Made By Monkeys

In theory, a LED light should last for ten years or so, unlike the typical 4W incandescent lamps used in night lights that seem to burn out in only a few months. But as engineer and founder of the website Discover Circuits Dave Johnson discovered, this Chinese-made unit from Costco (apparently designed by some real dim bulbs) didn't last but 12 weeks:

"I bought a pack of three of these night lights, made by Elumina Lighting Technologies, for about $15. The unit has a pushbutton switch to toggle between settings (dim and bright) and a CdS photocell that turns off the device during the day.

Inside are three white LEDs, wired in series. When I first plugged the device in, it seemed to emit an acceptable amount of light. But in a short time, the light gradually faded until it was virtually useless.

This has happened to me several times with other inexpensive LED lights. I think some manufacturers from China are using inferior phosphors inside the LED assembly, which fatigue after only a few hundred hours. Opening the thing up, I traced out the circuit and determined it was one that I could easily modify.

I made some component value changes and pulled out the three dim LEDs and replaced them with 10 high quality, super bright surface-mounted units from Osram Opto, which I soldered together into two strips of 5 LEDs each. I paid about $1.00 each for the LEDs. So now for an extra $10 per unit (and therein lies the engineering trade-off!), the light now emits a nice bright white light and should last many years with no risk of someone taking a header down the stairs in the middle of the night!"

Automatic doors are ubiquitous. But this product that we all pretty much take for granted represents one of the most vexing engineering exercises on the planet. The challenge: Design something that is open for a pedestrian to walk through (but only then) and otherwise closed. Detailed engineering specs have been established to help engineers cope with the complexity, but what happens out here in the real world is a whole other story.

Bad LEDs don't die. They just fade away and sometimes exceedingly quickly, like this LED nightlight example. Observant reader Clive Mitchell sent in this rather amusing example of a large display LED clock gone all wrong:

"This white LED digital clock displaying departure times at the Glasgow Central Station is clearly suffering from LED fade in a large scale manner. The clock, installed in 2005 and subsequently junked, was one of the first uses of low-quality, Chinese white LEDs. Up to this point, the traditional Gallium Arsenide LED had been considered almost indestructible. So it was a real kick in the teeth to a lot of companies when unreliable LEDs hit the market. I, too, got my fingers burned when I used a load for a TV production. Fortunately there were enough in the application to compensate for the ones that failed."

Low-quality LEDs are something that some manufacturers today admit is problematic, in large part because the design flaws are not evident until after thousands of hours of testing." So what's a design engineer to do? A good adage to follow is, "If it seems like too good of a deal, it probably is." But since all inferior products don't necessarily carry a low price tag, Georg Bogner, Director, Visible LED Engineering at OSRAM, stresses that engineers should be demanding their vendors to, 'Show me the data.' Poor color stability and a reduced lifetime are two key hallmarks of an inferior LED design. So at minimum, engineers should request data on luminous intensity over time and color coordinates over time. And they should try to get the data over a temperature range as well." Of course, the mere act of supplying a printed sheet of "test data" isn't a guarantee that any actual testing has been done. "Getting this data is expensive," says Bogner. "An engineer needs to make sure a potential vendor is in it for the long haul -- that they have a serious intention to design a good product and have made the appropriate investment in R&D."

Chart: Luminous intensity over time:View image

Chart: Color coordinates over time View image

Those portable shake-to-charge devices seem like a good idea, especially for the battery challenged, but how well does this sort of thing really work? Engineer Dave Johnson took this flashlight to the test and found the performance decidedly lacking:

"The maker used some very cheap 1N4001 diodes in the bridge rectifier circuit instead of more efficient Schottky diodes. They also used a small 0.5 Farad cap with a 5.5V rating. I noticed that that this kind of super capacitor was originally designed for maintaining data in memory chips and has a rather high internal equivalent series resistance. This reduces the overall efficiency, since the device can't be charged or discharge very quickly. Some of the power that should go to the LED will end up being dissipated inside the capacitor. Better super capacitors do exist.Most white LEDs draw about 20ma of current with a voltage of about 3.6 volts. As the voltage drops from 3.6v, the current will also be lower. Without any regulation, the circuit will not have a consistent light output. I measured the LED current in this circuit at only a few milliamps, even after many minutes of vigorous shaking. This suggests that they decided to sacrifice light intensity for light duration.
View circuit

