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AgX
06-26-2007, 11:12 AM
A digital swing lens camera would need a bend sensor chip.
I doubt if ever someone begins with that. (Let`s say, before flexible sensors arrive...)

Ooooh, I just realized I posted absolute nonsense...
Of course one could do it via a line scanning device as in those rotational cameras. Then we would have the same discussion as with those film-based camera types.

AgX
06-26-2007, 11:17 AM
ben-s,

How do you steer the rewind or wind motor. Are they originally stepper motors too, or is a potentiometer sufficient?

Roger Hicks
06-26-2007, 01:18 PM
Roger,
There was a misunderstanding; I meant digital rotational cameras.


That's what I thought, but I wasn't sure.

Cheers,

Roger

ben-s
06-26-2007, 05:04 PM
ben-s,

How do you steer the rewind or wind motor. Are they originally stepper motors too, or is a potentiometer sufficient?

The motor in the film advance is a small DC motor.
I drive it with PWM (Pulse width modulation - skip the next bit if you know what this is)
----lecture mode on----------
PWM is a method used to drive analog devices such as motors or lamps at a variable power from a digital source.
A digital signal is either on or off, so anything connected to a digital signal source will be either fully on or fully off.
This isn't very useful for many applications, as we often require variable power.
This is accomplished by flicking the digital signal on and off very rapidly, so that the attached device is only powered for part of the time.
By varying the ratio of on time to off time, the power (eg speed or brightness) may be varied.
----lecture mode off-----------

In the program, I can vary the PWM rate (and thus the speed) of the advance motor, and I can also vary the step rate of the rotation motor.

When I reach the end of the film, I reverse the polarity to the film advance, and apply full power. This automatically flips a gear into place inside the camera to rewind the film. (The wind/rewind changeover part was originally in the camera, so I just left it there and made use of it)