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United’s Magic Trays

Thursday, September 3, 2015 

@United has new coach trays that are coated with a material that has an amazing coefficient of friction.  They are not sticky at all—there’s no adhesion effect—it is all friction.  Even low surface energy plastics don’t slide on it at all.

The approximately 75-80° angle in the picture is the point at which the cup topples over itself.  It isn’t adhered to the surface and it doesn’t appear to slide at all before toppling.

Super Friction Tray

This would be the perfect coating for a smart phone pad in a car.

Posted at 11:00:39 UTC

Category: Fabricationphotoplanestechnologytravel

Summer Blooms

Friday, July 24, 2015 

Roses Bird of Paradise Closeup Bird of Paradise Blooms Cactus Blooms

Posted at 13:41:13 UTC

Category: photoweather

Tortuga Stalking the Yard

Thursday, July 23, 2015 

Tortuga Profile

Tortuga quarter

Tortuga facing

Posted at 01:24:04 UTC

Category: catsphoto

The Avocado Tree is Fruiting

Tuesday, July 21, 2015 

A couple of years back a random sprout appeared in the yard. It looked like a volunteer avocado and grew bizarrely fast. After a few years, it is about 15′ tall and this year it fruited for the first time. It really is an avocado tree.

Avacado Tree Fruiting


Posted at 23:15:30 UTC

Category: photo

Low Voltage LED Lighting

Monday, July 13, 2015 

My kitchen has had halogen lighting for 20 years, from back when it was a slightly more efficient choice than incandescent lighting and had a pleasing, cooler (bluer, meaning the filament runs hotter) color temperature.

LEDs Installed

Progress has moved on and while fluorescent lights still have a lead in maximum luminous efficacy (lm/w), for example the GE Ecolux Watt-Miser puts out 111 lm/W, they’re less versatile than LEDs and installation is a hassle while low voltage LEDs are easy to install and look cool.

System Design

The goal of this project was to add dimmable, pleasing light to the kitchen that I found aesthetically interesting.  I wanted a decent color rendering index (CRI), ease of installation, and at reasonable cost.  I’ve always liked the look of cable lighting and the flexibility of the individual, adjustable luminaires.

I couldn’t find much information on how variable output LEDs work and what can be used to drive them.  I have a pretty good collection of high quality power supplies, which I wanted to take advantage of, but wasn’t sure if I’d be able to effectively dim the bulbs from the documentation I found. So I did some tests.

Test Configuration

I bought a few different 12V, Dimmable LEDs and set up a test configuration to verify operation and output with variable voltage and variable current.  The one bit of data I had was that using standard commercial controllers, the lowest output is typically stated to be around 70% of maximum output: that is the dimming range is pretty limited with standard (PWM/Transformer) controllers.  The results I found were much more encouraging, but revealed some quirks.

I used a laboratory-grade HP power supply with voltage and current control to drive the LEDs, decent multimeters to measure voltage and current, and an inexpensive luminance meter to measure LED output.

I measured 3 different LEDs I selected based on price and expected compatibility with the aesthetics of the project and because they looked like they’d have different internal drivers and covered a range of rated wattage.

Test Results

These bulbs have internal LED controllers that do some sort of current regulation for the diodes that results in a weird voltage/current/output response.  Each bulb has a different turn-on voltage, then responds fairly predictably to increasing input voltage with increasing output, reaches the controller stabilizing voltage and runs very inefficiently until voltage gets over the rated voltage and then becomes increasingly efficient until, presumably, at some point the controller burns out.  I find that the bulbs all run more efficiently at 14V than at the rated 12V.

As a side note, to perform the data analysis, I used the excellent xongrid plugin for excel to perform Kriging interpolation (AKA Gaussian process regression) to fit the data sets to the graphing function’s capabilities.  The graphs are generated with WP-Charts and the table with TablePress.

Watts v. Volts

This chart shows the wattage consumed by each of the three LEDs as a function of input voltage, clearly demonstrating both that the power consumption function is non-linear and that power consumption in watts improves when driven over the rated 12V.  Watts are calculated as the product of the measured Volts * Amps.  Because of the current inversion that happens as the controllers come fully on-line, these LEDs can’t be properly controlled near full brightness with a current-controlled power supply, though it works well to provide continuous and fairly linear dimming at low outputs, once the voltage/current function changes slope, the current limiting controller in the power supply freaks out.

