LED lamp efficiency - Page 1
Forum section: electronics / general

author: G7PSK
author_rank: Super Contributor
timestamp: December 09, 2024, 03:01:45 pm
content: An outside PIR controlled flood light failed so I got this replacement from amazon. It claims an efficiency rating of F, most LED lamps seem to claim B or C I wonder how this one got so poor a rating.

author: IanB
author_rank: Super Contributor
timestamp: December 09, 2024, 03:18:41 pm
content: That's not an efficiency rating, that's a power consumption (30 kWh / 1000 h = 30 W).Given that it's an outside floodlight, it is reasonable that it might be brighter than an indoor bulb (e.g. 500 W equivalent rather than 60 W equivalent).

author: G7PSK
author_rank: Super Contributor
timestamp: December 09, 2024, 03:22:09 pm
content: It is only about 150 watt equivalent in reality. It is no brighter than the ten watt one it is replacing.

author: IanB
author_rank: Super Contributor
timestamp: December 09, 2024, 03:26:10 pm
content: How many lumens does it claim?

author: G7PSK
author_rank: Super Contributor
timestamp: December 09, 2024, 03:31:46 pm
content: 2820 lumens I will have to measure the output as soon as I can find my fathers old exposure meter which will also give readings in lumens and candle powers I put it away when I inherited it and not seen it for a few years.

author: IanB
author_rank: Super Contributor
timestamp: December 09, 2024, 03:39:42 pm
content: I am looking at a Feit Electric 60 W bulb that claims 810 lumens from 9 W, which would be 90 lumens/watt.At the same efficiency, 2820 lumens / 90 lumens/watt would be 31 W, which matches what it says on the packaging.

author: woody
author_rank: Frequent Contributor
timestamp: December 09, 2024, 03:44:41 pm
content: And these labels get updated every now and then. What used to be 'A+' might be 'F' now.

author: IanB
author_rank: Super Contributor
timestamp: December 09, 2024, 03:48:01 pm
content: Also, if the 9 W bulb is 60 W equivalent, then by ratio, the equivalent watts of the floodlight would be approximately 60 / 9 * 30 = 200 W equivalent. Which seems reasonable.

author: G7PSK
author_rank: Super Contributor
timestamp: December 09, 2024, 04:07:27 pm
content: I have just checked power efficiency of the fridge freezer which I still have the rating for it is 85 watts and rated at A+ so I guess this lights rating is down to the new ratings. Beginning to look like to get an A rating or above the appliance will have to use no power at all or even magic it out of no where.

author: coppice
author_rank: Super Contributor
timestamp: December 09, 2024, 05:15:22 pm
content: Quote from: woody on December 09, 2024, 03:44:41 pmNo, no, the very old designs are just a lot more efficient than more recent technology.Those letter ratings are a farce. They need to update them every now and then, but the stickers don't clearly state which version of the spec the product was tested against. I think they should be marked with both an old system letter and a new system letter. That would let people make more meaningful comparisons during transitional periods. Being realistic, being in a transitional period between these specs is a permanent thing.

author: amyk
author_rank: Super Contributor
timestamp: December 10, 2024, 02:53:02 am
content: They should just print the lm/W and leave it at that.Some of the most efficient lamps don't emit light that's pleasant at all (e.g. low-pressure sodium.)

