Enchanted Rose 2.0 with Falling Petals

Revisiting the Enchanted Rose project four years later, this time with an open-source build based on Raspberry Pi.

Four years ago, my daughter was in a school production of Beauty and the Beast, and I volunteered to build a stage prop “Enchanted Rose,” which could drop these petals on cue. The initial project was fun, and the play was a total success. They did about ten productions in the spring of 2019.

I documented the build in a two-part blog series.

Those articles and their accompanying YouTube video made their way around the search engines. And in the years since, I’ve gotten emails from more than a dozen stage managers around the world (Colorado, Texas, California, London, NY, Florida, Hawaii, Scotland and more.) Stage crews, parents and students are looking to build the working prop.

Some even inquire about rental. Well, rental of the version 1.0 prop is out of the question. Not only was the original design based on servo motors and springs and fishing line, far too delicate to ship, the version 1.0 isn’t even in my possession anymore. I gifted it to the director. She’s also the school’s computer teacher, and she really wanted the prop.

As people trying to re-make it have let me know, the original instructions are now fairly out of date in at least two major ways. First, the Bluetooth board that the prop relied upon has since been discontinued. And second, the controller was a native iOS app written in Swift 3.0. Apple has updated the Swift language app so much that the old native app no longer compiles. Though I could get the app working again, Apple has made it fairly difficult to distribute apps ad-hoc, and I have no interest in publishing the app in the App Store as it is far too specialized.

But with every new inquiry from a hopeful production manager, I’ve felt it would be a nice thing to do to rebuild the prop, to better explain how to build one.

And so, here it is. Enchanted Rose 2.0 is a web-based one with a Raspberry Pi and an open-source approach. The basic mechanics are now working:

Enchanted Rose 2.0

Features

  • Control via private wifi network and mobile web browser, not native app
  • Total cost no more than $200
  • Durable enough to ship
  • Do NOT require that it connect to a local internet
  • Easy to use interface that an elementary school stage crew could use
  • Easy on-site setup. Ideally, just turn it on and it works.
  • Battery operated — most productions like to keep the illusion (and stage safety) by eschewing cords.

The main functions of the prop are to remotely:

  • Turn stem light on and off
  • Turn accent light on and off, and set colors and pattern
  • Drop 4 rose petals, one by one, on cue

Basic Approach

Lighting: The lighting circuitry is the same as in v1.0 design. That is, for the “stem lights”, a Raspberry Pi uses its GPIO port to send a signal to a resistor’s “base,” to allow a 4.5V circuit to complete.

For the Accent Lights, there are Neopixels; I found the 60-LED strand to be the right size. There’s a very good article on Adafruit telling you how to use a Raspberry Pi and Circuit Python to power Neopixels. Just as they recommend, I used a level converter chip (the 74AHCT125) to convert the Pi’s 3.3V output up to 5V without limiting the power drawn by the NeoPixels.

Both of the lights are powered by 4.5V, delivered by 3 AA batteries in a battery pack.

Drop Mechanism: For the drop mechanism, I made major changes from v1.0 to v2.0. Version 1.0’s use of magnet-spring-fishing-line servo-motor works for local productions just fine, and has some advantages (reliability once calibrated.) But it is far too delicate to ship. I experimented with electric solenoids pulling on magnets, but the smallest ones were too weak, and would require an enormous “bulb” to house.

I hit upon the idea of using pneumatic pressure! That is, pumps create puffs of air in tubes, which jettison the petal.

Software: Control of the prop is via a Python-based API, which has a front-end control app (link to repo below.) That is, the prop itself hosts a web server on the Raspberry Pi, and presents its own private “ad-hoc” network. The stage manager connects the prop’s ad-hoc network, and accesses the controller software. This general pattern can be used to build “remote control” devices.

There are three main components to this stage prop:

  1. The front-end control software, written in React/Next.js. You’ll find that code in the enchantedrose repository. From a technical standpoint, all this repo does is present a nice front-end layer onto the API.
  2. This hardware API, in this repo: Enchanted Rose Python API. This repo is the essential python-based API software. This controls the GPIO pins on the Raspberry Pi and presents an API on port 5000 to the world. The role of this software library is to provide an API for turning on/off lights, dropping petals, etc.
  3. The prop hardware itself.

Software

The two key pieces of software, other than the Raspbian Operating System itself, can be found here:

You’ll also need to install the NeoPixel driver libraries, which are well documented over at the Adafruit website.

Hardware

Each pump motor needs a circuit like the below. Since RPi cannot output 9V, we’ll make use of a transistor to switch a supplied 9V current on and off. (Note that in production, I ended up boosting the power supply to 8 AA batteries, or 12V. The motors can handle this higher voltage for short duration, even though they’re rated for 6-9V.)

Since these motors generate current spikes when they are powering down and powering up, it’s very important to protect your RPi with a diode, as follows (the directionality matters! pay attention to the line on the diode and the positive lead from the motor):

Wiring diagram for pump motors

There are four such circuits, with the power source and RPi being shared between them.

Accent Lights

The circuit and software to control Neopixels is well documented at Adafruit’s website.

Configuring Raspberry Pi for “Ad Hoc Network”

I was excited to hit upon the idea of having the prop create its own “Ad Hoc Network” (i.e., it’s own Wifi SSID that you can join.) Not only did this eliminate the need to have the stage manager at each playhouse somehow find a way to connect the prop into their own local network, but it removed any requirement for a display or keyboard to ship with the device for configuration purposes.

All they have to do is plug in the device, wait for boot-up, and it presents its own Wifi Network (“EnchantRose”.) They then simply enter the password, bring up a web browser on their phone, and visit a pre-determined IP address which I’ve configured: http://192.168.11.1. It took a while to figure out how to configure Raspberry Pi to do this, since the instructions have changed seemingly with every release of Raspbian, the RPi operating system. But I figured it out by adopting existing instructions, and blogged it here.

What’s most exciting about this is that it’s a pattern that can has many applications in the world of “Internet of Things” — run Apache2 on your Raspberry Pi to host a website, and render that website visible via the Rpi’s own password-secured wifi network.

Current Status

The new version 2.0 prop is fully functional. I’m now in the “arts and crafts” stage of making it look much more realistic. There’s more work to be done there, as well as documenting a setup guide for stagehands.

I’ve gotten four more inquiries since November 2022, and will be selling this prop to one of them. I had considered renting it out, but it’s a bit of a logistical hassle to ship and receive. If you’ve got specific questions on assembly or the software, drop me a note. On with the show!

Author: Steve Murch

Steve’s a Seattle-based entrepreneur and software leader, husband and father of three. He’s American-Canadian, and east-coast born and raised. Steve has made the Pacific Northwest his home since 1991, when he moved here to work for Microsoft. He’s started and sold multiple Internet companies. Politically independent, he writes on occasion about city politics and national issues, and created voter-candidate matchmaker Alignvote in the 2019 election cycle. He holds a BS in Applied Math (Computer Science) and Business from Carnegie Mellon University, a Masters in Computer Science from Stanford University in Symbolic and Heuristic Computation, and an MBA from the Harvard Business School, where he graduated a George F. Baker Scholar. Steve volunteers when time allows with Habitat for Humanity, University District Food Bank, Technology Access Foundation (TAF) and other organizations in Seattle. read more