Positive

Green Lacewings

Sunday, January 10, 2016 

I noticed that my avocado tree was developing brown spots on the leaves, which were almost certainly the result of Persea mites.

Leaf Symptoms

 

So I looked up some possible cures, and it seemed like introducing a predator would be the best option and the least hassle.  I’d had good luck with introduced ladybugs a few years back, which formed a stable population that survived for many years after introduction.  For this pest, green lacewings are recommended.  I found a nearby insectary that could provide larvae on cards and they shipped them overnight.

Green Lacewing egg cards

 

 

The little guys look cute just waiting to hatch…

Green Lacewing Eggs

 

I hung he cards on the leaves of the tree after incubating them overnight in a warm room, and they should hatch sometime in the next day or two, as long as the ants don’t find them first…

Card in tree

 


Update 8 Sept 2016:

The green lacewings seem to have eaten all the mites.  It has been 9 months and there aren’t any signs of damage to this spring’s leaves.  Yay!

No mite bites

The new leaves that grew seem to be developing without any bites at all.  The old leaves that were too damaged have fallen off, but the surviving older leaves still show the scars of the mites.  Green lacewings seem to have done the trick.

Posted at 14:40:47 UTC

Category: photoPositivereviews

Signal Desktop: Probably a good thing

Tuesday, December 8, 2015 

Signal is an easy to use chat tool that competes (effectively) with What’sApp or Viber. They’ve just released a desktop version which is being “preview released/buzz generating released.”  It is developed by a guy with some cred in the open source and crypto movement, Moxie Marlinspike.  I use it, but do not entirely trust it.

I’m not completely on board with Signal.  It is open source, and so in theory we can verify the code.  But there’s some history I find disquieting.  So while I recommend it as the best, easiest to use, (probably) most secure messaging tool available, I do so with some reservations.

  • It originally handled encrypted SMS messages.  There is a long argument about why they broke SMS support on the mailing lists.  I find all of the arguments Whisper Systems made specious and unconvincing and cannot ignore the fact that the SMS tool sent messages through the local carrier (Asiacell, Korek, or Zain here).  Breaking that meant secure messages only go through Whisper Systems’ Google-managed servers where all metadata is captured and accessible to the USG. Since it was open source, that version has been forked and is still developed, I use the SMSSecure fork myself
  • Signal has captured all the USG funding for messaging systems.  Alternatives are not getting funds.  This may make sense from a purely managerial point of view, but also creates a single point of infiltration.  It is far easier to compromise a single project if there aren’t competing projects.   Part of the strength of Open Source is only achieved when competing development teams are trying to one up each other and expose each other’s flaws (FreeBSD and OpenBSD for example).  In a monoculture, the checks and balances are weaker.
  • Signal has grown more intimate with Google over time.  The desktop version sign up uses your “google ID” to get you in the queue.  Google is the largest commercial spy agency in the world, collecting more data on more people than any other organization except probably the NSA.  They’re currently an advertising company and make their money selling your data to advertisers, something they’re quite disingenuous about, but the data trove they’ve built is regularly mined by organizations with more nefarious aims than merely fleecing you.

What to do?  Well, I use signal.  I’m pretty confident the encryption is good, or at least as good as anything else available.  I know my metadata is being collected and shared, but until Jake convinces Moxie to use anonymous identifiers for accounts and message through Tor hidden nodes, you have to be very tech savvy to get around that and there’s no Civil Society grants going to any other messaging services using, for example, an open standard like a Jabber server on a hidden node with OTR.

For now, take a half step up the security ladder and stop using commercial faux security (or unverifiable security, which is the same thing) and give Signal a try.

Maybe at some later date I’ll write up an easy to follow guide on setting up your own jabber server as a tor hidden service and federating it so you can message securely, anonymously, and keep your data (meta and otherwise) on your own hardware in your own house, where it still has at least a little legal protection.

 

Posted at 10:21:22 UTC

Category: PositivePrivacyreviewsSecuritytechnology

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 rated output.  An oversized switchmode power supply can be extremely inefficient.

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; I 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 12V rated LEDs to 14.63V improves plug 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.

Parts

Raw Data:

LED_power_graph_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

Futurama is Awesome

Saturday, January 5, 2013 

I learned two things about Futurama recently which added to my already deep appreciation for the show. The first is that the theme song came from a very cool song by Pierre Henry called Psyche Rock from 1967, which is on youtube. It was remixed by Fatboy Slim in an appealing way.

But what was most interesting recently was to see episode 10 of season 6, the Prisoner of Benda, a spoof of the Prisoner of Zelda but including what may be the first tv-episode publication of the proof of a relatively complex mathematical theorem in group theory as a core plot element.

Prisoner_of_Benda_Theorem_on_Chalkboard.png

The problem in the plot is that the Professor’s mind swapping machine creates an immune response which prevents swapping back in one step. So how do you get everyone back to into their original bodies? Well, as Sweet Clyde says, it takes at most two extra players [who haven’t swapped yet]. As the entire cast, including the robo-bucket, have swapped bodies, the situation is pretty complex, but fortunately one of the show’s writers, Ken Keeler, has a PhD in applied mathematics from Harvard and found a proof, which is actually shown in the show (above), and then worked in a fast montage that restores everyone.

