Engineering in Reverse

Hanging out in Rumney

2012-01-08T13:40:00.000-08:00

After leading nothing below 5.10 all weekend, Giuseppe attempts the upside-down second pitch of Giant Man (5.12 b/c) in Rumney's Hinterlands...

The nice thing about sport crags is that there's bolts everywhere - perfect for setting up photo ops. Here is our protagonist looking good on the approach:

Behind the scenes exclusive:

And hanging out, looking for the move...

Why LED Christmas Lights Flicker (on camera)

2011-11-06T14:11:00.000-08:00

This is a problem that I was wrestling with a little over year ago, building an LED prop for a friend's movie. That was before I started taking math classes...

To simplify it, many "efficient" light sources are efficient because they flicker- they are not constantly "on" like incandescent lights. Filmmakers love incandescent lights because they don't flicker (see note).* More efficient sources like HMI's are very carefully engineered to flicker in sync with the camera shutter, so that the camera doesn't notice the flicker. And most LED light sources are battery powered with a constant DC voltage, so there is absolutely no flicker.

This is where we come to the problem of LED Christmas lights- long strings of LED lights in series, that plug into AC power. LED's don't normally run on AC power because the voltage is too high, and LED's are at their hearts, diodes, which means they only pass current in one direction. Most LED circuits you plug into your wall go through both a transformer, to step down the voltage to a safe level, and a rectifier, to invert the negative half of the AC wave, and provide a constistent DC power supply.

But LED Christmas lights are an ingenious solution to this problem... almost. They take 60-70 LED bulbs, and wire them in series. LED's tend to drop about 1.2-2.0 volts individually, but put 60 in series, and you've got yourself a circuit that can drop 120v. That eliminates the transformer (wall wart) from the equation. However, it does not adequately address the flicker problem. LED's are still diodes, and if you have 60 of them, all pointing in the same direction, they will only be "on" when the AC wave is positive. That means, they will only be on for half of the AC wave.

You may notice this flicker if you look with the corner of your eye. The first time I noticed this was rigging on the set of a pretty big movie that will go unnamed. If you can see a light source flicker with your eye, a movie camera will definitely pick it up, and possibly ruin the shot (I wonder how much it cost to fix that...).

That's because movie cameras generally shoot at 24 frames per second, and the shutter speed is 1/48 of a second. That means that the camera only sees HALF of the time you're filming (they say half of every movie is darkness), and the camera ONLY sees things 1/48 of a second at a time. This being a film camera with a mechanical shutter. Digital cameras (and digital shutters) make things even weirder.

Hence, some math:

I've approximated the 60Hz AC power with the red sine wave, and the 24 fps camera shutter with the green sine wave. The LED's are only on when the red wave is positive, and shutter is only open when the green wave is positive (shutter speed is calculated from when the shutter is half-open to half-closed, probably because it's constantly moving).

So each positive half-wave of the green curve is one frame in the movie. The exposure (brightness) of the LED's in each frame would be equal to the intersected area beneath both curves, when both are positive. Keep in mind there are 24 frames per second:

This is done by adding up piecewise integrals. A1 is the "brightness" of the first frame, and A2 is the "brightness" of the second frame, which is slightly more than the first. Keep in mind these are abstracted, and don't actually correlate to any real measure of brightness. However, the proportions should be accurate, and Frame 2 is 18% brighter than Frame 1. That's not good.

Another interesting thing is that 5 AC power cycles = 2 camera shutter cycles. The waves line up every 2 frames, or 5 flickers. So all the even frames are the same, and all the odd frames are the same- which means every other frame is 18% brighter than the one before it. There's your flicker!

Thanks to Maple for doing the heavy lifting for me. I need to figure out how to code in Maple. It would make my life much easier...

*Note: Incandescent lights also "flicker" because they are on AC power, but they are so hot (read: inefficient) that the flicker is negligible.

RoboRadar

2011-08-24T01:18:00.000-07:00

Working on making a radar type sensor with a Parallax rangefinder mounted on top of a servo motor. Left is raw distance data (2-300 cm), drawn in polar coordinates, and right is *supposed* to be corrected into rectangular coordinates. But they look eerily similar so I'm not sure that's working yet.

