My Journey to Tesla, Postscript

My previous two blog posts chronicled a trip to the Tesla factory to pick up my friend Joshua’s Tesla Model S electric sedan. One week after picking up Joshua’s Tesla Model S, my wife Pat and I had our usual Saturday morning breakfast get-together with Joshua and his girlfriend Mandy. Joshua and Mandy had driven their Tesla Model S around a bit the previous Saturday and then took it home. Joshua drove the Tesla Model S around town on Sunday. Then on Monday morning, he went to the garage and found his brand new Tesla Model S sedan had gone dead.

Nothing even lit up on the dash.

Joshua called the factory, which is literally just down the road from his house. The representative at the Tesla factory tried to help Joshua coax the Model S back to life over the phone, but it was not to be. A flatbed truck came to take his brand new car away.

When a Tesla Model S is inoperable, it can’t be rolled onto a flatbed truck with just a winch because the car’s electric parking brake is engaged and cannot be disengaged. The car won’t roll. Knowing this beforehand, the towing crew had brought skids to slide Joshua’s car onto the truck. The car went back to the factory mid-day on Monday.

On Tuesday, the Tesla factory called to say that they’d located the problem with Joshua’s car; it was a loose connector. (First rule of electrical engineering: it’s always the connectors.) The on-board computer had detected unspecified intermittent failures due to the loose connector and had shut itself and the car off as a safety measure, which was probably an excellent idea. You really don’t want a loose connection causing problems at 60 or 70 mph on Highway 101. My friend soon got his Tesla Model S back from the factory and it has continued to operate correctly.

In addition, Joshua has been monitoring energy costs for his Model S. In Northern California, the Pacific Gas and Electric utility company has implemented stepped pricing for electricity. There’s a base rate and then there are stepped rate increases as you consume more electricity than your base. Nearly everyone I know seems to consume more than their base so no one I know pays just the base rate.

Joshua said he’s paying about 30 cents per kilowatt-hour to charge his Tesla Model S. In one day of driving around town, he consumed 20% of a full battery charge. The battery stores 85 kWh, so that day’s driving consumed roughly 17 kWh and Joshua’s energy cost for that 20% charge works out to about $5.10.

I suggested that Joshua could take his Model S to one of Tesla’s Supercharger stations and get a quick recharge for free. He is entitled to free charging at Tesla’s Supercharger stations because he bought the big 85kWh battery. (That’s a $20,000 option over the base vehicle’s 40kWh battery.)

Joshua surprised me, explaining that there currently was no Supercharger facility at the nearby Tesla factory. The nearest Supercharger was in Gilroy, he said, which is 50 miles from his house. It’s not worth the trip to Gilroy for a free charge as the round trip would consume about a third of the Tesla battery’s 300-mile battery range. However, if or when Tesla builds a Supercharger station (and a Starbucks to wait at) next to its factory, Joshua will be all set.

As I write this post, regular unleaded gasoline is running about $4.03 a gallon at my local Valero gas station here in San Jose. I get roughly 20 mpg in my 2003 Saturn Vue, so $5.10 works out to about 25 miles of driving with my SUV’s mileage, which is about exactly what my daily round-trip commute to Xilinx requires. If I had a newer, smaller car that got 30 or even 40 mpg, I’d get about 40 to 50 miles of driving for the same $5.10.

From these numbers, I see that the per-mile energy cost of the Tesla Model S and a gasoline-powered vehicle aren’t all that different right now if you have to pay PG&E’s higher electricity rates. So Joshua has a plan. He’s putting in solar photovoltaics so he can charge his Tesla Model S with “free” energy from the sun. When he does, you can bet I’ll write a blog about it here on Low-PowerDesign.com.

Update from Joshua on May 1: Hi Steve, I’d just like to add an update on the cost of electricity for the Tesla Model S. About 3 weeks after receiving the Model S I received a software upgrade via the car’s internet connection. The major change was the ability to schedule the charge. Previously the car would charge as soon as I plugged it in. Now I can schedule the charge to start after 12 midnight. This makes a big difference in cost on our time-of-use meter. Instead of about 30 cents we are down to 6 cents a kwh. Of course I haven’t gotten my bill from PG&E yet so I don’t know what shenanigan thresholds they may be adding. I am still in love with the Model S.

Posted in Green Design | Tagged , , | Leave a comment

My Journey to Tesla, Part 2

This is the second half of my experience in picking up a new Tesla Model S all-electric sedan at the Tesla manufacturing plant in Fremont, California. On a sunny Saturday morning in March, my friend Joshua and his girlfriend Mandy (the proud new owners) along with my wife Pat and I ate breakfast and then drove over to the Fremont plant to pick up the car and to take a factory tour. See Part 1 for a description of the car and its features as described during our initial checkout in the vehicle. After that, it was time for the factory tour.

 

 

A short walk up a ramp took us from the customer reception center into a dark portion of the actual factory where a tram was waiting. There were about twenty of us on the tour. It was remarkably quiet for an automobile manufacturing facility. And dark. Did I mention dark? No lights were on in the tram-loading area but three people stood nearby with bright worklights. They were inspecting a dashboard cover that appeared to have been taken from one of the shipping boxes stacked nearby. The dark portion of the Tesla plant is being used for parts storage.

Tesla is only using about 20% of the floor space for actual manufacturing at the moment. In full production, the NUMMI plant could build more than half a million cars per year according to our enthusiastic tour guide. Tesla plans to build 20,000 Model S sedans this year. The good news: there’s plenty of room for expansion just waiting for Tesla Motors to take off.

Unfortunately, no photos were allowed during the factory tour and no one except for VIPs can go upstairs where the batteries and motors are built. However, I did snap the following photo in the customer reception area. It shows some of the robotic assembly going on in the plant.

 

 

Our Saturday morning factory tour started with the stamping operations. The Tesla Model S is an all-aluminum car with a unibody design. The stamping operation takes in large rolls of aluminum sheet, cuts the rolls into smaller blanks, and then stamps the blanks into car parts using a huge number of stamping dies. The dies were stacked neatly in meters-tall stacks all over the stamping area. There were hundreds of them. That’s because it takes several sets of dies to successively shape the metal into a finished part. A massive overhead crane moves the dies back and forth between the storage stacks and the huge hydraulic presses. Bright red robot arms located between closely spaced presses moved parts from press to press as the metal took shape. Exterior stamped body parts are all hand sanded to get a smooth finish.

Next, we toured the assembly area where more red robots stood ready to weld parts together to form the unibody. This section of the plant was not operating during our tour. However, you could see a double line of welding robots flanking a conveyer where the car body takes shape. Additional robots stood ready to pick up large sections of the car, like an entire side, to position and hold in place during welding. The body panels are aluminum instead of steel, so Tesla’s robots must grip the parts with suction cups instead of magnets, which are more standard in the industry.

The assembled car gets painted after welding. That’s another part of the Tesla manufacturing operation we did not see on our tour.

The painted car body then receives all of the bolt-on, clip-on, snap-in parts. Wiring harnesses go in first. The Tesla Model S is a high-tech car, so there’s a lot of wiring including some really heavy cables that carry the electricity from the battery to the motor. There’s a special area just for assembling the high-tech dashboard console with that huge 17-inch, center-console touchscreen. Our guide told us that it initially took more than 30 minutes to assemble all of the components into the dash console. After refining the assembly process, they’re now down to 7 minutes.