4W LED  5W LED  7.5W LED

Lux v. Volts

This chart shows the lux output by each of the three LEDs as a function of input voltage, revealing the effect of the internal LED driver coming on line and regulating output, which complicates controlling brightness but protects the LEDs.  The 5W LEDs have a fairly gentle response slope and start a very low voltage (2V) so are a good choice for a linear power supply.  The 4W LEDs don’t begin to light up until just over 6V, and so are a good match for low-cost switch mode supplies that don’t go to zero.

4W LED  5W LED  7.5W LED

Lux/W v. Volts

This chart shows the luminous efficiency (Lux/Watt, Lumen measurement is quite complicated) by each of the three LEDs as a function of input voltage, showing that overdriving the LEDs past the rated 12V can significantly improve efficiency.  There’s some risk it will overheat the controller at some point and result in failure.  I’ll update this post if my system starts to fry LEDs, but my guess is that 14V, which cuts the power load by 20% over 12V operation with the 7.5W lamps I selected, will not significantly impact operational lifetime.

4W LED  5W LED  7.5W LED

Total System Efficiency

The emitter efficiency is relatively objective, but the total system efficiency includes the power supply.  I used a Daiwa SS-330W switching power supply I happened to have in stock to drive the system, which cost less than a dimmable transformer and matching controller, and should be significantly higher quality.  The Daiwa doesn’t seem to be easily available any more, but something like this would work well for up to 5A total load and something like this would handle as many as 40 7.5W LEDs on a single control, though the minimum 9V output has to be matched to LEDs to get satisfactory dimming. It is important not to oversize the power supply too much as switch mode supplies are only really efficient as you get close to their

With the Daiwa, driving 13 7.5W LEDs, I measured 8.46A at 11.94V output or 101 Watts to brightly illuminate the entire kitchen, and providing far more light than 400W of total halogen lights.  I measured the input into the power supply at 0.940A at 121.3V or 114 Watts.  That means the power supply is 88.6% efficient at 12V, which is more or less as expected for a variable output supply.

Increasing the output voltage to 14.63 Volts lowered the output current to 5.35A or 78 Watts without lowering the brightness at the installation (measured at 168 lux at both 12.0V at 14.6V). The input current at 14.63V dropped to 0.755A or 91.6 Watts, meaning the power supply is slightly less efficient at lower output currents (as is usually the case).

  • Overdriving the LEDs to 14.63V improves efficiency by 20%.

At the low end, the SS-330W’s minimum output is 4.88V, which yields 12 lux at the counter or a 14x dimming ratio to 7% of maximum illumination, a far better range than is reported for standard dimmer/transformer combinations.


Raw Data:


(MS Excel file, you will need the xongrid plugin to update the data as rendered in the graphs)

Posted at 02:45:36 UTC

Category: FabricationphotoPositivereviewstechnology

Basra Snow Storm

Sunday, February 8, 2015 

I was feeling a little left out, reading posts by people digging out of snow storms and here I am in Basra where it gets down to 10C at night sometimes and usually hits the mid 20’s during the day.  Rough.  But the weather here came through with our own sort of snow storm.


Blizzard Brown-out conditions

Starting to look like a brown-out!



Snow covered yard furniture!


Obligatory shot of the yard furniture getting covered.


I've got snow on my head!


Kitty’s head is starting to show some accumulation.


Can't see more than a few hundred meters with this snow!


With all this blowing through you can barely see a few hundred meters!


starting to accumulate!


It’s really starting to accumulate. Where’s the snow blower?


Takes special cleaning to get that snow off.


It takes some special cleaning after playing out in it.

Posted at 06:20:38 UTC

Category: catsphotoplacestravelweather

Cat Watch

Monday, February 2, 2015 

Cat Watch
The twins resting after a busy day.


The Twins

Posted at 17:48:24 UTC

Category: catsphototravel

Lizard Visit

Saturday, January 31, 2015 

A New animal visitor came by today.

Gecko Top
Just hangin’

Gecko Face


Posted at 14:00:58 UTC

Category: photo

Merry Christmas from Gaylords

Wednesday, December 24, 2014 


Posted at 14:47:42 UTC

Category: Eventsphoto

The East Bay Hills

Tuesday, December 23, 2014 


Posted at 17:38:00 UTC

Category: photo