But the big accomplishment is the beginnings of an object detection system, as note by the white boxes. Basically if the points are close enough together, there must be an object there.

The problem is figuring out how close is close enough. As you can see, there are lots of tiny boxes that should probably be combined into one big box, as well as really big boxes that are overlapping smaller discrete objects.

Too many little boxes are a problem for memory & speed (right now it's sensing over 4,000 objects, but there are only 90 dots!). It would make more sense to combine them into one "wall" object, with the same effect.

The really big box is a problem, because the robot would see that entire area as an object, and avoid it; it would never move forward.

The moral of the story: weak object detection makes for slow, paranoid robots. Smarter = faster = more risk tolerance = more exploration!

Richard Serra Driving

2011-08-23T19:25:00.000-07:00

Pieces of a Richard Serra sculpture driving toward the George Washington Bridge...

Finally, some art in the suburbs...

Inspecting the Internet Plumbing

2011-07-28T22:50:00.000-07:00

Ever wondered how a website gets from there to here? Me too.

Especially when "there" is halfway around the world...

The Black Dot is Brooklyn (because Brooklyn is too cool for silly colors). The white dots in the upper right are a website in Italy. The other white dots are the servers in between that the website had to travel through to get to me.

The signal went from New York to New Jersey (which are so close they overlap), to California out left, and then magically to Italy.

Pay no attention to the line going straight through the Earth. I actually have no idea how the signal got from California to Italy. Must be either a satellite or an underwater cable... but an underwater cable wouldn't go direct to Italy... very curious indeed.

Also, the white dot on the lower right is an anomaly. It actually represents the IP 0.0.0.0, which is a dummy IP (which I believe is my computer talking to my router). Since it's a dummy IP, it was assigned (0,0) as a location, and so it pops up at the intersection of the Prime Meridian and the Equator.

Other points of note are Greenwich, England (green dot on the Prime Meridian), and the Magnetic North Pole (yellow dot on the yellow meridian). The rest are cities around the world.

At some point I will have to figure out how to add continents and draw arcs around the world rather than tunnel straight through it... however convenient that might be. For some reason my problems keep coming back to moving things around spheres...

A Different Perspective

2011-04-30T21:49:00.000-07:00

Finally getting things to line up... but the perspective is not quite right. It looks fine on the top half of the mountain, but the horizontal trail should be much lower; in fact, part of it is behind the camera, which just ain't right...
This is the same view with placemarkers drawn in: the green cross is the GPS peak of Blackhead, which is the point where the photo is inserted. The red cross is the camera position (with compass and XYZ directions drawn in), and the pink cross is the peak of Black Dome mountain. There enlies the problem-

This is a side view of the whole thing, looking North. The red cross is still the camera, and the white line is where it's looking. Black Dome is behind the camera, but somehow the camera still sees it. I think this has to do with the ortho() function, again because the perspective on the path is not quite right. I've tried adjusting the clipping planes, but that doesn't change the perspective, only what renders and what doesn't render. So how the camera is seeing behind itself, I don't know...

But this is what it looks like with the "standard" perspective:

And this is where I think the trail should be:

Into the Void... aka Progress!

2011-04-27T15:34:00.000-07:00

Making progress orienting the OpenGL virtual camera, and fixed the rotation of the image so it's [very nearly] square to the virtual camera. Note to self: degrees are not the same as radians.

In theory, all I need to do is make some fine adjustments to the image orientation to compensate for the pan and tilt of the real camera (when the picture was actually taken). And then get it to scale properly- the image should take up the whole gray area. And hopefully the perspective will correct itself with the scaling... hopefully being the key word.

Blackhead (annotated)

2011-02-23T14:59:00.001-08:00

This is Blackhead Mountain in the Catskills, from a lookout on Black Dome, and somewhere in the middle is the trail that links the two. If I can figure out the scale of the photo, and the direction that the camera is pointing, I can use my GPS log to draw the trail.

I know the GPS position of the Blackhead peak and the camera, and using those I can calculate the distance and bearing between the two. But since the peak is off center, I need to figure out the direction the camera was pointing, even though it's only off by a few degrees.