The human mechanical power to electrical power conversion efficiency for a shaking device, such as this flashlight, is poor. To measure how much power I could get from the shaking magnet generator, I first completed the flashlight dissection process by disconnecting the coil from the flashlight circuit. I then connected the coil to a Schottky diode bridge, made from four 1N5817 diodes. These diodes have a much lower 0.35V drop instead of the 1.0V for the 1N4001 diode. I then placed a high quality 10 Farad super capacitor from Maxwell (www.maxwell.com) across the output of the bridge.

To measure the capacitor voltage, I connected a digital voltmeter across the cap. Before the test, I made sure the capacitor was completely discharged. I started a stopwatch, and then started shaking the flashlight's magnet. After 120 seconds, the capacitor was charged up to 1.0 volts. This corresponds to an energy increase of 5 joules using the equation 0.5CVV, where C is 10 Farads and V is the 1.0 volts across the capacitor. So, I got 5 joules (watt-seconds) of energy in 120 seconds. That means that the magnet shaking was only able to produce about 0.042 watts of power. This is a dismal amount -- and I am no weakling! To put this into perspective, a single 1.5" x 1.5 " solar cell, placed in bright sunlight, would generate more power than the shaking magnet generator. I bet many of the hand crank generator flashlights I have seen for sale would do much better. A pull string type generator would work even better.

But let's imagine a different kind of flashlight altogether.

EDN Editor and Blogger Paul Rako seems to have the same sort of luck that I do -- we both are constantly under seige by an army of appliances from Hell. In his latest battlefield skirmish chronicled in his Anablog blog, he describes how a failed override switch in his Maytag refrigerator brought a whole new meaning to the term "automatic ice dispenser."

Writes Paul: "A few weeks ago I am sitting upstairs in the office/loft/warehouse/lab/shop/consulting-place megaplex and suddenly my Maytag refrigerator starts running the icemaker and plopping ice cubes onto the floor via the convenient refrigerator door-mounted delivery system. I ran to the fridge, poked the door-switch and few times and then yanked the freezer door open to stop the cubes from raining down on the floor. I soon found a cut-off switch under the bezel that could be thrown to stop the icemaker.I pulled the unit off and the burn mark by the switch was not encouraging....View image
I suspect the failure mode was due to water being trapped inside the rubber boot meant to keep water out. Since the icemaker just started running by itself I have to believe there was a creepage breakdown across the switch that conducted enough current to start the motor. Either that or the contacts were actually closed with some high-impedance film that suddenly broke down and started to conduct."

Engineer Andy Morris recently discovered an unwelcome feature among several Chinese-made stereo sets he owns: Shoddy design work.

Andy bought this Emerson model ES50 stereo new and to his dismay after 9 months of fairly light CD use (no teenagers in the house, presumably), the CD player literally melted.

Where to begin, really, in our recitation of the design flaws? Starting with the miserable execution of a compact footprint [...the designer just squashed the transformer down and spread it out sideways to fit the envelope and get the desired wattage] to what can only be described as thermal mismanagement, to the inexplicable use of certain components, the list of egregious design errors goes on and on. My these monkeys were busy.

Andy describes the key design flaw that resulted in the player's quick demise and some scorched pinkies (his): "The voltage regulator output transistor was mounted on the copper side of the PC board with a small amount of copper (almost none) used as the heat sink. It was required to drop 10 volts at 500mA, dissipating 5 watts of power. It failed and shorted out, applying 18 volts instead of 8 volts to the CD circuit, essentially frying the CD player. The voltage regulator circuit is similar to the one shown here except for no Q1, D1, D2 and a different zener diode. View circuit

Click on the link below to see Andy's redesign of the circuit and transformer, though his warning to the wise: Stick with quality brands like Sony and Panasonic.