The cars became more recognizable as we walked to the end of the assembly line and then into final test. There’s a test track at the end with speed bumps, cobblestones, and waffle patterns designed to exercise the newly assembled cars’ suspensions looking for squeaks and other problems signaled by strange noises. There’s also the “monsoon” chamber where each car gets a 30-minute soak to check for water leaks. Remarkably, all of these final tests take place inside of the assembly plant. That’s because the Tesla Model S is a zero-emissions vehicle. It can be driven indoors without trouble.

This ended the formal tour. We returned to the customer delivery center. Joshua and Mandy got into their new Tesla Model S, waved goodbye, and drove off leaving us to walk back to my 2003 Saturn Vue.

However, as it turns out, that wasn’t the end of the tour. Just as Joshua and Mandy drove off, a guy in a t-shirt and jeans strolled up. “What do you think?” he asked. Looks like a great car, I said. “Going to get one?” he asked. According to Wikipedia, the base price of a Tesla Model S is now $59,900 and it’s another $20,000 for the large 85kWh, 300-mile battery, making it just under $80K or so for the car before adding other options like the huge sunroof or the Tech package with navigation. The most expensive car I’ve ever purchased, my Saturn Vue, cost just a bit more than the Tesla Model S battery.

Unfortunately, the car’s not in my class (or I’m not in the car’s class, depending on how you look at it). Besides, there’s that pesky problem of charging an electric car in my condo parking area to deal with. (See my blog post “Charging the Chevy Volt.”) Our HOA will have to solve that problem someday. It won’t be solved this year, I’m guessing. Or next year either. And I’m Vice President of the HOA.

However, the guy in jeans turned out to be one of Tesla’s chief design engineers. He was watching the delivery of the new cars and getting quite a kick out of the experience from what I could see. We spent about ten minutes talking about the Tesla Model S sedan and Tesla Motors. You could hear in his voice how proud he is of Tesla Motors. “The experts didn’t give us a chance to succeed,” he said. The cars we saw rolling out of the delivery lot spoke otherwise.

We also discussed the design of the Tesla Model S. He was pretty proud of that too. In fact, he’d been out driving one the night before. (He doesn’t yet own one). He said he’d pulled up to a new Chevy Corvette at a stop light.

You know what happened next.

“I smoked the ‘vette,” he said, smiling broadly.

“That’s what I’d expect,” I replied. “The torque curve on the electric motor…”

“…goes up in a straight line,” he said, finishing my sentence with a grin.

My wife Pat is a mechanical engineer. I may work in marketing these days but I’m still an electrical engineer at heart. The three of us talked engineer talk about the design of the Tesla Model S for the next few minutes. Design. Reliability. Testing. Batteries. Talking about cars is fun. Talking about cars with as much technology packed inside as the Tesla Model S, that’s great fun. Talking about all of this stuff amongst just us engineers, that’s the best.

Not a bad way to spend a Saturday morning.

Oh, and Tesla. If you want an engineer to test drive a Model S sedan and write about it, I’m just down the road in San Jose. Call me, maybe.

Posted in Green Design | Tagged , , | Leave a comment

My Journey to Tesla, Part 1

Once, there were at least two automobile manufacturing plants in Silicon Valley. One belonged to Ford and it’s now a shopping mall called The Great Mall in Milpitas. The other was built by GM in the late 1950s in Fremont, California. It opened in the early 1960s; closed in 1982; reopened two years later as a joint venture between GM and Toyota as NUMMI (New United Motor Manufacturing, Inc.), which made a variety of cars starting with the 1984 Chevy Nova and ending with a red 2010 Toyota Corolla S when it closed again on April Fool’s Day, 2010; and then it reopened later the same year as the new manufacturing facility of Tesla Motors. The Fremont auto plant puts about 5.5 million square feet of space under one roof. That’s the area of 88 US football fields. Tesla plans to manufacture 20,000 electric Model S sedans this year in the facility.

As a condo resident, owning an all-electric vehicle like the Tesla Model S is problematic for me. (See my blog about my 3-day test drive of the Chevy Volt gas/electic hybrid, “Driving the Chevy Volt.”) I wish I could say that I’ve now gotten a review copy of the Tesla Model S to test drive for Low-PowerDesign.com but I have to say that’s probably not going to happen. However, the next best thing did happen: my good friend Joshua bought one and invited me and my wife Pat to join him and his girlfriend Mandy when they picked it up at the Tesla factory. A factory tour was included. How could we say no?

We began the Saturday like most, eating breakfast with Joshua and Mandy. Then we all piled into my 10-year-old Saturn Vue SUV and drove a few miles North on I-680 to the Tesla plant. There’s a customer delivery center newly built onto the front of the plant and there were a couple of dozen new Tesla Model S sedans lined up outside waiting for their new owners.

Joshua signed in and a Tesla customer representative named Nick took the four of us out to Joshua’s new dark green Model S for a walk through. (Actually, it was more of a sit-through.)

There are many, many cool things about this car.

First, there’s the key fob. It’s a small fetish in the shape of a Tesla Model S sedan. Push on the roof of the fetish and the four passenger door handles “present.” They slide out of the doors, quickly and silently. If you ignore them for a while, they slide back in. These disappearing door handles supposedly reduce wind resistance. To me, they just look cool.

(Note: My wife suggests that my use of the word “fetish” in the preceding paragraph might conjure naughty, incorrect images in your mind. I would hate for that to be true, so just to be clear, I am referring to the similarity I observe between the Tesla Model S key fob and small stone carvings of animals created by Native Americans. Those are called fetishes.)

Push on the trunk section of the Tesla Model S fetish and the rear trunk lid opens. Tesla engineers have made even the trunk of their creation high-tech. Let’s say you regularly park somewhere with limited overhead clearance. You can manually place the trunk lid at any level, held in place by gas shocks, and then press a small button inset in the trunk lid’s bottom edge to set the maximum upward travel of the trunk lid. From then on, the trunk remembers how wide to open. Slick.

Press on the hood of the Tesla Model S fetish and the front trunk opens. Yes, there’s a trunk in the front too where the internal combustion engine would be if this were a normal sedan. The electric motor sits under the rear seat and the battery’s in the floor of the passenger compartment.

 

 

With the rear trunk open, Nick showed us the charging cable. The Tesla Model S has an internal charger. It just needs juice from an outlet to charge. The car’s electrical charging port is located behind part of the taillight on the driver’s side. It pops out on command. Inside is a proprietary Tesla charging connector, shown in this photo. You can also see the electromagnet that normally keeps the spring-loaded door to this charging port closed.

 

 

Tesla’s charging-port connector is proprietary so that the car can use special Tesla charging equipment called Superchargers, which Tesla says are the “fastest charging stations on the planet.” A Tesla Supercharger can half-charge the Model S sedan’s 300-mile, 85kWh battery in 30 minutes, adding 150 miles of range to the car’s existing charge. Tesla’s site says that there are currently 9 Superchargers operational along “well-traveled routes in North America” and the company plans to have 150 Superchargers operational by 2015. Tesla is placing Superchargers at locations where you’d likely eat or shop, with that expectation that you’ll go do something while your car is charging. If you buy the optional “big” battery for the Tesla Model S, you can use the Tesla Superchargers for no additional fee.