The peak is offset by 114 pixels horizontally (the black triangle). If I can figure out the scale of the photograph accurately, I can use this to figure out angle the camera is pointing. Of course, the original image is much larger, but the ratios should stay the same.

If I can figure out the scale and rotation of the image, I should be able to line up the GPS log of the trail with the picture...

This is a crudely oriented view of the GPS trail. The red cross is the camera position, and the green cross is the peak of Blackhead. So all I really need to do is line up those two points over the picture... simple enough, right?

Ultimately it should look something like this, but with more picture and less black void...

Mt. Hight, New Hampshire

2011-02-07T20:54:00.000-08:00

3D view
Elevation vs. Time

Total Time: 5:51:49
7.93 miles
1.36 miles / hour (not taking stops into account)

1472.1 feet (base elevation)
4706.5 feet (peak elevation)
4079.3 feet (elevation gain)

Red: <>Yellow: <>

Green: > 1.0 m/s

Eclipse Timelapse- Second Attempt

2010-12-27T09:22:00.000-08:00

Heard there was going to be an eclipse, so I broke out the 5D and tried my very best to catch it.

This is one frame every 30 seconds, starting around 2:30am and going for about an hour and a half, using a 105mm lens.

Timelapse is complicated because you really can't recompose in the middle of a shot- you have to plan it out ahead of time, lock off the tripod, and cross your fingers. Or build a motion control rig- maybe next time...

The moon was much smaller at 3:30am than it was earlier in the night, so I zoomed all the way in, and the moon was still tiny. This reduces the frame size which is why it kept falling out of the frame. Luckily I caught it, and for lack of anything better to do, recomposed the shot.

I also made a big no-no by changing the exposure toward the end (when it gets redder), which kind of killed the subtlety of the eclipse... but after seeing this, I have a lot more faith in the low end of the 5D's exposure range.

Next time I think I'll try shooting earlier in the night, when the moon is huge, so I can use a wider lens. It will probably take a few more tests to get a feel for the passage of the moon, so I can frame it better.

I need to make friends with an astronomer, and practice some more before the next eclipse...

Pictures!

2010-12-17T11:35:00.001-08:00

Updated the Elevation Profile part of the program... same GPS Log (Catskills Blackhead Range) with new graphics & live animated elevation marker...

Will elaborate later, but here's some pictures for now!

Hiking the Catskills in 4D!

2010-11-01T14:52:00.001-07:00

This past weekend I had my first introduction to what is known among the hiking community as "Peak bagging". From wikipedia:

Peak bagging (also hill bagging, mountain bagging, Munro bagging, or among enthusiasts, just bagging) is an activity in which hillwalkers and mountaineers attempt to reach the summit of some collection of peaks, usually those above some height in a particular region, or having a particular feature.

We bagged three peaks, two of them twice, since we had to retrace our route to get back to the car. This is known as a lollipop loop:

This is the overhead 2D map view. Latitude vs. Longitude. Pretty simple. And now that I finally have some interesting altitude data, I started working on the third (and, inadvertently, fourth) dimension to my program-

This is the Altitude Profile of our hike. Altitude vs. Time. If you notice, the first two peaks and last two peaks are nearly mirror images of each other, which is an interesting result of the lollipop loop.

The heights of the peaks are the same, but the widths are different, probably because I was going faster on the way out. It was starting to get dark...

So, now I have two 2D abstractions of our hike. Now, all I need to do is mash them together (that's a technical term) and I'll have 3D!

Better Late than Never?

2010-10-28T05:38:00.000-07:00

All's I'm saying is... nevermind...

Shooting the Moon

2010-10-09T09:37:00.000-07:00

Live-blogging the shoot!

Using Processing to control the moon. The physical controls are nice, but limited in their capabilities. Very handy for Backpack Mode, so the kid can run around in the woods with the thing. But Processing allows for much more fine control, and better random number effects (and processing speed!) too.

Moon Timelapse Test

2010-10-01T11:51:00.001-07:00

Shot this "manually" by holding down the shutter button until the memory card got full, hence the jumpiness. Or as I like to call it, the "hand-cranked aesthetic".