Engineers buy and use development kits and evaluation boards to minimise their risk and speed the design cycle -- many say they expect to get something working on a new board in a mere 30 minutes or less. So when the documentation sucks, often contradicting itself or leaving out critical details, it can be insanely frustrating. And it's especially wrenching when the hardware is interesting and useful, as engineer/writer Jon Titus recently discovered trying out a new microcontroller dev kit from Freescale.

"I have a Freescale kit here that could let engineers compare performance of
8- and 32-bit MCUs in the company's new Flexis family. The same code should
run in either processor type, which sounds like an interesting capability
for engineers. But the written instructions are so awful many engineers
will give up. And, nowhere in the instructions does the kit explain its
purpose or provide examples readers can use to compare performance, code
size, and other characteristics for each of the two processor types.

The announcement last month that 46 million Nokia-branded lithium-ion (Li-ion) batteries made by Matsushita Battery Industrial could potentially short circuit and overheat was just the latest in a spate of product advisories and recalls of the technology over the past two years.

But it’s not as if Li-ion batteries are at the early point in their life cycle when you would expect these sorts of problems to crop up. Sony invented the technology back in 1990. So why is it failing now?

The theories behind the technology’s recent spotty performance are complex and varied, which makes fixing the problem a perplexing engineering challenge.

Roger Platt gleefully spotted this heavily shaded, solar-powered parking meter in Bargates Car park, High Street, Burton upon Trent. He wonders if the fact that the area is famous for beer and brewing had something to do with the decision to locate it under a leafy canopy and notes the irony in chopping branches or cutting down trees to accommodate these environmentally-friendly devices.

The website Ecofriend also notes that the UK's notoriously gloomy weather has plagued the performance of these meters. Adding further to the woes -- Platt says he's noticed a number of these panels installed facing North, something he says "your average Boy Scout can figure out is not the best direction to point a solar panel."

The recent brouhaha in this blog over the underwhelming performance of lithium ion batteries and the care that must be taking when charging them reminded me of a case in Design News that involved an explosion of near-Hindenburg-like proportions

Oh I know what you're thinking -- it's those incredibly thermodynamically unstable lithium ion batteries up to their old tricks again. Wrong!! This culprint in this case was a lead acid battery for a lift truck.

Let's just say the sucker really got shredded, as noted by Myron Boyajian, the forensic engineer who was called in to investigate the case on behalf of the singed plaintiff:

"If a lead-acid battery could discharge and charge with perfect electrochemical efficiency, there would be no emission of hydrogen or oxygen gas, just the quiet conversion of the plate material, one of lead and the other of lead oxide, both to lead sulfate while the sulfuric acid electrolyte changed to water while discharging; and the reversal of this process during charging.
One hundred percent efficiency, like perfection, is only to be hoped for. Excess or rapid charging/discharging, plate age and condition, excessive temperature, and other reasons may cause hydrogen and oxygen gas to be emitted from a lead-acid battery."

And kapow!

Andrew Morris cautions readers to beware when you see one of these made-in-China (shocking, isn't it?) mini-drills as engineers made some bad trade-offs in the design.

"I see many of these things at flea markets and garage sales. Highly useful for PC work, but I think people buy them and then are disappointed with their performance. The motor screams at high RPM unloaded and the small 9 or 12 volt AC adapter is almost useless. It is so underpowered that the drill motor slows to a crawl, not to mention that it has no speed regulation.

The whacked-out temperature controls on EE Mike Kotecki's Viking fridge were keeping things just a little too cool:

"We moved into a new, used home two years ago that had a built-in bar in the living room. (Talk about closing tactics!) Anywho, it had a very nice 15-year-old built-in “under-cabinet” Sub Zero beverage refrigerator, that, as far as I could tell from the constant hum, cost about $400/month to keep my beer and tonic cold. So, I went out shopping and soul searching for an energy-efficient replacement.

Click to view parts

Not dazzled by the special effects of a cheap fibre optic light, Clive Mitchell decided to hack his own:

"Fibre optic lights like this one have been about for a long time. They were originally made using glass fibres illuminated by a candle shaped light bulb, but these days the fibres tend to be plastic with a focused low voltage lamp as the light source.