 

 

If there’s no Supercharger nearby, the Tesla Model S is happy to charge from a 110V or 220V outlet or from a standard public car-charging station such as the ones I used during my Chevy Volt test drive. There are cable adapters for all three types of outlets. Naturally, none of these charging alternatives will charge the Tesla Model S as fast as a Supercharger, but you’ll find at least one of these three alternatives almost anywhere you go, except for the garage level in my condo. (See my blog post “Charging the Chevy Volt.”)

Next, we piled into the car. Joshua took the driver’s seat with Mandy in the front passenger seat. Pat, Nick, and I piled into the back seat. The Tesla Model S is supposed to seat three in the back. All I can say is that it’s a good thing that Nick and my wife are skinny. He sat on the hump (actually, the Tesla Model S doesn’t have a middle hump) so that he could point out things to Joshua through the gap between the front seats.

 

 

The first thing you notice about the Tesla Model S is the enormous flat-screen display in the middle of the console. It’s a 17-inch touch screen and it gives you touch access to most of the car’s systems including navigation, rear-view backup camera (it works when the car’s in “drive” too), climate control, entertainment, ride control, sunroof, and system parameters. It looks and works pretty much like a large tablet, with finger-touch scrolling and pinch-finger zooming, and the screens look very much like Web pages.

The car is connected to Tesla continuously through a cellular connection and it automatically downloads system updates, which you then install manually at your convenience. New software versions show up every couple of months or so, according to Nick, and the car is offline (i.e. doesn’t run) for a couple of hours during the software update. So it’s best schedule the update for 1 am or during a time you don’t plan on using the car. Joshua’s car came with version 4.2 of the Tesla software. Nick told us that version 4.3 was imminent.

There’s another LCD set in the dash in front of the driver. It displays conventional-looking car controls including the speedometer and a battery gauge instead of tabbed Web-like pages. There’s also a smaller navigation section and a system-control area that’s managed by a thumbwheel set into the right side of the steering wheel. Another thumbwheel on the left side of the steering wheel also controls some functions such as the small driver’s navigation screen.

 

 

It took us at least half an hour to walk (sit) through this internal checkout. After that, Joshua signed the papers and the car was his. But we didn’t drive it. Not yet. Time for the factory tour, which I’ll describe in Part 2 of this blog entry.

Posted in Green Design, Uncategorized | Tagged , , | Leave a comment

Low-energy microprocessor operates 40nm transistors in near-threshold mode to run on 0.4V@1MHz

Late last month at ISSCC, Belgian research center imec and its affiliated Holst Centre in The Netherlands discussed a microprocessor that can run at 1MHz on a 0.4V power supply with the processor’s CMOS transistors operating in near-threshold mode. The device was fabricated using 40nm process technology. The processor needed only 79µW to run an FFT algorithm. The target here is to develop processing capabilities compatible with the low-energy sources available in biomedical applications including continuous ECG and EEG monitoring. The ISSCC paper’s title is “Reliable and Energy-Efficient 1MHz 0.4V Dynamically Reconfigurable SoC for ExG Applications in 40nm LP CMOS”.

Here’s a closeup photo of the chip mounted in a ceramic package:

One of the biggest problems with using CMOS transistors in near-threshold mode is that transistor threshold voltage varies quite a bit at nanometer geometries due to the extreme sensitivity to doping levels; at nanometer geometries, transistor thresholds are set by a very few dopant atoms.

The imec/Holst researchers circumvented this problem by adding “canary” flip-flops to the processor design within the most timing-critical circuit nodes. These canary flip-flops are designed to fail from below-threshold supply voltage before the associated operational circuits do. The microprocessor can diagnose its own operational health by monitoring the operational status of these canary circuits.

The microprocessor is designed into an SoC that includes peripherals and the SoC employs the usual low-power techniques designed to minimize energy consumption such as fine-grain power gating at the functional-block level and software-controlled voltage scaling. The voltage-scaling feature allows the SoC to goose the power supply voltage if the canary flip-flops stop operating properly. The operating voltage range of this device is 0.4V to 1.1V. Of course, you must also have an efficient means of regulating the processor’s core voltage or much of the power savings associated with this approach will be lost.

This imec/Horst design follows a previous development called CoolBio, which was discussed at ISSCC in 2011.

The following image appears to be the chip layout of the second generation device, as taken from this imec Web page:

That’s clearly the microprocessor block in the upper right corner of the design. Note that Samsung appears to have manufactured this SoC based on the ISSCC paper’s listed authors.

Please be aware that it’s one thing to get a research project like this one to work and it’s entirely another thing to get these kinds of devices to work in mass production. Assuming the “canary” circuits are a good solution however, imec/Horst has made a huge leap towards making near-threshold digital integrated circuits a production reality.

For an interesting discussion of near-threshold digital CMOS design, see “Ultralow-Power Design in Near-Threshold Region” by Dejan Markovic, Louis P. Alarco, and Professor Jan M. Rabaey.

Posted in Clock Gating, CMOS, Low-Power | Tagged , , , | Leave a comment

Can a miniature xenon flashtube find its way into smartphones because of a new miniature capacitor?

Associate Professor Lee Pooi See at Singapore’s Nanyang Technological University has developed a high-voltage, miniature, multilayer polymer capacitor with the hope of producing a power source small enough to operate a xenon flashtube in a mobile phone. The work is being done under a Proof-of-Concept grant from Singapore’s National Research Foundation (NRF) and is being done in partnership with the world’s largest flashtube vendor, Xenon Technologies.

Xenon Technologies is reacting very intelligently to a tectonic shift in its market. The world is shifting from compact cameras, which each sport xenon flashes, to smartphones with built-in cameras, which overwhelmingly use white LEDs for shooting pictures under camera-based illumination. Xenon Technologies has to choose between:

  • seeing a major market for its products dry up or
  • finding a way to go with the flow

Based on this recent announcement from Nanyang Technological University, Xenon Technologies has chosen to go with whatever’s behind Curtain Number 2 and is developing an even smaller flashtube module to work with this miniature polymer capacitor.

You can see a photo of the capacitor below. The image shows a compact camera flashtube assembly and an electrolytic capacitor. The new multilayer polymer capacitor is the flat object that looks like a 35mm slide in the image’s foreground. The smaller smartphone flashtube assembly is not yet ready for its closeup, but is expected to be available in September.

(Photo credit: Nanyang Technological University)

As a result of this announcement, I did some research on polymer capacitors and discovered that they’ve been around as alternatives to low-voltage electrolytic capacitors since 1983 when Sanyo went into production with its OS-CON line. The dielectric material used in these capacitors is a solid, high-conductivity polymer instead of the wet electrolyte used in electrolytic capacitors. The high conductivity gives the polymer capacitors low ESR (equivalent series resistance) and they’re reportedly more stable over time than electrolytic caps.

Professor Lee Pooi See’s polymer capacitor gets its high-voltage characteristics from its multi-layer construction. According to the Nanyang Technological University press release, “the new capacitor is at least four times smaller than current electrolytic capacitors and is several times faster than current ceramic-based capacitors.”

