POV bike wheels with the MSP430

Being an intern a Texas Instruments isn’t all fun and games, but from [George], [Valerie], and [Ryan]‘s TI intern design project, it sure looks like it. They built a persistence of vision display for a bicycle using the ever popular MSP430 Launchpad board.

The team of interns created a POV display by combining the power of the TI Launchpad with a row of 32 RGB LEDs soldered onto a booster pack. Once the whole circuit is fastened securely to the bike wheel, a hall effect sensor mounted to the bike frame allows the MSP430 to detect how fast it is going. From there, it’s just a matter of flashing LEDs at the right time to create a stationary display inside a rotating wheel.

Although the display will theoretically work with just one Launchpad/Booster pack combo, the team decided to use three of these circuits, totaling 96 LEDs per wheel, to create a really nice RGB display. The video (available after the break) shows a little bit of flicker but this is an artifact of the camera. In real life, the POV bike wheel display is simply stunning.

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extremely detailed light painting bar

[Matt Pandina] has been documenting his build of a very nice light painting bar on his G+ page. His light painting bar has 64 RGB LEDs being driven by an ATmega328P and four TLC5940 chips. He wrote his own libraries to talk to the TLC5940 as well as his own libraries to pull images off of a MicroSD card. He also wrote a cross-platform program that automatically converts a directory  of pngs to something the TLC5940s expect. He says the secret to getting his24-bit color correction looking right is gamma correction. It seems that when the LEDs were run too bright, he couldn’t get the colors quite right.  In case you’re curious, those images are 15 inches tall!

You can follow along through his posts as he starts with just a few LEDs and slowly updates and grows it to the impressive state it is at currently.

Analog clock display uses a Nipkow disk

Although [Serokoy] is not thrilled with the outcome of his Nipkow disk clock (translated), but we really enjoy it. It uses the Persistence of Vision concept to create a light display from a rotating disk.

We’ve come across a lot of rotating disk clocks. Several were based off of the platters of a hard drive, using a slit, or series of slits to make up the display. This Nipkow disk uses a similar technique but in a more general way. The series of holes arranged in a spiral pattern allows a grid of concentric rings to be used as pixels when the disk is spinning. The bottom portion of the disk is used as the display area. Each pixel is illuminated at just the right time by LEDs below in order to freeze that pixel in the viewer’s eye. The demo is a bit rough, and [Serokoy] mentions that the precision of the hole layout makes all the difference. He drilled these by hand in a CD which was spray painted matte black. Even though he used a computer to lay out and print a template, it took four tries to get a suitable disk.

[Thanks Svofski]

Wind-powered POV weather station

The more we think about this one the more we like it. [Michael] built himself a wind-powered persistence-of-vision weather station. Okay, that sounds interesting, but he ups the ante when you find out what’s included in the system.

A stepper motor acts as the generator which powers the electronics. As we’ve seen before; if you spin the shaft of a stepper motor electricity is produced. [Michael] is actually spinning the housing of the motor, with the shaft mounted to the base that holds the weather station in place. This way, the electrical contacts are spinning along with the blades of the generator. By mounting all of the electronics on these blades he gets around the problem of transferring power onto a spinning platform.

A set of LEDs on the end of the blades display temperature and relative humidity readings. A hall effect sensor pulled form an old floppy drive syncs the display with the rotational speed. He’s even got a shunt system which keeps the input voltage at a safe level, and will act as a break in high winds to keep the rotors from spinning out of control. See what we mean? An interesting idea because a fantastic project when you build in features like these!

Plotting pictures with light

Flashing LEDs for a persistence of vision display are on bicycle wheels, alarm clocks, and even light painting sticks to draw images in the air. What if you wanted to plot an image in the air (translation) with a single LED? That’s what [acorv] did after taking a cue from a polar plotter.

Like the polar plotter and Drawbot, [acorv]‘s build began with a pair of stepper motors and fishing line (translation). [acorv]‘s brother upped the stakes a bit and suggested replacing the marker with an LED and taking long exposure photographs. Armed with a DSLR and a lot of patience, a few experimental pics were taken. To plot the image, the Lightbot flashes its LED as it goes across the plot area. The process of building an image pixel by pixel takes a while – eight minutes for this image – but the brothers were encouraged enough to take their rig outside.

After setting up the polar plotter between two tripods, [acorv] and his brother made this image in the dead of night. It’s an interesting spin on the POV LED builds we’ve seen before. Check out [acorv]‘s Lightbot slowly drawing something after the break.

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POV clock spins light filter instead of LEDs

This hard-drive based POV clock is a treasure trove of great design choices. Now, we’ve seen a bunch of spinning clock builds. Several of the hard drive versions use slits cut in the platters to create a display by illuminating an LED behind those slits at just the right moment. This is a similar idea but [Jason Hotchkiss] ditched the platters all together and replaced them with a light filter. The filter disc has digits 0-9 as well as a colon (not seen above because the colons blink each second). As this disc spins, the Arduino compatible controller lights up LEDs in the eight digital positions to illuminate the correct number.

The filter is made from an etched copper-clad disc. This is a great choice because the fiberglass substrate is strong, light weight, translucent, and available. The filter idea also means you don’t need to get power or data to a spinning platform. [Jason] has also designed a very impressive controller board that is the same size as the footprint of the laptop hard drive he’s using. Check out the video after the break to see his description of what went into the hardware choices he arrived upon. Continue reading “POV clock spins light filter instead of LEDs”

Bending a printer control board to output POV messages

Confronted with the issue of finding a use for his mounting pile of junk electronics, [Rue] set out to build a persistence of vision device using a hardware state machine. We have a suspicion that his original link may go down if there’s too much traffic so here’s a cached link just in case.

Any board that is MSC-51 or MCS-48 based would have worked for his purposes. This is because the addressing scheme of the hardware makes it an easy hack. The image above shows him cutting off the processor from this board. It was chosen because of a 74HC373; it was a mistake at first but since it’s pin compatible with the 74HC374 that he needed a simple swap did the trick. From there a clock source was added, and the address information necessary to display the message was burned into an EEPROM.

Step twelve of his writeup shows a Morse Code message created by attaching the board to a broomstick and twirling it around in an arc. We took  just a minute to decode the message and believe it’s a shout-out to Hackaday. Nice, thanks for reading [Rue]!