, not on every device at least. It depends - the Nest devices are very good and thoroughly test their hardware but many Chinese detectors just sound the siren, and that goes for devices with a low battery too.Your best bet is the aerosol cans, just limit tests to once every few months, and spray a good distance away from the detector (at least 3 foot). They should alarm within 30 seconds with a small cloud, if you spray about 5-10 seconds worth. Excessive spraying will contaminate the sensors but as long as it is fully aerosolised this should be fine. The test tunnels that are used to calibrate the detectors essentially pass a fine aerosol through the detectors at a constant 0.8 m/s, but the concentration is very low.The problem with burning paper etc is that you could contaminate the sensor with soot, generally the recommendation is after a house fire, even a minor one, you should replace your detectors because they might be sooty and less effective. So I can imagine this is where manufacturers are coming from.

author: Cerebus
author_rank: Super Contributor
timestamp: November 19, 2019, 11:35:02 pm
content: Quote from: bd139 on November 18, 2019, 09:07:14 amEnough about your cooking skills. He asked you how you test the fire alarm.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 20, 2019, 12:49:11 am
content: I see from the picture a test/reset button and their table below:https://cdn2.hubspot.net/hubfs/2274469/FireAngel/Manuals/WST-630%20Manual.pdfQuoteA red led that flashes to say it works and and doesn't work when it is with a chirp.When there is a fault or it is tampered with (removed from the ceiling or a breakage in the mechanism when it is put back) I would want it to go off and there to be a dedicated LED that is clearly marked in the plastic as fault for faults. Would that increase costs but they did get in there another amber led, a radio communication module and the decorations.If the fault causes it go off constantly and the battery is sealed in there that can become a nuisance.QuoteSounds scare mongering to me and the way it is written sounds a bit silly advising not to open it for one wanting to damage the battery.

author: tom66
author_rank: Super Contributor
timestamp: November 20, 2019, 09:56:31 am
content: If you open the device you will probably damage the precise optical sensor, flexing the board to remove the board from the plastic or when desoldering the battery. If you want removable batteries buy a device designed for that. It is a life safety device. One thing I would never repair is a smoke alarm unless I could thoroughly test it. And that really requires a calibrated test tunnel.If you have removable batteries you need a tag that sticks out to warn the users that the batteries are removed. And reverse polarity protection. This is a requirement in EN14604. It adds a fair bit of expense to the product, both in assembly and parts.The FireAngel devices are £10 smoke detectors. That means they're coming out of the factory in China for £3-4 each. If you want a really good smoke detector buy a Nest detector. Removable batteries, clever sensor design, substantial self diagnostics, wifi connectivity. It's a good device. But it's a £100 device because you're paying for some decent hardware.No one want to listen to the guy who actually designs these for a living? These decisions aren't made on the basis of things being there to frustrate engineers, they are designed to be cheap. It is better to have smoke detectors that not installed in a building. Even if they aren't perfect.

author: bd139
author_rank: Super Contributor
timestamp: November 20, 2019, 10:26:26 am
content: I know that a singular market focused opinion is a data point and not something we can base a conclusion on thus I can't solely take your points onboard. I know as a contractor, looking in from the outside has a lower degree of assumptions than looking out from the inside.I disagree on a couple of your points.Firstly, I can't possibly agree that anything with the complexity of a Nest device is a good thing. The thing is an IoT device that actually presents multiple attack surfaces and doesn't necessarily have sound functionality. I cite this as my source:https://www.cpsc.gov/Recalls/2014/Nest-Labs-Recalls-to-Repair-Nest-Protect-Smoke-CO-Alarms/The failings are:1. Nest Wave was turned on.2. This disabled the smoke alarm if there was any activity near it.3. It had to be cloud connected and pull a software update to disable the feature.Alas the last issue due to the sheer number of unaccounted for devices, ended up in a full recall of 440,000 devices. This "seemed like a good idea at the time" is how most of the IoT market operates. The inevitable reply I'm going to see which I will mention here was "that was an old version" and "it doesn't work like that now". That's not an excuse for fucking it up to start with.And then there's the problem of what happens if your smoke alarm is silently bricked or broken by an update? Google, Nest's parent company, hosed 25 handsets we had via automatic updates. And what happens when Google eventually decide to can it. It's no longer smart. It's an attack surface and a risk. IoT devices are already posing a significant risk to security.Secondly, price does not necessarily reflect fit for purpose. A £3 device may be considerably better than a £100 device. That's what your aforementioned EN 14604 standard is about. Both the £3 and the £100 device should pass functional testing to conform to that standard.What is important for smoke detection really based on my trite evaluation?Well the risk appears to be defined by two classes:1. It didn't go off.2. It packed in.Thus evaluating that into characteristics to operate smoke alarms:1. Diversity. One class of device from one vendor is clearly untrustworthy. That is obvious by the sensor disparity between optical and ionisation sensors and the functionality that is provided. Deploy multiple optical and ionisation detectors from different vendors (I have 2 of each in my house for ref now).2. Regular testing. Weekly basic "is the device still working". Quarterly "does this thing actually still detect smoke". This builds a failure model for the devices and pre-empts failures.3. The MTBF appears to be pretty shit despite advertisements otherwise. Replace it every year. That pre-empts failures. This is cost effective.That's slightly more sound engineering thinking than throwing all your eggs in one IoT basket.