Now, let’s look at this xenon flash development from an engineering perspective:

First, as a light source for still photography, xenon flashes offer one significant advantage over LED illumination. They are considerably brighter and will therefore produce better images taken with camera-based illumination. However, if you’re a photography fan, you already know that the small flashes located adjacent to the lenses on compact cameras can produce less-than-ideal images. They are so small that they do not produce enough light to illuminate very far and they produce a lot of red-eye images of people because the flash is located close to the lens’ optical axis. The light from the camera reflects off of people’s retinas, picking up the red coloration, and producing demon-eyed images of people.

The light from a white LED can easily be pre-flashed to get the subjects’ pupils to close, reducing the red-eye effect. You can certainly do this with xenon flashes as well, but you’ll need a larger capacitor to store the energy to permit multiple flash cycles in rapid succession, which is something that most compact cameras can do these days if properly configured.

Second, the white LEDs currently incorporated into smartphones serve multiple purposes. In addition to serving as illumination for still photos, they also light scenes for video. Xenon flashes cannot provide continuous illumination and therefore cannot be used for video. The white LED also serves as a flashlight. I’ve downloaded an app for my smartphone that turns my expensive smartphone into a $2 LED flashlight. It’s very handy because I’m far more likely to have the smartphone with me when I need light.

To me, that means that all smartphone users will continue to want white LED illumination in their phones. LEDs are more than adequate for posting Instagram photos of your Doritos Locos Tacos lunch at Taco Bell and for sexting, which would appear to cover more than half of the smartphone photo users out there. More advanced users may be the only ones who end up wanting both the xenon flash and the white LED in their phones.

Higher-end cameras such as DSLRs often have both types of illumination, with the LED serving as an effective red-eye reduction tool. However, pennies are critical in smartphone BOM costs, so I see the addition of a xenon flash to most smartphones as doubtful unless smartphone vendors find some way to drum up demand for the superior still-photo abilities of a xenon-equipped phone. Nevertheless, the development of the flat, miniature, multilayer polymer capacitor with its high energy density could well have many other interesting uses in the development of small, power-efficient electronic systems.

Posted in Low-Power | Tagged , , , | Leave a comment

Boeing isn’t the only one with Li-ion battery problems. Me too, with my Panasonic shaver!

As I write this, the entire worldwide fleet of fifty Boeing 787 Dreamliner aircraft is grounded thanks to a problem with a Li-ion battery pack in the planes. The planes are grounded because of two incidents where smoke and fire were associated with the batteries. If there are two words you do not want associated with a plane that’s built largely of carbon fiber, those would be “smoke” and “fire.”Here’s an NTSB photo of one of the failed batteries:

Elon Musk has offered to help Boeing. If he does, it will likely be another multi-million-dollar feather in his cap, following Tesla Motors, SpaceX, and PayPal.

I’ve got no insight to reveal here about the Boeing 787 battery problems but I suddenly do have a Li-ion battery story of my own. Although I’ve no design experience with Li-ion batteries, I use several devices containing Li-ion batteries and I recently experienced a failure with one of those devices—my Panasonic ES8077 electric shaver.

I’ve had this shaver for about five years or so. It’s the best electric shaver I’ve ever owned and I’ve had Braun’s, Remington’s, and Norelco’s before the Panasonic ES8077. (The Panasonic cleaning station for the ES8077 shaver, now that’s a whole ‘nother story.)

I change out the Panasonic’s cutter and shaving foil about once a year and it’s kept on doing a great job. It’s always been able to go about a month between battery charges. Two months ago, that period between charges suddenly dropped from one month to three days.

Let me tell you, it’s pretty frustrating when the shaver dies a third of the way into a shave.

The Panasonic ES8077 has a wall charger but it won’t run from the charger. The charger only charges the battery. You can’t switch on the shaver while it’s charging. Imagine that.

Fortunately, I was able to charge the shaver for a couple of minutes and get enough energy into the battery to finish my morning shave. However, a sudden 10x drop in battery capacity from 30 to 3 days indicates imminent battery failure in my book so I figured it was either time to replace the battery or the shaver. For green purposes (and because I’m basically cheap), I preferred to change the battery. Not as easy as you might think.

Curiously, the Panasonic ES8077 shaver has a replaceable AA-sized Li-ion battery that’s not designed to be replaced by the consumer. To underscore that point, try finding a retailer that will sell you a Li-ion battery for this shaver. Even Google has trouble with this task.

The only Li-ion battery vendor I found for my Panasonic ES8077 was an eBay vendor named “softbutton.” Fortunately, softbutton has a 100% eBay feedback rating, which was somewhat encouraging. The cost for a replacement Li-ion battery for my Panasonic ES8077 shaver was $20.47, which includes shipping. For another $3.50, I could get a small vial of silicone grease to reseal my wet/dry shaver after the battery replacement.

Softbutton also conveniently posted a disassembly diagram of my shaver in the eBay listing itself since this too seems to be out of Google’s reach. The assembly diagram wasn’t exactly for my model, but it was close enough:

I elected to spend $23.97 and ordered the battery-replacement kit with the silicone grease. The kit arrived in a few days, packed in a zippered plastic bag. Here’s a photo of what was in the kit:

Notably, the battery has copper-post terminals that I’ve not seen before. Also note that the battery is a generic 3.7V, 1200mAh Li-ion battery made in China. To the left of the battery, you see a microcentrifuge tube filled with silicone grease that cost $3.50 extra. A slick piece of packaging, no? I guarantee you that I’d never have thought of using a microcentrifuge tube to mail small dabs of grease.

With a replacement battery in hand, the next step was to open the shaver and replace the dying battery. Shaver disassembly was easy. One screw holds the plastic bottom cap on the shaver. Then you lift the large, black, rubberized grip from the shaver. It holds tightly to the razor body, so there’s a bit of stretching and tugging needed to free the grip from the shaver. Actually, I had to pry it loose because it was a bit crusty, which you expect from a shaver that’s seen five years of use.

Once you remove the grip, you can back out the four screws and remove the two side clips that hold the two case halves together. Then you pull the two halves apart. This is what my disassembled shaver looked like before I cleaned up the five years of shaving crustiness.

You can see the Li-ion battery in the center of the shaver. It looks like a conventional AA alkaline battery with the exception of the additional terminal posts. The Li-ion charging circuitry is on a board that sits beneath the battery, which you can just see in the photo.

I snapped out the old battery and snapped in the new one. That was the easy part.

The hard part was getting the shaver back together. I applied some of the silicone grease to the recessed waterproof gasket in one of the case halves using a toothpick and then smoothed the grease with my finger. You only need a thin film for sealing. The two case halves then rejoined with no problem but replacing the grip proved a problem for me. The grip incorporates a mechanical switch that locks the shaving head in place. It does so by moving a small black lever back and forth to actuate a plastic head-locking mechanism.

The problem was that there’s nothing in the grip design to retain that locking switch so of course it fell out while I was fiddling to expand the grip to fit it around the shaver body during reassembly. Worse, the switch fell down onto the carpet after it popped free. A bit of searching on my hands and knees located the switch and I was ready to try again. This time, a small white plastic insert in the switch fell out and onto the floor. I needed a flashlight to find it.

