EEVblog

[@okaro6595]

The apparent power is not real, it does not have to be produced. It does, however, cause losses in the wires because of the resistance.

[@EEVblog]

It does if there is no PF correction to compensate for it. Look at it this way: If you suddenly added 1,000,000 of these devices to the grid then you most certainly *would* have to generate an extra 100MW to handle that (if you want to maintain the same output voltage). Until such time as the power company figures out there is this extra poor PF load on the grid and installs more PF correction gear to compensate for it. Without the PF correction gear there is no free lunch. And the further up the grid you install the PF correction gear the more losses in the wires and transformers further down the grid.

[@vihai]

@@EEVblog nope, it does not. The generator will not require 100 MW of additional power at the *shaft*. It will require an additional power equal to the increased current by the resistance of the wires (and windings).

[@EEVblog]

@@vihai Where does this magical additional power come from if not from the generator and it's fuel? And if the generator is producing the same voltage, that increased current *must* translate to real power at some point.

[@vihai]

@@EEVblog it comes from the rotor (+turbine) inertia for half cycle, it goes back for the other half cycle, that's why you need some rotating mass as flywheel for apparent power "production".

[@EEVblog]

@@vihai Ok, but surely this translates into a larger generator? Or more generators if that one is already maxed out. At some point there must be no free lunch.

[@mcconkeyb]

I've been the designer for several consumer products, and the pressure to reduce BOM costs is completely INSANE! I've attended dozens of meetings and wasted hundreds of hours all for the reduction of 12 cents on a product. Since I opposed this insane cost reduction, I no longer work in the design of consumer products.

[@EEVblog]

LOL, well done!

[@Rob2]

That is because there is one of those insane "economists" in the company. When a device is sold for amount of X and the BOM cost is Y, those people calculate that the factor between turnover and BOM cost is X/Y and therefore the effect of reducing the BOM cost by 12 cent will be X/Y times higher on the profit margin. That is of course a big delusion, but you cannot hammer that out of an "economist".

[@NukeDMAn]

The whole fun of working in this area is to design a good product and still be able to squeeze every possible cent out of the BOM. It's not that hard to design things without budget constraints, boring.

[@saddle1940]

But then you get the other end of the scale where a product seems to do wonders with very little in it and we all sit around gwaking at it to work out how the heck does it do that.(ie:ZX81s running video without any video chip)

[@charlieangkor8649]

I feel strongcontempt towards your ex employer

[@Stuntman707]

Maybe the companies asked for a low Iq but that was misinterpreted and they hired lazy engineers instead.

[@sensiblewheels]

Haha. Good one.

[@stevetobias4890]

Lmfao

[@nukemanmd]

So, how many kilometers of solar roadways would be required to power 5 of these devices?

[@MiniLuv-1984]

I keep trying to do the calculation for you, but my calculator keeps spitting an error...seems anything divided by zero gives calculators the heebeejeebies.

[@azmanabdula]

Are trucks driving on this solar roadway?

[@azmanabdula]

@@Okurka. Are trucks driving on your roof?

[@pomonabill220]

I have a GREAT idea!!!! We could use the baterizer!

[@azmanabdula]

@@Okurka. Can you stop a truck on that one panel *You know im being a fuckwit for a reason* : P

[@ats89117]

Smoke alarms are put in by builders and builders couldn't care less how much you will be paying for power. So if they can save a few nickels with a poor design, they'll do it every time...

[@anthonyselby8337]

All ways presumed that these things were low energy every thing else we fit is supposed to be glad Dave’s done this vid is there no regulatory body that’s supposed to sort this out and check Electricians that fit these know minimal and micro electronics Yer sure they taught about power factor but they don’t check it or have the meters to check it that I’m aware of Great video Dave opened my eyes

[@chrisw1462]

@ats89117 Absolute truth. I imagine over the term of a 30 year mortgage, replacing 5 smoke detectors with better, lower power ones would give you a net cash back in energy savings.

[@chrisw1462]

@@anthonyselby8337 Again, multimeters with power factor are more expensive, testing takes time and that is more expensive. Not going to happen in the construction industry, no matter how well taught the electricians are.

[@johncoops6897]

@@chrisw1462 - over a THOUSAND years, replacing a THOUSAND smoke detectors with better lower power factor ones would save exactly ZERO dollars in energy savings. Domestic customers are not billed in kVA. Commercial customers have lagging PF (from motors) so the capacitors in soke detectors etc make the PF better, not worse.

[@chrisw1462]

@@johncoops6897 I wasn't talking about VA vs. watts. Just plain power consumption.

[@Scrogan]

Make half of the smoke alarms use capacitive droppers, and the other half use inductive droppers, problem solved!

[@jamesbrown99991]

Haha. That might correct the VA, but you still have ~1W wasted in the zener

[@volodumurkalunyak4651]

inductive droppers??? Proper PFC + LLC switching converter will be cheaper, take less physical space and cost less than 1/2 of inductive dropper with even lower standby power. Standart flyback converter or PFC flyback converter versus inductive dropper for low power products - there is no contest there

[@allmycircuits8850]

In fact in older days we had problem with too much inductive load: quiscent power of transformers, luminescent lamps with inductive ballast, motors etc. If this is still true, these capacitors actually take part of PF corrector, because industrial PF correctors are EXACTLY huge capacitors with commutators to turn on as many as needed.

[@volodumurkalunyak4651]

@@PhilfreezeCH PFC LLC setup will be cheaper than a inductive-dropper, forcing ( 1/2 devices cap dropper + 1/2 devices inductive dropper ) out of existence

[@NukeDMAn]

@@volodumurkalunyak4651 Why would anyone design a Flyback for that? Non-isolated buck is the way to go. You can even try to find the one that syncs the current waveform with the input voltage for active PFC... This beats the transformer cost easily.

[@12201185234]

So, just get the 9 volt battery operated version and change the batteries when they chirp every 5 years or so.

[@EEVblog]

Yep. But here in Australia if you have a new house or renovation you have to install the mains one otherwise the job won't get signed off.

[@WilliamHaggerty]

@@EEVblog North America has been doing this for years.

[@12201185234]

@@EEVblog Makes sense. I'm in Los Angeles and we have the same kind of absurd building codes here. Want to add a garage to your 100 year old Crafstman home in Pasadena? Well, your garage has to be engineered to handle an 8.2 on the Richter scale centered directly underneath you.

[@maximilianmustermann5763]

@@EEVblog In Germany you just need smoke detectors with a lithium battery under the newest regulations (not a rechargeable but a so-called "10-year lithium" battery). I can't believe we actually got at least one new regulation here that makes more sense than regulations in other countries.