In the following table, the heading shows the character name of the body, row 0 shows the occupant of that body by the end of the plot’s permutations and before the globetrotters start the transformations. Rows 1-7 show the steps to restore everyone to their original bodies.  Each transformation was animated as a pair using the two “extra players” except the last rotation to restore Sweet Clyde and the Bucket.

Posted at 16:34:18 UTC

Category: filmsPositivereviewstechnology

2012 Mitsubishi Spyder

Thursday, November 10, 2011 

Hertz gave me this very nice little convertible as a rental when I found my allocated slot empty and they didn’t have my allocated class in the lot, a nice upgrade.IMG00291-20111110-1653.jpg

It has two defining features:

  • it is a convertible and a sporty one at that,
  • it comes with a subwoofer equipped stereo which defines the target market.

This is definitely not a car targeted at classical music listeners. The stereo with the fosgate “punch” setting cranked up is a base heavy “boom car” experience. It sounds fine, the base is clean and well rendered, but it isn’t the balanced, well staged clarity of the sound system in a Mercedes, for example, but fits a particular demographic well.IMG00290-20111110-1622.jpg

The car itself is quite sporty and handles well. Unlike a lot of lower end convertibles, including the Mustang, the body is very stiff and and takes turns and bumps without any tangible body flex. The car corners flat and understeers predictably and with good control (I discovered unintentionally while making a quick u-turn). The car also has more power than one would expect for such a small vehicle, and can spin the back wheels from a stop without resorting to a neutral drop, also an unintentional discovery. Really.

Road noise with the top up is pretty good for a convertible, and better than most at freeway speeds with the top down.

I’d say it is a pretty good choice for a low cost, youth-oriented convertible.

Posted at 20:35:54 UTC

Category: photoPositiverental carsreviews

Fantomatik Orchestra at Borgo a Mozzano

Thursday, November 3, 2011 

The Fantomatik Orchestra performing at Halloween at Borgo a Mozzano

[youtube]http://www.youtube.com/watch?v=FZc_5GvsqSk[/youtube]

That’s our local butcher dancing with the cow’s head and eyeball.

(on youtube the video is available in 1080)

Posted at 04:03:03 UTC

Category: GeopostplacesPositivereviewstravelvideo

Scrapper

Thursday, October 20, 2011 

I went to see Scrapper, the documentary by Stephen Wassmann, that was showing as part of the SF Documentary Film Festival.   It is the story of the people who live between the Salton Sea and the Chocolate Mountain Bombing Range and make a living gathering scrap metal off the range between bombing runs.

It’s quite a frank and intimate portrayal of some extremely eccentric characters.  They spend their time divided between driving around the range gently prying the aluminum tail fins off unexploded ordinance, heating the booty over open fires to loosen the scrap-value-reducing steel rivets, and doing crystal meth and drinking, though the last activity isn’t so much divided from the former two.

The most entertaining character is an old guy who set up camp on the isolated East side of the range, far from humanity, and cruises around the range in a highly modified VW bug living a life pretty much straight out of the Road Warrior.

It is definitely a movie where every moment seems to balance precariously on the edge of a ravine or on a delicate trip wire on a 2,000# bomb that failed to release when it buried itself fins-deep in the desert sand.

[vimeo]http://vimeo.com/11457549[/vimeo]

Posted at 04:18:18 UTC

Category: filmsGeopostPositivereviewsvideo

Latte Art at Gaylord’s

Saturday, October 1, 2011 

Sent via BlackBerry by AT&T

Posted at 14:30:37 UTC

Category: funnyPositivereviews

TFF38D2F4 The Kid With A Bike

Monday, September 5, 2011 

The Kid With A Bike is a film by the Dardenne brothers, who brought “The Child” to the Telluride Film Festival a few years back. There is a strong family resemblance between the films: durable but trouble prone protagonists in gritty, lower class struggles where their every step forward seems to result in a step back and who’s troubles are mostly self-inflicted, and yet sympathetic and identifiable responses to difficult circumstances.

Thomas Doret plays a little boy named Cyril who’s proof to all external harm, but victim to the internal consequences of being abandoned by his father. He is adopted by an attractive and indomitable hair dresser played by Cecile de France who has an affinity for Cyril that seems driven by something strong, but offscreen.

The story moves Cyril from victim to victimizer and finally to redemption in a way that is satisfying and compelling.

Posted at 00:36:35 UTC

Category: filmsPositivereviews

TFF D1F3: Albert Nobbs

Saturday, September 3, 2011 

Albert Nobbs is an great film.   See it.

It is the story of a curious butler in 1890s Dublin who suffered a difficult childhood and to survive took a job as a waiter, and the worked his way up to being a butler in a small but swanky hotel.  The thing is, he’s a woman played by Glenn Close.

His carefully controlled life is turned upside down when he has to share his room with a painter working on the hotel and his view of the world and of his own future changes dramatically.

Glenn Close introduced the film an described it as a labor of love that she has spent 15 years working on.  Her acting is superb and the story is very funny when it tries to be and truly touching without being cloy or saccharine.  While Glenn’s performance stands out, none of the cast come up short and Janet McTeer is also particularly strong.

Posted at 00:52:45 UTC

Category: filmsPositivereviews