I finally managed to retrieve the plastic insert but unfortunately, I had not snapped a photograph of that assembly so I had to figure out how everything went back together. Take a tip from me: use your digital camera to record the disassembly process in detail so you can get things back together after the repair, no matter what product you’re repairing.

Another ten minutes of trial-and-error fiddling and I had the shaver back together. I switched it on and nothing happened. (Cue the chirping crickets.) At this point, I hoped the battery was completely flat. Otherwise, I was out $23 and change and it was time for a new Panasonic shaver.

I charged the shaver for just one minute and pressed the soft on switch. The shaver started up. Success! I finished the button-up by replacing the bottom cap and let the shaver charge in its cradle overnight. There’s a simple 4-bar LED charging graph on the shaver’s handle so I could see that it was charging. According to the bar graph, it was fully charged after just a couple of hours in the charger.

In this era of greener design when we’re trying to give consumers every opportunity to recycle, it seems like a good idea to engineer products with replaceable batteries. The battery inside of the Panasonic ES8077 shaver is indeed replaceable.

However, not easily so.

First, it’s hard to find a replacement battery for this particular Panasonic shaver model. It doesn’t appear to be that hard to find an AA-sized Li-ion battery, although I’ve certainly never seen one before, but finding a battery with those little copper end posts was fairly difficult. If only one eBay vendor carries a product, that’s a pretty rare product in my book. The $20 Li-ion battery from softbutton on eBay is the only one I found from a US vendor although there’s an eBay vendor in Slovakia selling them too at slightly higher prices and presumably longer lead times. Through Google, I also found the Li-ion replacement battery offered by a vendor in the UK for £14.50, which is a bit more than $20 and didn’t include shipping. I don’t even know if the UK vendor ships to the US.

I presume that the Panasonic Li-ion shaver battery is hard to find because Panasonic didn’t engineer the ES8077 shaver to allow for consumer replacement of the battery. The shaver is somewhat hard to disassemble and you need to use silicone grease to reassemble it if you want to preserve the shaver’s wet/dry capability. Most people don’t have a vial of that stuff lying around either.

The company obviously planned for the shaver to be re-celled by a technician if it was to be repaired at all. However, that seems to be a very unlikely scenario for a consumer product like an electric shaver with a replacement cost that’s less than $100. What consumer is going to try to find someone still engaged in the dying art of shaver repair? There used to be shaver-repair stores in the occasional strip mall but these have disappeared, like VCR repair stores.

Even if you do manage to find someone who repairs shavers and other low-cost consumer electronics, what business can afford to charge less than $50 to replace a $20 battery? At that point, you might as well toss out the shaver and buy a brand new one. I consciously make this choice each year when considering the $30 cost for the Panasonic replacement blade set. Still, it seems a shame to consign the shaver to the landfill without trying to repair it if you have the skills.

So the next time you design a battery-powered product, give a lot of thought to the ease of battery replacement. If you possibly can, use a battery that people can purchase from “normal” retail vendors and provide an easy way to access the battery. If the unit needs to be waterproof, take a cue from other vendors that have managed to design accessible battery compartments in waterproof designs. Fluke DMMs are a good example to learn from. The examples of good green design are out there, if you look.

 

Posted in Battery, Low-Power | Tagged , , , , , | 2 Comments

Out, out damn halogen. My LED replacement story.

About ten years ago, my wife bought a fancy china cabinet with a pair of halogen display lights recessed into the top of the cabinet. The halogen down lights highlight two compartments with glass shelves containing pieces that have special meaning to our family. The halogen bulbs do a good job of illuminating the cabinet interior but the bulbs run darn hot inside the china cabinet and they’ve started to burn out with regularity—every month or so. It could be the cheap halogens I’ve been buying ten at a time on eBay. However, I just can’t bring myself to purchase $5 halogen bulbs from lighting stores that might be no more reliable even though they cost perhaps ten times more than the eBay cheapies.

When my latest stockpile of halogen bulbs started to dwindle, I considered another bulk purchase of ten bulbs on eBay. Then I realized that it might be time to replace the halogens with LEDs. As it turns out, that’s not as easy as it sounds even though LED replacement bulbs are now the “big thing” in residential lighting.

Our china cabinet’s light fixtures use 12V halogens with G4 pin bases. You can find many LED replacements for G4 halogen bulbs on eBay (they’re hard to find at Lowe’s or Home Depot), but most of the puck-style, 12V G4 LED replacements are designed for dc supply voltage, which you need if you’re replacing bulbs in an RV or a boat. However, my china cabinet and most halogen-using indoor light fixtures run on 12Vac.

Some slightly more restrictive searching on eBay turned up a very few ac-powered LEDs with G4 bases. The trick here is that the LED puck must incorporate a regulated dc power supply in addition to the LEDs and associated current-limiting circuitry. I finally selected some warm white ac/dc-powered pucks from Wired Communications. The price was $9.95 per puck plus shipping—about ten times the cost of the halogen bulb that the puck replaces—but if I could avoid the need to get out a stool and replace one or two bulbs on a monthly basis, I was willing to spend the extra money.

I placed the eBay order and the pucks arrived in a few days inside of a bubble-pack envelope. Here’s a photo of the front and back sides of the pucks from Wired Communications:

 

The photo shows that the business side of the LED puck has ten warm-white surface-mount LEDs soldered in place. The back side of the puck has four surface-mount power diodes in a full-wave bridge configuration plus a large electrolytic filter cap and what looks to be some dc power-regulation circuitry. There’s an inductor in there, so I presume the power regulator is a switcher. The full-wave bridge allows this LED puck to run on ac or dc so you need not be mindful of socket polarity in dc applications.

When the pucks arrived, I pulled out my old HP 6236B bench dc power supply (purchased on eBay from Loveland, Colorado and complete with a genuine HP asset tag so you know it came from some HP engineer’s bench, maybe even mine) and hooked it up to the puck. The puck started to light at perhaps seven or eight volts. It was a lot of light. A painful amount of light.

Those SMT LEDs can burn spots in your retina. I now know from experience. Clearly, some additional diffusion was in order.

At first, I considered diffusing the light with some theatrical film used to scrim stage lights. I’ve got sample books of Roscolux filters and there are several white diffusion films in the Roscolux line that would have worked. (I first discovered Roscolux filter books through the Strobist blog. They are perfect for gelling camera flash equipment and I bought a bunch when you could get them for two cents apiece from B&H Photo and Video. Thanks to their success through Strobist notoriety, they now cost $2.50 and are still a big bargain.) However, after some consideration I felt that film diffusion would to be too thin (not enough effective diffusion) and flimsy for use on the LED pucks and so I decided to take a different approach.

Tap Plastics had a partial answer. They sell 1-inch cast clear acrylic disks at 25 for $6.25. I’m lucky enough to live near a Tap retail store, so I picked up two for 65 cents apiece. Unfortunately, the acrylic disks are crystal clear and so they provide no diffusion as sold. Some 330 and 150 grit sandpaper and a little elbow grease provided me with the required diffusion. I sanded both sides of the disks.