[@m3chanist]

5 years.....yeah right, dreaming. Dreaming that's interrupted by a CHEEEP in the middle of the night.

[@Offsettttt]

Actually, "Chip of the week" segment is a great idea for EVblog2! ))

[@1over137]

I wrote a billing system for commercial customers and it doesn't even charge based on consumption. They (the distributor) don't even send you consumption figures for large commercial premises. They only send you the per 15 minute peak demand and the KVar stats. The bill for that 15 period is based on their peak load during it, even if transient and a surcharge factor is applied based on the reactive power. When you broke it down that surcharge was applied mostly in the transmittions and distribution costs which are individually calcualted and charged to commercials. When I enquired as to why they don't bill on consumption like residential, the response was that the grid operators don't really care how much a large industrial place uses, they really only care about the peak load they will put on the grid. If that goes up, it will really effect them and their capacity for the area. So they translate that figure directly to the "plants" pockets to discourage them from suddenly increasing their power demands.

[@Richardincancale]

Here in France with our new connected smart meters we now pay for VA and our contracts were subtly altered to kVA from kW! So it hits our pocket!

[@qwertyasdf66]

So big clive's prediction is coming true, then.

[@PuchMaxi]

@Dingo Nates Yikes, do you have a source?

[@robina.jensen6114]

The same meters are used in Denmark.

[@KarlAlfredRoemer]

Not nice. Here in Germany, we still pay for KW. But therefor, our KW-price is about 0,30€.

[@BullCheatFR]

AFAIK contracts in France have been in kVA for quite a while (if not forever). However old meters were only able to measure kW so that’s what it was in practice. The new meters tripping on kVA instead of kW would actually be a good thing (force individuals to correct their PF) *if users were notified when they trip because of bad PF*

[@pulporock]

Your exactly right; everyone thinks of just one running, not the millions around the world installed. Think of the millions of products doing exactly the same. No interest in conserving energy at all.

[@Wiresgalore]

Its the consumer way!

[@yoksel99]

"It is a safety product" -- I'm curious how frequently you'd hear this argument to justify the poor design characteristics that are unrelated to the actual safety.

[@rkan2]

You could power several computers that would be able to take a human rated space capsule to moon with the power that these things require. .

[@jayleno2192]

Kidde smoke alarms aren't even reliable. The last one I took apart had the wires to the speaker routed right over the big 1/2 W resistor, which melted the insulation and shorted out the wires. So if anything the poor design makes them less safe.

[@GamingWithNikolas]

I know right

[@stuartremphrey228]

@@jayleno2192 Sad... On the bright side, maybe it'll _start_ a fire, then, if still working, _detect_ it and warn the occupants... :-( Thereby demonstrating it's usefulness and justifying it's existence. ;-)

[@simonm1447]

Mine are powered by a battery, which last 10 years, so no 230 V supply. They work, if something is smoking on the stove they switch on. Such products can be also found in other places, I have already seen a TV antenna amplifier which was rated for 150 Watts (which means it consumes 1300 kWh per year - a unbelievable waste of energy)

[@maxine_q]

Why do you need a mains powered smoke alarm anyway? So you have a product there, with a backup battery, that you still need to check periodically and eventually have to replace. Might as well use it to power the device?

[@mortenlund1418]

I simply cant thank you enough for this video. It is an important one. Governments need to take action. I have a modem in my house. It costs me almost $ 200 a year. The designers should care and it needs to be a topic.

[@GoldSrc_]

That "chip of the week" might make a nice new video series, Dave.

[@rayceeya8659]

I lived in a house that had Live and Neutral swapped on a few outlets. It caused a significant amount of voltage on the ground contacts of the coaxial cable. Never did figure out which one was the problem.

[@tomcleaveland4325]

I discovered that the live and neutral were swapped on a light switch in my house when the socket went POP and showered sparks in the kitchen when I was trying to remove a broken light bulb base with a pair of needle nose pliers. I was glad that I'd decided to put on gloves at the last minute before starting work.

[@Rob2]

Here in western Europe we have symmetrical mains outlets - no way to tell which pin is live and which is neutral. So they cannot be swapped either :-) But what you describe there can occur nonetheless. It is usually not caused by "swapped live and neutral" but by a symmetrical mains filter in the equipment (small caps from either mains lead to chassis) causing the chassis to float to 1/2 the mains voltage when it is not grounded. Indeed, this can cause nasty surprises e.g. when you grab a grounded antenna cable and try to connect it to a device touching both the cable shield and the device...

[@slartibartfasttynsol420]

I've thought for some time that it would make sense to standardize around some DC voltage (12v?) to extra pins on the household mains sockets, and have a central AC-DC converter(s). You'd have to deal with volt drops around the house, so you might need more than one AC-DC converter in the house to keep the cable runs short, but you wouldn't need one per socket. If you had specified a nominal 12v it would actually be between 8 and 16v, and a max of 500mA maybe. That would be enough for clocks, smoke alarms, and the standby circuits in lots of the consumer electronics (TVs, CD players, microwaves clocks, oven clocks... etc). 2 main advantages: 1) The central converters could be much more efficient, maybe even specified in building codes. 2) It would reduce the cost and complexity of all devices that can take advantage of it, especially those that only need low current DC - a cheap small switcher and you're done. Unlikely to happen, but I think it's an idea with some merit...

[@johnherbert7489]

the same here, most new lamps are low voltage LED connected to main power, millions are installed every year for example. If you have PV even better, avoiding losses converting to DC to AC

[@deathpony698]

I would want something more like several amps max. So you can charge phones and stuff on it

[@geovani60624]

the voltage drop would be a big problem since people would not like to invest in the correct wire gauge to lower the voltage drop and it would be another wire running around your house making the wiring more complex and creating more confusion for people who can barely wire the line and neutral wires the correct way around.

[@martijn3151]

Real eye opener here. So much waste. I wonder how many other crappy mains devices are out there. Perhaps make a section about this dave? We should all inform our local representatives to take notice so products like these come with a “waste” warning, or better still, are banned from the market unless they do it right.

[@EEVblog]

There are TONS of other devices! The Energy Star legislation for example was bought in to reduce standby power consumption on plugpacks.

[@alexandrecouture2462]

I remember Apple Powermac G5 computer having very very high ''off state'' current.

[@martijn3151]

Here in Europe we have energy labels per product. But I haven’t seen those on these “low” consumption devices. They only use it for big devices such as refrigerators. And I’m not even sure if that label incorporates the power factor to measure the actual consumption. Either way, I’ll try to ask for more info on this. Thanks a lot for reporting this! I always suspected that there was a lot of waste with these rectifiers, but never knew it was so massive.