author: Siwastaja
author_rank: Super Contributor
timestamp: December 10, 2024, 11:08:16 am
content: EUfinallychanged the efficiency ratings of lamps a few years ago, since the previous ratings were from 1990's and were stupidly planned back not to leaveanyroom for future improvements (it was possible to achieve A right from the start), such that even crap products of today were A++ or something and good products would have required A++++++.So it's a good thing they were changed. But it creates the issue that you can't easily know if the label is the "old" or the "new" one. But really, the difference between the old and new efficiency classes is so big, it's easy to guess. Those that were below A on the old rating have been illegal for many years. And in the new rating system, achieving A is almost impossible. So if it's A or better, it's the old rating. If it's B or worse, it's the new one. And in the new scale, B is really good.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 10, 2024, 11:33:23 am
content: Quote from: coppice on December 09, 2024, 05:15:22 pmIt doesn't need to be. As I wrote above, the "original" rating for lighting fixtures was botched from the start by choosing 'A' for what was the best easily achievable, normal COTS product back then.Zeromargin foranyfuture improvement. Also, even the crappiest incandescent bulbs got the second-worst rating, not the worst, leaving unused margin on the bottom. The old system made significant differences between "normal" incandescent bulb and "10% more efficient halogen bulb", while any crap CFL bulb was straight A.And it still lasted for over two decades. Granted, with the stupid +++ notation.Now the new one seems to have more margin on the top (not the bottom), someone learned from their mistakes. I'm expecting this to last for quite some time. Possibly many decades. I haven't seen any new "A" bulb yet, it certainly isn't as easy to achieve as "A" was back when the old scale was published.But yeah, informing people on the label that there is transition period going would be important. Now people choose less efficient products because they show better ratings. What a farceQuote from: amyk on December 10, 2024, 02:53:02 amReally, yes. That would be a simple, well understandable linear scale even for non-technical laymen. Combine that with the color scale ratings.Instead, they print some ridiculous kWh/1000h or something figure which does not make any sense to technically oriented or non-oriented people. If you are comparing lighting product against another, all that matters is efficiency, because the runtime would be the same with either one.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 02:51:53 am
content: Quote from: Siwastaja on December 10, 2024, 11:33:23 amIts not just LED lights. They same happened with TVs, and I think a few other products, and they botched the transition in the same way. So, old TVs look more efficient than modern ones when judged by the label.

author: wraper
author_rank: Unknown
timestamp: December 11, 2024, 03:31:41 am
content: Quote from: Siwastaja on December 10, 2024, 11:08:16 amYes, however most of the floodlight type LED lamps have quite poor efficiency, and flicker on top of that. Even stuff sold in EU where normal bulbs are not allowed to flicker.

author: tom66
author_rank: Super Contributor
timestamp: December 11, 2024, 11:03:13 am
content: Quote from: coppice on December 11, 2024, 02:51:53 amYes, I found this funny. My 65" OLED can pull a peak of about 300W from the wall, average is around 150W. Yet, it has an energy class 'G', whereas the plasma it replaced, that was 50% smaller and could pull 400W from the wall, had an energy class of 'C'.They should have made it so the energy class was 1-9 instead, a bit like how when GCSEs (UK secondary school grading) changed they changed the system to numbers to make it clear the two systems are not directly comparable.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2024, 04:19:00 pm
content: The whole energy class thing is a bit silly, because I am going to buy a product based on its overall features and functionality, not because of its efficiency label. If the product I want has the features and performance I want then I will purchase that one and not another. If the one I purchase happens to have a lower efficiency, well that is a pity, but it will not stop me buying it.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 04:28:09 pm
content: Quote from: IanB on December 11, 2024, 04:19:00 pmThat might depend on whether you run the product for a few minutes now and then, or, with something like a fridge, run it continuously. A lot of continuous operation products have a "You can save $XX per annum with this model" sticker on them in shop displays. If you put potential savings in direct terms I think that matters to purchasers. What doesn't work is "This only consumes xW, but that consumes yW". It just washes over 90% of the population. Even the difference between power and energy is a deep mystery to most people.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2024, 04:36:36 pm
content: Quote from: coppice on December 11, 2024, 04:28:09 pmEven with a fridge, it's complicated. They used to be constructed with shaded pole induction motors that might not have the best efficiency, but they run for decades without ever failing. New fridges tend to have permanent magnet DC motors (required by legislation in some markets). These motors are more efficient, but they tend to fail every few years or so and need repair or replacement. So now you have the regular cost of a fridge repair, or a new fridge, plus the cost of the spoiled food.I would rather have the overall lower cost of a more reliable device.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 05:52:41 pm
content: Quote from: IanB on December 11, 2024, 04:36:36 pmI agree but "buy our model, as its so inefficient its probably going to last" might be a hard sell.

