Buy a dozen per room, for the same price 😭

And yet they have a place in poor countries.

That and military gear. Remember 'mil spec' means the same thing as 'built by the lowest bidder.'

Well it works better than none.

@@dutchdrifter8740 no, they don’t. Manufacturers make the name brand ones for about 5 bucks each, they then charge people 20-30 bucks for that same item. (statement is true for everything actually). Life saving equipment should be forced to be sold at reasonable markups. But this is a greedy capitalist society, so that’s not gonna happen.

I expect that unless you did that immediately before setting the fire, or maybe took the battery out, set the fire, blew a mouthful of smoke in and reconnected the battery immediately before scooting, they would eventually reset and recalibrate down to a lower set point. The way you would sensibly program something like that is to take the differential of the detected reflection level, as well as considering the DC level itself. Signal value rising faster than a certain cutoff rate, or the level simply being higher than a particular set point anyway (indicating an environment already so smoky or dusty that your detector hasn't a chance of working as intended) = set off the alarm. That then protects both against fires that are close by (causing the internal smoke density to rise quite fast), with the alarm going off even before the smoke actually reaches a dangerous level, and the more insidious case of a slower or more distant burn filling the air with smoke too slowly to set the detector off by rise rate alone, but reaching a dangerous enough level that if you haven't already picked it up by smelling it building up, or being awoken with a coughing fit, at a point where you could still safely escape, then you definitely need an audible jolt to get you out before you suffocate. With the additional case that if you connect the battery and the environment is already dangerously smoky, it will go off immediately... with the user then having the option of just taking the battery back out (as the alarm will trigger before you've even properly clicked the terminals into the connector, let alone put the lid back on), or taking heed of the warning and vacating the area.

And, well, if you had the opportunity to do such a thing, you could probably have just took the battery out, set the fire, then snuck back in afterwards to reconnect the battery. Or cut one of the cables right where it's soldered to the board (or desoldered it?), set the fire almost immediately underneath, and let the flames destroy - or at least heavily distort and disguise - the evidence for you...

@@markpenrice6253 Or just stick something to the ceiling with wax, enclosing the detector. Set fire, it's well established by the time the wax melts and drops the cover, and shortly any remnant wax will be vaporizing and the cover will be a nondescript patch of melted plastic on the floor, possibly intermingled with the remnant plastics from the detector body itself.

@@markpenrice6253 Or replace the battery with a totally depleted one.

You’d probably enjoy more of Clive’s videos, they’re hilarious.

You're in the right place, at the right time. Just grab a whiskey and you'll be all set.

Well your name does your comment justice. Welcome.

@randonness productions: You're either really lame or wishing you had a better electronics understanding.

Something about long-form content with people talking over. I watch beekeeping videos for the same reason.

That should be in the user manual :D

That's actually a poor design. What happens is there's a weak battery, the device detects smoke and starts alarming for a while, then the voltage drops underneath the operating threshold and it resets. Then it will remain silent rather than trying to alarm again.

@@straightpipediesel You ought to change batteries once per year. Furthermore, I'll assume blinkenlight pattern changes when battery goes low.

@@volo870 Most people are too lazy to. That's why California banned smoke detectors with removable batteries; they have to be 10 year permanent lithium type. Poor people were apparently not replacing and worse taking the batteries out.

@@straightpipediesel Why the hell would you buy a smoke detector then? It's better to rely on your smell and guts than on a malfunctioning device. In my neck of the woods smoke detectors are VERY rare. But those installed are being taken care of.

Do it!

Thank you for your service. Firefighters are heros.

The fire department here says test once a year and change the battery 6 months later. Also, you are supposed to replace your smoke detector every 10 years minimum. Kidde (pronounced kid-uh for those that care) now sells 9V batteries that they guarantee for 10 years in their smoke detectors. One detector, one battery, one decade. I also use a carbon monoxide alarm in my room and between my furnace and water heater.

Can't say I'd be wanting to trust my life to a 9volt battery anywhere near 10 years old.

If they're anything like our fire alarms the figure isn't far off, plus the thing doesn't die quietly. You will KNOW when the battery runs dry.

That's probably the best use-case for it! i'm not quite sure i'd trust it as a safety device, but for analysing you wife's culinary talents, sure!

@@theafro well that does show it works so it's more like a reason to trust your smoke alarm.

Yep, the old *Cooking-Alarm!*

If you have the money buy a more costly one but as a student i.e. a cheap one is better than none at all. You saw the circuit they came a long way and chinese slave markets made it possible to have quiete good ones for 10 bucks or less

Result !, Oh wait...….

benni5541 consumers prefer China slave labor products

If you drop them, they become kinetic dividers.

Or just reflow the solder on it and meassure "design" value?

"cap tolerances are always negative" - false. It depends on the manufacturer, and even then, expect 10% to be outliers. Source: I measured about 200 caps just to see for myself.

Many of the fire departments have teams that will fit them free too. But the downside of that is that if they reduce the number of fires they get their funding cut. Because that's the mentality of politicians.

It is still the same number of fires with a lower amount of fatal casualties. Stopping funding would be mad. Certain British politicians do not seem to be interested in serving the public interest or common good.

