Lighting-Gallery.net
General => Off-Topic => Topic started by: dor123 on December 06, 2017, 01:42:07 AM
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Hello:
Yesterday, when I went to eat my supper, one of the tutor of my hostel, said me that the washing machine cycle still operates after more than 3 hours, preventing him to wash the next laundry he wanted to wash. I checked, and discovered that the washing machine, has been stuck for more than 2 hours in ballancing the drum before the final spin, since the stupid imballance detection system, detected imballance inside the drum preventing the spin to be done.
Why the heck front loading and top loading horizontal axis drum washing machine with electronic control, have an imballance detection system? This causes them to skip spins, as well as prolonging the washing program significantly?
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the washingmachine here in my house likes to get kicked off balance sometimes and it will jump around... perhaps it is to keep it from vibrating roun when the laundry becomes off balanced within the drum?
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Usually the drum vibrating when the drum bearing becomes weak. Mechanical controlled horizontal drum washing machines here, usually didn't had their drum vibrating (Judging by the noise of the spin cycle), until something with the drum bearing failed.
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Simply to prevent getting damaged by excessive vibration.
The thing different on new machines compare to the past:
The spinning is way faster (2krpm is not that uncommon, 15years ago 800 was about the maximum you could get; the motivation is to cur energy consumption on the dryer)
The load size is larger from the same outer dimensions, so less "wiggle" room is left for the inner part. The motivation is the ability to just handle higher loads or allow for smaller form factor.
Both means, the machine can not tolerate that much imbalance anymore. So the system needs to detect, when it is happening and somehow treat that (rebalance attempts, limiting spinnig speed, terminating the program with an error message,... - depends on what each maker choose). 20years ago such detection wold be cost prohibitive, so maker just choose lower load size to get larger wiggle room and slower spinning speed to make the system tolerate the imbalance. Today the detection means (there are many different methods, quite a lot ) are cheap enough, so makers moved to be more aggressive on the mechanical side and allow less imbalance and employ the detection and protection means.
The problem I see there for practical use is not presence of such detection/protection, but the way how the SW handles the situation when it gets triggered and when the "rebalancing" is not effective due to some reason (e.g. the laundry load get tangled into a solid ball - that happened to me, nearly killing the 10year old machine I have still without that protection, I was glad I was nearby and stopped it in time)
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Most washing machines here in Israel, have 800rpm max spin, and some have 1000rpm or 1200rpm. My mother former Crystal mechanical top loading horizontal drum washing machine from the 80's, had 400rpm spin.
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The washing machine here is a front loader, and has a spin speed of 800RPM. I've had it now for over 15 years, and it's still working without a problem. I haven't seen a top loading machine in years. In fact I can't even begin to think where I would buy one.
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I have a top loader, no clue of the RPM's though... likely around 800.
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Washers!You need to see the "Automaticwasher.org" forums!I am a member there.There is an issue with some FL washers-and some TL HE washers.People try to wash waterproof items in these and the machine balances correctly at the beginning of its 1200RPM spin-the water in the load shifts adn the washer "Spin-Splodes" in the laundry room destroying the washer adn damaging sorrounding items-some people have been hurt.The washer makers-mainly LG and Samsung relabel the cycles on their machines.They also pay for a replacement machine adn the damage to property.don't know if they comensate for injury.Often they look away since it could be considered user misuse.
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Washers!You need to see the "Automaticwasher.org" forums!I am a member there.There is an issue with some FL washers-and some TL HE washers.People try to wash waterproof items in these and the machine balances correctly at the beginning of its 1200RPM spin-the water in the load shifts adn the washer "Spin-Splodes" in the laundry room destroying the washer adn damaging sorrounding items-some people have been hurt.The washer makers-mainly LG and Samsung relabel the cycles on their machines.They also pay for a replacement machine adn the damage to property.don't know if they comensate for injury.Often they look away since it could be considered user misuse.
To be honest, this problem really IS a user stupidity.
All water-proof items I've ever seen bear a picto showing you should never spin these at all. The makers exactly knew why they've put it there. If someone treat this as "an idiotic limitation", then it really is 100% his fault...
To be honest, washing these in the machine is dumb from other perspective: By washing at higher temperature and a strong detergent, you damage the surface, which then stop being hydrophobic, which means such clothes are immediately ruined... And the spinning makes this issue way worse (it makes the fabric loose, so way easier to pass liquids, so the water), even when the raw material is inherently hydrophobic itself (so still not damaged by the detergent).
It is like crashing a car into a tree and then suing the car maker...
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Click here (https://www.youtube.com/watch?v=vROdVsU_K80) to find out why they have an imbalance sensor, this is about the best example I could find, the results of a large machine with rapidly spinning parts with nothing to shut it down when it becomes imbalanced is impressive and I don't think I would want this to happen in my house..