Just one more reason to get back to work on the Arduino intervalometer- Check out the Camera Axe page for more info.

The beautiful thing is that the original images are really big- 21 Megapixels big, in fact. 35mm movie print, anyone?

IT'S A BOY!

2010-09-28T20:49:00.000-07:00

I think I'm going to call it Red, short for "The Great Red Shark". It's fast. Of course, I dropped it within 5 minutes of leaving the store, but scratches build character.

And it's recycled, kind of. At least the frame is. Most of the important parts are new, which is a good thing. Custom built by Brooklyn Bike & Board. Same day service, who would have thought?

All this (and a lock!) for $100 less than my old bike. I feel like I might wind up spending less on the bike, and more on locking it up... but that's the world we live in, unfortunately.

For more information on how to tell a boy bicycle from a girl bicycle, ask your parents.

So it goes...

2010-09-23T05:37:00.000-07:00

If ever I was going to eulogize an inanimate object, this would be the one. But a bicycle is hardly an inanimate object. A bike embodies the phrase "I want to go fast." In the words of the late Kurt Vonnegut, so it goes...

[Cue sappy music and "trip down memory lane" montage]

This was the day I rode all the way to the end of Bedford Ave. Note the boat in the background. Not pictured: the Applebees on the corner. Nobody wants to see that...

Manhattan Beach, same day.

The greenest grip truck in the city. Not going to lie, this was a little unwieldy, but I didn't have far to go.

Battery Stuff

2010-09-18T21:37:00.000-07:00

Just a note- using a DeWalt XRP 14.4v battery for the "Backpack Mode" moon (portable & self contained, so the kid can run around with the moon lit up).

Ran most of the day. Forgot to meter the battery at the start of the day, but about halfway through the day, it metered 15.7v, and by the end of the day it was only down to 15.6v. I guess the LED load pales in comparison to the DeWalt drill motor... I have a feeling this will last for a while, despite not having done the math to confirm this fact...

Also can't find the mAh rating for the battery, but maybe I'm not looking hard enough.

Shoot day 2 coming up... just found out the moon has to get wet. That should be fun...

The Controls for the Heart of the Moon, v2.0

2010-09-17T01:11:00.000-07:00

04:17am Sept 17- Finished the enclosure, and [hopefully] all the troubleshooting for the controls. Not taking it apart again, it took long enough to squeeze it in there...

I feel like I'm back in school pulling an all nighter to finish a project on time... which is pretty much what I'm doing, minus the school part.

I promise better pictures, and better writing, after I get some sleep...

Good night.

EDIT 00:43am Sept 18:

Four hours of sleep, then driving two hours to stay at a friend's house to make a movie for the weekend. I feel like I'm in college again... oh wait, I am.

Much progress tonight... figured out, in record time, how to get Processing to control the Arduino dimmer (and thus push my painstakingly constructed hardware controls into obsolescence, almost).

The manual controls will suffice for simple "breathing" effects loops, and they're key for self-contained Backpack Mode, but being able to control the finer aspects of the dimming cycle from Processing will really come in handy when we get into making the moon act like it's sick on the next shoot.

Figured out why the dimming has been so jerky- I've had it outputting a lot of debug data over Serial, which has been slowing down all the loops. So now that it's working, I don't need the debug data and now it's much smoother- italics used to emphasize smoooooothness.

The one issue I'm having (and it very well might be a software bug...) is that the new TIP31 transistor is not behaving the same as the old one... it seems like it goes from 0-100% brightness in the first 10 or so steps of the PWM (of 255 steps)-

MS Paint is probably the only thing I miss from my Windows days...

So we have the batteries charged and are gearing up for Shoot Day 1 tomorrow... time for bed.

Security Through Obscurity

2010-09-07T20:55:00.001-07:00

Had to return the camera from the wedding today... Decided I didn't feel like attracting attention to myself carrying thousands of dollars worth of borrowed camera equipment through my neighborhood, after our rental car was broken into recently and we lost a lot of important stuff.

