This is my senior capstone project as a Technical Director student at the University of Cincinnati College-Conservatory of Music.
My name is Christian Mikkelsen, I graduated with my BFA in Technical Direction in 2014. Please check out my website.
Have you ever had to make something magically fall from the sky for a specific duration of time on a show? Have you drilled holes in sonotube and put a crewperson on a rope to shake it? We have a better solution, the automated Petal Drop is a relatively simple device that can be built with items that can typically be found in most scene shops, and with a few hours of diligent wiring you can make a REALLY cool(and, of course, incredible useful) cutoff switch activated Via a photosensitive resistor and two LED’s. In this article I will walk you through the steps to make your very own leaf drop that can be turned on from anywhere in the theatre, no ropes required!
Step 1: Acquire Parts
You will need the following to build ONE(1) Petal Drop Box
1’ – 1” ID Pipe
1’ – ½” square steel (hollow or solid, it doesn’t matter)
1’ – 2”X1/8” flat stock steel
3’ – 1”X1/8” flat stock steel
1’ – 1”X1/4” flat stock steel
6” – 3”X1” 16 GA square steel
3” – Piano hinge with a 1” butt
1” – ¾” Angle Iron
2 – ¼” Threaded Insert
2’ – 2” dowel rod
a relatively small amount of B/C Plywood
1 – 12 V DC motor, I used a BOSCH windshield wiper motor.
Model # 6 004 PA1 018
1 – ¾” Universal socket(12 Pointed) – it fits the drive perfectly
An assortment of #10 Machine screws, nuts, and washers
Step 2: Acquire Board Parts
You will need the following parts to make 1 board for your Petal Drop
1 – 100K Resistor
1 – 1K Resistor
1 – 2M2 Resistor
1 – 1M Pot (Variable Resistor)
1 – 10 uF/25V capacitor
1 – LDR – 10K under shade
1 – Relay, big enough for your motor, I used a 5V FRT2H-S
1 – 9V Battery Snap
2 – 220 Ohm Resistor
2 – White LED’s 5MM
1 – 5V voltage regulator - MC78L05A, TO-92 Package
1 – NPN transistor - 3904
Step 3: Build Box
Start by cutting out your pieces of ¾” Ply
2 @ 13-1/2” X 5”
2 @ 12” X 5”
1 @ 13-1/2” X 13-1/2”
Assemble all pieces EXCEPT ONE 13-1/2”X5” piece
-Attach them well; you want this puppy to last!
Drill 1-1/2” holes at specified points, Refer to drawing below
Weld and attach sliding arms and brackets to free piece and box
Once the sliding arms are placed, attach the motor to the box in the specified hole (across from the sliding side) and make the appropriate standoffs to place it properly. For my motor, I used a Half inch piece of the same ½” square steel that is on the parts list.
Paint the whole sucker black
Step 4: Build Rollers
Thought the first part was easy eh? Well now it gets fun
Start by cutting your dowel rod to 11”, you should have two pieces. Paint these either white or a metallic color, either way, make it HIGH GLOSS, this is critical for the circuitry to work properly
Next, cut four ¾” pieces of the square stock and four 2” pieces of flat stock, weld the square stock in the center of the plate steel, THESE MUST BE PERFECTLY STRAIGHT! I cannot emphasize that enough.
Cut four 1-1/2” pieces of your steel tube and grind them nice and smooth, inside and out, place it on the plate steel with the square stock and center the square stock, this is very delicate and MUST be as close to perfect as you can make it.
Once you’ve assembled the dowel ends, clip and grind it down till all sides, inside and out, are nice and smooth
Then, attach it directly to the precut dowel rods, centered on each end. It must be pretty, so take your time to find center. Use a screw through the center and JB Weld to ensure a solid, and permanent connection
Step 5: Make Your Silk
This one’s easy, don’t worry!
First, cut your silk to 10 ½” wide and however long you want(the longer the silk the longer the effect can be, mine was 24’ long)
Then, serge ALL edges to avoid fraying.
After you’ve serged the edges, upholstery staple the fabric ends to the dowel rods, finish with a strip of gaff tape to ensure good connection.
Step 6: Make Your Board
This takes time, make it look pretty, simply follow the attached schematic, refer to the photos section to see what your final product should look like, DON’T FORGET TO PUT THE LED’S AND PHOTOSENSITIVE RESISTOR ON THE BACK SIDE 1” OFF THE BOARD!!
Step 7: Attach Board and Circuit Box
line up the LED's and Photosensitive resistor with the NON-DRIVEN roller, centered on the box and dead center on the roller, drill holes for all three and stand the board off the box using washers so all three are flush with the interior face of the box top, once attached place and secure the Circuit box to completely cover the board as well as battery, grind slots for the wires to run out of the box while it's closed. Connect the positive lead from the voltage regulator and positive motor power(through the relay of course) to a euro-strip, this makes it easy to hook it up to control. do the same with the emitter of the NPN transistor and the negative motor power.
Step 8: Test Circuit
Run the motor and when it hits the end of the roll it should stop on its own, the reflection of light from the roller should set off the photosensitive resistor. if it doesn't adjust the Pot until it does. if it trips while there is still black fabric add resistance through the same pot.
Step 9: Done!
congratulations, you've just made a pretty cool little piece of theatrical magic, go drink A beer!