Split Flap Assembly and Design

Welcome to our Split Flap Assembly and Design Instructable! Split flap displays are a fun, and quirky way to display messages in alphanumeric text. Since the instructions here are pretty lengthy, we've grouped the steps into 4 major categories:

1. Electrical Assembly
2. Hardware Engineering
3. Character Lettering Design
4. Software Programming

Materials for the Electrical Assembly (per split-flap unit):

1x Arduino nano (every) 1 https://www.amazon.com/dp/B07VX7MX27

1x Perfboard 24x18 holes (5x7cm) https://www.amazon.com/dp/B07LF78ZY3

1x Stepper motor Nema 17 with step angle 1.8deg https://www.amazon.com/dp/B094CQ4DBQ

1x A4988 Stepper Motor Driver with Heat Sink https://www.amazon.com/dp/B07BND65C8

1x Male header pins 4-pin https://www.amazon.com/dp/B0774VBJ3J

2x Female header pins 15-pin

2x Female header pins 8-pin

2x Female header pins 3-pin

2x Female header pins 2-pin

3x Female header pins 1-pin

1x Hall Effect Sensor https://www.amazon.com/dp/B07QS6PN3B

3x colors 22AWG Solid Core Wire https://www.amazon.com/dp/B07TX6BX47

4x TOTAL (for up to 8 split-flaps) Wire Nuts https://www.amazon.com/dp/B01MPXUEPO

2x TOTAL (for up to 8 split-flaps) 5KOhm resistors https://www.amazon.com/dp/B07HDFN3NV

Materials for Hardware Design (per split-flap unit):

2x Wooden Housing Case

1x Front Acrylic Panel

1x Acrylic Laser Cut Side Panel

1x Acrylic Laser Cut Right Wheel

1x Acrylic Laser Cut Left Wheel

1x 3D Printed Hub

1x 3D Printed Motor Mount

50x Split Flap

1x Acrylic Spring Holder

1x Aluminum Spring Holder

1x Spring Tin Strip

1x Motor Coupling + its screws

1x Magnet (for hall effect sensor)

4x #4 Washer

4x 4-40 Nut

4x 4-40 Bolt

11x #4 Wood Screws

4x 2/56 Nut

2x 4-40 Nut

2x #4 Washer

2x 4-40 x 1/2” screw

2x 4-40 x 3/8” screw

4x 2/56 x 3/8 Screws

4x 8mm M3 Screw

Materials for Character-Lettering Design

2x sheets of vinyl per 50-flap split-flap in the colors that you want the lettering to appear in

1x Silhouette Cameo

1x cutting mat

Here is an image containing all the supplies you will need to assemble the electrical wiring. See the supplies section above for a comprehensive list of all the needed components and links to purchase each

The diagram is what we will be building today. Feel free to build it your own way or follow our detailed instructions below!

First, solder wires to the hall effect sensor. Make sure the sensor is flipped the right way (when the face with chamfered edges is facing you, the wires are power, ground and signal left to right)! Add heat shrink for insulating the wires.

Cut the header pins down to the following lengths:

1x male 4-pin

2x female 15-pin

2x female 8-pin

2x female 3-pin

2x female 2-pin

3x female 1-pin

Place and solder components to perf board according to our design here. Your perf board's coordinates might not exactly match our spreadsheet, so be sure to still count the coordinates!

(For assembly, use the Top View; for soldering, use Bottom View, flipping around a left-right axis)

1. Plug 2 female 8-pin into the driver
2. Plug 2 female 15-pin into Arduino
3. Put Arduino onto the board and solder the pins to the board (Bottom View, solder D2-16, J2-16)
4. Put driver onto the board and solder the pins to the board (Bottom View, solder M7-14, R7-14)
5. Put 1 male 4-pin onto the board and solder (Bottom View, solder S9-S12)

   TIP: Unplug the Arduino and driver to better solder the small pins
   TIP: For the small pins, tape the non-solder side before flipping it over and soldering.

6. Put the 2 female 3-pin onto the board and solder them (Bottom View, solder K11-13, L11-13).
7. Next, do the 2 female 2-pin (B8-9, C8-9), and 3 female 1-pin (C13, K12, K14).

Wire the 4 wires from Top View, A->A (K13->S11), B->B (D16->S4), C->C (B13->S10), and D->D (K8->T10).

Following the Bottom View design, bridge neighboring cells in the same color in the diagram with solder.

Plug the Arduino and driver back into the board. From a top view when the Arduino is on the left and the driver is on the right, the Arduino's USB port should be facing up, and the driver's silver phillips screw knob should be facing the other way (you can check against the picture).

If you haven't already, now's a good time to stick the heatsink on the central chip of the motor driver.

