Trying To Measure The Speed Of Light With An Arduino

December 1, 2011 by Brian Benchoff 63 Comments

We know that measuring the speed of light with an Arduino is possible. It’s just that the implementation is hard.

Last month we saw [Udo]’s blinkenlight shield that can be used as a line scan camera. It’s a neat piece of kit, but [Udo] really wants to submit something for the Buildlounge laser cutter giveaway, so he figured measuring the speed of light would be an easy project. If a kid and a chocolate bar can do it, surely it can’t be too hard.

[Udo] hit upon the idea of pulsing a laser pointer and measuring the time of the reflection. Because his blinkenlight shield can be used as a light sensor, all that’s needed is a mirror and a pretty long line of sight. There’s a few problems with the setup though: with the Arduino running at 16 MHz, a photon will travel 19 meters in one clock cycle.

Even with some very clever coding, we’re not really sure detecting an emitted photon is possible at such (relatively) slow clock speeds. We’re thinking [Udo] could source a few hundred meters of optic fiber so the entire experiment could fit on a desk, but feel free to drop a note in the comments if you’ve got a better idea. [Udo]’s demo of his blinkenlight/laser mashup is after the break.

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Custom Massive LED Panel Lights Up The Party

November 30, 2011 by Mike Nathan 12 Comments

giant-led-sign

The guys at BuildLounge wrote us to share a giant LED sign they came across in the submission pile for their “Win a Laser Cutter” contest that’s currently under way. [Stephen Shaffer] helps run a huge party called Fantastic Planet, for which the group typically outsources the lighting arrangements. They got tired of hiring light guys several times a year and built their own mega display for the festivities instead.

The LED sign consists of 1,474 LEDs that output well over 10,000 lumens. The sign was produced for just about $800, which is very reasonable for a display of its size. The whole thing is controlled by a pair of Arduinos paired with 34 MIC5891 shift registers, all mounted on custom designed PCBs that the group produced in-house.

The display looks great, but don’t take our word for it – check out the video below to see it in action.

If you are interested in taking a closer look at how it was built, swing by the build thread to see more details.

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DIY Car Lighting Illuminates Areas The Designers Overlooked

November 28, 2011 by Mike Nathan 26 Comments

[Dave] just can’t seem to get enough of modifying his new car. Where he lives, it’s typically dark on his ride home from work and he finds himself dropping things on the floor of his car all too often. Nissan decided not to include lighting in the Juke’s foot well or glove box, so [Dave] decided that he needed to rectify the situation.

As you might have noticed by his previous tinkering, [Dave] is a big fan of LEDs and ATTiny microcontrollers. He added some Lego-supported LEDs to the driver and passenger side foot wells, installing an additional light in the glove box while he was at it.

The Juke had a couple of usable blank spots on the dashboard, so [Dave] installed a pair of capacitive touch sensors and a small switch into one of the open slots. When touched, the top-most capacitive pin pair ramps up the foot well lights, while the lower pair turns on the LEDs in the glove box. The switch at the bottom is used to toggle on a light in the back seat which he installed a while back.

It’s a simple addition, but it makes all the difference when he is hunting around on the floor in the dark. We are a bit surprised by how many amenities are missing from the Juke, but tweaking them to his liking seems to keep [Dave] happily occupied.

Continue reading to see a short demo video of his interior lights in action.

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LED Sconces Spice Up Dorm Room Parties

November 28, 2011 by Mike Szczys 10 Comments

This dorm room is ready to entertain, thanks in part to the LED wall sconces that [Joseph] hacked together. Inside each fixture you’ll find three 3-Watt LED modules. For proper heat dissipation he mounted them on sheet metal which he cut out, including some fingers for additional surface area. The shape for the heat sink was chosen to fit behind the diffuser of the sconce, which is an incandescent light fixture with the socket removed.

[Joseph] designed his own control boards for the base station and LED modules. They communicate with each other via RS485, which lets him run CAT-5 cable to each, but the lights do require external power as well. The controller itself is a USB dongle which takes the serial commands from a computer and pushes them out over the RS485 protocol. In the video after the break you can get a good look at the hardware and the overall performance of the system.

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Building A 1300 Lumen Bike Light

November 28, 2011 by Mike Szczys 48 Comments

[Brainiac27] isn’t going to let the absence of sun prevent him from biking. He has no trouble lighting his path with this 1300 Lumen bike light he built.

The light source is a 3-up star by Cree. It puts off a lot of light, but also generates quite a bit of heat which is the reason for that large heat sink. It is meant to be used with a CPU but works well for this purpose thanks to the adhesive thermal paste used to unite the two parts.

The mounting bracket is a custom job, bent from 1″ by 1/8″ aluminum bar. [Brainiac27] had some issues with length the first time he tried making it. For his second attempt he started with an overly long piece, made the bends from the center out, and only made cuts once the bends were all completed. The bracket makes it easy to mount to his bike, with the battery stored in a bike bottle and a remote switch (with attaches to the jack you can see on the project box above) hidden underneath one of the brake hoods.

The intensity of this light nearly doubles one of our other favorites.

This Giant Hand Made LED Matrix Must Be Ours!

November 20, 2011 by Mike Nathan 16 Comments

giant-led-matrix

[Martin] wrote in to share a project his company has been working on for some time, a gigantic 1470 pixel LED wall. The group provides lighting for clubs, parties, etc, and their hand-built LED matrix is always certain to be the hit of the show.

The amazing matrix was designed from the ground up and built by hand in [Martin’s] living room. They designed small 32x32mm “pixel” boards, each of which features 6 PLCC6 RGB LEDs driven by a single WS2801 LED controller. The PCBs were populated by hand and each one was reflowed in a small pizza oven that [Martin] owns. After the pixels were completed, they were attached to aluminum bar and combined to build thirty 70x70cm frames which are connected together to form a giant matrix.

As you can see in the collection of videos below, the display is very impressive. We just hope that they will be compelled to release the schematics for their boards so that we can build one of these in the office.

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Video Display From RGB Strips Makes It Seem So Easy

November 18, 2011 by Mike Szczys 15 Comments

[Fabien] wrote in to share a link to this RGB video display which he made. He’s got some pretty cool routines that make it more functional than you would think, but first we want to comment on the construction. He used an RGB strip, which makes this look like an incredibly simple build. The strip has a data and power bus running the length of it. You can it into smaller segments, then just solder jumper wires to reconnect the buses. That’s exactly what he did here, making it what must be the fastest method of putting together a display of this size (16×10 pixels).

It’s driven by a Netduino which easily addresses the LPD8806 drivers responsible for the LEDs. It gets input from a computer via Xbee, making it easy to include data from the net, or to push visualizations. The video after the break shows a [Van Gogh] self-portrait. Since 160 pixel resolution wouldn’t do it justice, the visualization software shows a zoomed in portion of the painting which is constantly panning to let you see the entire work. It’s a fabulous effect.

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