Holo Projector Motivator

Posted: August 5, 2017 in Uncategorized

The holo projector is the thing in the 1st Star Wars (Episode IV) that projects Princess Leia’s message. It is located on the front of R2’s dome, right next to the radar eye. For my R2 build I wanted it to move. This will add a little bit of life and motion to an otherwise rather static droid. I want to the holo projector to move around randomly, as if it were scanning or looking at different things.

I saw a mechanism on Edwardo’s builder log over on the Astromech.net forum and that gave me an idea. Having become a huge believer in 3D printing, I thought “I could do that” and set out to build my own holo motivator (My own name for it). What I came up with works pretty well and slides right over the back of the holo projector. I imagine I will end up gluing it in place eventually, but for now it press fits decently enough to test it out:

I believe in part reuse and trying to get as much functionality out of a single piece as possible. With that in mind, the linkages and control arms are identical. To build it required only three different stl files, with two of the files run twice. These three parts were the Base, Control Arms and Linkages:

Figure 1-Base

Figure 2-Control Arm

Figure 3-Linkage

All that was required to complete the assembly was to drill out the holes (3D printing results in holes shrinking a little) and bolting everything together. In all, you will need:







Control Arm






Standard Servo



#6-1/2in Bolt



Small servo arm screw (Came with servo)




I choose to only bolt the servos down with two bolts each, but you can do 4 if you feel it is necessary. The control arms will rest on top of each other with one upside down. Finally, the control arm file (Not seen in the pictures below) has two holes for mounting to the servo. These holes are 1/4in apart and allow for a little bit of adjustment in the way the control arms are moved.

With everything installed I wrote a quick Arduino Sketch based on the provided servo example to test it out:

#include <Servo.h>


Servo Servo1;

Servo Servo2;


int S1Min = 25;

int S2Min = 25;

int S1Max = 165;

int S2Max = 165;

int DMin = 500;

int DMax = 3000;

int pos1 = 0;

int pos2 = 0;


void setup()


Servo1.attach(5); // attaches the servo on pin 5 to the servo object

Servo2.attach(6); // attaches the servo on pin 6 to the servo object




void loop()


pos1 = random(S1Max-S1Min)+S1Min;

pos2 = random(S2Max-S2Min)+S1Min;






The results were pretty good. Here are two videos of the holo eye moving from the inside and outside of the dome:






I will probably refine the code a little. As you can see the two servos move completely independently. I will probably change the code to allow force the movement to be linear.

That’s it for now.


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