Well, having used microforce zoom controls when I was operating on arris (backinnaday), I became very used to controlling zoom that way. There used to be an Israeli company that made them cheaper than the $6K models. I don't think they are around any more...

All cool ideas, but what is the use of a servo FF when you can't use it on a sound take?

Hey guys, after checking the USB back channel again, I'm sure it needs a USB host controller (as there was no simple on/off signal transmitted).

So, I will go the Arduino way.

Using an Arduino UNO and a www.iteadstudio.com Dual Step Motor shield 1.0 to controll a stepper motor from my Mac will be the first step. After that I will add a USB shield and incremental encoder to complete the package.

@kavadni a servo won't work, as it is loud and has only a very limited angle of rotation.

@andyharris thanks for the link to the stepper controll library - I hope it works with the iteadstudio shield?

@goanna @andyharris @kavadni you really got me convinced that the Arduion route is the way to go ;-)

First I really have to check the USB back channel on my wireless system (how it responds to direct voltage pulses). But if thats turns out to need USB controller chips I will buy an Arduino package and learn how to programm it.

With the Arduino it will also be possible to controll the focus motor from a Laptop with preprogrammed focus points. Quite some work ahead, but looks interesting. Thanks for all your input.

PS: Stage 2 of my rig is nearly finished - hand held Steadycam system (vest and arm are stage 3).

Do you need the follow focus to be wireless? If a cable is ok, use a servo and a cheap servo tester.

Servo controller

http://www.ebay.com.au/itm/Servo-Tester-3CH-ESC-Switch-CCPM-Consistency-Master-Checker-Indicating-Lamp-/300684584341?pt=AU_Toys_Hobbies_Radio_Controlled_Vehicles&hash=item460232a595

@psyco

Arduinos are simple enough, however note that the standard library for the Arduino is blocking. Have a look at this library:

http://www.open.com.au/mikem/arduino/AccelStepper/

This will simplify stuff.

I used a similar approach on my crane head control:

http://personal-view.com/talks/discussion/comment/78784#Comment_78784

@Psyco I was only pointing out the Arduino as an option. Yes , if you stick with some sort of signal coming via USB, you'll need to get usb pins 2 and 3 from your wifi transmitter connected to your stepper motor driver (and yes a shield will do it, as in http://www.circuitsathome.com/products-page/arduino-shields/usb-host-shield-2-0-for-arduino).

Once again, that's overkill. But in case you were hoping to connect the stepper motor to USB using analogue or logical pulses only, the ICs like nand-gate switches and buffers you'll need are already best used bundled into prototype stage circuit boards like Bssic Stamp, Pic and, best of all, Arduino. Once it works, you could look for something more elegant, (even a patent!)

@Psyco

As I understand it, you need a computer.

Yes, you use a computer, inasmuch as you write and test your program or "Sketch" and then transfer the compiled program to the Arduino:

From Wikipedia: "It is designed to introduce programming to artists and other newcomers unfamiliar with software development. It includes a code editor with features such as syntax highlighting, brace matching, and automatic indentation, and is also capable of compiling and uploading programs to the board with a single click. There is typically no need to edit makefiles or run programs on a command-line interface".

http://en.wikipedia.org/wiki/Arduino

There are good books to begin programming; also sites like http://www.psurobotics.org/wiki/index.php?title=Arduino_Programming

@goanna And how do you tell that board what to do? As I understand it, you need a computer.

Having a laptop controlling the stepper motor would be interesting, if I want to use predefined (key-framed) focus points, but thats not my goal at the moment. I want a wireless user controlled FF with the least amount of electronics.

Arduino is a computer. I cannot imagine how it could not be done - even if you need to build a whole robot;-)

http://arduino.cc/cgi-bin/yabb2/YaBB.pl

Indeed on of the best DIY rigs i have ever seen. Light and stable at the same time as it seems. Congrats! about usb backchannel: Guess there is no solution out of the box, but two arduinos could do the job.

@Alfi666 I was not talking about the low price chinese copies. I was talking about the American/European companies that sell the same parts for 3-5x the price but still use the same bold "design", instead of adding a couple of code lines to the CNC program and making the parts more usefull, light weight,... . They are just to lasy and to many people (with more money and less brain) pay for that BS.

If I would have a CNC milling machine, I would start my own business - and I would call my rig "The Hiper DSLR Pro Cinema Rig" and sell it for 10x the normal price...and there would be my name in big golden letters all over the parts, and I would start to make big DSLR shoot outs with my gear,...hahaha;-)