Next, I had to decide how to attach the disks to the LED pucks. The first try was a disaster. I was out of epoxy but I had some Pliobond rubber adhesive. I dabbed a bit on the outer corners of each outer LED on the puck and set the sanded acrylic disks in place. The next day, I had finished assemblies to try out. That’s when the disaster struck. You need to use a bit of force to plug the G4 lights into their sockets and the shear force proved way too much for the Pliobond adhesive. The acrylic disk tore off of the LED puck as I was inserting the first puck.

Back to the drawing board.

Some additional research suggested I’d have some difficulty with using most glues and epoxies on the plastic SMT LED housings so I finally settled on a plastics-specific epoxy called Permapoxy Plastic Weld, which I bought at the local Orchard Supply Hardware store for about five bucks. Permapoxy is methacrylate-based so it smells to high heaven. Use it in a well-ventilated area. A really well-ventilated area.

Overnight curing produced some rugged assemblies that look like this:

This closeup photo shows that my sanding might have been more consistent but you can’t deny that there’s diffusion going on here. Another test with the HP power supply demonstrated adequate diffusion. My eyes no longer hurt when I looked at the lit puck.

I plugged the LED puck assemblies into the china cabinet fixtures and hit the power switch. Both lights switched on and my wife approved of the illumination. The LED pucks actually seem a bit brighter than the halogen bulbs they replace, which was a surprise. The color of the LEDs’ white light is about the same as the halogens and the pucks run a lot cooler. Here’s a photo of the installation.

So, what do I conclude? There was way too much effort involved in this particular replacement adventure for mere mortals. Most consumers aren’t going to understand that they need ac pucks not dc pucks. Most consumers aren’t going to look on eBay for these products and they will not find them in Lowe’s, Home Depot, or Orchard Supply Hardware. Most consumers will not be happy with the light from the undiffused SMT LEDs mounted on the pucks because looking at the lights (unavoidable when looking at the items illuminated by the pucks) will be painful. Most consumers do not shop at an arcane store like Tap Plastics and are not familiar with theatrical lighting films. Finally, most consumers are not experts in plastics-specific epoxies.

So the barriers to adoption of halogen-replacement LEDs appear to be many and frankly, I do not see how we’re going to hurdle these many barriers in the short term. But my problem’s solved, for now.

 

Posted in Low-Power | Tagged , , , , | 3 Comments

Building communities: The Hacker Dojo Experience

I attended a lecture on building communities by Katy Levinson on January 15 at a meeting of the Consultants Network of Silicon Valley the Agilent Headquarters in Santa Clara, California. Levinson is associated with the Hacker Dojo just up the road in Mountain View. It’s a sort of communal space for technical people who want to develop new products. The Hacker Dojo’s emphasis is on collaboration and a supportive peer environment rather than access to tools (which is the emphasis of the Bay Area’s TechShop according to Levinson). The Hacker Dojo currently has 300 members who pay $100/month for facility access. It also has a mailing list of 16,000 interested people, giving you a sense of scale for this community.

Levinson is currently the Director of Development at the Hacker Dojo. She has an MSEE from Worcester Polytechnic and has worked for NASA and Google. She’s was responsible for raising $250K so that the Hacker Dojo could move to better quarters (Mountain View condemned half of the Hacker Dojo’s building, making it unusable) and she has also been responsible for getting national PR for the Hacker Dojo. Her boss, David Weekly, was supposed to deliver the lecture but he had to cancel due to an interview with CNN.

I heard many interesting and often profound things during Levinson’s talk, which I will discuss here:

“It’s easier to use a carrot rather than a stick.”

Levinson used a chore list as an example. If we give our kids a chore list, what happens? When the kids don’t do their chores, as will happen, we scold them. We then become the bad guys. “You’re mean!” and “I hate you!” are often-heard responses to such discipline. The approach is often ineffective and it’s not fun for the person holding the stick.

Levinson runs a “dorm” in Palo Alto with eleven residents. They too have a chores list (wash the dishes, take out the garbage, clean the bathroom, vacuum the carpet, etc.) Chores weren’t getting done in the dorm so Levinson raised everyone’s rent by $100/month. There’s a price list for chores and dorm residents have the opportunity to earn back some or all of their own monthly $100 and some or all of other resident’s monthly $100 by doing these chores. The carrot approach seems to be working.

“We are what we celebrate.” – Dean Kaman (inventor of the Segway and the home dialysis machine).

If you believe this, then you should be designing a culture where the right things are celebrated.

“The basis of any community is to make the first user happy.”

Then build from there. Your power scales when you have a million people who are willing to follow you anywhere. I found it significant that Levinson uses an Apple MacBook.

“The idea behind a community needs to seem bigger than it actually is. Otherwise, people get bored.”

“Overpricing your machine (your community) is a good way to make it stop running.”

People need to see immediate value coming out of the machine or they won’t follow you.

“Pray for scaling problems.” – David Weekly.

Scaling problems mean you’re succeeding, wildly.

On diagnosing your community: If you see hoarding, it’s a sign that there’s a breakdown of trust. People no longer believe they’ll see a flow of good things from your machine and they’re storing up for the expected bad times. You need to have an immediate conversation with your community when you see this before you lose your followers.

Here’s how you experience a community:

  1. Your experience = Value output – Value input
  2. If a community member perceives that the value output received is less than the value input relative to other community members, that member will become jealous. Levinson showed a video of a hilarious experiment with Capuchin monkeys documenting this jealously reaction. Two monkeys were taught to hand over a rock on command. One monkey was rewarded for performing this task with a cucumber slice. The second monkey was rewarded with a much more desirable grape for performing the same task. This happened in full view of the first monkey who only got a cucumber slice.The monkey getting the cucumber was satisfied with the reward only the first time. After seeing the second monkey consistently get a grape as a reward, the first monkey would no longer accept a cucumber slice. In fact, it threw the cucumber slice at the researcher, beat on the cage, and desperately reached through the cage to get at the grapes. It became very agitated. The 1-minute video Levinson showed is from a TED talk on moral behavior in animals.

  1. If a community member perceives that the value input is much greater than the value output received compared to other community members, that member will become resentful. “Someone isn’t pulling their weight.” When this happens, you tend to see passive-aggressive notes posted in public places: “This is a dishwasher. I am not a dishwasher. Put your plates in the dishwasher.” Levinson seemed particularly unhappy about passive-aggressive behavior in a community.

“Too often, we put too many constraints on a system too quickly.”

New systems need freedom and time to evolve naturally.

Lessons learned:

  1. Anyone who holds a stick is a bad guy. You only want carrots. Traditional societies more often use sticks.
  2. Role-based authentication is better than having one guru. If there’s only one go-to guy, that guy will get burned out and will lose interest. What happens when the go-to guy isn’t available? Problems don’t get solved. Better to have a go-to committee. Whoever answers first gets the credit. (A lot of online forums work this way.)
  3. If you need a bad guy, let the computer do it. If you don’t pay your dues at the Hacker Dojo, the computer disables your RFID building-access tag. There’s no one to have a tantrum in front of, because the computer doesn’t care. Pay your dues. Don’t make a scene. No one’s the bad guy.

“10 years of hard work will make you an overnight success.”

The chase alone must be worth the effort because the goal may not be reachable. Not everyone who moves to Silicon Valley becomes a millionaire.