[@circuitsmith]

We were incorporating switchmode power factor correcting IC's in designs where I worked 35 years ago

[@samslog]

Great video. Addresses EXACTLY my concerns about power consumption of late. So i'm building my own switching power supplies with standby circuits for stuff more and more lately, its not rocket science, you go to a semiconductor catalogue and find a chip that allows the features and there is a plethora of stuff in the 'ù' amp range for hibernate/standby. Build that chip into the design. Its time people started lobbying the politicians: demand very strict energy efficiency. Revise it every 18 months as the stuff that keeps coming out is getting better and better. Another gripe: Don't want E-waste? Then mandate a 10 year manufacturers warranty for EVERYTHING. That'll elliminate dodgy power supplies, cheap electrolytic caps etc in no time ;-) Solutions literally sitting on the shelf!

[@thewhitefalcon8539]

Manufacturers will conveniently go out of business right when their products start failing. And news ones will start up with the exact same products

[@rudolphriedel541]

What do you need the 15V for when the main chips in smoke detectors are designed to work with

[@TheWebstaff]

Omit the whole pcb? :D Actually best not suggest that or we'll end up with dummy fire detectors.. This is the sort of thing that need an energy rating and maybe legislation to set a max power draw..

[@satibel]

I wonder if we could make a 250VAC rated smoke sensor

[@Golem386]

If it's mostly *harmonic* distortion as opposed to voltage-current-phase shift, can you power-factor-compensate that on a grid-level?

[@svampebob007]

all this talk about smoke alarms...when are they going to make a smoke alarm that doesn't embarrass me when I'm cooking?

[@cambridgemart2075]

They do, swap out to optical ones as they don't give nuisance alarms, unlike the ionisation type.

[@SianaGearz]

@@cambridgemart2075 I just had the optical Ei Electronics 650 smoke alarm beep at me while i was cooking in the middle of the night just a couple nights ago. I made quite a jump to silence it, luckily at least the button is huge.

[@drstefankrank]

There are ones out there that only react to heat. They ignore cold particles. Most of them are dual sensor and you can disable the optical one. They are designed to be used in kitchens or other areas with steam or dust in the air.

[@johncoops6897]

LOL at the "woosh factor" in the replies above.

[@Lane42]

So, you're looking for a smoke alarm that gives cooking lessons?

[@mcpa2991]

Out of curiosity, is there a benefit to overall reliability or certifiability of the circuit with the less-efficient design? I am just curious about other factors - apart from cost - that might have informed the design decision.

[@direchannelstream9278]

Yeah, so everybody is looking for energy effecient lights, but their smoke detectors might piss away watts 24/7

[@onemanshow4116]

5x 1 Watt smoke detectors vs one 60 Watt light bulb: 120Wh for 24 hrs of smoke detection = 2 hrs of light. Probably best to get those light bulbs in check.

[@saddle1940]

My son just asked me, "Why don't we just turn it on when there's a fire?" As I stare at him, I'm thinking "saving up a college fund might be a bit too optimistic".

[@johncoops6897]

@@saddle1940 - Your son is a GENIUS. Let's use a Peltier (or similar Heat > Power device) to power up the alarm using the fire's heat for power! We could also include a small wind turbine to harness the energy in the convection currents.

[@kapu4369]

@@johncoops6897 Thats pretty crappy smoke detector. When the peltier is heated up enough to produce power, there is already fire mayhem. Smoke detectors detect smoke, not fire.

[@johncoops6897]

@@kapu4369 - whooooosh! Over your head, huh?

[@jumilifyify]

Capacitive power supplies help correct the low PF of inductive motors. The big waste here is not the large VA but the use of linear voltage regulation from 240V to 12V.

[@dem0n1k]

When are the EEVblog brand smoke detectors gonna hit the market!? :D Nice work Dave.

[@dem0n1k]

@@Okurka. How do you figure that adding a regulator to the circuit would require firmware?

[@redsquirrelftw]

EEVSmoke(TM) (that could potentially also be a brand of cigarettes lol)

[@stuartremphrey228]

Electric ones. With Bluetooth, so they need firmware. Which will need upgrades.

[@russell2952]

The EEVBlog smoke detector only detects magic smoke

[@willynebula6193]

If you stop and really think about how much energy is wasted every day, you'll probably feel sick in the stomach!

[@johncoops6897]

There is NO electricity wasted here. The capacitive dropper in these creates a LEADING power factor, which improves the inherently lagging power factor on the supply grid. Dave is wrong.

[@neur303]

@@johncoops6897 No, he gives Watt and VA rating .. and even the Watt rating is way too high (because of the Zener diode solution). Additionally the ohmic loss (think supply line) increases if the current increases, which it also does if only the reactive power increases.

[@AlexFlockhart]

I'm typing this reply while on night shift at a production facility with no other employees in for the weekend, yet heat and light is on full for almost a square kilometer of buildings. A 2W smoke detector is the least of my worries.

[@Real_Tim_S]

Hmmm... I'll pass this onto my company, we're building a new campus and we're interested in total CO2 emissions and TCO of all operations. We put in a bunch of stuff that's supposed to be "energy efficient" it might actually be a good idea for us to audit the hardware the site planners have selected.

[@johncoops6897]

You should check the facts first. The use of capacitive droppers like these will IMPROVE your site's power factor. That will take the load of the expensive on-site Power Factor Correction devices that you will be installing to add capacitance and reduce your kVA loading onto the grid. Capacitance is capacitance... add it with these or pay thousands to add it anyway. Don't listen to Dave, he is clueless about this stuff, despite a squeaky voice and massive fanboi base.

[@lucaskendc]

If the current THD is high there wont be the perfect inductive power factor compensation that is expected from capacitor load.

[@johncoops6897]

@@lucaskendc - Of course loads with lots of distortion and harmonics (THD) will not be perfectly inductive or capacitive. However, in order to be significant to the power grid, those "distortion components" have to be associated with a large load. These smoke detectors are a tiny tiny load, so the THD is literally "a drop in the ocean" compared to a (say) a 150W switchmode PSU, even if it has higher PF and lower THD..

[@stuartremphrey228]

Except the zener PS wastes in heat almost all the power the device draws from the grid... _(independent of PF)_

[@kai990]

Is there a law to prevent people ruining the PF of their appliances at home on purpose just to mess with the infrastructure?

[@stuartmcconnachie]

6:23 Dave needs a Cliff Quick Test....

[@Brian_Of_Melbourne]

I'm sure BigClive could send one. Although it will have to be the southern-hemisphere version, these can be harder to source.

