Hacking the Crayola Digital Light Designer

[Harry] wrote in with his hack of the Crayola Light Designer. The Light Designer is a pretty unique toy that lets kids write on a cone-shaped POV display with an infrared light pen. [Harry] cracked one open and discovered it has a spinning assembly with a strip of 32 RGB LEDs for the display and a strip of photodiodes to detect pen position. These were ripe for the hacking.

The spinning assembly uses several slip ring connections to send power and data to the spinning assembly. [Harry] connected a logic analyzer to several of the connections to determine which lines were clock, data, and frame select (the strip is split into 2 16-led “frames”). He went on to reverse-engineer the serial protocol so he could drive the strips himself.

Instead of reverse-engineering the microcontroller on the product’s PCB, [Harry] decided to use a Leostick (Arduino Leonardo clone) to control the LEDs and spinner. He mounted the Leostick on the shaft of the spinning assembly, and powered it over the slip ring connections. After adding some capacitance to make up for noisy power from the slip rings, [Harry] had the POV display up and running with his own controller. Check out the video after the break to see the hacked POV display in action.

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A USB-Controlled POV Light Stick

Wanting to showcase their USB LED strip controller, the folks at Maniacal Labs built a POV LED stick this weekend. Yes, it’s pretty much the same as any other POV LED display you’ve seen; set a camera for a long exposure, wave the POV light stick around, and get a cool pixely image in mid-air. This build is a little different, though: it’s controlled over WiFi with a Raspberry Pi connected to a WiFi network.

The USB LED strip controller in question is the AllPixel, a small board that controls NeoPixels, WS2801, LDP8806, and a bunch of other LED strip controllers over USB. The Stick used for this project consisted of two meters of LPD8806 LEDs, giving 96 pixels of horizontal resolution. A big battery and Raspberry Pi rounds out the rest of the electronics.

Building a LED POV display isn’t that much different from building a LED matrix display; all you have to do is break up the image into individual columns and display them sequentially. To do this, the Maniacal Labs folks whipped up a LEDPOV class that does just that. To get the images, just open the shutter on a camera, wave the stick around, and if you get it right, you’ll have a great pixely image of nyan cat or the rainbow wrencher.

Measuring the Length of WS2812 Strips

[Tim] discovered a simple way to measure the length of WS2812 addressable LED strips from a microcontroller. This is great for any project that can have an arbitrary length of addressable LED strip attached to it.

The simplest (and perhaps most reliable) way to measure strip length is by feeding the serial output pin of the end of the strip back to the microcontroller. The microcontroller keeps clocking bits into the strip until it receives data from the end of the strip. [Tim] didn’t want to run an additional signal to the end of his strip, so he found another solution.

[Tim] used the ADC of his microcontroller (an ATtiny) to measure supply voltage droop as LEDs are turned on. Each LED draws around 60mA at full brightness, so [Tim] sequentially turned on each LED and watched the ADC for slight voltage changes. If the voltage changed, there must be an LED at that address. [Tim] does note that this method is extremely dependent on the power supply used and only works on short strips. Check out his blog post for more details.

Larson Scanner Namesake [Glen Larson] Passes Away

[Glen A. Larson] passed away on Friday at the age of 77. He may be most widely recognized for being a producer of the original Battlestar Galactica, Magnum, P.I. and Knight Rider television series’. But for us his association with a row of LEDs which illuminates in a back and forth pattern will always be his legacy.

When we heard about his passing we figured that we would hear about his invention of the Larson Scanner but that was not the case. A bit of research turned up a pretty interesting Wikipedia bio page. He has origins in a music group call The Four Preps and actually composed or collaborated on a number of television theme songs among other notable accomplishments. But nothing about electronics. Did this man of many hats actually invent the hardware for the Larson Scanner used as the Cylon Eye and on the front of K.I.T.T., or does it simply share his name?

Evil Mad Scientist Labs claims to have coined the term Larson Scanner. [Lenore Edman] confirmed to us that EMSL did indeed start the term which is used to name their electronics kit and directed us to [Andrew Probert] who lists effects for the TV series on his portfolio. We’ve reached out to him for more information but had not heard back at the time of publishing. We’ll update this post as details emerge. In the mean time, if you have any insight please leave it below including the source of the information.

If you are not aware, a Larson Scanner is so interesting because the pattern calls for a fading trail of LEDs. It is not simply a fully illuminated pixel moving back and forth but includes dimmed pixels after the brightest one has passed. This is an excellent programming challenge for those just getting into embedded development.

Those interested in learning more about [Gary] may find this lengthy video interview of interest. Otherwise it’s time for the collection of links to past Larson Scanner projects which we’ve covered.

[Thanks Bruce]

A Watercooled Headlamp, Because Why Not?

There are extremely high powered LEDs out there, and most of the ‘creative’ uses of these are extremely high-powered flashlights, complete with heatsinks, forced air cooling, and beefy power supplies. [Christian] wanted to play around with one of these LEDs, but he wanted something a little more unique. He chose a headlamp, a build that is made even more impressive by the fact it is watercooled.

The body of the headlamp was milled out of aluminum, with a space for the LED in the front and channels in the back for coolant. Also in this enclosure are two buttons, a temperature sensor, and a port for the hose that carries the tubes and wires.

This hose connects to a large battery pack that houses four large lithium phosphate batteries and a boost converter built around an Arduino. The pack also houses a pump and reservoir that is able to keep the LED cool even at 130W.

8×8 LED Arrays Make for one Creepy Animated Pumpkin

[Michal Janyst] wrote in to tell us about a little project he made for his nephew in preparation for Halloween – a jack-o-lantern with facial expressions.

Pumpkin Eyes uses two MAX7219 LED arrays, an Arduino nano, and a USB power supply. Yeah, it’s pretty simple — but after watching the video you’ll probably want to make one too. It’s just so cute! Or creepy. We can’t decide. He’s also thrown up the code on GitHub for those interested.

Of course, if you want a bit more of an advanced project you could make a Tetris jack-o-lantern, featuring a whopping 8×16 array of LEDs embedded directly into the pumpkin… or if you’re a Halloween purist and believe electronics have no place in a pumpkin, the least you could do is make your jack-o-lantern breath fire.

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Simple POV Bike Effects with WS2811 Strips

[Andrew] wrote in with a new take on the classic persistence of vision bike spoke hack. While many of these POV setups use custom PCBs and discrete LEDs, [Andrew]’s design uses readily available off-the-shelf components: WS2811 LED strips, an Arduino, an Invensense IMU breakout board, and some small LiPo batteries.

[Andrew] also implemented a clever method of controlling his lights. His code detects when the rider taps the brakes in certain patterns, which allows changing between different light patterns. He does note that this method isn’t incredibly reliable due to some issues with his IMU, so now he senses when the rider taps on the handlebars as well.

If you want to build your own bike POV setup, you’re in luck. [Andrew] wrote up detailed instructions that outline the entire build process. He also provides links to sources for each part to make building your own setup even easier. His design is pretty affordable too, coming in at just under $50 per wheel. Check out a video of [Andrew]’s setup in action after the break.

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