Why I Do This, In Pictures

The control system from Flux and Fire (2010):

The same control system, on one PCB (in a sketchy looking enclosure):

Never doing that first thing again.

Seeed Studio GPRS Shield v2.0 Audio Jack

I've been working with the Seeed Studio GPRS Shield in a project for a flame effect controller. The shield and underlying SIM900 module are great; sending and receiving calls and SMS messages has been very easy.

A problem with the shield that I've run into is that there is very little documentation for the two-in-one audio jack. It's a 3.5mm four-connector TRRS (tip-ring-ring-sleeve) jack for the handset speaker and microphone:

The shield schematic shows the following for the audio jack:

Testing the continuity of the connection to components on the board confirms that the pinout for the jack should be:

Tip Speaker +
Ring 1 Speaker -
Ring 2 Mic -
Sleeve Mic +

This is obvious in retrospect: visualize it as the audio connector is inserted upwards into the bottom of the schematic symbol. The pins connecting the jack to the board don't seem to be numbered sequentially counterclockwise from the upper right; the S+ pin (4 on the schematic) is on the lower left, and the upper left pin is not used.

The standard 4p4c wiring for a phone handset has four wires: black, red, green, yellow. Black and yellow are for the speaker, red and green are for the microphone. To use a standard phone handset with the shield, wire the TRRS connector this way:

TRRS 4p4c
Tip Yellow
Ring 1 Black
Ring 2 Red
Sleeve Green

The dial-a-flame-effect details post will undoubtedly happen at some point soon.

New PCB Business Cards

I recently ran out of my PCB business cards. Rather than just get another run printed, I designed a new one. Inspired by my last post on using DMX512 with a fenode board, the new cards are Arduino-compatible three channel controllers with an RS-485 interface.

As DMX is not supposed to be used with potentially dangerous devices, these boards are meant to turn 12V RGB LED strips into cheap DMX fixtures. Why a separate load power input (suitable for a deadman switch) remains on the board is left as an exercise for the reader.

The design files are on GitHub - you too can have PCB business cards with a small amount of KiCad know-how!

DMX512 as a flame effect controller

Flame effect controller, or LED lighting controller?

Using a fenode board and a 12V RGB LED strip, it's easy to make a DMX512 lighting fixture. DMX addresses 1-4 directly adjust the output of the 4 PWM channels using the controller's sliders. Channel 1 is red (above), channel 2 is green:

The fenode and dmxfire boards use RS-485 for communication, which is the serial communication protocol that DMX512 runs over. One simple Arduino sketch later, the boards take DMX512 commands from an off-the-shelf lighting control system. I'm using the Chauvet Obey 10, because it was cheap on eBay ($100 including 4 XLR cables). The only extra work was making an XLR-3 to RJ45 adapter cable; the next version of each of these boards will have a dual RJ45 and XLR footprint for data in and out.

The DMX512 specification states that it is not meant to be used for pyrotechnics and other potentially harmful devices due to the lack of error detection. (This is why the communications protocol used in Super Street Fire and other projects has error detection built in.) However, commercial DMX512-controlled flame effects do exist, and generally use multiple addresses for arming and firing. While I don't recommend using DMX512 as the communication protocol for a flame effect controller, it is possible.

The Charcade at Burning Man

This year's big fire art project was called the Charcade - a collection of seven fire art games set up in one big flaming arcade at Burning Man. Site 3 Fire Arts brought two projects: Super Street Fire, a reimagining of Street Fighter 2 in a ring of 32 flame effects, and Riskee Ball, 10 giant Skee Ball lanes that shoot fire when you score points. We also collaborated with five other fire arts projects and groups: Dance Dance Immolation by Ardent Heavy Industries; Rock Inferno, by Ar[sonic] Creations; Flamethrower Shooting Gallery, by Matisse Enzer; Toxic Bloom, by Ethan Garner, Christopher Linder, Joel Greenwood, and David Dowling; and Touch Me, by Noah Rosenthal and Nathan Clark.

The Charcade was a huge hit, and we burned approximately 10,000 pounds of propane (and ~100 gallons of gasoline - thanks, Matisse) over the week.

Photo by Neil Girling - theblight.net

Everyone loved Riskee Ball - apparently everyone who has ever been a kid, at least in this part of the world, knows and loves Skee Ball.

Photo by Neil Girling - theblight.net

Super Street Fire and Riskee Ball both use the control hardware I've developed - SSF uses individual fenode boards on each of the 32 flame effects, and each Riskee Ball lane is run entirely off of a dmxfire board that controls not just the flame effects but also the LED lights for scoring and the gameplay itself. Mens Amplio, by Don Cain, also used a wifire board to control its flame effects over I2C.

At the end of the week, the Ardent crew retired Dance Dance Immolation - by dropping a piano on it from a variable reach forklift. No joke.

Now that Burning Man is over, I'm going to return my focus to developing the line of flame effect controllers and accessories, and improving the firmware to make it easier to use as a drop-in solution for any project that wants to incorporate fire. Have an idea for a project and think this could help? Let me know!