Turns out my hypothesis was right- people don't seem to pay much attention when you're carrying an awkwardly heavy garbage bag through Brooklyn. And if someone does ask what's in the bag, tell them it's stuff infested with bed bugs... that'll make 'em think twice before they try to steal it.

If Film Crews Ran the World...

2010-09-05T21:23:00.001-07:00

I've discovered that having a background in show business really comes in handy when your best friends decide to throw a backyard wedding on three weeks' notice.

Compared to the long hours and stress of producing multi-million dollar films and television shows, a wedding is a piece of cake.

I did the lighting, video, and a significant portion of the photography for the event, as well as AD-ing (Assistant Directing, or keeping things on schedule, for those of you not in the biz), and impromptu sound reinforcement, and I must say I'm really proud of the results. It was also helpful having a TV producer on the bride's side of the aisle.

My elaborate spiderweb of rope and wire caused some palpable amount of anxiety for the bride and groom at first, and understandably so. Things aren't always pretty behind the scenes-

But I told them, "Hey, trust me, I'm a professional," with all the inflated self-assuredness I could muster, and a big wink at the end, to instill confidence and calm their fears.

We couldn't put up all the China lanterns until the day-of, for fear of rain (and hurricanes), so we didn't know how it would all look until it finally got dark...

The bar/dance floor, looking toward the garage. The ceremony was under the grape leaves in front of the garage, with a wall of French doors and beautiful silk drapery to set the scene. (I'll have to find pictures of it, as my eye was glued to the video camera for that part.)

Wide shot of the back yard/seating area, and the pool with candles floating in it. Surprisingly none of us drunks fell in, on purpose or by accident...

Roughly 580 watts of China balls... outside was actually brighter than inside. I actually threw out a quick-on plug and replaced it with a real 15-amp plug after realizing the tiny quick-on contacts were kind of a fire hazard... I think in total we pulled a respectable 15 amps... not bad for a bunch of Christmas lights.

The wedding cake(s). Pay no attention to the only dead string of lights behind it. The candlelight is prettier anyway.

The happy couple, and the presiding minister/brand new sister-in-law. I think they approve.

Eat your heart out, Nextel.

Christmas in August

2010-08-31T05:57:00.000-07:00

Doing the lighting for my friends' wedding next week... used to having a whole grip truck's worth of rigging hardware at my disposal, but unfortunately that's not in the budget for this one. So back to basics... good ol' Boy Scout knots:

I was inspired primarily by the Big Bambú exhibit at the Met, and my primal yearning to build something using only rope...

The lashing was also inspired by my innate distrust of the structural integrity of zip-ties... they're great for re-attaching body panels to your car (which I've done many a time), but you have to keep in mind that they periodically snap & need to be replaced... which is not really an acceptable solution for rigging lights over 80+ peoples' heads. Even if they're just China lanterns–

This is the end of Day #2, with roughly 25% of the lights are hung. That means 75% more awesomeness next week. And a real camera to actually do it justice...

Hey ConEd, wanna make some money?

2010-08-15T10:08:00.000-07:00

Here's an idea- drop some power outlets for street vendors. You know, the food carts and ice cream trucks that sit there, idling their gas- or diesel-powered putt-putts and stinking up the whole block. Who wants to eat street meat smoked in diesel fumes?

Do something that's actually green for once. It would make your claims of environmental friendliness just a little bit more credible. Taking advantage of existing infrastructure to eliminate hundreds of engines (with unregulated emissions!) is pretty damn green, no?

Once you get that all set up, make it illegal for them to run gas powered generators on the street. It's already illegal to idle your car in a school zone (though it should be illegal to idle your car everywhere)... Why should we let them run their generators all day in public places?

And I'm sure you guys can figure a way to bill them for the power. If there's one thing you guys are good at, it's billing. Be creative! And they'd be instant customers, since you guys already monopolize the power grid here.

And the vendors would probably benefit from this too. They'd have healthier working conditions and quieter carts. They'd probably even save money on power and fuel, so long as ConEd doesn't decide to gouge them too hard. And they'd have some extra space in their carts, once they dump the putt-putts.

So, ConEd, you have the power, now put it to good use!