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The video you put, has nothing to do with the drum become imbalanced. This is just the idiot Photonicinduction, destroying a perfectly working washing machine by connecting its drum motor directly to the mains, while bypassing the motor controller, and throwing a stone into the drum while spinning. This video has sadly, turned into a negative internet meme.
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The imbalance detection is there not because some i***t throwing a rock (or brick, or what it was) into the drum, but to control imbalance effects of rated laundry load.
The thing is, to save water (and consequently the electricity to heat it), you need as small drum for as large laundry load.
But large load mean risk of large imbalance.
In the past, it was solved by limiting the load size and spin rpm.
Today they allow more load for the same drum size (today common 7..8kg ratings use the same drum size as 4kg rated machines 15..20 years ago), with more intelligent filling it means reduction of water usage more than factor of two and similar with the energy need. The drawback is, this filling is more prone to dangerous imbalance (for the drum suspension it does not matter if the imbalance comes from a 2kg rock or 2kg of tangled shirts; the motor power is usually far insufficient to reach any higher speed in such state, so it does not matter if it is connected directly or via a controller), because the tangled shirts are plausible with normal use, so the need for the imbalance sensors.
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I was only answering why they have them, imbalance detectors are very simple little devices with a black box with a funnel shaped bottom in them which a ball bearing sits in the ring and there is a phototransistor under the ball bearing and there is an IR LED on the top of the box, when they light is detected because the ball bearing starts to move to much the computer does it's thing and shuts it down or slows it down, this is done to stop the machine from literally violently shaking itself to pieces, Yes Photoinductions video is showing the worst case situation but this can happen without a shutdown lots of newer machines have 2000 plus RPM spin cycles, all you have to do is wash some thing made of neoprene rubber to see it happen at home, it doesn't take much weight imbalance at a few thousand RPM to damage things, just look at the size weights used on a car tire, and with tiny plastic shock absorbers, light springs and a few pounds of cement counter balance you can only do so much, the only real advantage a front loader has is a lower center of gravity so it's less likely to tip over when there is a critical failure so engineers have designed them to be safe and shut down, they will unlock so you can unload them and fix the situation which is easier then trying to wrestle down a rouge washing machine throwing a temper tantrum on the floor..
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I was only answering why they have them, imbalance detectors are very simple little devices with a black box with a funnel shaped bottom in them which a ball bearing sits in the ring and there is a phototransistor under the ball bearing and there is an IR LED on the top of the box, when they light is detected because the ball bearing starts to move to much the computer does it's thing and shuts it down or slows it down, this is done to stop the machine from literally violently shaking itself to pieces, Yes Photoinductions video is showing the worst case situation but this can happen without a shutdown lots of newer machines have 2000 plus RPM spin cycles, all you have to do is wash some thing made of neoprene rubber to see it happen at home, it doesn't take much weight imbalance at a few thousand RPM to damage things, just look at the size weights used on a car tire, and with tiny plastic shock absorbers, light springs and a few pounds of cement counter balance you can only do so much, the only real advantage a front loader has is a lower center of gravity so it's less likely to tip over when there is a critical failure so engineers have designed them to be safe and shut down, they will unlock so you can unload them and fix the situation which is easier then trying to wrestle down a rouge washing machine throwing a temper tantrum on the floor..
I've always thought the imbalance detection worked by a pendulum that is attached to a switch so that when there is an excessive imbalance the pedulum swings far enough to activate the switch and break the circuit.
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I've always thought the imbalance detection worked by a pendulum that is attached to a switch so that when there is an excessive imbalance the pedulum swings far enough to activate the switch and break the circuit.
I though the same thing, until I took one apart, and I looked at it and though that is so much simpler and way more reliable then any mechanical switch, which would be constantly moving and wearing until it fails...
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Actually in many designs you won't find any sensor that could be called an imbalance detector. They implement the imbalance detection just by evaluating the movement/motor torque by the firmware in thecontrol processor. So the only sensor involved is the motor with its speed sensor, nothing else. The way how it works is not tha complex either: The processor knows exactly, how many pulses the sensor gives per drum revolution, so the only thing it has to do is to look for a speed (or torque, so triac firing angle, when the speed governor is able to correct the speed at low rpm) variation to have significant component which is synchronous with the drum rotation. The thing is, the imbalance affect the speedand causes it to vary, in sync how the imbalance rotates around. So the whole detector is infact just a few lines of code.
Of course, this needs very tight integration with the speed governor function, so it is practical only innewer machines, where both functions are in the controller software (and that needs a bit more powerful computer than was available decade ago), it is impossible with the governor using separate ic (most older designs).
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The video you put, has nothing to do with the drum become imbalanced. This is just the idiot Photonicinduction, destroying a perfectly working washing machine by connecting its drum motor directly to the mains, while bypassing the motor controller, and throwing a stone into the drum while spinning. This video has sadly, turned into a negative internet meme.
