>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 25 January 2006 18:02
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Drive/Control Coil?
>
>
>
>
>On Tue, 24 Jan 2006, David VanHorn wrote:
>
>> I could be wrong, but I thought these were current driven 
>devices, as 
>> in more current = less light, in a linear sense.
>
>More current = more light. The drive coil will spin the rotor magnet 
>against a (weak) spring. It works exactly like an analog meter 
>except it 
>is moving magnet not moving coil, and it has a feedback winding.

Bearing in mind that these coils are normaly driven in a closed loop from the video output amplitude, I have to wonder how repeatable the mechanism would be from just applying fixed currents.  Any stiction will give some hysteresis in the transfer function, which could make getting a repeatable aperture setting a little tricky.

Regards

Mike

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