[Pun intended, grudgingly.]

Hiding Things in Plain Sight

2010-08-14T13:17:00.001-07:00

Spent several hours last night searching through the Android Source Code for their method of calculating GPS distances, to use in a Processing sketch I'm working on... very frustrating. If I knew what I was doing, I might have known intuitively where to look, but searching through an entire operating system worth of code is a very imposing task for an amateur. The Android javadocs are great, but a direct link to the source code would be very helpful.

Finally I came across this seemingly obscure forum, and without further adieu, the Android Java Core source code: platform/frameworks/base.git

And for those interested in the GPS capabilities, the Location class source:

platform/frameworks/base.git/location/java/android/location

The distanceTo() and distanceBetween() functions are part of the Location.java class, and both make use of the private computeDistanceAndBearing() function, which is certainly complex enough to justify having spent so long looking for it...

Anyway, the whole purpose of this is to make pretty pictures-

This is one of the early tests, just riding my bike, using GPSLogger for Android. I love this one, and the beauty is that it's completely unintentional. I just went for a bike ride around the park and through the neighborhood, and this is what came out.

The high point on the far left is a random GPS anomaly (read: error), but it really makes the picture. I think it looks like a fairy about to whack someone on the head...

This one is a little more somber and a little less whimsical, but also something that just fell randomly into my lap-

This is a test run of the Wikileaks Afghan War Diary files (specifically, the NATO file). I was completely floored to find out that this huge dump of classified information was made available in the exact same KML format I've been building my GeoGrapher program around. And I only had to change one line of code for it to work.

The Wikileaks files are much more detailed than my personal GPS logs, with information on events, how many missing, killed, detained, etc. which, politics aside, are an incredibly rich resource for creating visualizations of the data.

Damn I really wish I had a headphone splitter lying around somewhere...

2010-08-04T10:29:00.000-07:00

Good thing I ordered a bunch of extra 3.5mm stereo jacks :)

A few more parts and I'll have my own mini-DI box!

FYI: If you turn up the gain (volume) all the way while recording to QuickTime, your computer CAN create feedback. Though this was not your normal high-pitched-glass-shattering feedback, it's more like runaway white noise (static) steadily increasing in volume. I did manage to kill it before it got out of hand, but I am curious as to where it was heading...

Perhaps the greatest tragedy of this weekend...

2010-08-01T13:31:00.000-07:00

Coffee aficionados (addicts) know how important it is to squeeze all the air out of the bag (using the convenient one way valve vacuum valve built into all coffee bags worth your time)... and environmentalists know how important it is to buy Fair Trade Organic coffee in biodegradable bags.

This particular coffee bag happened to be of the biodegradable plastic variety and ostensibly environmentally sound. However, it turned out not to quite as structurally sound, as the seam failed catastrophically as I was attempting to evacuate the air inside.

Upon forensic investigation, it appears that the one-way pressure relief valve (aka blowout preventer) failed to perform its eponymous task. Consequently, as the external pressure increased rapidly, the internal pressure increased proportionally, exceeding the maximum pressure rating of the adhesive used to seal the seam of the bag.

This internal pressure built up so rapidly that the seam ruptured, and the particulate contents of the bag were forcefully ejected in projectile motion.

I intend to take full responsibility for this accident and will be setting aside an escrow account to compensate all legitimate claims of damage from this unfortunate event, including iced-coffee shortages and related caffeine headaches. But I must stress that local tourism and beaches will not be affected by the spill and I encourage anyone who has booked vacations in the area to continue with their plans and come support this great kitchen.

The only saving grace of this unfortunate accident is a potentially new breakfast condiment:

That is not black pepper. That, my friends, is an omelette impregnated with high-velocity aerosolized coffee grounds. And it was wonderful.

New York, I love you, but you're bringing me down...

2010-07-30T18:33:00.000-07:00

Long story short, while loading up for the shoot this weekend, we left the rental car unattended, in broad daylight, on a busy street, for no longer than 5 minutes, only to return to a smashed window and a few bags missing.

