A New Crystal Sync Motor for the Arri 16s

Kamran Pakseresht · December 10, 2024

Hi all,

It's been a few of months since I started my project of developing a crystal synchronized camera motor. At first I wasn't really targeting any camera system - I just wanted to prove that I could control a motor with a very fine level of precision. Well I made it a little further than I expected and we now have a completely new crystal synced motor for the Arri 16s:

I intentionally developed the motor with easy to obtain components as it is my intention to open source the design files and the code, allowing anyone to build and repair these motors themselves. There are no custom PCB boards and many components can be swapped for alternatives if needed.

The motor bypasses all of the internal electronics of the Arri 16s and directly drives the camera through a 12v power source provided by the 4-Pin XLR port on the rear. There are 2 available crystal speeds: 24 and 48fps. The USB-C port on the top allows you to re-program the motors micro-controller easily, and you can even change which speeds are mapped to the slide-switch through this port. There is a led on the top which illuminates white when power is applied, red when the motor is not up to crystal speed, and green once it achieves locking.

It took quite a bit of work to just find the right components to build this motor - the Arri 16s is a particularly difficult camera to build a motor for, not just because of the space constraints, but because it takes 3 full rotations of the shaft to expose a single frame, so a 24fps speed actually requires 72 rotations or 4320 RPM and twice that speed for 48fps. These are relatively insane speeds for 16mm camera motors, and explains why the Arri 16s has been known to have a particularly heavy current draw.

A very big thanks to Friedemann Wachsmuth who took the time to help explain and even share some code with me to get me started on this project.

I am selling these motors for $350 at my website here.

I have relentlessly tested these motors myself against stroboscopes and also compared with other crystal motors, but the proof is in the pudding as they say, so I've also included two youtube videos here, one from the 24fps test and one from a 48fps test - you can also get a sense for how loud the motor is by watching these - it is a bit quieter than the constant speed motor, but let's be honest, you're gonna need to be creative with your mic placement - I recorded on a Tascam digital field recorder with a small boom:

Sebastian Bock · December 10, 2024

Kamran, you are a genius!
This is so great! Thanks for sharing your fresh ideas to keep our beloved gear running and for supporting the 16mm filmmaking community.

Cheers,

Sebastian