Simple answer: Don't vote Tory.

Come to rural America where you have to pay a yearly fee or the Fire department will just let your house burn down. www.npr.org/sections/thetwo-way/2010/10/08/130436382/they-didn-t-pay-the-fee-firefighters-watch-tennessee-family-s-house-burn

Even if you don't need them as actual life saving measures, you could use them for... Let's say hacking in some smoke-triggered automation. Wouldn't mind adding this and a latch relay to a 3D printer or something.

::groan::

Get 'em while their hot.

A smokin' deal !

Ba-dum tish!

Baby You Light My Fire LOL

Experimental Fun don't deal to bad, it's 3 A.M. were i'm at now. Try to go to bad early for work and this is what happens

+Experimental Fun "I have always enjoyed taking stuff apart to see how it works" For many years I did the same, and invariably ended up breaking stuff; but in due course I learned how to fix stuff and then how to make stuff.

Yup. I've taken apart tons of stuff I got for free from the local thrift store. If you find somewhere local that is already tossing stuff that doesn't power on, it's a great source for random parts and repair/troubleshooting/circuit lessons. Some second hand stores are even paying for hazmat recycling just to throw out electronics stuff. So your actually saving them money by taking the e-junk off their hands. Eventually it dawned on me that my time is better spent learning with intentionally selected components where I know what I have, know that it works, and have spares readily available -if- or rather when I make a mistake. It's still handy to have a bunch of junk boards laying around to reference to though. Personally, I limit playing with junk box components mostly by the datasheet. If the DS is a page or few, it's worth goofing around with. If the DS is longer, that's the kind of thing I want new spares for. There's nothing quite as annoying as spending a bunch of time troubleshooting a broken part or breaking something after spending time on it without a spare on hand. I also highly recommend trying to remove and reattach some more advanced surface mounted packages like QFN's on junk boards. It's very easy to assume "I'll fix this easily" just to learn the reason why rework stations are a thing. I think the best stuff to salvage and study are power supplies. There are lots of cool things you can learn, and no matter your field of interest your going to need at least one power supply. -Jake

@@infarno91 loop ll

I should have added that at the end. "Remember to test your smoke detectors."

"Take up smoking" doesn't resonate anymore.

change batteries once a year nuts if they need them or not...............with good quality ones

The year 1921: Cinema fire caused by motion picture film. The year 2021: House fire caused by lithium ion battery in thermal runaway... One step forward, one step back... The thing in common is both have their own oxidizer.

The algorithm working well and recommended this to me after watching Tom's video too

turbidity is a good word

a what?

Surface scatter turbidity monitors are routinely found in clean water treatment plants where they are used to monitor drinking water quality, which in Britain is tightly regulated. Turbidity can be loosely described as cloudiness, which at high levels is unsightly, and can indicate contamination.

There use to be 2 types. The ionisation kind which is interesting since it contains Americium 241, about 0.3 ug (I think), which comes out to 0.9 uCi. It is an artificial element. It is somewhat fissile, which means that you can make a nuclear bomb with it, if you can collect about 10 to 20 kg. The other type is the photodetector type. A new one on the market is heat detection.

Sounds like story time!

My best was when I emptied a lunatic asylum accidentally. I was working on the alarm system and it went off. The system used a huge air-raid type siren on the roof and my legs literally went like jelly when it went off.

@@bigclivedotcom ohhh god that sounds horrible XD I'm surprised you can still hear

Air raid siren in a lunatic asylum? That's sounds like Broadmoor! They are talking about decommissioning their former WWII air raid sirens - it would be amazing if they could send one to you for a tear down.

@@bigclivedotcom Reminds me of the time when I was working overtime, during the weekend, alone in a data center. Which was not known to the guys who thought it would be empty during the weekend, for their test of the fire suppression system. I was not aware of them and they were not aware of me. The fire suppression system just flushes the room with CO2. The ingenious part is the acoustic alarm. The high pressure CO2 enters the room through a klaxon. Extremely simple, extremely effective and extremely right behind me. It was so shocking that I was paralyzed and couldn't muster any clear thought for a few seconds.

That's funny

I like vaping devices for their technology. I make my own nicotine-free and unflavoured e-liquid using glycerin diluted slightly with either propylene glycol or water to give it the correct wicking properties.

The optical detectors are widely available, but often use a dedicated chip that can test the chamber for functionality by detecting low reflections of test pulses. It also differentiates between temporary dust reflections and smoke, and also has proper low battery warnings. The cheap units (only marginally cheaper that the real thing) have debatable detecting ability, can drain the batteries fast and not warn about low voltage. Some have sounders that are as loud as your microwave oven beeper. They're basically fake smoke detectors.

In my experience landlords just don't replace them even 50 years later as long as they work. I did not trust the ones in my last apartment so old they made a buzz not beep which took us an hour to realize one was going off below us...and did not even have battery backup. Lease says they can not be removed or modified so I installed my own new name brand alarm adjacent to theirs.