Unfortunately, those bags happened to contain the director's laptop and personal effects, the cinematographer's Canon 7D, $3,000 worth of rented lenses, and associated support gear (which is not cheap), two Moon props, and all of the associated electronics. And a duffel bag full of my clothes. And my hammock.

I am kind of at a loss for words... but at least my stuff is replaceable. While it took roughly 1.5 months to develop the Moon hardware, it only took a few days to build it once I got it all figured out. And there are certainly improvements to be made for Version 2.0.

But if anyone knows a way to track a missing laptop (MAC address? anything?), or a seedy pawn shop in Brooklyn where nice cameras and MacBooks sometimes turn up, my friends would be much obliged.

In the mean time, one more picture of v1.0. This was the first LED puck light that I "hacked" apart... and it kind of shows. It wound up being the base of the Lunar Lander... note the blue smudges around the screws. I bet you've never seen someone use LocTite on an Erector Set before. I think for v2.0, I might spec my own LEDs. Forget vomit green Home Depot lights– v2.0 will actually be color correct 5600K.

The Eagle has Landed

2010-07-29T16:32:00.000-07:00

Ain't she pretty? The lighting is a little more consistent with the LEDs mounted more toward the center of the moon.

Note the screw at the very bottom of the frame. I drilled three holes, using five different drill bits, starting with 1/16" and going up to 5/32", in 1/64" increments, to avoid cracking the plastic. I feel like there will be a job waiting for me at BP once they see this...

This is the completed "Lunar Lander" module (it really looks like it with the legs attached :) It is secured with steel bailing wire, copious amounts of hot glue, and LocTite (actually, Permatex Threadlocker, but commonly known as LocTite). If this sucker comes apart, I will go jump in the lake myself. I just hope I don't have to take it apart to fix it... but copious amounts of solder, and hot-glue reinforced wire joints ought to prevent that from happening.

I must admit I am impressed with the strength of the hot glue, combined with its slight elasticity, to provide a very strong, but shock-absorbing joint.

I also must admit that I am NOT impressed with Home Depot and their child brand Hampton Bay, as far as product consistency goes. The first light I bought had a pretty bluish-white glow, so I bought a 3-pack to complete the pyramid. The 3-pack, however, though it came from the same shelf in the same store, has a really hideous green cast to it. We'll probably have to correct it with some Minus Green gel if we can find it... so if you buy these for your house, beware, they might have a vomit-green color cast to them... not so good for kitchen cabinet under-lighting, but might match your fluorescents!

This is a view of what was originally going to be the "dark side of the moon," but it is now lit for 360˚ coverage... in Three-Dee... so really 360^3 degrees. Right? Why not...

And finally, my way of removing solder (and hot glue) fumes from the air. Might I add beforehand, DO AS I SAY, NOT AS I DO:

Obviously, DO NOT DO THIS if you (or anyone else with keys to the apartment) is planning on taking a shower any time soon. Please note that the extension cord is knotted around the shower curtain bar, thus preventing anyone from closing the curtain completely and making it quite obvious even to the lay-person that it is not safe to shower right now, if only for the sake of modesty.

However, since the cord is knotted up high where the water should (REPEAT: "SHOULD") not touch it, it is not completely unsafe to shower with this configuration. And it is plugged into a GFCI outlet ;)

I do wish we lived in a world where jokes did not require big bold disclaimers, but, in closing, DON'T RUN EXTENSION CORDS THROUGH YOUR SHOWER, THAT WOULD BE REALLY DUMB, ESPECIALLY IF YOU ARE A PROFESSIONAL ELECTRICIAN!

;)

All in a day's (month's?) work...

2010-07-28T22:40:00.000-07:00

Today was a very busy day...

Soldered the control board. Six 100k pots in parallel might be conflating Ohm's Law and Murphy's Law, so I'll have to figure that out...

The offending area...

This one is for all my Grip Brothers (and Sisters), demonstrating the proper use of a Cardellini clamp. I do wish I had a knuckle to go in between though...

And finally, a first glimpse at an [almost] finished product :)

It's nice to have the right tool for the job every once in a while...

2010-07-27T10:33:00.001-07:00

Saves you from having to literally "hack" your way through things, and makes the end result just a little bit prettier...

