Low cost follow focus

[chuck colburn]

Yep, i went that route too in the beginning of my Steadicam career. But I found the slack/lack of precision specially with lenses that need a high torque or have a large barrel (so have a large circumference) too much.

 

To counter that i made the mark on the handunit moving slightly with the direction of the turning of the handwheel en so compensating for the slight distance in the handwheel where the motor does not move.

That worked well, but had to be adjusted to the type of lens.

 

a higher resolution system would work better, but at that time only 1024 bits were available, giving 512 steps, theoretically. Nowadays you might find better?

 

Still i think that this kind of DIY is important for the future career, i encourage it!

 

Hello Rob,

 

There have been improvements to the hobby radios, this one might help those who want to DIY.

 

http://www.towerhobbies.com/products/futaba/futl8926.html

 

Perhaps with the servo modifications for continous rotation and the increased resolution, (see the little video on the above web site) of the Futaba it might do for those not in the high end market.

[RobVanGelder]

Andreas, this is a link to that futaba servo:

 

http://www.futaba-rc.com/servos/specs-line...s-futm0099.html

 

 

And about the driver for the Heden, I made that from a drawing from Cinema Products, i found somewhere a schematic diagram that they used back then to convert the 5volt RC values to 12 volts.

I don't have those diagrams anymore, they got lost when i moved to thailand, but it wasn't very complicated.

Some opamps as drivers, to make everything very small was more of a problem and i did my first smd- soldering back then.

[AndreasKielb]

Andreas, this is a link to that futaba servo:

 

http://www.futaba-rc.com/servos/specs-line...s-futm0099.html

 

 

And about the driver for the Heden, I made that from a drawing from Cinema Products, i found somewhere a schematic diagram that they used back then to convert the 5volt RC values to 12 volts.

I don't have those diagrams anymore, they got lost when i moved to thailand, but it wasn't very complicated.

Some opamps as drivers, to make everything very small was more of a problem and i did my first smd- soldering back then.

 

Thanks a lot for the link, Rob. I might give it a try.

 

It's a petty that the drawings for the Heden driver got lost but I already curios to try it without :) .

I found the pinouts of the 5 pol. Lemo (1B 305) connector in the BFD manual:

1: MOTOR -

2: POT CCW (-) END

3: POT WIPER

4: POT CW (+) END

5: MOTOR +

 

Now I think I understand what I need to do. It's basically to integrate the electronics of an RC servo into the receiver and build a amplifier to bring the motor signals up to 12 volts. If somebody knows the resistance of the pot in a motor like Heden that would be great though...

 

Thanks again,

Andreas