Code will probably require hardwired interconnected systems for rental units. These are for people who want the security of a smoke alarm, but only want to put a fiver toward their fire safety budget. Oh, and the cost of a warranty is not included here. Even more expensive "cheap" smoke alarms have high failure rates. They come with a warranty though, which you are paying for in the price. Part of the $13/£10 you are paying is going toward sending you a new one when it breaks in 6 months.

Yep slum landlords. Dishonest landlords. Cheapskate landlords. Or people that just want to collect the insurance when the smoke detectors don't work. Need I say more don't think so.

Thankfully in Australia (or at least the state I am in) has laws requiring landlords to have proper smoke alarms (and my landlord recently send a guy out to check the smoke alarm for compliance)

Andy Lundell, if they do they probably take the batteries out the first time they false alarm, like when they've burned their toast. I have a full fledged commercial Fire alarm system, but that's only because I designed it when I worked for a company that made them.

You do get dust and dirt building up in them over time. Especially when near a steamy or oily area like a kitchen. It's a good idea to replace them fairly regularly.

Yeah, I like the idea of the decade smoke detector. Now if only they had energy budget for WiFi or BLE for ten years...

If you want the alarm to be sent out over bt or wifi, it only needs power once when you configure it, and once more when there's a fire. But the radio chips add $5 even to cell phones, which means $10-20 more in the retail price. Ante up.

I've got the BRK ones with an RF base wired into the house lighting circuits they all have 10 year lives, and Li batteries for backup. They are the ionisation and optical ones. Since I had to fit mains interlinked alarms when I built a new house extension to meet building regs it was easiest to do it this way and I can fit extra ones or replacements in a matter of seconds. Recently bought 2 spare bases from a closing Homebase for £7 each. Newer UK houses will all have mains detectors so these battery driven ones will be of little or no use in them.

I smashed my smoke detector nearly 20 year's ago.

I recommend changing smoke detectors completely every five years. They do accumulate dust. In greasy or dusty areas they should be changed sooner or a rate of rise detector fitted.

John Francis Doe It really does not matter in this case as it is just a rough and dirty drawing to convey the basic logic behind the circuit, which is all that is really of importance in these discussions. What surprises me far more in this example is that they got away with the far off filter capacitor as most low dropout regulators tend to be very particular about placement location and the ESR of their filter capacities lest they go into oscillation.

Not in the software kit, available as a hardware kit :D

Not all electrically programmable ROM is UV erasable, some technologies are physically irreversibly altered.

If they are using eprom rather than fusable links then it may be possible to erase them using soft x-rays.

It could. It would depend on finding xrays with high enough energy to penetrate the plastic but not so much that it causes damage to other devices within the chip.

I'm not sure if this unit does test the operation of the chamber.

The main difference being the Nest alarm probably packaged the same sort of components with a $399 price tag, rather than the $3 Clive paid! ;-)

@@ddragon8154 I will say that the nest seemed very well built inside. Although it's the only smoke alarm I've ever owned that has actually failed.

+Do R/C! A lot of times people miss smoke detector failures because they don't test them often enough. Assuming that smart detectors can run a thorough self-test and report faults to the user right away, it's one of those few cases where having domestic tech connected to the network is a *good* thing! :-)

I would add another every year if I was that paranoid just because it would be fun to cover the entire fucking celling with those red eyed blinking boys.

You can program a microcontroller to do a test and then go to sleep for a predetermined amount of time. That means the average current consumption can be microamps. But it does require quite careful programming.

The nuclear reactor type is an Ionization smoke detector.

twocvbloke The other type is an ionizing detector. The best smoke detectors contain both optical and ionizing units as each has its strength and weaknesses, what one detects earlier the other takes longer and vice-versa. But most of the less expensive detectors are optical and they are very good at detecting fires that produce a lot of smoke while the ionizing detectors are better at detecting slow smoldering fires and the combustible gasses they give off well before they have produced much detectable smoke - so one is great at detecting slow simmering fires and the other fires that are fast burning and/or produce a lot of smoke (or steam, even).

Ethan Poole the landlord put a small rubbish battery powered one on the ceiling in the kitchen a few years ago, what is that one? Its over my gas cooker, it's fine if I use the oven but when I boil things in water on the hob the bloody thing goes off, it's done so twice this week once with rice and once with a boiled egg, I had to take the battery out with the egg as flapping a towel at it didn't shut it up. Is that the steam or the burned gas

All smoke detectors will detect fog. In theatres they have to use heat detectors or use a temporary bypass system during a show.

the latter sounds scary. I regularly visit Theatres

I use conventional current flow theory since it's more confusing to people entering electronics when the diodes and other components point in the wrong direction.

You are absolutely correct. But it is sad that we must baby feed those who are not interested in the truth in this day and time. Again keep up the good work.

@@bigclivedotcom I support your policy and don't think it's dumbing down at all. A student may also struggle with the gravitational asymmetry when burger flipping at macdo....

Adam Bryant see that in my hospital too usually stuck a rubber glove over them.

It's really odd to see a chip like that with good English documentation. I've been reading through its PDF and it's very readable.

Definitely, even from a coders perspective it's better than most API documentation.

I think the real things do use an ADC.