A Flicker of Light

"Birds" is closed. Here's what I learned about remote lighting effects:

This is one of the effects modules. Off-the-shelf, no custom PCB, and all purchased at Adafruit:

Feather MO/RFM69 board: Arduino-compatible with an ARM Cortex processor, hosting a 900mHz packet radio (as well as power regulation, LiPo charge management, and native USB capability)

NeoPixel Jewel; seven 5050 RGBW LEDs with internal controllers so the whole thing can be run from a single data line.

And a 3xAAA battery pack with switch and "JST" connector.

These are two of the "lamps" -- rather, incense holders. After fumbling around with a couple different ideas for diffusion the final choice was surprisingly low-tech; I stuffed bubble wrap inside.

And this is the setting. A little neighborhood church, minimal lighting setup. The transmitter (all the RFM69 chips are transceivers) is wired to a matrixed keypad and, to get just a little more power, a proper antenna also sourced from Adafruit. That's one of our musicians down there; the actors were doing photos before the house opened.



Radio performance? Fine. This is the lower power version of the chip and I've verified free-air transmission of half a block. I did have problems with one of the units when it was inside a brass ball; on the final weekend I stuck the wire antenna outside the lamp and it worked flawlessly after that. I also found they dropped connection when the batteries got low.

Battery? I didn't try to program sleep mode on either CPU or radio. One unit I turned off between performances and it lasted part-way into the second weekend. Another I left on night and day and it made it through two performances. A self-test and battery monitoring (which is quite possible with the transceivers) would be a good idea moving forward.

Intensity? Not spectacular. I only had eight standard theatrical fixtures (500W range) in the show, and even with all of them on the illuminated diffusor was quite visible. But they were incapable of putting useful face light into the acting area, at least in this configuration. I'm coming around to 3-5W as the minimum for a practical lantern or flashlight prop.

Software? This was a thrown-together mess, using a combination of library examples and repurposed Holocron software.

The most successful "look" I had programmed was a flickering lamp (since these are warm-white RGBW's, green+red to get an amber and a little white to make it brighter). It is a surprisingly good flicker considering it's simplicity:

At the heart of the program is a little function that compares a target value with the old value (for each channel of the LEDs), then divides the result by a rate, giving a float value of the difference per program cycle.

Then it cycles through, again by the rate, adding or subtracting this float, arriving at a new float (aka a fractional value), and temporarily converting it to the nearing integer to send it to the LEDs.

This allows me to fade up, down, or cross-fade between static looks. It also allows animation; for that, at each completion it will fetch a new number. In the case of the lamp flicker, this number is a random(constrained) intensity and rate. So sometimes it will quickly make a small change, sometimes it will slowly make a large change, etc., etc. The result is surprisingly realistic.

    By the way. I gave the musician one of my old Arduinos to play around with.