justDIY Project Log

I don’t have much to say on these, other than I scored a bunch from Future for a seemingly great price.

These appear to be HEAVY DUTY leds, destined for the automotive market. They’re discontinued now, as Lumileds is pushing the all mighty rebel for every application under the sun.

Apparently lumileds marketed these leds strictly as automotive indicator grade leds. Their design guide shows a stop light made of six of these leds, spot welded in a 2 x 3 array to heavy solid aluminum buss bars instead of a typical PCB mounting. I won’t be doing any of that, but I did draw up a layout in Eagle and came up with a 2 x 8 array for my mint tin bike light.

This board is etched and waiting to be cleaned and assembled, more pics to follow!

Nothing much new on a technical note. I do have a new pcb layout ready to iron on to some blank copper, should get that done this weekend. I ordered more switchers and LEDs from Future on Wednesday. Originally I was excited, the estimated delivery date was 8/21. However, it has now been pushed to 8/26, oh well!

Here are some new pictures, and some video worth posting in the blog:

This is my new 2010 Trek 3700 Mountain Bike… I’ve upgraded to alloy pedals and a super tough downhill rim for the rear wheel. I had been buying cheap-o department store bikes, on average two or three per year and trashing them basically riding on streets and trails. So I wanted to upgrade to something that should hold up a bit better.

Same composure, dialed down the flash output and decreased the shutter speed a little.

Video “tour” of the bike with both lights going.

Strobe effects demonstration on some reflective signs near my house. Sorry for the wind noise, a storm is rolling in!

I started this project a little more than a year ago, but shelved it because it wasn’t working right and I didn’t have the correct components. It was a seasonal project that would have little use over the winter, so I sort of forgot about it.

This year I’ve been going on a lot of bike rides with friends, sometimes on public roadways, sometimes after dark. My bike has a nine watt 500 some odd lumen headlight, which makes it easy to see where I’m going, and definitely makes me visible head on. The tail of my bike however still has the stock reflector, plus the little reflector stripes in my shoes, not exactly high visibility. Not wanting to pale in comparison to the headlight, the taillight is a three watt 140 lumen beast powered by three AA rechargeable batteries.

The light is based on a boost converter from National Semiconductor, the LM3410. I’m using the 525kHz SOT-23 version, the LM3410Y. Originally I had trouble with the chip self destructing, as discussed on the Linear1 forums. It was hypothesized either the inductor was underrated or the diode was too slow. Ordering parts for another project later in 2008, I bought some better inductors and diodes, which more closely resembled the specs of parts used in National’s web bench simulator. So, lacking sufficient rear light, I rekindled this project and have a “working prototype” that’s gone on two rides with me so far.

The basic function is fairly simple. The 3410 is a constant current boost (step-up) driver. A small inductor is used to ramp up the input voltage, from 3.6vdc nominal to 15.4v at approximately 200mA. The current is monitored by a one ohm resistor. A pair of output capacitors help smooth out the ripple and an input capacitor helps the batteries cope with the high demand current (as high as 1.5a in some cases). I’m using nickle metal hydride batteries, which have a rather low internal resistance – they’re designed for high demand applications and when fresh, barely sag at all under the load.

Originally I had planned on carrying the batteries directly on the PCB, using some through-hole spring clip battery holders I found in the Sparkfun library. However, AA batteries must be bigger in Colorado than they are in Michigan, because using Sparkfun’s layout gave me about a quarter inch gap between the spring and the battery. The pads were also woefully undersized for physically mounting the clip and holding it securely enough to survive the stress of batter insertion and extraction. So I dropped their layout and drew my own that looks exactly like it, but is based on measurements from a real AA battery.

Along for the ride is a Microchip PIC microcontroller, the 12F683. It provides a bit of user interface for the light, creating different blink patterns as well as putting the light into a “stand by” mode, with the switcher shut down. I’ve programmed several blinking patterns, and somewhat organized them into “modes” which I can select using the little button.