This is the switchboard for the LED dimmer, which I am really excited about.

Counting down, 3.5 days left to finish it...

I miss doing sound...

2010-07-22T20:46:00.001-07:00

But once a year I get to indulge myself at the Falcon Ridge Folk Festival, barefoot in the mud for 4 days (used to be 5; four days felt short this year...). More pictures to come...

The first thing I've built that I've been legitimately afraid of plugging in-

2010-07-21T10:18:00.000-07:00

I've had a slight fear of large capacitors ever since I took apart a 220v camera flash circuit when I was a child... lesson learned.

Hence the cardboard box "blast shield" for lack of anything better... Yes, cardboard is flammable, thank you for pointing that out. But I decided I was much more prepared for a small electrical fire than for chemical burns. Safety glasses, bucket of water, and thick soled shoe (to stamp it out) at the ready, I [reluctantly] flipped the switch. Luckily my fears were much exaggerated, and nothing jumped except for the needle on the meter.

However, it's still not working right... I am getting 21.7v dc out of a 16.2v ac input... Possibly because there's no load... but until I figure out this over-voltage thing I'm reluctant to hook anything up to it...

Ideas?

If I had an oscilloscope, this is what it would look like.

2010-07-08T21:35:00.000-07:00

Sadly, though, I don't have one. So I spent the day figuring out in theory why my lights are flickering. But I think I've found the problem, through roundabout and purely theoretical equations. Right now I really wish I hadn't slept through 3 years of high school math...

Briefly, this shows 1/48 of a second, the exposure time (Tv, if you're a Canon person) for a movie camera shooting at 24 frames per second (triangle wave). The effective exposure time is when the shutter is at least 50% open, exposing light to the film/sensor (thanks M&P!).

The tall sine wave is 120vac power at 60Hz, with peaks at 120Hz. I drew all the peaks as positive, as we're only concerned with "on" and "off" here, not polarity. This is the "flicker rate" of an incandescent bulb, but they don't really flicker due to a sort of "heat momentum" that carries the light through to the next peak. LEDs, being much more efficient, however, do not have this momentum, so they are much more prone to flicker.

The very short arches are the 12vdc rectified power, with positive peaks also at 120Hz. But the taller 120v peaks are easier to see, so we'll use those for reference. The vertical axis is not necessarily to scale, as we're comparing a lot of different things here.

The gray bars represent the PWM dimmer signal, at 1kHz. The width of the bars shown is at 100% duty cycle; as the light is dimmed down, the bars would get narrower. This is the amount of time that the power is "on" to the LEDs. The positive bars are "on time" and the negative bars are "off time."

Now, for why I've spent so much time doing this: The problem is that the LEDs are flickering visibly toward the low end of the PWM dimmer (picture much narrower gray bars). This is no good for camera. I had thought the problem lied with the PWM frequency, or the fact that I broke the legs off the rectifier's smoothing capacitor.

But it appears now to be the latter. If you look, there are 2 dips of the 120Hz power within the exposure time. Even though the PWM may be up full (100% duty cycle), if the input power is rising or falling, it is not putting out 100% brightness. If we assume, like the effective shutter speed, that the LED is only effective at 50% output or greater, the gaps widen significantly, and the flicker becomes even more apparent.

The Arduino PWM can allegedly go up to 64kHz, which is great, but without a clean DC power source, it wouldn't make a difference. Too bad I exploded the replacement capacitor today... apparently there is good reason behind the adage "don't plug it in while the power is on..."

LED Project 1

2010-07-06T21:17:00.001-07:00

Before:

Current scheme:

After:

Sadly, the capacitor is no longer with us, due to an accident...

ikea is smarter than you

2010-07-01T11:56:00.000-07:00

Meet Patrull, our new shower alligator. We found him in the impulse purchase section of Ikea. We will be sending samples from our previous shower mat to the CDC and several university laboratories to identify exactly which plague was growing on it. But Patrull will stay clean, because he can hang up and air dry. Ikea is smarter than you.

Hello World

2010-07-01T11:49:00.001-07:00

Testing 1 2 3...