These cheap gimmick fibre sprays are available in the UK from "one pound stores" which would probably equate to "dollar stores" (make that 'two dollar stores' with the current exchange rate!) in the USA. They tend to be battery powered and have a few flashing coloured lamps inside.Inside are three self flashing lamps with small bi-metallic contacts inside. They pulse and flash irregularly, making the fibre optic spray pulse in a rather vulgar manner. It's a complete waste of a good bunch of fibres, so I developed a project to convert one to LEDs and make it run directly from the mains.

It's a terrible twist of irony. The Chinese can't seem to keep the lead out, while everyone else may be doing too good of a job keeping it out. So reports the LA Times, in the article Lead phase-out may destroy electronics. The problem? Tin whiskers, like the ones on terminations, shown here..

View lit necklace

You know what's scariest about Halloween? The avalanche of cheap seasonal merchandise (like the LED necklace shown here) that descends upon the stores around this time. This ever-increasing parade of gawdy, noisy schlock underscores just how low some companies have stooped by trading off any semblance of quality or actual fright-inducing gore in favor of tawdry, unrealistic special effects, To wit, just this weekend I saw on display an offensive rubbery-lipped, talking slug. A nasty piece of elastomer, IMHO.

In honor of Halloween and a step-function-up from those truly dreadful store-bought special effects, here's a great little project from the ghoul's workshop of Clive Mitchell. This USB powered, fiber-optic slug is guaranteed to inspire envy, awe, possibly even fear amongst your co-workers.

Over two million pets in the UK have an idENTICHIP RF tag in the scruff of their neck that works as a kind of electronic ID tag. So what are the chances that two new devices based on the same technology -- which has had a good track record up until now -- would fail in three different dogs (including Barney, shown here with his pal Georgia, who coincidentally lives next door to one of the other dogs). And then to have those same devices weirdly and spontaneously rectify themselves after "xray"' investigations?

The odds must be, well, big enough to be almost impossible.

Bad. Bad. Bad.

That's how Dave Goldstein describes recent problems with a coolant leak in his Apple Power Mac G5 -- the first popular computer to incorporate water cooling as a standard thermal management strategy.

He writes:

"The late G5's are very messed up. Oh man. I don't what the liquid is that sometimes leaks from the cooling system, but it's corrosive. Don't know whether it's a poor engineering design or a manufacturing defect. I have an earlier G5 with no problems."

The holidays are just around the corner, which means it"s time to find out how many light strings survived 11 months in the attic. When we find a clunker, the quest for the bad bulbs usually leads to some really creative expletives at my house.

Engineer Scott Wayne, bought this inexpensive (<$200), FineDrive 400 aftermarket GPS system for his car last year -- only to find out quickly what sorts of unhappy performance trade-offs the manufacturer had made to get to a lower price point:

Discover Circuits founder Dave Johnson found this broken solar powered path light near a railroad track. Like many engineers who find things and think the parts might one day come in handy, he stuffed it in his pocket. (Why does broken stuff seem to have a natural affinity for railroad tracks??)

Upon closer inspection, he realized that instead of filling the 3-square-inches of available space with solar cells, the unit skimped out, using four skinny cells that yielded an active area of only .83 square inches (28%).

Craig Johnson, who runs the website www.ledmuseum.org, where he posts some highly entertaining product reviews, had a few choice words to say about this Chinese-made flashlight advertised as "no battery needed."

Last night the new Times Square New Year's Eve Ball, commemorating the 100th dropping of the Ball, successfully helped ring in 2008. The new Ball is brilliant, literally: It sports 9,576 LEDs in place of the 600 incandescent and halogen bulbs of the previous Ball.

But the marketing claims about its "greenness" are nothing short of ridiculous.

Guess I wasn't as good of a girl last year as I thought I was -- Santa skunked me with a broken toy in my stocking.

This little $7.95 gizmo called a Battery Eater made by Kikkerland is just the thing for the environmentally concerned -- you stick an old battery in and his ferocious red LED eyes blink.

Yeah, right! Note how the eyes above are dull and not the least bit ferocious-looking! Though this thing is described as a device for "sucking the last bit of juice out of your old batteries," the only thing mine did is suck money out of my husband's pocket!

