See you there!
It’s that time of the year again! The 2013 Maker Faire Bay Area is next weekend (May 18-19th) in San Mateo, California.
I haven’t had time to post about it, but over the past few weeks I’ve been busy working on a special project for the Maker Faire this year.
This year I am bringing a new and improved version of the “Geiger counter-powered ambient music thing” that I threw together at the last minute last year (and never really came up with a good name for). In that project, I connected five of my open source Geiger Counter kits to an Arduino that sent MIDI commands to a Sparkfun Music Instrument Shield. When each Geiger counter was triggered by background radiation or one of the weakly radioactive sources nearby, the Arduino would send a command to the shield to play a musical note.
This year I’m bringing a new and improved version that uses a new piece of hardware that I designed specifically for the Faire – the Geiger Pad.
Each Geiger Pad contains a fully functional Geiger Counter based on my Geiger counter kit. The output of the Geiger counter is connected to a cluster of 14 very bright 5mm UV LEDs. On top of the Pad is a petri dish filled with uranium marbles. Each time the Geiger counter detects that a gamma ray was emitted by the marbles, it flashes the UV LEDs. Since the uranium marbles fluoresce green under UV light, this produces a brilliant green glow.
Today (yes, once again at the last minute) I finally got all the pieces together and working. If you come to the Faire you’ll be able to see it in person, but I also posted a short video on flickr:
The Maker Faire website lists me in Expo Hall, but it’s more likely that I’ll be somewhere in the dark area of Fiesta Hall instead. Check the Maker Faire website later in the week for more details.
See you at the Faire!
It’s officially event season! I was sorting through my calendar this afternoon and I thought I’d share a few geeky hardware/arcade/pinball/open source/hackercamp events that I’m looking forward to over the next few months.
May 18-19: Maker Faire Bay Area, San Mateo, CA. I’ll be there with a booth this year (Glowy Geiger Chimes).
May 17-19: Dayton Hamvention, Dayton, OH. I want to check out this HUGE ham radio event sometime, but my attempt to go to Dayton this year was thwarted because, yet again, it falls on the same weekend as the Maker Faire. Maybe next year.
June 7-9: Northwest Pinball and Arcade Show (NWPAS), Tacoma, WA. Definitely checking out this local show this year.
June 8-9: Seattle Mini Maker Faire, Seattle, WA (Another geek event collision, this time in Seattle.)
July 13-14: California Extreme (CAX), Santa Clara, CA. This might be my first year at CAX, if I don’t have to cancel at the last minute like last year!
Sept. 6: Open Hardware Summit, MIT (1st year held separately from the World Maker Faire!)
Sept. 21-22: World Maker Faire, Queens, NY.
Did I miss anything? What other events are folks excited about?
I visited this small but convenient Halted branch often while I worked in Santa Rosa, and I’m sad to hear this news. Fortunately, I’ll be in the area next week and will have one last chance to visit before the store closes. (Unfortunately, I’m traveling by air, so I won’t be able to bring too much surplus junk back home.)
HSC closed their Sacramento store in 2007. With Rohnert Park closing next month, the original Santa Clara location will be the only one remaining.
More details below.
Attention HSC Customers:
After 27 years in the Santa Rosa area, HSC Electronic Supply of Rohnert Park is closing its doors for good on May 4, 2013. Halted Specialties Co. Inc. will continue to operate its main store, HSC Electronic Supply of Santa Clara.
Store Closing Sale!
Rohnert Park Location Only.
20% to 80% Off Entire Stock.
Saturday, April 27th to Saturday, May 4th
Our shelves are spilling over in Santa Clara so we’d rather blow it out than truck it back to support on-going Santa Clara operations. Please stop by to check out this last opportunity for deals in Rohnert Park and stop by our Santa Clara store when visiting Silicon Valley. Don’t forget to visit us at www.halted.com as well.
via South County ACS
(photo credit: alvaroprieto)
This year I decided (in true last-minute fashion) to build a couple demos to show off my Geiger Counter kit at the Maker Faire Bay Area. One of these demos used my Geiger Counter kit to create ambient music:
(Thanks to @j_jwalrus for the interview and video!)
The PULSE output of each Geiger counter is connected to one input of a 74LS04 hex inverter on the Protoshield. Each time a Geiger counter detects a radioactive decay, it sends a 0.1ms 3V high pulse to one input of the inverter. The 74LS04 functions as a level shifter and outputs an (inverted) 5V pulse that is suitable for driving an ordinary (5V) Arduino.
Five outputs of the 74LS04 are connected to input pins on the Arduino. For convenience, I used Analog inputs 0-1 as digital input pins. The rest of the gates are connected to digital pins 10-12.
I used the PinChangeInt library on the Arduino to trigger an interrupt handler every time a falling edge is detected on one of the geiger inputs. This interrupt handler stores the pin number to a variable and sets a flag to tell the main() function that something has happened.
The main() loop polls the interrupt flag and waits for something to happen. When it detects that an interrupt has occured, it sends a “Note On” midi message to the Music Instrument Shield, using the SoftwareSerial library built in to Arduino 1.0. I had to hack the library a bit to get it to work in conjuction with the PinChangeInt library, since the SoftwareSerial library automatically installs interrupts for all pins (bad, bad SoftwareSerial!)
The value of the note depends on which Geiger counter triggered the interrupt. In the video I am using note ‘C’ over five octaves, centered around middle C (midi note 60). (I am not a musician, but this seemed to provide a pleasing sound that wouldn’t annoy me or my neighbors at the Faire too much.)
The Arduino sketch is a complete disaster right now, having been thrown together at the last minute, but I plan to clean it up and post it soon.
Things I learned while creating this demo:
- Sparkfun doesn’t include stacking headers with their shields unless you buy them in retail packaging. $30 in overnight shipping fixed that.
- Arduino is still a pain to program for if you do anything moderately unusual, like try to use two libraries together that both use pin change interrupts.
- You can get away without issuing “Note Off” commands for midi instruments that fully decay. (I think the MIDI spec frowns on this, but it works on the Sparkfun shield, at least.) This greatly simplified programming the demo, so I took advantage of it!