USB car charger, 2A

Posted on June 24, 2013 by gregorykimball

The more I’ve learned about switch-mode power supplies, the more amazing it seems to me.  So a voltage source across a wide range of values can be converted into another voltage, just by pulsing current though an inductor.  Of course, switch-mode power supplies are even easier to set up with ICs like this one:

IC REG BUCK BOOST, 296-17764-5-ND

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So here is my first implementation of a 2A 12V-to-5V buck converter.  The finished device hooks up to the automobile 12V adapter and outputs to four USB terminals.  Now you and all your passengers can charge your phones on the go and at the same time!

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Cree XM-L Color

Posted on May 14, 2013 by gregorykimball

This one is truly a beauty.  Here is the new RGBW high-power LED from Cree.

XLAMP XM-L COLOR LED RGBW (XMLCTW-A0-0000-00C3ABB02CT-ND)

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I got the mount from a company in France who makes MCPCBs, or metal-core printed circuit boards, and thanks to PayPal I was able to quickly get test out my new RGBW LEDs.  The picture above was taken with each LED using a 5V PWM driver set to match the camera saturation for each device.  Each one of these LED chips have wire-bonded contacts and are embedded into a single dielectric hemisphere.

Now I can make all of the colors!

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Flea market wafer

Posted on April 13, 2013 by gregorykimball

Well this week I went to check out the Silicon Valley Electronics Flea Market and I’ve never seen anything quite like it.  Collectors, hoarders and electronics gurus of all shapes and sizes gather under the solar panels of De Anza College to buy and sell just about everything.

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I even got to play the rube and ended up paying $20 for a 8″ silicon IC wafer.  I think this one was the most beautiful one the vendor had in stock:

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I think this wafer is full of processors and I believe it was taken out just after front end processing before any metallization.  Correct me if I’m wrong!  I doubt this wafer would have sold for $20 whenever it was built, but it’s worth more than $20 to me!

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Photon Battery Device (PBD)

Posted on March 13, 2013 by gregorykimball

Hey it worked!  Finally put together my new solar-powered ultra-high power LED and it’s sweet!  The solar cell is 1W and the LED runs at 2W, so for every two minutes of sun you get one minute of light!

led_pv_batterylight_on_high

The end-to-end energy efficiency is a bit low, so don’t try to string a bunch of these together with LEDs lighting up solar cells.  The LED is about 20-25% energy efficient and the PV is about 15% efficient, making the system probably 2-3% efficient at recycling light energy.  Just for fun, I added a mode to drive the LED exclusively with PV power.  Here with room lights:

room_light_led 

Long-live the photon battery device!

  • PV cell: 2 parallel strings of 12 Si solar cells with reverse blocking diode
  • LED: Cree XM-L2 with thermal substrate, basic optic  and 0.5/2 ohm resistor switch
  • Battery: 3-cell NiMH with bypass switch 

disassembled_led_pv_battery

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LED First Light

Posted on March 9, 2013 by gregorykimball

Wow, LED’s are amazing!  I just fired up my Cree XM-L2 LED with a 3-cell NiMH battery pack and a 0.91 ohm resistor to keep the current under control.  The circuit runs at 500 mA, which corresponds to 1.4 W for the LED and 0.4 W for the resistor… or 75% circuit efficiency and probably just shy of 200 lumens.  With 2000mAh batteries I should get about 4 hours of light.

 led_first_light_small

In fact I’m a little surprised I didn’t destroy that poor LED.  Surface mounting the LED to the thermal substrate was definitely the hard part.  I couldn’t get enough heat for the solder paste to reflow with my soldering iron so I had to bring out the butane lighter.  The lighter did the job after about 10 seconds, but it left a lot of charred flux on the substrate.  It may be time to invest in a heat gun!