A year ago, I didn’t have any sort of enclosure in mind. The led array was assembled on a ‘standard’ sized protoboard, so I probably thought about using a plastic or aluminum prototype enclosure. However, this year, I was thinking it would be a nice fit for a large mint tin. After printing out some mock-ups and messing around with battery configurations, I settled on using three batteries and having the electronics crammed into one side of the tin with the led array mounted in the lid of the tin. This setup might have worked, except for the battery snafu. I’m using a plastic three cell holder right now, and the extra thickness it adds is preventing the lid from completely closing. It closes enough that the light is easily held shut by some big rubberbands, and it survived bouncing around under my seat for two short rides. The next revision will have the battery situation resolved and I might have a better mounting solution by then too.

Overall I’m very pleased with the outcome of this project. I have more parts on order to make a few more lights for my other bikes and friends, and I want to experiment with other array configurations and colors. There are a two videos of the light on my youtube channel, but they’re nothing to get excited about.

Thanks for reading!

The train has spent the last few hours speeding Eastward, I think we start heading North after Marshall Texas.

Here’s a screen-cap from Streets 2009, click on it for a huge version.

The sleeper car is a little different this time. The tiny closet has been replaced by a large hook and an open storage area. The single large step which you climbed to get into the bunk is now two steps, a little narrower. The halls feel narrower too, i think the room might be a tiny bit larger.

Our conductor is doing a better job keeping this rig rolling. The trip North is progressing more smoothly, we’re spending a lot less time at the stops.

My seat is on the west-facing side of the train again, so I’m seeing the same scenery again in reverse… I don’t really think I’m missing anything on the other side.

My EVDO connection has been working pretty good, I’ve been getting 15-20kb/sec uploading all these pics and videos.

Greetings Everyone…

The Faire is behind us now, and to sum up “how was it?” in one word: disappointing.

The fair reminded me of our local Independence Day festival in Manistee. It’s mostly arts, crafts and performers. The difference is, there were a few nerds in the corner, and fighitng robots.

The Faire had several major areas; the arena area housed some big ass tesla coils, some sort of lame robots with balls competition and the ComBot cage. The tesla coils were cool, but they were mostly just a light show to some midi controlled drums and a really loud PA system. The fighting robots were the coolest thing at the fair. It was very impressive to see the heavy weight and super heavy weight bots go up against each other. The smaller bots just sort of danced around until time ran out.

Next we have the Maker Stage, which was an outdoor tent covering raised platform and rear-projection screen. Different Makers and visionaries had scheduled talks. In general they were hard to hear, and the projection was useless. The tent was open on three sides and kind of small. The screen was washed out, and the PA wasn’t very loud – it had to compete with the human mousetrap and the electric guitar bicycle contraption.

Indoors we had the Maker Shed, selling many of the commerical projects covered on the Make blog. Lots of leds, arduinos and other assorted electronic gizmos. The shed had three tiny areas dedicated to demostrations and hands-on. If you purchased a kit from the shed, you could solder it together there which was nice, especially for the young folks just starting out.

In the rodeo barn there was the craft sellers. A little further down a company selling big CNC mills was cutting various things, and demoing a snap-together kit house they’d developed for temporary housing usage. Further down were some home-made CNC’s cutting away at various designs. Sparkfun had a decent sized booth at the end of the barn, showing off some of their eye-candies and doing soldering tutorials. On Saturday there were a few large LEGO cities setup, which were quite impressive. A few real hackers had their tables grouped together, show casing musical gizmos, nixie tubes and surface-mount soldering. A computer club named Austin Modders had some nice looking rigs on display, but they weren’t really doing anything. Duke University had several different teams displaying their work on parallel computing. I spoke with one of the engineers for about twenty minutes – he was very informative, it looks like a great program to be in.

Outside there were some art-bikes, a stage playing eccentric music, model rocketry, kite building and flying, and last but not least, a small trebuchet. I was lucky enough to stumble upon it right before a launch; it was most impressive.

I’m going through my pictures and videos right now, uploading as best I can with my evdo connection. Right now I think I’m on the sprint network and it seems pretty fast.

find some videos here: http://justdiy.blip.tv
and pictures here: http://picasaweb.google.com/gordonthree

More to come!