Not bad for an hour’s talk.

 

Posted in Uncategorized | Tagged | Leave a comment

Timepieces behaving badly: A Tale of Two Clocks (and two bad capacitors) and a Tale of Redemption for the New Year

Let’s start the New Year with a tale of redemption. We have two bedrooms in our condo and in each bedroom you will find what eBay might call a “vintage” LED clock. One is a Timex T133T electronic desk clock with a jumbo 7-segment LED display and a trio of “Nature Sounds” for its never-used alarm. The other is a Radio Shack Chronomatic-290 AM/FM desk clock radio. Both clocks were purchased at some indeterminate time in the distant past (it looks like the Radio Shack clock radio is from the mid 1990s based on a fax-back document I found online) and both recently started to run noticeably fast. In fact, both clocks started gaining minutes per day. Now this is a pretty strange failure for plug-in digital clocks that need do nothing more than count power-line cycles to keep accurate time.

A Timex T133T desk clock and a Radio Shack Chronomatic-290 clock radio

Because of the coincident failures, I suspected that someone in the condo had started to do something funny with the power line in the building. Perhaps they were running power-line Ethernet signals that caused enough EMI to fool the counting circuits in the clock. With that suspicion, I dug out an old EMI extension strip that I’d cobbled together using an industrial EMI power-line filter, a line cord, two deep-drawn aluminum enclosure halves, a duplex outlet, and a 6-outlet power-tap expander. It was easier to start with this approach rather than ripping into the clocks. I know that I built this EMI unit in the 1970s because it has a unique push-on, push-off illuminated power switch that I could only have gotten from lab stock while working as a lab engineer at Hewlett-Packard’s Desktop Computer Division in Loveland, Colorado.

I decided to tackle the Timex clock first. I plugged the filtered power strip into the wall outlet, plugged the Timex desk clock into the filtered power, and set the time. Then I waited a day. The Timex kept on ticking all right, but it was still ticking fast. Wrong guess.

The next step was to pull the Timex apart and look for obvious signs of component failure. I pulled an unbelievable nine screws to open the case of the Timex and was pleasantly surprised to find an isolation transformer, which meant that troubleshooting was going to be a lot safer than I’d feared. Then I took a closer look at the innards. The Timex was a cabling nightmare! No way could it be built these days for any reasonable amount of money. Too much hand assembly.

There was a main circuit board with a clock chip on it, a small circuit board for the snooze bar, another small circuit board with three signal diodes and the time-setting push buttons, and yet another small circuit board with slide switches to set the alarm sounds (birds, ocean, and brook) and to dim the display (which is why we bought this particular clock model). There was also a small daughter card soldered directly to the slide-switch board at a right angle, which appeared to carry nothing more than the birds/ocean/brook sound chip. The sound board was assembled using chip-on-board technology and the sound chip lay under a lump of epoxy.

All of these circuit boards except for the snooze button and sound daughter card were joined by hand-soldered, solid-wire ribbon cables. The main board also joined to the large LED display with yet another hand-soldered, solid-wire ribbon cable. The three boards and the LED display were all bolted in place with more than a dozen screws of at least two sizes. The amount of hand-soldering required to make this clock startled my eyes, which have become acclimated to 21st-century electronic assembly techniques. It’s becoming harder and harder to remember that we once built everything this way.

Unfortunately, there were no visibly obvious component failures. I first looked for swollen electrolytic capacitors because there was a rash of bad, counterfeit capacitors right during the time these clocks would have been made. The telltale indicator of electrolytic failure is a bulging or burst top but nothing appeared amiss.

Time to take one more step up the troubleshooting ladder. It was time to get serious.

The Timex main board had but a single integrated circuit on it so that had to be the clock chip. What a strange chip! It was a 28-pin through-hole DIP (dual-inline package) package but the pins were not on the standard 0.10-inch centers. They were closer together than that. A shrunken DIP! Unfortunately, the clock chip’s part number was obscured with some sort of brown crust that looked like solder flux. A wipe down with an alcohol-soaked Q-Tip swab took care of that problem and the part number was revealed. It was an LM8560. Google told me that an LM8560 is a digital alarm clock chip and then coughed up an 8-page data sheet with some handy reference-design schematics.

Interior of Timex T133T clock with LM8560 clock chip and new 470µF electrolytic cap to the left of the clock chip

Lordy, this is a PMOS clock chip! I haven’t seen such a beast in decades. It was a good thing I was using a line filter from the 1970s because that’s precisely where you will find PMOS—back in the distant past. PMOS was big in the heyday of calculator chips and that was four decades ago. It was the original process technology for LSI devices. PMOS was supplanted by NMOS and then CMOS back in the 1980s, yet hobbyists still seem to be using this clock chip judging from what Google dredged up on the Internet.

With no obvious physical problems in sight, I had no choice but to break out my Fluke Scopemeter 97 portable scope. Naturally, it wouldn’t turn on. I opened the Scopemeter’s battery compartment and found that the NiMH batteries I’d installed a few years ago had started to salt up. Nasty. I cleaned out the batteries and the battery box and left it empty. Then I plugged the Scopemeter’s power brick back into the wall and old ’97 finally powered up. It was time for some signal probing.

A check of the clock chip’s clock input showed some reasonable—if ugly—60-cycle clocking. (At 60Hz, your clock can be plenty ugly and still work just fine.) According to the LM8560 data sheet, the power supply for this device is anywhere from -7.5V to -14V. A check of the negative power supply rail showed about -12V with some ripple—actually a bit more noise than I’d expect to see even for this simple, unregulated power supply. No doubt the 470µF, 16V electrolytic power-supply filter capacitor had started to fail. The capacitance had probably fallen and the ESR probably jumped up, but running fast seemed a funny symptom for a slightly noisy power supply rail. Perhaps the clock chip was reading the power-supply ripple as clock pulses or it might be taking the odd power supply level as a signal to use its free-running, uncalibrated 900Hz RC oscillator, which allows the clock to keep time during a brief power failure in conjunction with a 9V backup battery.

Whichever it was, my next step was to get a replacement electrolytic capacitor and install it. There are only two retail establishments where you can buy an electrolytic capacitor in 21st-century Silicon Valley on a late Sunday afternoon: Fry’s Electronics and Radio Shack. I checked on the Web and quickly found out that Radio Shack’s in-store capacitor inventory isn’t what it once was. I could order a 470µF radial capacitor from Radio Shack central and get it in a few days (I can do that on eBay, Amazon, Digi-Key, Jameco, and Element14 too) but I couldn’t drop by and purchase a 470µF capacitor at any local Radio Shack that evening. Apparently, there are now fewer capacitors in Radio Shack stores to make room for more cell phones. That’s probably a smart move on the part of Radio Shack’s management. After all, how many people still visit Radio Shack to purchase electronic components, even here in Silicon Valley? Answer: Not many.

So the choice on a Sunday evening narrowed down to just one: Fry’s Electronics.