Yes he bypassed the motor controller, but that was because it was beyond repair and the machine was EoL. So he connected the drum motor directly to the mains and then had some fun.
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The video you put, has nothing to do with the drum become imbalanced. This is just the idiot Photonicinduction, destroying a perfectly working washing machine by connecting its drum motor directly to the mains, while bypassing the motor controller, and throwing a stone into the drum while spinning. This video has sadly, turned into a negative internet meme.
How do you know the machine was in perfect working order.?
And Photon, is far from being an idiot, he is a very skilled engineer with a warped sense of humour.
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Actually in many designs you won't find any sensor that could be called an imbalance detector. They implement the imbalance detection just by evaluating the movement/motor torque by the firmware in thecontrol processor. So the only sensor involved is the motor with its speed sensor, nothing else. The way how it works is not tha complex either: The processor knows exactly, how many pulses the sensor gives per drum revolution, so the only thing it has to do is to look for a speed (or torque, so triac firing angle, when the speed governor is able to correct the speed at low rpm) variation to have significant component which is synchronous with the drum rotation. The thing is, the imbalance affect the speedand causes it to vary, in sync how the imbalance rotates around. So the whole detector is infact just a few lines of code.
Of course, this needs very tight integration with the speed governor function, so it is practical only innewer machines, where both functions are in the controller software (and that needs a bit more powerful computer than was available decade ago), it is impossible with the governor using separate ic (most older designs).
While this will work, even brand new top of the line units use a simple beam break with a ball bearing, they are simple, reliable, and basically indestructible, plus they will detect the machine being placed on un-level ground or being tipped over which the software won't and they will allow for some vibration just not stuff that will do damage..
@Ria and Miss Cuddly, he shows lots of people why they shouldn't do these things at home, which while some might view that as being an idiot really it's smart, the people that watch the video's and then repeat them at home are the idiots, And I think he is an electrical engineer..
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While this will work, even brand new top of the line units use a simple beam break with a ball bearing, they are simple, reliable, and basically indestructible, plus they will detect the machine being placed on un-level ground or being tipped over which the software won't and they will allow for some vibration just not stuff that will do damage..
Well, are you sure they are really of thr beam break type? Because I can not imagine any worse technology for that purpose. The thing is, all opto-mechanical sensors are notorious to fail very soon, once even a bit of dust becomes involved. Plus the components are rather pricey, both to purchase, as well as to design them into some sensor.
I would rather expect really just a ball making contact on metal studs. The thing is, even when this dos not seem to be that reliable switching element, first the imbalances (those not detected by the motor sensing method, so happening above the critical rpm; I would guess the direct sensor is just a backup sensor there) do not happen that often, so they wont experience that much cycles over the whole washer life. And second, if the sensor hasto act, it means the ball is forced onto the prongs with some speed, so it will easily break any contamination there. And third, even when it does not make the contact the first hit, we are talking about a violent shaking problem, so there are many retry attempts without causing any significant extra stress to themachine (the spin down time will take much longer time so cause greater stress anyway).
So in the end I would expect such simple mechanical contact to be way cheper and more reliable for this use. And don't believe just the first one would not be enough motivation for the makers...
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I've cracked a few of them open, they are simply sealed black plastic boxes with a small funnel shape in the bottom and a hole to fit the photo detector and an IR led on the top and a ball bearing, they use three wires two for power and one for the output, I was surprised by the simplicity of them, and as for failure because they are pretty much sealed so dust is not an issue even water intrusion isn't a major issue as it's transparent to ir, about the only thing that will fail is the led leads rust and the washer shuts down, because they measure the current going to the led and they are looking for a small current returning across the detector, this is the only thing I've seen so far fail on them, rusted leads, and it's a simple fix just tye-wrap a plastic bag over the sensor to stop the condensation from using cold water in the drum from dripping on the sensor or apply a small amount of clear silicone grease on the leads if you can't fit a bag over them..
As for the costs they use a simple 3/5 MM LED and a IR detector with an injection molded housing and a plated ball bearing, so I can't see the production costs being more then about a dollar in Samsung/LG/Maytag/Bosch type volumes, the fancy chrome plated knobs on the front of the machine more then likely cost more to produce...
About using a ball and studs, you still have to deal with corrosion and the wear on both the ball and studs from the constant vibration in a washing machine, if you want a fully electrical, mechanical combo with no optical, you would be better to have a weighted spring suspended in a conductive metal tube, kind of like what they use in automotive shock sensors for alarm systems, and with enough vibration the weighted tip of the spring will contact the tube and allow you to shut it down and for the most part automotive environments are pretty hostile with large temperate swings moisture, rain, oils and fuels, and lots of vibrations, they are way worse then those found inside a washing machine. But's it's hard to detect a problem with the switch and shut the machine down if there is an error as it's a normally open circuit all the time or you could go old school and simply use a simple mercury switch but they can't use those anymore in most of the world, even though they will outlive the machine..