Note the apparent flashing and "off" time in the following movies is a result of the synchronization of the scan frequency of the camera with the strobe frequency in the Autophenakistoscope

Click here for short movie.
Click here for another short movie.

The Autophenakistoscope - A Study in Time and Motion

While looking into the history of the moving picture, I recently came across a reference to a device called a Phenakistoscope. The Phenakistoscope is an early predecessor to the motion picture. By studying this device, it's easy to see how it has evolved into television and movies. Invented in 1831 by Joseph Plateau this device creates a moving picture from a sequence of still pictures. It is simply a disk with a sequence of pictures and strategically cut slots that creates the illusion of smooth motion when it is spun and viewed in a mirror.

In this project, I have combined this 19th century technology with 21st century technology to create the Autophenakistoscope. First I have motorized the Phenakistoscope disk to produce a smooth, controllable, rotation speed. Next, I have added a strobe with a user settable frequency. Between the motor control and the strobe frequency control, the user can experiment with persistence of vision and sympathetic frequencies that produce a number of interesting visual effects. Finally, I have added hardware to automatically synchronize the strobe with the disk by detecting when the slits pass by the infrared (IR) sender/receiver (using an Arduino and a simple C program). With the flip of a switch, the user can toggle between manual strobe control to micro-controller strobe control. The result is a fascinating learning experience in motion picture technology, electronics, and programming.

By building this project, you will connect with the 19th century origins of the motion picture and apply 21st century tools to improve the experience.

Step 1. Materials List

A An otherwise useless CD
B Matte board or similar non-corrugated cardboard.
C 1/8 inch hard board panel (masonite) for the stand and box.
D Power Supply - See the choosing a power supply section of the article.
E 3000 mCD LED with holder/diffuser
F Infrared Emitter and Detector Pair (RadioShack part number 276-0142)
G 22 Gauge Solid Core Hook-up Wire - multiple colors makes things much easier.
H Wood Glue (white glue is fine too)
I Masking Tape
J Spray Adhesive
K Arduino Motor Controller Shield
L Arduino Duemilanove
M Lead Free Electrical Rosin Core Solder
N SPST Micro Switch
O 2 x 5K Linear Potentiometers
P Heat Shrink Tubing
Q Terminal Strip
R Wire Ties
S 1/4 Watt Resistors: 100 Ohm, 10K Ohm (2)
T Knobs for the 5K Potentiometers
U Knob used to fasten rotating parts to your motor
V Motor mounting screws and shaft collar
W DC Gear Motor. I used a Banebots model FIXME. Note that the rated voltage of the gear motor is important but it is not critical that it match your power supply exactly. We will be using Pulse Width Modulation (PWM) to drive the motor. This essentially pulses the motor at full power in very short spurts. A motor rated at 6V is likely to run just fine with a 9V power supply when run with PWM.

You might ask is why we need a gear motor for this application. Small DC motors need to run at high RMP to function properly. For this application, we need to be able to run at very slow RPM - as slow as about 10 RPM up to about 400 RPM. If you visit the associated web sight, you will see that I first tried to add a Lego gear chain and other similar contraptions to a bare DC motor. I can tell you right now that this is an exercis in frustration.

Preparation

Go to foo.com and download/print the paper templates for this article.

Step 2. Cut out and glue the disk

Select and download a sample phenakistoscope image from foo.com and print it on a color printer (color laser is best). Use scissors to cut it out but do not cut out the center hole.

Glue it to the CD using the spray glue. Apply a complete but not too thick coat of glue to the back of the paper. Too much might bleed through. When you apply the paper to the CD, you will have a few moments to slide it into place if it is not quite square.

Allow it to dry for 30 minutes then trim the center hole out with an Exacto knife.

Step 3. Cut out the sync wheel

Now cut out the sync wheel. First mark the matte board with a protractor that you have adjusted using the paper template (see downloads section). Make sure the protractor pointy bit marks the center of the wheel.

Cutting the matte board can be difficult with scissors or even an Exacto knife. The good news is that it does not have to be perfect. I used some electric scissors (really) and that made it pretty easy. Only cut out the circle this way, not the slots.