[@stuartremphrey228]

@@Brian_Of_Melbourne Yeah, they need to work right-way-up, since they're mounted upside-down on a ceiling which is itself already upside-down. If you get the wrong model for your hemisphere the smoke falls out before it can be detected. I'm very fortunate: I'm an ex-pat Aussie at the moment living in Singapore, and I've found that we're so close to the equator that both types work fine here.

[@isettech]

Interesting rant on the VA of the device, it may be overlooking that this is most likely Capacitive, and 180 from the Inductive power factor of the transformer supplies in the microwave, home router, and the inductance of the fridge, and other appliances with a motor, such as heat pump, AC, and furnace? Don't overlook the inductive load that is the utility transformer on the street feeding the house. This may actually reduce the total VA connected load of the house. Individually this looks bad, but it may fix some of the large amount of connected inductive load on the utility. Have you put current transformers in your main panel to find the total power factor of your house and if it is leading or lagging?

[@userPrehistoricman]

This is a case when low Iq is a good thing.

[@Zonkotron]

WAHAHAHAHAHAAAAAAA. Good one :)

[@yxcvbnmmnbvcxy544]

That's why the humans won't get more intelligent, because the intelligent ones kill them self because the bad world

[@wesleymays1931]

@Pete In other words, smart people are shoving themselves out of existence.

[@MattHollands]

You should pay more for these alarms! They’re a combined fire alarm and space heater.

[@vihai]

There is no such thing as "generation" of reactive power. Apparent power just causes an increase in current in the transmission cables, transformers and generators. Of course the increased current causes losses due to resistances and ultimately some additional active power to be produced but nowhere near the total apparent power.

[@willgeorge5644]

I can tell who has a degree in electronics!

[@samanthafox8273]

I bet the springy metal switch contacts on the Quell unit cost a lot more in terms of storage space and automation. I bet it's a lot easier to get production line fixtures for your surface-mount button than to fit those metal spring contacts at just the right angle.

[@berniwa]

You can actually use a high voltage depletion mode MOSFET to modify any "normal" regulator (7805,LD118,...) to support serveral hundret volts on the input.

[@absalomdraconis]

Not so good for improving efficiency though.

[@berniwa]

@@absalomdraconis That really depends. In standby its efficiency is near perfect, with iq of a few microamps, under load it is as unefficient as you'd expect from a linear regulator =)

[@Rob2]

@@berniwa Don't forget that all idle current of your linear regulator is REAL power, as opposed to the APPARENT power that a capacitive dropper has. In the shown circuit only the power dissipated by the zenerdiode is real power, all other power is apparent power. But drawing even only 1mA in a linear regulator that operates on line voltage will cause a big real power usage. That effectively precludes any use of conventional devices like a 7805.

[@berniwa]

@@Rob2 Sure, with a 7805 the current draw will be problematic, but technology progressed since then and TIs 7805 cousins (like the TPS783xx) have an iq of 500nA. So the real power consumed by the regulator would be a moderate 115uW at 230V ;-)

[@Rob2]

@@berniwa But once the alarm starts beeping and draws 50mA or so, your solution draws over 10W of power and dissipates that all in the regulator/fet, while the capacitive dropper solution still only draws about 1W as it always does. Not important from energy consumption perspective, but the design has to accomodate the dissipation of those 10W at least occasionally.

[@uK8cvPAq]

I often wonder if LED bulbs suffer from similar issues with low power factor and high peak currents on the input, not to mention the environmental impacts of the built materials (plastic and components etc). It's like we've traded lighting power consumption in return for having more e-waste to deal with, I'm not sure how LED bulb failure rate is now but a few years ago it was a pretty high.

[@userPrehistoricman]

Bigclive often tests LED bulbs on their power consumption and power factor. You get what you pay for usually.

[@puckcat22679]

The problem with the smoke detector is that it has to use a capacitor dropper that is sized for the max current draw (when the alarm is sounding) When the alarm isn't sounding, it still draws that power and just dissipates it as heat. A similar power supply on an LED light bulb will be sized for the light bulb itself- there is no appreciable excess. Also, it's only drawing power when the light is in use. The smoke detector draws power constantly. A capacitor dropper is fine for something like an LED bulb that is either on or off. But in a device that only needs a tiny amount of current most of the time, and occasionally needs a lot more, there should be a switching power supply. But that's more expensive than a dropper, which always draws the same amount of power whether it's needed or not.

[@kevinmartin7760]

The trouble with zener-regulated supplies like this is that the series reactance has to supply the peak current demand, without dropping the voltage too much, which as you observe is in the ballpark of 15mA when the alarm is sounding.But even given that, as designed, it is drawing 70mA, so they could have used almost 4 times the reactance (reduce the capacitor value by a factor of around 4 to, say, 0.27μF) and get the same voltage drop with only 17.5mA of quiescent current, and it still would have been enough to run the alarm when sounding. I have to wonder if they are using exactly the same circuit for 120V systems. this would give a slightly less feeble justification for a whole 1μF dropper capacitor, though that would still be about twice as large as necessary and the circuit would still draw twice as much current as necessary

[@excitedbox5705]

That thing uses almost as much power as having 4-5 odroids or raspberry pis running.

[@rkan2]

You could keep your bitcoin wallet up-to date with that kind of power... And they say Bitcoin consumes too much power... (yeah, i know mining will always take more.)

[@rkan2]

In VA yes, but not in W

[@radekc5325]

Speaking of which, that NBN modem I received gets HOT. Do you think anyone anywhere calculated how many extra power stations we need in Oz once we install them in every single household? And I'm pretty sure it has no fundamental reason why it needs to use any of that power, especially when idle.

[@gblargg]

9:28 "That's 65,000 times the power consumption!!" Hmmm, maybe a 16-bit overflow problem in the microcontroller? /s

[@105d11]

So... Does the negative battery terminal share the same ground? These things are not unplugged when changing the battery! I really hope the neutral is wired correctly. Aside: Canada also requires wired smoke alarms.

[@shaunclarke94]

Could it be that they chose such a "simple" power supply design because it's simplicity makes it more robust and reliable which is an important consideration in what is basically equipment used in a life safety application?

[@sixstringedthing]

Whilst the argument might have some validity, in the real corporate world of "products built down to minimum BOM cost for maximum profit margin" the decision was probably made because capacitive dropper supplies are as cheap as it can get. A passive transformer-based linear supply would use minimal extra components, would be just as reliable as a cap dropper (if not more so), and could easily be designed to have better power factor. But such a design choice would add 20-30 cents to the BOM cost per unit.

[@rogerfroud300]

Spring lever clamps are way more satisfactory for retaining tension on the wires in the long term. Old installations often have loose connections where the Copper has relaxed and the screw clamps aren't holding them tightly any more.

[@joelstienlet1641]

Totally agree. ( I don't want to make an advertisement, but wago 221 series are fantastic. They have PCB versions too.)