Rule No 2: If you have ignored Rule No. 1, expect your device to be defective in the exact same way as the display model was, and to exhibit that particular defect very quickly

I bought this Orvis LED timepiece from a Levenger store, with the optimistic idea that I could use the carabineer spring clip to hook it onto my bag and put something prettier than my old plastic-banded digital watch on my wrist. The LED light was just one of those nice, but not must-have features.

Design engineers often complain that development kits that rely on a host PC provide no isolation. The resulting ground connection between the dev kit and PC can wreak havoc on the dev kit and, worse yet, fry your PC.

Jon Titus, who blogs over at EDN's new DEVmonkey site and has used and reviewed plenty of dev kits in his day, describes the problem and suggests two solutions for frazzled engineers trying to track down elusive grounding problems:

"Take a look at a galvanic isolation device [Jon suggests two options] for the USB bus. Such devices optically isolate the PC side of the USB bus from the application side and eliminate most grounding problems."

A frustrated design engineer whose company uses a proprietary lithium-ion battery made in China complained recently here in the Made by Monkeys blog about significant problems with those batteries swelling up.

Bloated batteries sound like fodder for yet another “Made in China” recall story – and it’s not inconceivable that some manufacturing defect could turn out to be the culprit in this case.

But when it comes to lithium ion batteries, it turns out that how you charge one can mean the difference between a well-functioning device and one that bears a resemblance to a certain top criminal underlord in the galaxy.

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If an incredibly low price isn't an obvious enough tip-off, here's a surefire way to tell a cloned product from the real thing: In a lame effort to "prove" that the fake has been through some sort of rigorous quality-control process, it usually carries at least one official-looking label to that effect.

Take this $20 clone of the $270 U2 SureFire Ultra LED flashlight, which is one of the toughest and brightest flashlights out there. The clone is the one in front with the gold "Q.C. Passed" label on its bezel.

Of course, there's other telltale signs that this Chinese-made light doesn't come close to the real thing, as Craig Johnson, operator of the website www.ledmuseum.org, a site devoted to all things LED (including some highly entertaining reviews of LED-based products), discovered on closer inspection:

Having been born and raised in Minnesota -- Land of 10,000 Lakes, as modestly claimed -- I've always had a fondness for fishing. We mostly caught sunfish and walleye.

Though I had a strong aversion to baiting the hook, when I saw this circuit designed by engineer Dave Johnson, who runs the website Discover Circuits, for harvesting your own bait, I just had to pass it along! Explains Dave:

"When I was a kid my engineer uncle built a circuit similar to the one below. My cousin and I used it to force earth worms out of the ground to be used for fishing. It worked like a champ. Please be careful since there is high voltage at the probe tips."

When poorly aimed, a flashlight's multiple light sources can create a serious Van Gogh effect!

Doug Ritter writes about the clone flashlight that produced this hallucinogenic effect on his equipped to survive website, where he reviews outdoor gear and survival equipment. He writes:

"The "Pilot" lights by Holly Solar Products are a virtual clone of the original triple AA-cell Trek light, though of lower quality fit and finish, with a twist. Besides the Pilot 2 ($30) two-LED model, they also offer both a one- and a three-LED version. The single LED model, Pilot 1 ($20), didn't seem to offer much except extra long life and it was quite bulky for the light provided. The Pilot-3 ($35) served as an excellent example of the difficulty that having multiple light sources that are not well aimed can cause, as it provided three distinct lit areas. Not too bad for finding your way, but seriously annoying when trying to use the light for close-up work."

England's commissioner for children and a civil liberties group are taking their jobs way too seriously:

According to the AP, they're mounting a campaign to ban the Mosquito -- a device intended to repel packs of yobs by emitting an intensely annoying high-frequency (17.4 kHz) tone.

Old people are immune to it, because the ability to hear high frequencies drops off as the birthdays mount.

"This device is a quick fix that does not tackle the root cause of the problem and it is indiscriminate," English Children's Commissioner Al Aynsley-Green said."I'm very concerned about what I see to be an emerging gap between the young and the old, the fears, the intolerance, even the hatred, of the older generation toward the young."

The British go