Step 4. Cut sync slots into the sync wheel

Tape the template to the sync wheel that you just cut out. Using your exacto knife, carefully cut each sync slot into the wheel. These slots are used to automatically synchronize the strobe with the rotational frequency of the wheel. They do not have to be perfect because the software has been written to turn on the strobe on the rising edge of the signal and to leave it on for a specific amount of time. Making the slot width perfect will make no difference.

Step 5. Cut out the stand.

At this point you need to make some decisions. We have provided templates for both the stand and the box the stand is sits in. You may have a different box that you would prefer to use. If so, you need to adjust the width and height of this stand so that it will fit nicely into your box.

The next decision is for your motor. Chances are, your motor mount will look a bit different that the one in the template. When you cut the motor mount, cut it to fit your motor.

There is only one critical dimension when making the stand and box. That critical dimension is the distance from the center of rotation of your motor to center point of the IR sender/receiver (the single round hole just to the left/bottom of the vertical section of the stand).

I used a chop saw to make the rough cuts for the stand, then finished with a hack saw.

Step 6. Mark and cut out mounting holes

Use an awl to mark, then cut out the mounting holes. The size of the mounting hole for the IR/Sender/Receiver is FIXME. Obtain the mounting hole size from your motor.

Step 7. Be sure the sync wheel and stand match up

Place the stand segment over the sync wheel to verify everything lines up properly.

Step 8. Cut out the remaining stand components

Step 9. Glue the stand

Now apply some wood glue to the stand ends and tape it together with masking tape. Be sure the sides of the stand do not protrude from the other segments or you may have trouble inserting the stand into the case later on (though this problem is easily fixed with some medium grit sand paper).

Step 10. Assemble the case

If you are using the case from the template, assemble it according to the instructions using wood glue and masking tape to hold it together. Allow the stand and case to dry for at lest an hour (overnight is better). Do not yet glue the front panel cover. The top cover is never glued.

Step 11. Now its time to solder

Need some schematics here?

When I first built the prototype, I used a standard protoboard to put it together. It worked but it was a mess and fell apart if you looked at it wrong. In order to make it more permanent, we'll need to solder some of the pieces together.

Step 12. Wire up the Potentiometers

This project uses two 5K pots. One is for the motor speed control and the other is for the strobe speed control. The middle pin is the signal pin. We want to choose a unique color for each of the signal pins.

More notes on wire - The positive (red) wire and negative (black) wire lengths need to be longer than the signal wires because they have further to go. 12 Inches is good. Use about six inches for the signal wires. It is important to use different color wires for each of the signal wires and to take notes on which wire is which. Otherwise be sure to mark the wires with a label maker as you make the connections. Once they are bundled its painful to trace the wires to their source.

The two outside pins are for the positive and negative power supply hook ups. We do want the strobe hook-up to be opposite the motor hook up (see web site for why) so one of the pots should have the red (positive) wire soldered to the left pin and the other on the right.

Step 13. Pots complete

When soldering wires to posts, it is important to first make a mechanical connection - in this case, wrap the wire around the post, then solder the connection. These pots had very long tales that I clipped after it was done.

Motor Speed Wire Color: Blue
Strobe Speed Wire Color: Yellow

Step 14. Assemble the IR Source

The IR source will be connected directly to the power supply (its always on). We need to solder a black wire to the anode (FIXME verify I have this right) and the red wire to the cathode (FIXME verify) through the 100 ohm resistor (FIXME verify).

FIXME - explain how to tell which is the anode and which is the cathode

Test it: I have found that this particular source actully emits some visible light when viewed in a darkened room. You can test it by connecting the red wire to a 5V source and the black wire to ground (available on your Arduino).

If your can't see any visible light, grab your digital camer and point it at the this unit - IR light will show up on the cameras display. This is a great way to test remotes and any other IR emitter.

FIXME - maybe I should have a photo of how IR shows up on a digital camera LCD.

Step 15. Shrink tubing

Now seal it all up with shrink tubing. Use a heat gun to generate the shrinkage.

Step 16. Complete the insulation

Cover both wires and the first shrunken tubing with the second shrink tubing and hit it all again with the heat gun. It should be a nice tidy package when its done.