Twenty minutes later, my wife and I were at the Mayan-themed Fry’s on Brokaw Road—every Fry’s has a theme (Mayan, Egyptian, Old West, Museum, etc.)—and we found ourselves looking at a somewhat spotty collection of blister-packed electrolytic capacitors hanging on pegs and arranged in no discernible order (like by capacitance value, which would have made a lot of sense, at least to me). By getting down on my hands and knees with my head near the floor to look at the bottom row of pegs, I finally found a radial 470µF, 25V electrolytic capacitor. The original electrolytic capacitor’s 16V rating seemed a bit low to me considering the -12V supply voltage. I usually derate electrolytic capacitor working voltages by 50% to prevent premature failures, but then I’ve never designed consumer products so I haven’t had to pinch pennies in a design. Dollars, yes. Pennies, no. I plucked the $1.69 capacitor from its peg and got back up off of the floor. We made our big purchase for the evening and returned home.

I installed the new electrolytic capacitor (checking the polarity twice), folded it over and packed it on top of two other capacitors just as the original capacitor had been positioned. I then buttoned up the Timex desk clock by reinstalling about two dozen screws in the display, various circuit boards, and case parts and then plugged the clock in for a smoke test. The clock was still ticking (figuratively, not literally) so I hadn’t let the magic PMOS smoke escape during the repair. Twenty-four hours later, the Timex was showing the right time. One problem solved; one to go.

Propelled by my first success, I cracked open the Radio Shack clock radio (only four screws this time instead of the nine in the Timex!), did a visual inspection, and got a two unexpected surprises. First, there was the very same 28-pin shrink DIP that I’d seen in the Timex clock. Yep, another PMOS LM8560 clock chip. This was too easy! The second surprise was the use of a real electronic connector to connect the switches in the top of the clock radio’s case to the circuit board. Usually in this class of product, you’ll see direct point-to-point wiring and hand soldering. Connectors generally increase the BOM (bill of materials) cost, which is a problem in many consumer-class products.

Inside the Radio Shack Chronomatic-290 showing the switch connector and the new 1000µF electrolytic cap

To make it even easier for me, I spotted a congealed black puddle next to the 1000µF, 16V filter capacitor that looked very much like cooked-out electrolyte to me. Consequently, I didn’t feel the need to confirm my analysis of the problem with the Scopemeter this time because I had a pretty good idea of what the problem was based on my experience with the Timex.

A very bad electrolytic capacitor

I rechecked Radio Shack’s Web site and, as it so happens, 1000µF electrolytic capacitors can still be sourced at your friendly neighborhood store. I bought a new 1000µF, 35V capacitor at Radio Shack for another $1.69 during lunch time the next day (appropriate for a Radio Shack clock radio, no?) and took it home after work. Certainly, I could have found a less expensive electrolytic capacitor in one of the endless cardboard parts bins at Halted Specialties just off Central Avenue in Santa Clara but gasoline costs being what they are, it was cheaper, faster, and easier to visit the Shack just down Union Street in South San Jose.

After dinner that evening, I again opened the Radio Shack Chronomatic-290 clock radio, pulled the switch cable loose, and unbolted the circuit board from the lower case. After that, it took me just a couple of minutes to desolder the old 1000µF capacitor and solder in the new one. Another few minutes and I had the clock radio reassembled. I plugged in the clock radio and it came to life. It seems that it too had retained all of its magic smoke. Twelve hours later, with sufficient time to gauge the timekeeping accuracy, I knew I had a second successful fix.

You might well ask why I spent so much time resuscitating two old LED clocks. They could easily be replaced with LCD versions for less than $20 each and my time is worth money (at least in theory). However, clocks with LED displays are increasingly rare and increasingly expensive and we prefer them in some places for high-contrast readability. Also, there’s some satisfaction in keeping yet another two pieces of “lead-tainted” equipment out of the world’s immense waste stream—at least for another few years. Besides, it’s an easy and interesting way for me to be green.

Sadly, we are increasingly unable to repair such household electronic items. That is the price we pay for the rapid uptick in capabilities we can deliver using high-density components and semiconductors fabricated using advanced lithographies. Neither of my 1990s-era clocks contained surface-mount components. Had they been newer, I might not have repaired either of them because the replacement components just can’t be sourced locally (or anywhere at all for components greater than a certain age) or because the components are shrinking to a size that can’t be easily handled with my pre-SMT-era Weller soldering station and my ancient solder sucker.

For another take on this topic, see Ira Feldman’s post on capacitors, warranties, and responsibilities.

 

Posted in Green Design, Low-Power | Tagged , , | 2 Comments

PowerPot: Cook dinner and power your USB device in the wild

The latest issue of my wife’s university alumnus magazine, Utah Engineering from the College of Engineering at the University of Utah (yes, I married an engineer), has a back-page article on two students who developed a way to charge and operate low-power USB devices from the waste heat of a backpacking cooking pot. The concept is pretty simple: interpose a thermoelectric Peltier stack between the heat source and the pot and generate electricity from the thermal differential between the heat and pot. Note that this trick only works if you’ve got something in the pot to absorb heat. Otherwise, there’s not much thermal differential to exploit.

When I first joined Hewlett-Packard in the 1970s, I discovered that there was a Peltier cooler in the preferred parts catalog. I’d not heard of such a thing and have been fascinated by these devices ever since, but it took David Toledo and Paul Slusser at the University of Utah to see the potential for a combined cooking pot and power source. Their invention is called the PowerPot.

The PowerPot is based on a conventional camping cook pot. A thermoelectric Peltier stack is attached to the bottom of the pot along with a bottom plate to protect the Peltier stack, to spread the heat, and to provide a flat bottom that sits properly on a camp stove or a burner. Fill the PowerPot with something to heat—even water—apply heat and extract electricity. The Web site currently lists only one product, the PowerPot V, which is a 1.4-liter, 5W pot. The University of Utah magazine says that there’s also a 10W pot, but it’s not listed on the site. The power generated is enough power to run an LED lamp for reading. It’s also enough to charge or power a mobile phone.

If that were all there was to the PowerPot, it might just be considered an amusing invention. However, I think there are at least two other aspects worth exploring. The first is the way that Toledo and Slusser financed their first production run. They used Kickstarter. If you’ve not heard about Kickstarter, you should study up on it. It’s a crowd-funding site initially used to fund things like art and charity projects and music CDs with little hope of profitability but Kickstarter is now increasingly used for funding initial production runs of technology projects like the PowerPot.

A Kickstarter funding campaign starts with a specific fundraising goal and usually runs for a month. Toledo and Slusser initiated their Kickstarter campaign on April 4, 2012 with a goal of raising $50,000. After six days, they’d already reached 50% of their goal in pledges. One month later when the campaign formally closed, they’d raised more than $126,000 from more than 1000 backers. Some backers pledged a few bucks just to support the idea. About two-thirds of the backers pledged enough money to receive a PowerPot from the first production run.

The second aspect to the PowerPot story is a more global one. Half of the company’s customer base is already outside of the USA and according to the University of Utah College of Engineering magazine article, Slusser and Toledo are interested in getting their invention into third-world countries as a way to provide electricity to places not yet served by a power grid. They’re doing two things to achieve this end. First, they’re developing a 1-gallon, cooking-pot version. Second, they’re donating pots to non-governmental organizations and to Engineers Without Borders. They’re also encouraging like-minded PowerPot customers to do the same.

Posted in Low-Power | Tagged , | Leave a comment