Kudos to you for continuing to search for the culprit. I have to admit while I haven't experienced the bug problem, we've definitely run into similar issues with glass and other elements being trapped in places that block water flow and essentially wreck havoc on the dish washing cycle. Given that I hardly expect we're alone in this probem, it seems to me, a bit more engineering time could be spent on coming up with a better design for dealing with debris so it doesn't interfere with the unit's operation.
I had a pistachio shell that made its way to the pump. The noise it was making suggested a bearing had gone bad and that a new pump was in my future. I'm glad I decided to open the machine up and take a look before ordering a pump. That made me wonder about the people that don't own screwdrivers and what they would do. Call repair service and buy a new pump? We're all lucky to be engineers.
While I agree with you, (lucky to be engineers) I've been forced in many instances to rise to a higher, broader perspective, and know firsthand that the general public (family members included) don't always share that perspective.A colleague of mine has a book on his desk entitled Design Engineering, and depicted on the cover is a bridge spanning a great chasm; one side of the bridge says "Design Engineers" and on the opposite reads "The Rest of the World".Yes, we are set apart, and by our perspectives, happily so; but many times from the perspective of the "The Rest of the World" it's their choice to isolate us.Everything is relative. But that's just an engineer's opinion.
Oh, and about the dishwasher – funny story;too bad the insect wasn't the real bug; that would have been poetic!
This story makes me wonder about the filters: why aren't they designed to prevent small items like pistachio shells and broken glass shards from entering the pump, or for that matter, from ever leaving the dish compartment in the first place?
Good question, Ann. My dishwasher is designed so nothing larger than a sunflower seed can get through the main compartment. It's not a fancy filter, it's just that the holes for water passage are very small. Seems an easy and logical design.
It seems easy and logical to me, too, Rob, although experience tells me that's not good enough when it comes to the realities of machines. But a sunflower seed may be large enough to do damage, since others mentioned a pistachio shell and glass fragments. So I'm wondering if a filter small enough to keep out these objects might also be too fine to let water pass through at high enough rates, or that maybe there's another design problem such a fine screen would cause.
Good points, Ann. There may be a potential problem if the filter was so fine that it would quickly get clogged. So there is probably a design balance between having it fine enough to catch items like glass while still allowing a flush that doesn't quickly clog.
Rob, that's what I figured: there must be a (very imperfect) balance in designing these between filter hole size small enough to prevent damaging particles from passing through and filter hole size large enough to keep water flowing at the right rate of speed. Tim's dimensions are a lot smaller than a sunflower seed and larger than a size that I'd guess could cause a clog.
That's right, Ann. It seems a simple matter. So I'm surprised there are designs that make it so difficult for users. The fascinating part of this story, though, really is the bug getting into the control panel. How do you design to avoid that?
Mine has a filter screen as well, but all kinds of "crap" gets through anyhow. The most annoying are little pieces of plastic film that go through and clog the exit holes of the top/bottom rotating sprayers. Can't complain though - its going on 14-15 years and still does the job as long as it gets a routine clean-out.
Our $400 late-model Frigidaire dishwasher has a strainer in the bottom to capture larger debris, to prevent the larger debris from entering the pump. It's a regular maintenance item to clean-out the strainer (preventative maintenance if done on a regular basis, corrective maintenance if deferred until clogged). My wife cleans-out the strainer about once a year, easily accessible and easy to clean. The dishwasher user's manual explains and illustrates how to clean the strainer. We're also careful to rinse all excess food before loading items into the dishwasher.
Looking at the filter and setup, I still do not necessarily know how the glass got to the drain motor. There is a top filter with multiple small holes and a locking ring that holds this in place. The best I can figure is that somehow the edge of the filter was pushed up during the cycle and the glass worked its way in.
We had a dishwasher that seemed to chip plates and no one could figure out why. Turns out we found bits of broken galss lodged in the sprayer, and smaller bits were apparently circulating through the spray nozzles at high exit velocities. It took a careful cleanout to remedy the problem.
At least your dishes should be super clean as they were being sand blasted as well as washed. The each little chip probably became part of the blasting process. I wonder just how far it would have gone before blowing a hole through the door. Just a thought.
Interesting to read about a real bug in a circuit, but perhaps the problem was the bad pump and the insect didn't have any effect. Who knows; it's a good story.
Grace Hopper, a US Navy admiral, worked on many early computers and taped a moth in one of her lab notebooks. The story goes she found the moth between relay contacts in a Mark II computer, noted the problem, and told people she was "debugging" the circuits. Find more info and a photo of the mounted bug here: http://en.wikipedia.org/wiki/Grace_Hopper.
While inspecting circuit boards a friend of mine spotted an insect on the reverse side of a board. He turned the board over, but no bug. It was sandwiched between the fiberglass sheets used to create the substrate. I think I have a 35-mm slide of the encapsulated bugaround here somewhere. The board was "buggy," but thankfully the creature didn't affect any of the circuits.