[@rogerfroud300]

@@joelstienlet1641 - It's one of those rare occasions where it's cheaper to make them that way, ie without screws, and it's a better product.

[@CCCW]

power saving? in straya? Why, when there's so much coal!

[@pigrew]

The TI UCC28881 buck converter looks appropriate. Getting rid of the film capacitor might make up for the price of the buck controller. Perhaps the buzzer takes more than the 10 mA limit of the regulator mentioned in the video?

[@demoncloud6147]

I have seen the struggle to understand reactive power among engineers working at power plants ! There is this option to set pf from SCADA system in the power plant I worked, we used to set it 0.95 and that will increase the excitation current of the generator, meaning generators need to work more hard to make up the reactive power, thus needing more torque to rotate to maintain the same rpm (frequency) and more fuel. I am talking about generation sides , not load sides.

[@EEVblog]

Yes, it's seriously perplexing. See the pinned comment above for discussion. Would appreciate actual power generation engineers weighing in.

[@ryanb1874]

Where do they generate the exitatiion current from, and this is applied to the electromagnets on the rotor right?

[@bleughbloop8569]

@@ryanb1874 some of the current generated is fed back into the rotor through a rotating transformer i think. When you need to start the thing up there should be enough magnetism left in the rotor to start generating enough current to get the whole thing going again. Smaller generators use slip rings and can be shunt wound/series wound and all that stuff I don't remember from uni...

[@demoncloud6147]

@@ryanb1874 Well, it is but not directly ! The generators in the power plant I used to work had actually 2 generators in 1 genset shaft (made by ABB). Excitation controller will supply few Amps of DC to the stator of excitation generator G2, G2's rotor will make 3 phase AC which will be converted back to large DC current to feed G1's rotor with a 3 phase rotating rectifier, and finally the actual AC power comes from the stator of G1. Something like this - diary-of-electric.blogspot.com/2019/05/wiring-diagram-avr-of-3-phase-generators.html p.s. I am sorry if I explained something incorrect, it was almost a decade ago. Now, I live in embedded electronics world and care much less for electrical systems.

[@ryanb1874]

@@demoncloud6147 sounds complex, I was just watching a Don Smith video and the old fart could even get his Over unity, resonator to work. THANKS for the comment.

[@jeffreywhitney]

at less than 100mA, how many hours or days would it take to recoup the additional $2 spend, the difference in energy saved to break even. Likely around 4 years.

[@flipflop82ful]

Wish they would make an ionizing detector that also produced it's own power :)

[@Jimmeh_B]

Add to that the decommissioning of the copper network and home land line's now costing an additional PSU for the handset base station, a PSU for the fibre modem, a psu for the UPS if installed, a psu at every node....

[@KuraIthys]

I wish. Most of the country is stuck with FTTN. That means the old copper wiring is still with us in the house, but no longer functions the way it used to... Worst of both...

[@Jimmeh_B]

@@KuraIthys If you're stuck with FTTN, try to get them to connect you to hybrid fibre cable. It's much much quicker than the cooper pstn/adsl pairs and gives reasonable speed depending on how far you are from the exchange.

[@Lipdorn]

Instantaneous power is P = V*I. In an AC system with a resistive load (PF=1.0), the V*I is always positive, thus the load is always consuming power. As soon as the PF is not 1, then there are parts in the AC wave where P = V*I that is negative. Because of the phase difference between I and V. Thus, I will be positive while V is negative for some instances of time, and vice versa. That means the load is supplying power for those negative instances. You still have the real I^2*R losses, as those are PF 1 loads. The generator, and all the infrastructure, must be able to supply the V and the I. So yes, if I becomes larger than what the generator is able to supply, you would need another generator (or tranformer). The reactive power on the other hand appears as a torque ripple on the generator shaft. Not ideal either. The real power, as seen by fuel usage, is only P = V*I*PF, PF the power factor as seen by the generator. The I^2*R losses will change the PF at the generator from the PF at the load. So, bad PF wastes extra I capacity that could have been used to perform actual work.

[@otherbasis8505]

Hmm... I was thinking that for non-linear electronics load, negative V*I does not happen. Load is not sinusoidal. So V*I is either positive or zero. That will create torque ripple and generally mess things up for sure, but no extra I^2*R losses in down time. I think PF is somewhat misleading in those cases as "apparent power" is kinda BS in non-sinusoidal situations.

[@Lipdorn]

@@otherbasis8505 Non-linear loads does not preclude negative V*I. It just means that given a single frequency sinusoidal voltage, the current will have different frequency components than just the supply frequency. Also means that superposition does not apply. I have seen some add a PF based on the current total harmonic distortion to the normal lead/lag PF. Though that part I'm not too familiar with.

[@thecarl168]

29 years ago i went to a training for reliability , the closing speaker ( from rocky mountain institute) was addressing the issue of designing for energy economy , telling that it our responsibility as engineer to design energy efficient product especially when they are mass produced . he was given the exemple of instant start crt based TV that use 6 watts standby to keep the tv ready to turn on rapidly , he was saying that represent in USA the power of 3 nuclear power station just to keep TV ready to turn on rapidly !

[@uK8cvPAq]

Wow! You think the move to LCD screens has just been offset by the sheer numbers all consuming say 0.1w standby power?

[@TD-er]

You could also have a look at the alarm clocks sold. Probably the same amount of units per house hold and it could be battery powered or even wound up ones. But there are lots and lots of them on the market which draw more power costs in a year than you have to pay when buying them. And as they have a "clock" in them, they don't need to be sub 0.5 Watt stand-by as other devices must comply to. (ever bothered to think why lots of devices have clocks these days? :) )

[@sasodoma]

Can you point me somewhere where I can read more about this regulation? It sounds interesting

[@TD-er]

@@sasodoma As far as I know, it is at least an EU regulation. See for example: ec.europa.eu/info/energy-climate-change-environment/standards-tools-and-labels/products-labelling-rules-and-requirements/energy-label-and-ecodesign/energy-efficient-products/mode-standby-and-networked-standby_en

[@klintkrossa6885]

What is the electric car chargers power factor?

[@Baslucht]

Yet another reason to implement a DC circuit in your house?

[@charlieecosta5592]

I'd be interested to see the Nest fire alarm consumption. What with Wi-Fi, BT and 'pathway lights' with PIR installed. You'd be expecting a higher power draw, but it's 10x the cost! So better design...?

[@joshm264]

So in America, we have devices that just have (I think) a 24volt-ish line as well as a signal line to sound off the other alarms, as well as a 9v backup battery, but my home was built less than a decade ago, and older homes usually have just a 9v battery and the alarm line.