author: Zero999
author_rank: Super Contributor
timestamp: December 11, 2024, 09:06:30 pm
content: Quote from: IanB on December 11, 2024, 04:36:36 pmI've never seen a fridge with either a shaded pole or a permanent magnet DC motor. A shaded pole motor doesn't have the starting torque required for the compressor and the sparking of a DC motor's commutator would result in thermal decomposition of the refrigerant, which would contaminate it, so it wouldn't last long.If I were to design a more efficient fridge, I would focus on thermal insulation first and not do silly things such as have an incandescent lamp, then I would replace the single phase squirrel cage motor, with a three phase motor with a copper rotor and add a variable frequency drive. A higher efficiency could be obtained by a rare earth permanent magnet AC motor, but it's probably not worth it, unless it's really important such as battery powered application.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 09:33:17 pm
content: Quote from: Zero999 on December 11, 2024, 09:06:30 pmThey used to be largely induction motors, but they are mostly BLDC with variable frequency drive in the better ones these days.

author: Zero999
author_rank: Super Contributor
timestamp: December 11, 2024, 10:50:20 pm
content: Quote from: coppice on December 11, 2024, 09:33:17 pmA rare earth permanent magnet AC motor is a more accurate description of a BLDC motor.When did that change? I'm pretty sure my fridge, which came with the house, so made around 2016 is just an induction motor. It also had an incandescent lamp, which I changed to LED, as soon as I could.

author: IanB
author_rank: Super Contributor
timestamp: December 11, 2024, 10:51:24 pm
content: Quote from: Zero999 on December 11, 2024, 09:06:30 pmI dare say you are right about the details, but I believe fridge compressors have traditionally used single phase AC motors, if not shaded pole ones. And often there are fans to circulate air, which likely might use shaded pole motors.California seems to have legislated against those, and to my understanding the BLDC motors that have replaced them do have reported reliability problems.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 10:55:25 pm
content: Quote from: Zero999 on December 11, 2024, 10:50:20 pmBrushless DC is a very common term. A rare earth permanent magnet AC motor isn't.Quote from: Zero999 on December 11, 2024, 10:50:20 pmOur fridge is from 2017 or 2018. It has a variable frequency digitally controlled BLDC motor. Most of the Asian fridges had BLDC motors, many of them digitally controlled, at that time. The cheap Turkish fridges didn't. Recently I think the cheaper fridges are also going BLDC.

author: coppice
author_rank: Super Contributor
timestamp: December 11, 2024, 10:56:57 pm
content: Quote from: IanB on December 11, 2024, 10:51:24 pmI think there is a class action lawsuit in the US against LG, because of crazy failure rates for their high end fridges.

author: amyk
author_rank: Super Contributor
timestamp: December 12, 2024, 03:36:34 am
content: Quote from: Zero999 on December 11, 2024, 09:06:30 pmI think he's referring to the fans, which used to be shaded-pole but have gone to BLDC.Here's an interesting video about that:

author: wraper
author_rank: Unknown
timestamp: December 15, 2024, 12:24:34 am
content: Quote from: coppice on December 11, 2024, 10:56:57 pmDunno what's wrong with LG'slinear compressors(no rotating parts) but mine is doing fine after 9 years.

author: ajb
author_rank: Super Contributor
timestamp: December 16, 2024, 05:34:06 pm
content: Quote from: coppice on December 11, 2024, 10:55:25 pmBLDCs are in everything these days. I installed a new bathroom vent fan a while ago, even that uses a BLDC motor -- it was no more expensive than the shaded pole versions for the CFM, and is quieter, reliability is TBD. They've been pretty common in residential forced-air heating/cooling (as "Electronically Commutated Motors") for a while now, both for blowers and compressors. Speed control is basically free with the driving electronics, and being able to optimize fan and compressor speed to the operating conditions can make those systems much more efficient. In that sense, I think the central forced-air systems with outboard thermostats that are common in the US have been lagging mini-split heat pumps with their integrated controls for quite a while.