Jon, I heard the same story about Grace Hopper inventing the term "debug". A friend of mine who used to work tech support years ago told me that real bugs getting into electronics have in fact been the problem in many cases, at least on the old days with larger components.
Talking about large equipment: You can blame squirrels for many above-ground power failures, Ann. They run along wires and sometimes put their paws on a transforner terminal while standing on the metal case. That causes a brief short circuit that blows a fuse on the power pole. It kills the squirrel, too. I haven't heard about any squirrels in computers or appliances, though.
I hadn't heard about the transformer issue. But I'm familiar with the problems squirrels cause in gnawing wires. The first three times my internet cable connection failed out here in the forest the Comcast tech said it was all their fault. Maybe they've learned, since we haven't had that problem since. My friends in the drier areas where there are many mouse and rat species tell me they continually have car failures caused by mice and rats gnawing electrical wires.
Those little critters seem to gnaw at almost anything that might resemble food. My father in law had a porcupine or raccoon nibble through a brake or power-steering hose. The repairman said most likely there was road-salt on the hose and animals like salt in their diets. Who knew.
An interesting biology tidbit: rodents actually gnaw on all kinds of things that don't look or smell like food. It's to keep their teeth, which continue to grow throughout their lives, at a reasonable length, so they don't grow into their jaws. That's why they are the main wildlife, at least in temperate zones, responsible for destroying so many electrical wires.
Another interesting critter is the ant. When I lived "out in the country", ants swarmed the contactor on my air conditioning unit, rendering it useless. Also got into the telephone junction box outside and disrupted it, too.
I know this is a little off topic, but I heard a story of a grizzly bear getting into a high voltage power line. The story turns out to be true and with a little surfing you can find pictures of a grizzly bear that dug up a high voltage power line. I always wondered if the hum made him think the cable was somehow linked to a bee hive.
Ants seem especially attracted to electric fields. I lived in Plano, TX some years back, and my house there had a low-voltage outdoor lighting system. It was fairly extensive, with a several hundred VA transformer. I had a series of failures, including one that got me a new transformer (in warranty) because of an open winding. It had dual outputs (separate windings), and the other one still worked. It turned out that each winding had an internal overcurrent protection device (besides the primary-side circuit breaker, and non-repairable) that would blow only if there was a major overload that peaked too quickly for the breaker to trip. I had lots of "fun" excavating all of that LV wiring to isolate the wiring fault, that showed up as a 0.1 ohm or so short on one LONG run of 12 AWG LV "burial" cable. I finally got to the problem: a splice (thoroughly taped, and with "lock" type crimp connectors) at a break-out point to split in 2 directions. For some reason, it had attracted a whole mound of FIRE ANTS that chewed away enough insulation to cause the short. Of course, I had to first wipe out the nest, wait for all the ants to die or otherwise depart, then rewire and re-tape that part of the run. All was well for a few months. Then, the same run failed again. Same spot, same reason (only this time it didn't kill the transformer, as the breaker did its job that time). I fixed it again, and the problem recurred a couple more times (that I know of; sold the house and moved back to Atlanta!). I did some checking around, and found that indeed fire ants for no known reason WERE attracted to electric wiring! Apparently, normal line voltage lighting doesn't have the problem; maybe the fields are strong enough that the ants get zapped before they can do much damage!
Ratsky-- good to see your tag again. Can't tell you how many times bug-eaten wire insulation has appeared in the Sherlock Ohms and Made by Monkeys blogs. Seems there should be some off-putting chemical in the insulation to prevent this common problem.
Ratsky, please tell me if I'm remembering this correctly: Wasn't the federal government supposed to build a big particle accelerator in Texas in the 1990s, which ultimately had to be delayed (or cancelled?) due to fire ants being attarcted to the accelerator's huge magnetic fields?
I'm afraid neither I nor Google can remember or find anything about that! Try Snopes; sounds like an (non)urban legend! There may have been other reasons. Most of Texas has relatively unstable soil formations (that's why few newer houses have basements, because the codes now require floating slab foundations).
Waxahatchie is about 30 miles due south of Dallas, and certainly would have both fire ants and sandy/shifty soil structure. I suspect part of the "budget problems" was failure to see how expensive solving foundation problems would be! Typical government boondoggle IMHO. Thought so at the time, still do!
Squirrels seem to love to chew on vinyl. They've gnawed through a heavy vinyl birdseed container. Far worse was when they gnawed the insulation from the low-voltage wiring to my heat pump, causing continuous compressor start-stop cycling. The compressor wasn't designed for that and failed, necessitating replacement of the entire unit, costing a few thousand dollars.
Needless to say, the current unit has the low-voltage wiring run inside steel-jacketed "Greenfield" tubing.
When I was a young teen, we moved into a rented house, where the electric range did not work properly. On pulling the range out from the wall, we found a rat that had been electrocuted and cooked across the terminals where the 240 VAC feed from the wall socket connected inside the range.