[@jamess1787]

Most new homes have mains unswitched smoke detectors now. (At least in new builds in the last 10years in Canada)

[@jon_collins]

The problem is that the battery is not just the backup to the mains supply. The mains supply is also the backup to the battery supply and so must be able to power the buzzer and for newer designs also must supply 100s of ma for emergency lighting.

[@albear972]

6:02 Yes, those electric smoke alarm numbers are truly *shocking*

[@ZomB1986]

Can you talk more about the 'grid power factor correctors' and how they work?

[@dhpbear2]

5:41 - These are those 240-volt kind of watts too! None of that 120-volt Yankee watts rubbish :)

[@Thegonagle]

Morbo voice: WATTAGE DOES NOT WORK THAT WAY! GOOD NIGHT!

[@davidhunt240]

110V just a bit stingy, 240V is the baseball bat :P

[@whatthefunction9140]

For a given input torque. Is generating 3 phase ac at 240 more efficient than 120.

[@MrKillswitch88]

Pepperidge farm remembers when all smoke detectors needed was just a simple 9v battery and it lasted.

[@MrEdrftgyuji]

And ran out at 3AM and started beeping all night

[@ItsBBP]

I had some poorly designed battery operated fire alarms before, they'd chew through a 9v alkaline battery in under 2 months, whereas the good fire alarms i replaced them with can last a few years on a 9v battery. A good lesson to learn, never cheap out on safety equipment.

[@BitBanger41]

6:21 Almost became an episode of ElectroBoom!

[@Rob2]

The products are lacking a FULL BRIDGE RECTUMFRYER!

[@christophertstone]

FireX is also made by Kidde. I'm surprised you didn't get suspicious when the circuits were nearly identical, down to the same control ic.

[@jontylewis7301]

it does get cheaper!, that aint 55 yanky cents, thats 55 centsarydoos, ya switched to the aussie digikey site

[@iansimpson419]

What about the perils of mixing full wave and half wave rectifiers on the same incoming ac feed? If one smoke alarm manufacturer was to use a non-isolated half wave rectifier in their product and another chose to use to use a non-isolated full wave rectifier if their DC commons are tied together you will also be wanting to have on hand a battery operated smoke detector to detect the smoke the two hardwired ones will produce if they are connected to the same incoming AC feed. I think that may be why we dont see many non-isolated half wave and full wave rectified consumer products. If they have isolation transformers before the rectifiers then no problem but snce in most countries our neutrals are grounded back at the distribution panel keeping the DC commons from being connected is difficult without isolation of some kind before the rectifiers.

[@robertbackhaus8911]

With things as low power as these, it's not an issue. And you'll notice that in his reverse engineered davecad circuit, the zeners simply short out one half of the mains cycle(through the capacitor and resistor), so the draw them is still reasonably balanced. Yup, toss out half the input current, then toss out most of the other half. Uugh, I hate bad design.

[@iansimpson419]

Dave's reverse engineered Davecad circuit is of the manufacturers current inefficient capacitive dropper circuit. I am not questioning the manufacturers use of capacitive droppers but rather Daves suggested use of half wave and full wave rectifiers instead unless they are also isolated from the mains. If the proposed rectifiers dont have isolation from the mains this could lead to mixing full and half wave rectifiers together on the same AC feed which will not end well. Adding the required isolation before the rectifiers would increase the cost of these smoke dtectors even more than Dave's proposed 250V linear regulators. In the case of a hard wired smoke detector you would also want to be connecting them together in some way to allow for one detector to set off the others in the same building. and this could very well lead to interconnecting their DC commons. Mixing a non isolated half wave rectified power supply with a non isolated full wave rectified power supply on the same incoming AC supply with their DC commons tied to ground will result in their diodes shorting each other out as they find a path through ground. Proper incoming isolation and grounding would need to be observed or the magic smoke will be released from the rectifiers diodes.

[@biggiejohn3360]

I love the NOTE at the bottom of the page for the more efficient chip warning about blowing the ass out of your CRO . . . lol

[@ethanpoole3443]

Been there, done that. You do it once and never forget. Though in my case the scope was fine afterwards, but the probes didn’t fare too well with a dead short on the shield conductor.

[@electronics-by-practice]

They use that hinge system assembly to prevent electrocution when we replace the battery , try to test them with an over voltage and see if they detect their own smoke before catching fire .

[@uiopuiop3472]

Chinese products are notorious for this, but they could be fixed really easily.

[@pingumcping]

Kidde is an American company...

[@uiopuiop3472]

No way they make their PCBs in America, just sayin'

[@aamiddel8646]

Hi Steve, Ever wondered how much power is used by all the installed 'smart meters'. I know this is not paid by the customer, at least not directly. I never succeeded in finding in the specs of smart meters how much power they consume. I remember that once you investigated a smart meter. If you still have that meter you might investigate how much this meters draw or how the power supply internally works. Keep up the good work.

[@aamiddel8646]

Sorry, i meant Dave..

[@alch3myau]

Psssh, photoelectric .. pull apart ionization ones and become Hulk

[@AHaensel]

It might be interesting to look at the Sonoff Basic. It's less than 5 Dollars, has rather low power consumption, schematics are available and like 80% of those seem to be for the power supply.

[@ableite]

These smoke alarms should bring those "chinese power energy savers" in the box.

[@Tommyinoz1971]

Talking about pissing away power. Almost everyone in my company leave their computers running 24/7. If every office in this country does this, then I wonder how many power stations are required to keep these machines running during the night and weekends?

[@christopherwhull]

IT needs them all so they all do not update on Monday morning at 7am-9am. We work on your machines during the weekends. The energy is nothing compaiered to having a toady intern drive in to turn on a cube farm and turn on the motion sensor florescent grow lights. Yes there is a technique to turn PC on by network signal, but implementation was not the best. In the bad old days hard drive failures happened because the bearings had tight tollerances during spin up and the read write heads rested on the platter. Leave the PCs on.

[@FennecTECH]

You could fly to alphacentari on half a watt

[@EEVblog]

Imagine how far 20VA gets you!

[@FennecTECH]

EEVblog i could start a galactic empire with that!

[@joshm264]

@@EEVblog I'll get to the moon

[@czarodzi9967]

and 1.21 GW will get you back in time

[@jamesbeemer7855]

The alarm takes alot ready sound from the Sounders . We also have the U.L.L . To keep an eye on manufacturer .

[@Valtra103]

30min video, just uploaded, already has dislike... people should check their brains.

[@EEVblog]

This one will get a combination of the serial haters plus the anti-global warming crowd.

[@maximilianmustermann5763]

This is youtube. Even a video of a puppy playing with a kitten will get a bunch of downvotes.

