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As people trying to re-make it have let me know, the original instructions are now fairly out of date in at least two major ways.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!

Build Your Own Enchanted Rose Prop (Part II)

Part 1 of this article covers the basic parts list, code, and assembly.

UPDATE (January 2023): I’ve built a version 2.0 of this prop. See “Enchanted Rose 2.0: Raspberry Pi Prop with Falling Petals” for updated instructions. 

UPDATE (April 2021): The Bluetooth shield used in this Arduino-based project is apparently discontinued. If I were to build this project again today, I’d make it a Raspberry Pi Zero W with Headers (or 3B+) based device. Take note on that order page of the adapter cables and power supply you should also get.

The RPi would run a simple Flask (python) server to control the servo motors. I’d attach an Adafruit Servo Motor HAT to do the servo motor control, and then build a simple web application to control the prop. This would eliminate all the Swift Coding involved in the app controller, and allow for much easier building/debugging. I would absolutely use the same drop mechanism. That is, servo motors, spring loaded magnets mounted in a wooden golf-ball sized drawer handle.

To be clear, this updated approach would mean I would not order the Redbear Labs BLE shield nor the Arduino, nor would I futz with the fun but unnecessary iOS app. But nothing prevents you from building a nice one to control a Raspberry Pi based prop!

Now that the Enchanted Rose Prop is nearing completion, I wanted to cover a few final details. Here’s a video of the app and prop in its current form:

Aesthetic Touchup

Some paint and floral tape was used to give the stem a little more rose-like appearance. Still in progress, but you get the idea.

Ring Lights

The ring lights are a Neopixel 1 meter long strip. I cut the strip between the LEDs at roughly the 40 LED mark. Doing so has no effect on the Neopixel, as long as you cut between LEDs.

Big gotcha: These lights only want 5V maximum! I fried the first set by overpowering it. Don’t make that mistake — it’s irreversible.

Stem Accent Lights

I purchased a cheap set of LED lights to add some interest to the stem.

These are powered by their own 3-AA battery pack. I’m sure I could use the same 3 AA-battery pack used by the Neopixel strip, but after frying one of those strips, I chose not to risk wasting another $30 tempting fate. To turn these on and off, an N-channel MOSFET transistor is used, with its gate actuator tied to pin 10 of the Arduino.

Basically, the MOSFET transistor lets current pass through if voltage is applied to the Gate pin (pin 1 in the diagram above.) When voltage on the gate goes LOW, the LED accent lights turn off. When voltage on the gate goes HIGH, the accent lights turn on.

Soundproofing

The servo motors are a little squeaky when moving. I installed some foam sound barriers (ordinary shipping packaging) to help dampen the sound.

Drop Mechanism

The initial approach of using piano wire to move flexible wires up and down worked fine from a dropping standpoint, but it had two distinct disadvantages in practice:

  1. the vertical extension above the bud made it hard to get the upper petals to to look real
  2. the “re-set” procedure was going to be way too hard for young adults to do Did I mention that after I had the prop working for an adult, my wife told me that the crew would be entirely comprised of fifth graders? “Hardening” the prop for fifth grade use for 8 performances in ways such as this was actually the most time-consuming part of the project.

So instead, I revised the attach/drop mechanism, to fishing-line-pulls-a-magnet.

I drilled four holes into a wooden 1 1/2″ golf-ball. Tip: use two drill bits, a small one that goes all the way through (just for the fishing line), and a wider one for the hole where the spring mechanism sits. You’ll want to give the spring something to push against, so don’t go all the way through the wooden ball with the drill, as I mistakenly did.

The key part are rod magnets which are inserted into thread covers and put into a spring:

I later added rubber caps over these magnets (but first drilled a small 6mm hole in the center.) I then hot-glued these caps-with-holes over these magnets. In “normal” state, the magnet protrudes through the caps to make surface contact with the washers inside the petals. When the Servo motor moves, it temporarily (2-3 seconds, programmable delay) pulls the fishing line which separates the magnet from the petal, and then resets it to the normal position. The advantage of this design is that it only uses servo motor power during the drop operation.

Result: TOTAL SUCCESS. Worked flawlessly in production and could even be re-set by kids (though I admit I double-checked pre-show.)

The fishing line is pushed through the (orange) nylon thread cover and a double knot is used to prevent it from pulling through. Then, the rod magnet is inserted, finally that’s inserted into a spring. That subassembly is repeated three more times, and inserted into the four holes in the wooden “bud.” You’ll want to make the exit hole for the fishing line quite a bit smaller than the upper hole, so the springs have something to push against. The only thing that comes through the bottom of that wooden ball is four strands of fishing line, which are fed down into the stem, one to each of the four servos.

The petals have a small metal washer hot-glued to the base, which is magnetically attached to the bud. When the servo motor turns, the rod magnet is pulled down about a half inch to an inch into the chamber, and this action causes the petal to fall. The servo motor returns to “slack” position and the spring returns the rod magnet back to its ready position.

The petals can then be reattached.

This drop mechanism is much more durable, and now that the magnets are “self-resetting”, I’m thinking of switching the slider-control based drop mechanism to a simple push-button interface.

(Update: I did so, and those changes are reflected in the Github code. It’s a simple four-button interface for the drop mechanism, one for each petal; this initiates a retraction of the servo, a pause for a second or so, and then restoration to the ready position.)

Epilogue

The performances— all eight showings — were smashing successes!

Izzy, the fifth-grade prop controller, did a great job controlling it and the prop functioned just as designed.

Izzie and The Rose Prop

If there was a flaw, it was that one of the petal drops (of the 32) worked but got hung up on the LED light bush below it, so it appeared not to drop, but that was pretty minor and not a big deal.

Note that I did decide to replace the full set of AA batteries in the entire prop after the fourth performance. I can’t speak to whether that was unnecessarily premature, but there were no battery failures. Each performance was about 90 minutes, and the power to the prop was turned on about a half hour before and after each performance.

The Enchanted Rose Prop is now in the hands of the school theater director (and computer tech teacher; she’s one and the same) as a partial thank-you for all her great work with the kids.