author: IanB
author_rank: Super Contributor
timestamp: December 16, 2024, 06:54:51 pm
content: Quote from: ajb on December 16, 2024, 05:34:06 pmProspects for a long operating life are not good. See here, for example:

author: Siwastaja
author_rank: Super Contributor
timestamp: December 16, 2024, 07:29:57 pm
content: Quote from: IanB on December 16, 2024, 06:54:51 pmBullshit. BLDC fans have been there for... around three decades, and literally everywhere for nearly two. They last at least the same, or longer, one issue with shaded pole bullcrap was they were heating up like hell, especially after dust accumulated, to the point of lubricants drying out of heat. Normal failure mode is bearing seizing in less than 5 years and thermal fuse blowing. In worst cases they caused fires. Good riddance.By cherry picking you will always find outliers that fail in any class of products. In real world, it's almost always mechanical failure (e.g. bearings) which limits the lifetime, and getting rid of all those 20-200W random heaters around the house is a big positive. For something like a microwave oven with near-zero duty cycle it doesn't matter; for a ventilation fan (or fridge) it does.

author: coppice
author_rank: Super Contributor
timestamp: December 16, 2024, 07:38:26 pm
content: Quote from: Siwastaja on December 16, 2024, 07:29:57 pmYeah, that video isn't really saying anything against BLDC versus traditional motors. Its much more of a heavily engineered versus stripped down issue he is presenting. Very few fans from 50 years ago were like the old one he showed. Most were rather like the BLDC one, without the electronics. They needed a lot of oil, as they ran so hot they dried out the supply. Unfortunately few designs were like the one he showed, with a big reserve. The BLDC motor should run a lot cooler, unless they did something stupid in the electronics. It just doesn't need as much oil.

author: EPAIII
author_rank: Super Contributor
timestamp: December 23, 2024, 12:19:29 pm
content: 90% of the population wouldn't know how to interpret that.No wait, probably north of 95%. They wouldn't get past wondering what lm means. And W would be a total mystery if they did.Quote from: amyk on December 10, 2024, 02:53:02 am

author: EPAIII
author_rank: Super Contributor
timestamp: December 23, 2024, 12:22:44 pm
content: Those fans fail when the oil dries up. Been there many, many times.LPS, squirt, squirt and they run again for years.

author: SteveThackery
author_rank: Super Contributor
timestamp: December 23, 2024, 04:31:43 pm
content: Is there any term more wrong than BLDC? Who on earth decided to call them 'DC' when they are obviously AC motors?

author: coppice
author_rank: Super Contributor
timestamp: December 23, 2024, 04:34:05 pm
content: Quote from: SteveThackery on December 23, 2024, 04:31:43 pmIs there any term more wrong than "AC motor" for a BLDC? If you feed them with DC they run. If you feed them with AC they go bang.

author: tooki
author_rank: Super Contributor
timestamp: December 23, 2024, 05:08:50 pm
content: Quote from: coppice on December 23, 2024, 04:34:05 pmWell, the point is that the actual motor itself is a polyphase synchronous AC motor. In a BLDC, we are simply using a control board to take incoming DC and chop it up appropriately to feed into said polyphase synchronous AC motor.If we consider a BLDC assembly where the controller board is built into the motor (for example, a DC computer fan), then BLDC is an accurate way to describe the entire motor assembly.But then we look at things like the “BLDC” motors for RC drones, it is VERY common for those to be sold as “BLDC” but not include a motor controller (“ESC” in their lingo), so they are literally polyphase AC motors that will not work if DC is applied to them.

author: coppice
author_rank: Super Contributor
timestamp: December 23, 2024, 05:25:36 pm
content: Quote from: tooki on December 23, 2024, 05:08:50 pmAll motors, other than unipolar ones, are AC motors. Traditional DC motors are AC motors with a mechanical commuting mechanism. Modern DC motors are AC motors with an electronic commuting mechanism. A unipolar motor is genuinely a DC motor, but they are little more than toys.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 23, 2024, 07:53:29 pm
content: Quote from: SteveThackery on December 23, 2024, 04:31:43 pmIt's not so obvious. It's where you draw the line between "a motor" and "an inverter". Traditional DC motor uses a mechanical inverter on the shaft. BLDC name was coined when this commutator was nearly directly replaced with a stupidly simple hall sensor + transistor assembly which sat close to the shaft: it's a direct electronic equivalent of the brush assembly, so the name makes sense. Now, granted, nowadays the difference between BLDC and PMAC is pretty arbitrary when the inverter possibly sits meters away behind a long piece of wire (think about an industrial servomotor or EV traction motor); but fan motors are still quite close to the original BLDC legacy.Poor naming is my pet peeve but even still I have not much to complain about BLDC. However, people who shorten that to "DC motor", and I have seen it happen, should be shot.