[@ctyragdoll]

X2 Interference capacitors in series as droppers? Are they spec'd for that use?

[@mycosys]

they are specced for directly across mains input, so yes

[@ctyragdoll]

@@mycosys Thanks, I thought that was their only use. I had no idea that you could then inline like this as well, I thought I read somewhere that only Y2 or X2/Y2 caps could be used this way.

[@Rickmakes]

It’s winter time where I live (middle of US). The waste is just heating my house this time of year, right?

[@TD-er]

More like it is heating the wires to your house :)

[@uK8cvPAq]

@@TD-er Don't give solar freakin roadways any ideas!

[@TD-er]

@@uK8cvPAq well I do live in the Netherlands, where we apparently have those, although I had to learn about it on some Australian vlog channel ;)

[@davidhoelscher]

Yes...but a heat exchanger (your A/C unit) will do it more efficiently. But if you're just looking at financial cost, at even 1W, and estimate 10 cents per kWhr, then 1W * (1kW/1000W) * ($0.10/kWhr) * (24 hr/day) * (365.25 days/year) = $0.88 per year to operate a 1W smoke detector and incidentally heat your home.

[@Rickmakes]

@@davidhoelscher True. I have a heat pump and high efficiency gas furnace. I should probably work on shutting off electronics in the summer when I am cooling. In that case, the electronics are using electricity and I am then using more electricity to remove the heat from the house.

[@skuula]

How can those ICs have a voltage.reference which is accurate and runs on just microwatts? Are that those bandgap ones?

[@ottoreuter6279]

17:15 "Ya know, sniff of an oily rag stuff" 😅😅😅

[@mikelopez9893]

I am somewhat surprised to see how many electronic engineers somehow struggle to get their heads around the phase lag between voltage and current. The bottom line is that the overall lag in domestic installations is inductive (think motors fridges, etc. ). This is even more so for industrial installations. Adding a small capacitative lag will (slightly) improve the power factor!

[@uK8cvPAq]

I think Dave is getting at the additional I^R losses and extra carbon footprint required at the generation end to cater for low PF appliances.

[@mikelopez9893]

uK8cvPAq Yes, I know that’s what Dave is saying, but here’s the thing... we don’t have a separate grid connection for each appliance, just one to the household. In most cases the overall household load is inductive, so biasing the load with a small capacitive load will actually *improve* the overall household power factor.

[@uK8cvPAq]

@@mikelopez9893 I get what you're saying too, but isn't it better to fix poor pf at the source rather replying on loads to balance each other out?

[@mikelopez9893]

uK8cvPAq yes, I’d agree that we should fix the power factor. So, how will we do this? Again, the dominant problem is inductive load. This is prevalent in industrial applications, not so much in domestic. The standard “solution” to fixing an overly inductive load is to put a capacitor across the supply. That way, there’s a reserve of electrons to meet the out of phase inductive load. Oh dear, that’s where we started! Unfortunately, there’s a lot of BS on you tube on power factor. The only youtuber I’m aware of who calls it out is Big Clive. We need the EE community to take a stronger stand on this. Reactive power is not something else that needs to be generated. The only possible implication is *current* for line distribution companies, not power. If we have to have higher rms current to meet the power needs, we may need beefier wires. That’s a big if though! Here’s my challenge to any EE. Do the calculations. It might surprise you.

[@Rainbow__cookie]

i guess we need to download more electricity

[@clynesnowtail1257]

Tried those photosensor detectors. All failed within a year of purchase. I suspect that dust was loading them and eventually got to a point theres enough reflectivity to trip. They also seemed prone to false alarms from the steam coming from the bathroom after a shower. Once they failed, I could let them set for a few days, and they would still trip as soon as power is applied, and cannot be reset. I went back to radioactive detectors.

[@W4BIN]

Dave (as others have done) has just driven off of the road into the ditch. Homes and industry present a largely inductive (positive reactance) load on the power suppliers. Items like this and LED lamps with capacitive droppers (negative reactance) partly counter the existing positive reactance, they do NOT create a bad reactance. This is review is a dud. Ron W4BIN

[@wyrmofvt]

Power factor correction really only applies to the device in question, and PF can even vary how the device is used. You can't simply slap a negative reactance into your system and expect it to help. Besides, with more and more devices that have negative reactance on your house mains (LED bulbs being more common), you can no longer guarantee that most reactance presented to power suppliers are positive.

[@strehlow]

@@wyrmofvt True. Our house is mostly capacitive. The few motor loads we have are sporadic (fridge, boiler pump, clothes dryer). Most of the time it is electronic stuff with switching PSUs or capacitive droppers.

[@imark7777777]

The sad thing is I always assumed they designed these things for low power, I never thought to put a meter on the connection.

[@DrewAspinwall-1]

Maybe the next generation could run on 24Vdc and “network” together with the doorbell and also be a WiFi mesh network.

[@billward2264]

Excellent public service video Dave. This is the classic Capital Budget vs O&M Budget conflict we see everywhere, including public buildings equipped with low cost aluminum frame windows, cheap resistance electric heaters used in schools, even electric train lines that include zero provision for PV in station or trackway design. I’m outfitting my house now with 8 mains connected smoke detectors. If anyone is aware of a brand and model of energy efficient smoke detector, please reply here.

[@teresashinkansen9402]

A mains powered smoke detector? lol whats next a mains powered pacemaker?

[@philipandrew1626]

Good one! I think its just so that you cant ignore the warning chirps as the battery goes flat. The mains guarantee you will be nagged to replace the battery.

[@chasmosaurus3]

It's a safety device. More parts mean more potential failure points. What's the MTBF for the linear regulators?

[@bertblankenstein3738]

Certainly a consideration. Also what temperature are the components rated to?

[@chasmosaurus3]

@@bertblankenstein3738 A typical unit appears to be 85C (or 186F). A typical Zener, at the indicated power dissipation levels, appear to in excess of +150C. Naturally, that device is up against the ceiling where it will get hot first. Even at the relatively high 85C near the ceiling, it still might be survivable to occupants. Microchip's datasheet says: "Use of Microchip devices in life support and/or safety applications is entirely at the buyer’s risk..." I can understand why you might roll your own here. If they aren't going to stand behind their device, how can you? It's relatively easy to be certain how this device constructed with Zener diodes will behave.

