Tobin TCS ™-23 and Arriflex 200' magazine motor(No. 0175)

[Michael Leake]

I have a tobin variable speed motor. It needs 12V to run effectively.  I also have an Arri 200' magazine motor. I am not sure what voltage it needs to operate. I would guess 8V. It is not marked that it will support 12V.

I have a variable power supply which I can adjust from 15V down to 2V.  I thought I might be able to compromise and use 10V to power both at the same time. Any help would be welcome.  How can I identify what voltage the Arri motor requires without burning the motor? How could I change the Arri motor to 12V?

I could only post one photo on this post.

[Michael Leake]

[Michael Leake]

I found a compact circuit using LM7808 comnverter, a 330nf resistor, and a 100 nf resistor. I will be trying it out soon.

This will reduce 12V input to 8V output, just what the magazine motor needs

Edited March 23 by Michael Leake

[Duncan Brown]

The mag motor and the camera motor are usually both powered through connections inside the camera.  It will be tricky to convert the 12V to 8V somewhere between the camera and the mag motor, since the connector is hidden once the mag is installed.  Might require some fiddling about with the mag motor wiring, adding another connector, etc.

Duncan

[Duncan Brown]

Also, you might want to measure the draw of the mag motor powered with 8V and a mag full of film.  The 7808 is only good for 1.5A (and with a proper heatsink for that) and it's possible the motor draws more than that.

Duncan

Edited 10 hours ago by Duncan Brown

[aapo lettinen]

linear regulators are only good for low currents, typically something like less than 100mA in most useful applications. Higher current applications would typically overheat the regulator (it needing a large heatsink and a heatsink may not be enough if the voltage drop and thus the wasted thermal energy in Watts is high) either shutting it down automatically or damaging it. That is because the idea of a linear regulator is to drop down voltage by "converting all the voltage difference to heat". They are perfect for generating stable input voltage for sensitive electronics like microcontrollers and such but for motors I would always use a switching mode voltage converter which does not waste as much energy and does not have overheating problems with large current.

you could look for Pololu step down converters (the switching mode ones), most of them are relatively compact and might be one of the easiest ones to build into device and are pretty easy to find. Don't know if they fit inside the camera body but some of the might as they are more compact than cheap Chinese converters