author: Zero999
author_rank: Super Contributor
timestamp: December 23, 2024, 10:24:37 pm
content: Quote from: Siwastaja on December 23, 2024, 07:53:29 pmThat's why I specifically used the term rare earth permanent magnet AC motor, rather than BLDC. A BLDC motor is often used in cheap DC fans and is very different to a compressor motor.

author: IanB
author_rank: Super Contributor
timestamp: December 23, 2024, 10:41:08 pm
content: Quote from: Zero999 on December 23, 2024, 10:24:37 pmHow so? Both use permanent magnets and electronically commutated coils, do they not?Where there may be a difference is that low voltage motors will typically have a direct DC power supply, while higher voltage motors may be supplied by AC mains voltage and rectify that to DC internally.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 24, 2024, 07:51:37 am
content: Quote from: Zero999 on December 23, 2024, 10:24:37 pmThen again, compressor manufacturers all call their compressors "BLDC" and no one says PMAC. Despite the fact they don't have integrated inverters but just the three (AC) phase wires coming out.Some people think that the difference between PMAC and BLDC is small geometrical difference in how windings are shaped, affecting the waveform of back-EMF - BLDC being more trapezoidal, PMAC more sinusoidal. But that's a pretty small detail to choose the name on, especially since these "trapezoial" motors are still better driven exactly like the sinusoidal ones.

author: SteveThackery
author_rank: Super Contributor
timestamp: December 24, 2024, 10:04:57 am
content: Quote from: coppice on December 23, 2024, 04:34:05 pmNo they don't! Only if the switching electronics is inside the motor. All the BLDC motors I've come across* use external electronics, which makes perfect sense if it's a powerful motor and you want speed control - it's easier to cool external power switching components.*Except computer fans.

author: SteveThackery
author_rank: Super Contributor
timestamp: December 24, 2024, 10:12:33 am
content: Quote from: coppice on December 23, 2024, 05:25:36 pmSophistry. When you order a brushed motor from AliExpress you don't order the motor and then order the commutator - you order a device which produces rotary motion when you apply DC to it's terminals. That makes it a DC motor. The commutator is an integrated part of the whole.BLDC motors with in-built driver electronics (like the fans in my PC) are DC motors. BLDC motors without inbuilt driver electronics are poly-phase AC motors (like the ones in model aircraft).How the magic happens inside the motor is not relevant to it's naming: a motor that requires DC on its terminals is a DC motor, and one that requires AC is an AC motor. Simple.

author: Zero999
author_rank: Super Contributor
timestamp: December 24, 2024, 10:21:10 am
content: Quote from: IanB on December 23, 2024, 10:41:08 pmI suggest you have a look at some pictures of hermetic refrigeration compressor motors and compare them to DC fans.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 24, 2024, 12:41:14 pm
content: Quote from: SteveThackery on December 24, 2024, 10:12:33 amHow simple, and how obvious - in retrospect. I challenge you to create asimpleyetcompletedefinition describing when a motor with electronic commutation transforms from BLDC to PMAC. Consider things like: housing the hall sensors and inverter on the same enclosure; or putting them into separate enclosure but still mounted on the motor; or maybe separating them with a few inches of wire; what if manufacturer sells them as two boxes and lets end user to connect the phase wires; or maybe it's two separate product numbers but still from the same manufacturer; or maybe it's a separate motor + separate drive.At which pointexactlyandwell-defineddoes it transform from DC to AC motor? You will see how murky it is.Consider another different viewpoint, apracticalone instead of idealistic. Let's go back to 1970's or 80's (whenever the term BLDC was coined). We had AC motors which ran directly out of mains power, also called AC power. VFDs were a specialist product; 100% of capacitor start/capacitor run 1-phase AC motors and 99.9% of 3-phase AC induction motors ran direct out of mains, no DC anywhere. Then we had DC motors, they ran e.g. from batteries and used brushed.Then the new type emerged, permanent magnet synchronous motor which is unable to sync to AC grid, so itneededan inverter, and said inverterruns on DC. Therefore, the new type would be able to replace brushed DC, and would be able to run from batteries. Because it needs the inverter anyway. And the existing AC motor does not need an inverter - at that point no one thought that one day it would be much more popular to run 3-phase AC induction motors from inverters, too.Now if you take a bare PMSM without the inverter and call it "BLDC" that indeed is misleading in that someone will think it could run with DC applied to its terminals.But here's the bottom line:your suggested way of calling it an AC motoris equally misleading, because if you apply AC supply (e.g. from mains) to it, it will also fail to operate and just self-destroy, exactly like on a DC supply.Therefore, the motor type you are talking about isneither DC nor ACinput motor. It's a motor which requires amotor driverwhich takesinputfrom the motor and producescorrect signalsfor it to operate. It'sneither"DC" or "AC" "power", in the general sense of what "power supply" means to people.So as a result, if we want to apply either AC or DC in the motor name anyway, DC suddenly starts making more sense; after all, the motor not accepting any type of "power supply", we would have to talk about the power supplyof the inverter- even if the inverter is sold as a separate purchase. And that power supply is usually DC.Meanwhile, an AC motor (usually) is still a product which can be connected to a fixed frequency, fixed voltage AC power source such as grid.