Step 17. Wire up the IR detector

Similar procedure as with the emitter except we add a sensor wire between the FIXME anodle/cathode and the 10K resistor. Don\'t forget to take note of the color.

IR Detector Wire Color: green

Step 18. Wire up the switch

This switch is used to toggle between the manual strobe control and athe automatically sychronized control. Connect one side of the switch to positive, one side to negative through the second 10K resistor. The signal wire goes on the switch side of the negative connection. Don\'t forget to make a note of the wire color if you are using a different color to this article.

Mode Switch Wire Color: blue

Step 19. Glue the stand to the case

If you find that it is out of square enough to make it difficult to get the stand into the case, use some medium grit sandpaper to smooth down the interference points on the stand.

Step 20. Be sure to add hook up wire to the motor as well

The motor wires go to the first output on the motor controller board.

FIXME: Talk about how to select a motor. Why a gearmotor, what specs to look for, other important considerations (like the noise they make).

Motor Wire 1 Color: Orange
Motor Wire 2 Color: Brown

Step 21. Perpare the Positive/Negative Terminal blocks

Beacuse I am sometimes easily confused, I cut the terminal strip in half and color coded each side using a sharpie - Red for positive and Black for negative. Then attach about a foot of red/black wire to each side. These wires will be attached to the power source and ground on the Arduino.

Step 22. Jumper each terminal blck

After completely stripping a six inch length of the 22 gauge wire, I used it to jumper all of the terminals on the negative side. Do the same for the positive side. Check your work with an ohm meter. There should be near zero resistance between all of the terminals.

Step 23. Arduino and Motor Shield

Its time to make the connections to the Arduino but first mount the motor shield on your Arduino board. Verify that the pins line up properly. Its not idiot proof if you bend the pins - verify the pin numbers/5V/Gnd all match up when you mount it.

Step 24. Top view with Motor Mounted and Terminal Blocsk Installed

Motor and terminal connection wires get routed through the center channel.

Step 25. Install Pots and Switch

Mount the pots and switch onto the front panel using the hardware they came with. Sometimes pots have alignment tabs that may need to be clipped for this project.

Step 26. Mount the IR Sender/Reciever

The Sender is the darker one. It really doesn't matter which side they go on as long as they are hooked up properly. The Sender is always on so it is simply hooked up to the red/black terminal blocks so it is neater and easier to have the sender in the back.

FIXME: Talk about testing the pair

Step 27. Tidy up the wireing connect to Arduino

Now, gather your notes if you used different wire colors and make the connections to your Arduino board. Here is ho Yellow/Strobe Pot: Analog Pin 2
Purple/Motor Pot: Analog Pin 6
Green/IR Transistor: Digital Pin 2
White/Strobe LED: Digital Pin 13
Brown & Orange/Motor: Shield Motor A
Blue/Sync Switch: Digital Pin 3
Red/Red Terminals: 5Vp
Black/Black Terminals: Ground

FIXME - Verify Pins

Step 28. Mount the motor to the stand

Using the mounting hardware, mount the motor to the stand and attach the shaft collar to the motor shaft. Be sure the shaft collar is square ofter tightening and that it is close but does not interfere with the mounting hardware.

Step 29. Mount the synch wheel

If not already done, cut a hole in the center of the synch wheel to the size of the motor shaft. Again, it is not important that it is perfect but it should be close so that the wheel does not spin freely on the shaft. Be careful not to bend the wheel when mounting it on the motor shaft (make the hole bigger if necessary). Do the same with the smaller disc that is used to center the CD on the motor.

Step 30. Mount the image wheel

I have used a knob for this purpose but it is also possible to use another shaft collar for this. In my case, I did not want to cut the motor shaft so I drilled a hole into the knob to allow for the shaft. Be sure to have the knob snugly against the image wheel so that everything turns in unison.

Step 31. Ready for Testing

Before we tidy everything up and close the case, its time to run some tests. When power is applied to the Arduino, there will be a sequence of flashes from the strobe and the motor will spin up to about half power for a moment. The the board will start reading the inputs and react appropriately.

If its not working as described above, double check all your connections to the Arduino. If you are still having problems, see the trouble shooting guide at http://FIXME.FIXME