I would think the rat would stink and alert the occupants that something was amiss behind the stove. I once used rodent poisen to get rid of mice. They would eat the poisen, then crawl into the walls to die. We could smell them for a week, but we couldn't get to them.
My guess is that it did, until it was thouroughly dessicated by the current passing through it. We had just rented the house, and the cooked rat in the range came with it. Who can account for some people not investigating smells. I have always tried to locate the source of any unusual odors, whether foul or pleasant. In fact, I have often located the failed component on circuit boards by the smell, usually confirmed by either discoloration or deformity caused by the overheating when it failed.
When I used mousetraps it was easy to find the dead mice. But when they crawl into the wall to die after being poisened, it's not so easy. I could always locate the area, but I didn't cut through the wall. So I quit using poisen.
Good comments, John. Kudos for attributing "debug" properly to Grace Hopper.
My company makes electronic equipment for use throughout the world. The gear used particularly in the more tropical climates is often assailed by various and sundry "vermin". It's often a design consideration; water ingress is one thing, but is it vermin-proof? Ha! Maybe the most unusual incident occurred when we brought a pallet of gear into the factory for rework from the field. A lady opened up the housing of one unit to find a 6" long snake! True, it was dessicated and no threat, but still quite shocking (pun intended). Critters always seem to seek out warm hidey-holes.
@jmillion: Yes, like the "warm hidey-holes" in my swimming pool pump motor! The thing is black, of course, sitting in the sun, and close to the ground. It started making an awful racket, so I brought it down to my workshop to see if I could fix it. I hadn't gotten much more than the back cover off when out comes an 8-inch long garter snake! Boy, did I jump! Fortunately, all I screamed was "AHHH!" and it only took a moment to grab "Gregory" (as my son has since named "him") with a pair of pliers, run upstairs, and deposit him in the woods.
I put a piece of vectorboard over the vent holes after that.
My thirty year old Kitchen Aid dishwasher had a good screen to keep stuff out of the pump, and the design was such that the heavier stuff would accumulate in a wide channel below the screen so that the filter did not get dirty very often. In addition, the design of the filter system was such that the return water would slow as it approached the filter, assisting the chunks to fall into the collection channel, which was quite easy to wipe clean. It seems that the engineers responsible for that design knew a bit about fluid dynamics and how to drop stff out of a stream before it even reached the filter. Very good engineering.
As for the problems with the transformers and the fire ants eating the insulation, my conclusion is that those monsters came stright up from hell a while back and are never content unless they are causing problems.
I never intentionally use or purchase any transformers that include an internal nonreplacable device as mentioned. I have bypassed those devices in several transformers and never had any ill effects because of it. My impression is that the thermal protectors are very cheap quality and so some of them open at a temperature below the specified heat, rendering the product failed. So if a transformer has an external fuse, or other protection, removing the thermal fuse is not a problem that would cause a hazard.
Most transformers of this type need to have such a device to get their UL/CSA approvals. The unfortunate part about this particular one was the manufacturer's choice to use one embedded deep within the windings (presumably at the potential hottest spot), and to use a non-self-resetting one. This unit was potted, so I wasn't about to try to rewind it! A good example of what happens with the latter (self-reset) type can be found in most lamp ballasts: we've all seen fluorescent and other discharge-type lamps that SLOOOOOOOOOWLY cycle on and off all by themselves as the ballast and/or lamp gets old and triggers the device during "normal" operation. It's especially annoying in vapor-discharge (mercury or sodium) street lights (even more so if it's the one right beside you bedroom window!). However, I suppose that's better (from a safety standpoint) than a street light that's out and stays that way!
"A good example of what happens with the latter (self-reset) type can be found in most lamp ballasts: we've all seen fluorescent and other discharge-type lamps that SLOOOOOOOOOWLY cycle on and off all by themselves as the ballast and/or lamp gets old and triggers the device during "normal" operation. It's especially annoying in vapor-discharge (mercury or sodium) street lights (even more so if it's the one right beside you bedroom window!). "
Actually in this case it isn't a reseting cutout but a fundamental property of the gas discharge lamp. As the lamp ages the voltage required to maintain the arc discharge rises, eventually (about 20k-25k hours for HPS lamps, about 3/4 that for mercury & metal halide) reaching a level higher than the max running voltage available from the ballast and the arc extinguishes. The discharge tube then cools to a point that the arc can be restruck by the ballest whereupon the lamp's arc tube reheats and the cycle repears. The solution is to relamp the fixture.
The company says it anticipates high-definition video for home security and other uses will be the next mature technology integrated into the IoT domain, hence the introduction of its MatrixCam devkit.
Siemens and Georgia Institute of Technology are partnering to address limitations in the current additive manufacturing design-to-production chain in an applied research project as part of the federally backed America Makes program.
Most of the new 3D printers and 3D printing technologies in this crop are breaking some boundaries, whether it's build volume-per-dollar ratios, multimaterials printing techniques, or new materials types.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.