author: tom66
author_rank: Super Contributor
timestamp: November 20, 2019, 10:48:47 am
content: Yes, I'm deliberately avoiding talking about IoT because I don't use any IoT devices (attack vectors being one reason, but not the only reason.) My evaluation of the Nest device is based on it as a standalone device; and it is perfectly possible to never connect the Nest devices to the internet. You can create an interlinked network without Wi-Fi and the devices will sound without Wi-Fi too. They use Zigbee for in-home communication.The early Nest sensors were badly designed and prone to false alarms. The GenII device is far better with a dual blue/infrared smoke sensor. It is similar to an industrial EN54 type fire alarm and has a low false alarm rate but sounds alarms early. Sure, no excuse. But that's the Silicon Valley approach - move fast, break things. I don't necessarily agree with it. But I am saying the GenII Nest is a well designed, high quality device; I have never looked into GenI as they stopped selling that pretty quickly. I know one of the consultants who worked on the design of GenII with them, and I know the company who sold them the calibration and test kit. They know what they are doing. I have a badly abused Nest device on my desk. It complains it can't find its microphone or LED light ring and chirps about this. But it still works fine. Detects smoke at 0.03dB/m. Impressive.When it comes down to EN14604 there is little spec in the way of long term product life. If you build a battery into a device, it has to last 3 years minimum. If the battery is replaceable, it has to last 1 year minimum. And when the battery is low the alarm has to be able to sound for 4 minutes before dying; and the low battery fault chirps have to be able to go for at least 30 days before dying.There is no requirement to detect sensor fault conditions, such as an open circuit LED or implausible zero offset.In terms of sensitivity there, too, is no actual specification. This might sound a bit mad but the basis is the device has to pass on test fires (TF2-TF5; ranging from a petrol fire, to insulating foam, to wooden sticks heated by an electric heater, and one other I can't remember right now.) If it passes these then the sensitivity is adequate (but there is about an 8:1 range of acceptable sensitivity.) The key requirement is that the sensitivity remain stable (+/-60%) after applying some "abuse" to the device, like impact, high temperature, low temperature, battery low, humidity, corrosive atmosphere etc. Also, the devices you make have to be within a roughly 2:1 window for sensitivity, including the supplied test samples.I think that the lack of a specification for sensitivity is a mistake in EN14604 but it is how the standard is written. In theory manufacturers can release high sensitivity and low sensitivity alarms if required. And there are some alarms on the market that adjust their sensitivity with temperature in the room, in an attempt to detect real fires quicker.Your approach to diversity is probably reasonable, but at the rate at which you go through devices you might begin to consider a central fire alarm system, or more expensive, well designed devices like the Nest GenII. Also, a test with the aerosol cans, which are available for around £10 each, would be a good idea, once every quarter.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 20, 2019, 03:15:09 pm
content: Quote from: tom66 on November 20, 2019, 09:56:31 amI think I'd be looking at a commercial fire alarm. I have seen install smoke detectors connected up to burglar alarm systems back many years ago but I was told that regulations now require them to have their own control system and fire resistant braided kind of cables.

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 20, 2019, 03:34:28 pm
content: Quote from: tom66 on November 20, 2019, 09:56:31 amUsing Nest is asking for trouble. I have to agree with bd139's assessment here. Treating detectors as disposable makes a fair amount of sense.

author: Iwanushka
author_rank: Frequent Contributor
timestamp: November 20, 2019, 06:20:09 pm
content: I test my smoke detectors this way.1. Does it react to vape crap from 1m2. Does it react if I exhale cigarette smoke 0.5m away3. Spray can...Edit crap detectors that we have with fire alarm system at the office trigger only if you chain smoke cigar from 5cm away... and that's lots of smoke...., basically they react when half of the room is full of smoke, and according to all standards and fire dept its okay, its only okay if you set it this way in a damn smoking room e.g. hotel where you can smoke but then again that thing is 5-10m away smoking from the sensor and no chain smoking cigar or pipe will still trigger that crap