Parts from Digikey:

  1. Cree XM-L2 cool white LED: XMLBWT-00-0000-000LT60E3CT-ND 
  2. NiMH AA batteries (3): P220-ND
  3. Battery holder: SBH331AS-ND
  4. Resistor, 0.91 ohms: P0.91W-2BK-ND

Parts from Mouser Electronics:

  1. Bergquist Company Thermal Substrates – MCPCB: 804936
  2. Reflector optic: C12512_RITA-A
  3. Wahl Solder Paste ISO-Tip: 7459
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Energy Conversion Project

Posted on February 21, 2013 by gregorykimball

led_battery_pv_small

Semiconductor devices have never been cheaper!  I picked up a 5W, 650 lumens LED for single-digit dollars, along with a rechargable 3.6V NiMH battery pack and 6 solar cells for good measure.  I think it’s going to take a lot more solar cells to be worth it but hey, as long as they are no bigger than the batteries it will be fine…

Now how likely do you think it is that I will burn out that LED?  Stay tuned…

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Q2 2012 PV Quarterly Reports

Posted on November 17, 2012 by gregorykimball

In June 2012 I compiled my research into the quarterly reports of the major players in photovoltaics, and even though Suntech still hasn’t released its final Q2 2012 numbers, I think it is time for an update.  Companies such as Suntech, Trina, Yingli, Canadian, Sharp, and Hanwha Solarone focus on revenue from module sales and so a rough idea of their cost to produce panels can be found in their production numbers and cost of revenue.

Trina and Hanwha appear to be the cost leaders with cost of revenue below 0.80 $/W and gross margins around +8-10%.  Suntech boasts a high volume with 507 MWp shipped in Q2, but the weakest gross margin of -10%.

Other significant PV manufacturers such as JA Solar, Jinko Solar, LDK, Motech and Gintech focus on revenue from poly, wafers or cells, making them hard to compare to companies listed above that focus on revenue from modules.  Companies that focus on installation and solar projects such as Sunpower and First Solar are also difficult to compare.  Maybe I’ll figure out a useful way to compare everybody by the time Q3 financials come out!

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Carpentry!

Posted on November 14, 2012 by gregorykimball

So I finally got around to making a proper spice rack for the kitchen.  The old one was overflowing and spices were falling everywhere, but luckily there is a home depot a few miles nearby.  You almost can’t see it in the picture, but there is an acrylic sheet keeping the spices from falling out, while also leaving the spice labels fully legible.

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Suggested items:

  1. Ikea spice rack (notice how the crossbar blocks the spice labels!)
  2. 4”x1” by 6′ pine board
  3. 24″x18″x0.093” acrylic sheet
  4. sand paper
  5. hacksaw
  6. plastic scribe
  7. superglue
  8. hammer & nails

Procedure:

  1. Hack apart the Ikea spice rack and take the wall mounts
  2. Hack up the board and sand it down
  3. Hack up the acrylic and sand it down
  4. Nail the board to the Ikea wall mounts
  5. Glue the acrylic to the board
  6. Gloat
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Bike!

Posted on October 9, 2012 by gregorykimball

I finally got a bike!  It had been almost ten years since I had one!  I used to ride around the gulf coast of Florida like crazy when I was a kid, but I never tried out riding when I was living in New York City or Los Angeles. During college I was only in New York for a few months at a time, and the city is so easy to get around that a bike never felt that useful.  I did borrow a friend’s bike in LA for a while, but I was turned off by roads without bike lanes and crowded sidewalks.

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This is my ’85 Schwinn Sprint, an entry-level road bike.  It was made on November 7th, 1985 in Taiwan by Giant Bicycles.  The gearing is classic 10-speed with 40/52 crankset and 14/17/20/24/28 freewheel.

With its steel frame and accessories, the tool clocks in around 35 pounds.  It’s a heavy one, but I still weigh a heck of a lot more.  So when I come hurdling down a hill pushing 30 MPH, its basically just a 170 lb mammal rushing by on top of some paper clips.  A bicycle may count as a vehicle on the road, but it’s basically an unprotected person swerving around….

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Best Fossils Ever…

Posted on September 12, 2012 by gregorykimball

So I started getting a hankering for some fossil fuels.  The good stuff: light, sweet crude oil and anthracite coal.  These are the finest fossils that the earth has to offer us, refined and smelted over millions of years.  They burn clean and pure with a clear flame and a light wisp of carbon dioxide.

What a waste that we use such a bounty for a cause as pedestrian as spinning turbines!  We should be smelting ores with the coal and making plastic from the oil!

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