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Disclaimer: I’m an engineer, not a pro film maker. Be advised.

Disclaimer: I’m an engineer, not a pro film maker. Be advised.



Tonight’s Halloween project is another effect as old as time… Scary Shadows.


Shadows are obscure, raise suspicion, we can only imagine what creates them. The fear of the unknown is one of the basic, most natural fears. Even when a shadow is clearly defined, we still have a hard time gathering what it is exactly. Depending on the light source, the shadow of an object can be distorted and disorienting.


A shadow can be a monster, an entity, or just someone creeping up behind you. Young and old can get scared of a shadow.


To create a simple shadow casting project, I went about creating an Arduino stepper motor control system. Simply put, the stepper motor will move cutouts into a light source, casting shadows, for a few different effects.



The project by sections:


The concept is simple, cast shadows and control their movement.


To accomplish this, I used a stepper motor to turn a special 3D printed hub holding paper cutouts of various “monster” shapes. Placing a strong light source behind the cutouts will make a shadow on a surface.


I used a 1000lm LED flashlight for the light source. However, I found that removing the lens from the end of the flashlight produced a wider spread of light. With the cutout close to the LED in the flashlight, the shadows were large and distorted at times. Which was a cool effect.


Since I was controlling a stepper, I could control the direction and speed fairly easily. So, I had three modes of movement.


- Constant, clockwise

- Constant, counter clockwise

- Bounce between the two directions with a single button push. Like hitting limits.


A single potentiometer on the breadboard controlled the speed. Although I was in single-step mode, meaning the stepper moved one step per pulse, it was fairly smooth across most speeds.





1x Arduino Nano

1x Full-size breadboard

1x DRV8825 stepper driver

1x Low current Stepper motor

2x Momentary Push buttons

1x Potentiometer 100kOhm (I used these types, but you could use others)

1x 9V power supply. (I used a switching power supply from an old device.)

Project wires

1x Light source of choice. I used an LED flashlight


Schematic and design:


Not pictured is the 5V USB connection you also need on the Arduino Nano.


The actual build. The stepper motor bub is a custom 3D printed part. I could have just used tape and the paper.







If you connect the Arduino to a PC, I put in an option to output serial data.

In the Scary Shadow project, it will display the direction data.




-The paper cutouts were a pain to make a use, to be honest.



Other uses of the system:


- This is a prefect system to put inside the carved pumpkins. It will even turn on in the dark!

- You could also use them as eyes for the pumpkin too.

- Or, how about an overly complex nightlight?



If I had more money/time:


- First and foremost… 3D print the silhouettes as opposed to paper cutouts.

- I would like to explore digital shadow casting. Using an opaque screen, I could “turn on” pixels that could block light, hypothetically. I could animate the shadows! Now, that would be awesome.

- Sound is always good to add to effects.

- I wanted to create an effect of a crowd rushing behind someone. But, I think I would need more elaborate shadow casting apparatus. Perhaps a linear stage along with this rotary option.

- Add micro-stepping for a smoother turn



Oddities and observations:


- At the slowest speeds, there was a lot of vibration created by the single stepping.

- At high speeds, the stepper would slip. Which simply means that it was getting pulse faster than it could react. There is a maximum speed.