Plug motor and hall effect sensor into the perf board. Make sure the red motor wire faces the USB.

Connect all of your boards together with two wires for I2C communication by plugging male-male jumper wires (or lengths of solid core wire) into the 4 header pins in a 2x2 square next to the Arduino. The two pins on the side closer to the USB port are SDA pins, the two farther are SCL pins. There are two of each so you can chain the boards together. And remember that somewhere on the I2C bus you will need pullup resistors (approximately 5KOhm) connecting each wire to 5V.

Connect all boards to the power supply, we found wirenuts useful here.

Admire your handiwork! Here's what our final product looked like!

Now, we will start creating the housing for your split flaps! Make sure to prepare these items before starting. Refer to this video as you go through all the steps for the "Hardware Engineering" of this tutorial.

Attach the 3D Printed Hub with the Acrylic Laser cut Left Wheel using four #4 Wood Screws (make sure the row of holes are oriented away from the Left Wheel).

Attach the 3D Printed Motor Mount with Stepper Motor using four 8mm M3 Screws.

Attach the 22AWG Solid Core Wires and Hall Effect Sensor with the Stepper Motor (Make sure that the narrower side of Hall Effect Sensor is facing out/ towards the magnet).

Attach the Motor Coupling with the Acrylic Laser cut Right Wheel using four sets of 4-40 Bolts, #4 Washers, 4-40 Nuts.

Attach the Motor Coupling with the Stepper Motor.

Glue the magnet onto the inner wall in the center of 3D Printed Hub (Make sure you have tested out the magnet beforehand and have glued it onto the correct side).

Attach the Right Wheel structure with the 3D Printed Hub using four #4 Wood Screws.

Attach Split Flaps by constantly loosening/tightening different screws in order to slide in the flaps (Make sure to have the first split-flap align with the magnet, so it’s easier to calibrate later) After all the flaps are in place re-tighten all the screws

Attach the Acrylic Laser cut Side Pane onto the Left Wheel of the Structure by first sliding all the wires through the cut-out of the Side Panel, then attach by using three #4 Wood Screws.s

Attach the Assembled Perf Board onto the Side Panel using four sets of 2/56 x 3/8 Screws, 2/56 Nut.

Attach 22AWG Solid Core Wires and Hall Effect Sensor wires onto Perf Board and wire management.

Sandwich the Spring Tin Strip between Aluminum and Acrylic Spring Holders using two 4-40 x 3/8” screws

Attach the Spring Structure onto the Side Panel of the main structure using two sets of 4-40 x 1/2” Screws, #4 Washers, 4-40 Nuts

Now one full structure of Split Flaps should be done. Spin the structure, and adjust the Spring if needed.

Attach the Split Flats structure with the rest. Done!

1. Prepare vinyl in the color and finish you’d like your letters to be in.

For our project, we ordered white and aqua vinyl with glossy finish. Our vinyl.

2. Select a font for your split flaps and scale the letter size so that it will fit on a single split flap.

For reference, you can see the Adobe Illustrator File that we used with every character already scaled and vectorized for the cameo.

To scale properly, make sure to measure the dimensions of your own flaps so that your characters are sized accordingly.

Feel free to use our font (The Adobe Illustrator files we used are below and ready for vinyl printing!) or make your own! Notice how every character is divided in half to account for how the characters will appear on the split-flap.

3. Cut the characters on vinyl using a Silhouette Cameo.

NOTE: Regular laser cutters will release toxins when cutting through vinyl, so please use an electronic blade cutter like the Silhouette Cameo.

4. Stick the cut vinyl onto the split-flap.

Every split-flap will get half a character (see image above).

While sticking them on, keep in mind that two adjacent sides of each split-flap form one letter. See our video as a guide to help you out!

.High level explanation of code, what leader does, what follower does

Our system is controlled by a single leader arduino which sends commands and receives updates from several follower arduinos which interface directly with a corresponding stepper motor setup.

The leader handles communication between the different follower arduinos and assigns specific commands to each follower arduino. The leader arduino is not directly connected to any stepper motor, and solely facilitates broader inter-follower communication and coordination.

Follower arduinos either wait in place, calibrate using the hall sensor, search for a specific letter, or spin based on their current state. After receiving commands from the leader arduino, follower arduinos execute actions based on their given command then update the leader arduino when actions are completed.

Leader Code Overview

The leader arduino can either initialize (under Initializing state in LeaderState) to set up communication between the leader arduino and all follower arduinos, calibrate each follower (under CalibrateFollowers state) by sending a CALIBRATE command to each follower, update state and sends the command to spin to a specific letter under the SendingReceiving state, or do nothing under the DoNothing state.

Follower Code Overview

Changing options and modifications

Pictured above is our final product! And a video of it working to display a poem we wrote :)