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 Blindingly Bright Larson Scanner

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This hulking monument to illumination is [DJJules’s] 6-foot-long Ultimate Larson Scanner. If you’re scratching your head in confusion, the Larson Scanner is the ever-popular scrolling LEDs seen on KITT (the car) from Knight Rider and on Cylons in Battlestar Galactica (1978), named after the creator of the series.

[DJJules’s] iteration consists of sixteen 10W LEDs, each mounted on a heat sink which bolt on to a 6′ long piece of angle aluminum sourced from a local hardware store. He used a basic MOSFET constant current driver for each LED, attaching the MOSFETS to the heat sink with 4-40 screws. Each LED module then connects to a TLC5940 LED driver breakout board from Sparkfun, which plugs into an Arduino Pro Mini.

Check out the Instructables page for the source code and other important details, including safely powering the build (the LEDs can draw around 1A each), then grab your sunglasses and stick around for a quick video below.

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$15 toy becomes fully programmable robot

[Kevin] undertook a robot build partly for his own enjoyment, but also to include his kids in the action. He acquired a cheap toy and packed it full of programmable goodness. The starting point was a $15 toy called Rad 2.0. It’s a great starting point as it already included some motorized parts, and takes care of much of the mechanical issues like joints and structure.

The image on the left is the fourth update which [Kevin] has posted. The robot now responds to voice commands (with the same syntax as Chippu uses), moving its gaze to face forward or to either side. You’ll notice there’s a wireless webcam which lets him spy on what’s in front of the robot’s gaze. An ultrasonic range finder makes itself at home in the beak of the bot, and a Larson Scanner is nestled in the brow using the kit from Evil Mad Scientist Labs. Check out the video after the break for an overview of the hardware modifications.

The build log for this project is a forum post. That forum is run by [DJ Sures], a veteran at taking cheap toys and making them awesome. It seems like he’s taken a web forum and made it awesome too because the conversation about [Kevin’s] project is packed with constructive tips and encouragement.

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Challenge: Figure out how this logic-based chaser works

[Andrea] built this LED chaser using one logic chip. It illuminates all but one of the six LEDs, with the dim bit moving back and forth along the row in a chase sequence. This is something like an inverse Larson Scanner without the fading tail. But doing it with a logic chip instead of a microcontroller is a fun challenge.

Which brings us to the point of this feature. [Andrea] didn’t really post an explanation of how the circuit works. Usually missing details mean that we archive the tip and move on to the next one, but we think this provides a fun activity. Can you figure out how the circuit works? We already know that it’s using a CD4017 decade counter/divider chip. This gets its clock signal from a 555 timer circuit. [Andrea’s] schematic is a bit hard to read, but grab a copy, blow it up a bit (or use your browser zoom) and study the CD4017 datasheet (PDF) if you need to.

Want proof that it does actually work? It’s embedded after the break.

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Controlling shift registers via SPI

Hack a Day’s very own (and very prolific contributor) [Mike Szczys] put up a great tutorial on how to drive shift registers with an SPI interface.

[Mike]’s earlier tutorial of the 595 shift register goes through the functions of a shift register pin by pin. In a 595, bits for each position in the register are sent over one at a time. Most microprocessors have an Serial Peripheral Interface, and using an SPI bus means a lot less mucking about.

An ATmega168 was used for this build, although most Atmel chips can be made to work as an SPI master device. There are just three wires connecting the microcontroller to the shift register – SER, SRCLK, and RCLK. Like any other shift register setup, the build can be expanded by connecting the QH’ pin of the first 595 to the SER pin of the second.

[Mike] graciously made all the code for his build available. The video after the break is a 16-bit binary counter, a good stopping point before [Mike] rebuilds his Larson scanner/Cylon/Kitt, moving away from a PWM-based build to a register-based one.

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Detailed tutorial shows how to unleash your inner [Michael Knight]

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Our own [Mike Szczys] recently sat down and put together a great tutorial on building a Larson Scanner. The ubiquitous circuit is usually one of the first few projects on a budding hackers list of things to build, since they are just so darn fun.

Simple versions of the scanner sweep back and forth lighting the LEDs without any sort of transition between them. The configuration most familiar to us all as featured in Knight Rider and Battlestar Galactica are a bit more complex, and have a fading trail of light that follows behind the leading edge of the sweep. [Mike] notes that this fading is traditionally accomplished through the use of capacitors, which cause the light to gradually fade as the animation sweeps across the LED array. He decided to take a different route with his circuit, relying on PWM control of the LEDs instead.

Mike put together a simple circuit using an ATmega168, a handful of resistors, and of course, an array of LEDs. Utilizing interrupts and PWM, he was able to accurately recreate the iconic light sweep without the use of any capacitors. One big benefit to his design aside from the lower component count is the fact that he can easily adjust the speed of the sweep as well as the fading properties with a few small code tweaks.

Be sure to check out his blog at some point, where he shares his code, some circuit diagrams, and plenty more details on how his scanner was built. In the meantime, take a look at the video below to see the result of [Mike’s] work.

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Kraftwerk inspired LED tie

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If you didn’t land the job after your last interview, it might have been because you were not wearing this sweet Kraftwerk-inspired necktie. Although our own [Caleb Kraft] insists that this recent creation by the folks over at Evil Mad Scientist Laboratories is a tribute to him, [Ralf Hütter and Florian Schneider] beg to differ.

The inspiration for the tie actually comes from Kraftwerk’s 1977 video for “The Robots”, in which the band wore black ties with embedded scrolling LEDs. The effect is very similar to that of a Larson Scanner, though Kraftwerk’s ties light the LEDs in a single direction and do not fade in and out.

EVMSL has released a firmware update to the Larson Scanner they sell in their shop that replicates the Kraftwerk effect, and they also put together a quick tutorial showing how you can construct your own coin cell-powered LED tie. We’re not suggesting that anyone rush out and buy their kit, as it can be replicated fairly easily – we just thought it was pretty cool.

So, if you’re looking for a retro-inspired Halloween costume, search no further – Evil Mad Scientist Labs has you covered.

Continue reading for a video demo of their tie, as well as the original video that inspired it.

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