[@davidhoelscher]

"If the actual product itself takes less than 50uA, why does the product have to take orders of magnitude more than that?" So the real reason for this is because this kind of power supply draws constant power (all the time, regardless of the actual useful load current consumption), and you have to design for the maximum load current that you'll ever draw. If you have a 30mA load to power a 2V LED, then that also results in a 30mA input requirement at the AC mains voltage as well--which is a lot more power than you need. If you also want to chirp the alarm while keeping the light on, and that takes another 30mA, you now have a 60mA design requirement, so you will always draw power equal to AC mains voltage * 60mA. Add another 10 to 15mA for the microcontroller, etc. Then When you also factor in that that a lot of the resources for transformerless power supply design don't even do the calculations correctly, you end up with overdesigned transformerless power supplies, or worse, ones that are reused from previous designs without optimization because "they just worked" Also, at 240V, your losses for a given load are 2x that of a 120V mains system, so that's unfortunate. 50Hz vs 60Hz doesn't matter much in this type of application because it only affects the size of the DC capacitor you put on the output. I've put together a number of helpful design resources on this very specific topic (mostly because I couldn't find anything good myself a few years ago) at www.designercircuits.com/transformerless.htm, including a document that walks through the calculations and different topology options, spreadsheets and schematics for both capacitive (like the smoke detector) and resistive version of transformerless power supplies. One of the conclusions I've come to is that this is really only a viable topology for loads in the 10s of milliamps, because beyond that, it is difficult to even reject the heat generated. But if you do need more current, a very clever approach that greatly improves the efficiency is to target an intermediate output voltage, like say 40VDC (meaning less energy is burned up in the input resistance), then use a switching power supply to efficiently step that down to lower voltages. This lets you get upwards of 100mA without much cost, because switch mode controllers in that voltage range are still pretty low-cost. Beyond that, it really is a matter of going into the design with ultra-low power consumption components. And avoid LEDs.

[@davidhoelscher]

A quick addendum to the above; at 0.5W of real power consumption, that maps to about 2mA of current that gets consumed/dissipated. Still like 40x what is needed for a 50uA average load. A far better solution economically for the manufacturer and consumer would be to eliminate the capacitor (short across it), replace the 100ohm resistor with 1Megaohm resistor, and still have 100% margin in your load current (support for 100uA). Beef up the output capacitor to handle peak transients (beeping, LEDs, etc.)

[@davidhoelscher]

So it looks like the most clever approach here will be to use a resistive transformerless power supply to run the logic needing 50uA constantly, and whenever it is time to beep, since 15mA is needed for that, have a separate transformerless supply that you turn on with an SCR/thyristor controlling that second transformerless supply from the low side. You still save money because you can still avoid the capacitor for 15mA, and the diodes, resistor, and SCR is still cheaper than the 1uF AC mains-rated capacitor.

[@johnkilner2]

Power factor is difficult to understand, if the current is 90 degrees out of phase with the voltage the wattage is zero. The only power consumed is from the resistance in the wires, transformer windings and generator windings. You need to understand the difference between true power and apparent power

[@orondf343]

Mobile phone chargers. Many people leave them plugged in without any load, I bet the quiescent current is awful on many of those.

[@jhonbus]

They've spent a bit more money per unit and use switching supplies in those, though.

[@EEVblog]

There is the energy star legislation for plugpacks.

[@adymode]

Ive got one plugged in nearby but its cold to the touch so cant be worth fussing over.

[@robertbackhaus8911]

The quiescent current in phone chargers is very low. They use proper buck converters to drop the voltage, so when there is no load on them, they are basically turned off. Power factor will be horrible because they are only loading the peak of the sine wave, but a low power factor on a ~zero load isn't a problem. Good ones use circuitry that follows the sine curve to give them a good power factor under load.

[@83hjf]

TVs have outstanding standby current. My dad is a service tech for Philips. 20 years ago, the training tech was HYPED about the low power consumption on standby on those sets. It was so low, the standby LED would remain powered for a good half hour after you unplugged it. They used a big capacitor so in standby the TV would just "burst" the PSU to charge the capacitor and go back to sleep at milliwatts again. My old-ish LG LED TV has a relay to completely disconnect (not just standby) the main supplies. Only the standby PSU remains powered in standby. The rest of the TV is OFF. And then the PACE cable boxes just blank the HDMI output when "off". The tuner and decoder circuitry runs 24/7 and the device is a nice space heater...

[@kurtu5]

What is the duty cycle really needed to detect smoke? You could turn the darn thing on for a few milliseconds every second, and then go back to 'sleep'. I mean what is really the bottom can you get to?

[@blahorgaslisk7763]

Can't say what duty cycle they use, but the smoke detectors I've got run for over 5 years on a standard 9V Alkaline battery, and at least 10 years on a lithium battery. So the power draw has to be pretty low. And yes, these are more than 10 years old. I think the oldest one is more than 30 years, and it still works. At least it still gets crazy if someone lights up a cigarette anywhere in the house, not to mention when I get a bit over enthusiastic in the kitchen...

[@kurtu5]

@@blahorgaslisk7763 So theoretically if you could take it down to 1% duty cycle, and the battery chemistry didn't degrade, you could run one for a thousand years on a single Li cell.

[@blahorgaslisk7763]

@@kurtu5 I think the chemistry is a big part of the problem. A five year old alkaline isn't good for much even if it was just left lying about unused. I don't know much about the aging of lithium cells but I can't imagine they are impervious to it. Besides the batteries isn't the only thing that ages in a smoke detector. If nothing else they can get clogged up with dust over the years so changing them out every ten years is probably a very good idea. I'm keeping some of the first detectors my parents installed around just to see what happens over time, and so far the oldest one is still the first to react to my culinary mishaps in the kitchen. I thought I killed it when I cleaned it for the first time in at least 30 years, but after blowing it out it was working again. AFAIK it should have been scrapped over 20 years ago, but I'll keep it around to see what happen over time.

[@thecharliechan]

As an electrical engineer in the USA, there are so many reasons why 50hz is rubbish compared to 60hz. I think it would be interesting if you did a video comparing the two, and seeing your reasoning on why 60hz is rubbish.

[@TBFSJjunior]

Could you give a few reasons why 50Hz is rubbish? (To give an example of a disadvantage: 60Hz creates a bigger resistance and bigger losses in transmission lines).

[@ableite]

I prefer higher refresh rates. Lol

[@uK8cvPAq]

Whoosh!

[@Rob2]

Maybe a discussion about "what is beter, 115V AC or 230/240V AC for consumer mains outlets"...? Americans write that 115 is "safer" but I really question that. 115 is high enough of a voltage to get a dangerous shock, and with 115 the current of the average appliance will be double of what it is in the 230/240 system. The higher current contributes to fires due to bad connections, so 115 may be more dangerous as a whole.

[@RB9522]

In Japan we have both 50Hz and 60Hz power grids!

[@Spookieham]

I know it's bad for domestic but doesn't commercial use DC based systems linked back to a fire panel?