author: IanB
author_rank: Super Contributor
timestamp: December 24, 2024, 04:35:25 pm
content: Quote from: Zero999 on December 24, 2024, 10:21:10 amThey look much the same to me.

author: Zero999
author_rank: Super Contributor
timestamp: December 24, 2024, 09:46:55 pm
content: Quote from: IanB on December 24, 2024, 04:35:25 pmThen you aught to get your eyes tested.BLDC Fan MotorCompressor motor

author: IanB
author_rank: Super Contributor
timestamp: December 24, 2024, 10:05:58 pm
content: Quote from: Zero999 on December 24, 2024, 09:46:55 pmWhy?Compressor motor

author: Zero999
author_rank: Super Contributor
timestamp: December 24, 2024, 10:12:16 pm
content: Quote from: IanB on December 24, 2024, 10:05:58 pmThat's not a hermetic refrigeration compressor motor.

author: IanB
author_rank: Super Contributor
timestamp: December 24, 2024, 10:22:10 pm
content: Quote from: Zero999 on December 24, 2024, 10:12:16 pmWell, yes, it is. On the outside it looks like this:

author: Zero999
author_rank: Super Contributor
timestamp: December 25, 2024, 09:48:10 am
content: Quote from: IanB on December 24, 2024, 10:22:10 pmI've not seen one like that. It must be a US thing.Anyway, regarding BLDC fan vs compressor, on a BLDC fan, there's a circuit board fixed to the motor's stator which is in the middle and the magnetic rotor is on the outside, whereas on a compressor, the stator is on the outside, rotor is in the middle and any control electronics are external.

author: coppice
author_rank: Super Contributor
timestamp: December 25, 2024, 04:19:14 pm
content: Quote from: Zero999 on December 25, 2024, 09:48:10 amAlmost all small heat pumps are made by one of a handful of companies in East Asia. So, there hasn't really been a US thing in small heat pumps for maybe 3 decades.

author: IanB
author_rank: Super Contributor
timestamp: December 25, 2024, 05:19:26 pm
content: Quote from: Zero999 on December 25, 2024, 09:48:10 amThe past several posts in this thread have been about the move towards replacing traditional AC compressor motors with BLDC motors in fridges and freezers to increase energy efficiency. My pictures illustrate what such a BLDC compressor motor might look like.Yes, the electronics are external, on a separate control board.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 25, 2024, 05:26:10 pm
content: Ultimately, naming those things is arbitrary, and different field of markets chose different words.In world of air conditioning, these motors are "BLDC", regardless of their details, and driven by "inverters"In electric propulsion market, similar motors are "PMAC" or "PMSM", regardless of their details, and driven by "inverters" or "controllers"In industrial machinery, motors are "PMSM" and driven by "VFDs".And really, there are no enoughtechnicaldifferences to warrant those names, it's just whatever happens to be used.