SparkFun will be closed Nov 26th and 27th for the Thanksgiving holiday. Orders placed after 2:00pm MT on the 25th will ship out Monday the 30th.


Member Since: January 13, 2012

Country: United States



Design Engineer - Advanced Motion Controls / Owner, Design Engineer - OhmMyGadgets

Spoken Languages

English, Spanish, (precious little) Mandarin

Programming Languages

C++, assembly


BSEE California State University, Northridge


Microcontrollers, LED lighting, DMX-512, RC servos, industrial motion control


Halloween, animatronics, lighting, photography motorcycles



  • The halloween forum is another great resource for builds, and MonsterGuts is another good source for parts. I’ve been working with haunted attractions since ~1995. There are four main types of controllers out there right now: program yourself, key-bangers, computer controlled slaves, and a few all-in-one devices that store a show within the controller.

    The program yourself variety is pretty well represented by the Prop-1 controller by Efx-Tek. These are standalone devices (no computer needed after programming). They have several digital inputs and outputs that can be used to detect mat triggers and close relay contacts. Servo animation is usually more difficult here because of the complexities of trying to do multiple things at the same time in standard programming.

    Key-bangers are standalone devices that, like the “program yourself” variety, have a few digital outputs or relay contacts. These are programmed real-time by, you guessed it, banging a key. That is, you push a button when you want the relay to close, how many times, and with what timing. An input trigger sets the sequence off. The PicoBoo controllers from FrightProps are good examples of key-bangers.

    More advanced props can be controlled through live playback from computer animation software (requires the computer to be present and wired into the system on Halloween night). The one my customers, my friends, and I have used for many years is VSA by Brookshire software. This uses visual linear timeline editing (kind of like multi-track audio/video editing) to program out relay events, servo moves, and lighting animation. The output slave devices have evolved over the years. At first, the Parallax Inc SSC let you control servos with VSA through RS232 serial. These have been largely replaced by USB devices, but now many haunters are going the route of DMX-512. Some examples of DMX-controlled slaves are the Board (and Son) of Chuckee from Skulltronix, and the Medusa DMX by OhmMyGadgets (my product). DMX-512 is based on differential RS-422, so you get the advantage of using daisy-chained long cable runs. But the really nice touch is that, because DMX is used by club lighting, you can drop in lots of different moving head lighting fixtures, strobes, smoke machines, bubble machines, etc, without any hacking… not that anyone here is averse to hacking ;-) Here’s a good example from one of my customers, Aaron Coleman: Bohemian Rhapsody - Frank Skinnotra and the Gabbing Gourds

    The all-in-one players are usually programmed with software similar to VSA. But the advantage to these is once the animation is completed, it’s downloaded into the controller and the computer is no longer needed. Some of these include audio and/or video playback as well. The Terror Board, and Brookshire’s RAPU would be examples of this category.

    Hope this helps launch some fantastic new haunts! Brian

  • I’m happy to see the two companies teaming up. I just got my Core + JTAG adapter last week, and am waiting on a Photon. For someone new to both the platform and reliance on the cloud, it builds confidence that there will be support in the future.

  • Are you looking to project mixed light? The clear-lensed RGB LEDs I’ve seen so far tend to splay the different colors. Since each color comes from a different die, they can’t all be located in the center of the epoxy. So, on the clear RGB LEDs I’ve seen, one color will project straight, but the other two will be at a slight angle.

  • Yes, filters are the way to get rid of the noise. Consider the frequency range you’re interested in measuring, and make sure the filter you design falls well above that frequency range.

    You can use RC filters, or even better, an active filter (opamp filter). Like Pete showed in his diagram, ADCs have sampling capacitors that need to charge quickly to the voltage you’re measuring. If you have too much resistance from your source (like, through the resistor in your RC network), the capacitor may not charge up all the way during the acquisition time, which results in some measurement error. On the other hand, if you’re feeding the ADC with the (low impedance) output of an opmap, you don’t have to worry about that.

    There are also ways of filtering in software. As long as you’ve applied enough hardware filtering to avoid aliasing, you can use a digital filter as well. Look up IIR filters, to get some ideas.

    Stand alone ADCs will usually have much better specs than integrated ADCs. Higher precision (number of bits), better internal voltage references (accuracy), and faster sampling rates. See what you can get the Arduino to do for you, and if you end up bumping your head on these limitations, you can always add the external ADC later.

  • Hey! I see LEDs connected to collectors! Cool :-) It looks like the links to the design files are still pointing to the v12 revision, though.

    I know this is a little late… but if you guys ever end up reving it again, consider rotating the LEDs 90 degrees, so they can be bent in and out. I put a similar design on Batch PCB a year ago, for Medusa DMX users. The ability to bend in and out makes it easier to converge the light from the 3 LEDs, especially if they’re not soldered in quite straight.

  • I met these guys at MakerFaire a few years ago. It’s good to see them finally taking off. I like the idea of visual programming for would-be tinkerers who don’t know how to program. Maybe my dad will finally try it.

  • High five, and Asimov jive!

  • Are the outputs on the spark gap igniters isolated from the inputs, or are the in/out grounds electrically connected to one another? If they share a common ground, it might be worth it to try separate isolated 5V supplies for the different segments.

  • Have they started charging for non-selling booths now, too? I’m going only as an attendee this year, but I had a free booth last year for the Medusa board.

    I do remember talking with one of the organizers, and being surprised the booth was free. She impressed upon me how much the faire was really about the makers, not about pulling in dough, and said they charge for the selling and corporate booths in order to restrict the faire from becoming an overly commercial event, squeezing out would-be small presenters. I’m a skeptical kinda guy, so I would wonder whether that were really the intent at the corporate level. Regardless, she sounded pretty sincere about it. At the same time, though, I think SparkFun ought to have some kind of special dispensation, given how much of their layout is dedicated to education, rather than product. Hands-on is what Maker Faire is all about, after all.

    Regardless, I’m damn glad the Maker Faire exists. I’d never seen anything like it, when I first attended. And, heck - I got to meet Nate and Pete last year :-D

  • Just found out about this, from the news of the retail packaging. I’m curious… had you guys considered putting the load on the collector side? With the LED and drop resistor on the emitter side, the delivered current will be dependent on the voltage from your microcontroller. With a 5V micro, you’d have 5V at the base, ~4.3V at the emitter. But with a 3.3V micro, you’d only have ~2.6V at the base, which wouldn’t even turn on the Blue or Green LEDs. But if the LED and drop resistor were on the collector side, the current would be (more or less) independent of driving voltage.

    I made a very similar board for Halloween lighting, and posted it to batchpcb a few months ago. I did quite a bit of testing using 10mm 1W LEDs. One thing you may find, is that the Vf changes as the LEDs warm up. This may be causing some of the deviation you were seeing

No public wish lists :(