On Tue, 24 Jan 2006, Padu wrote:

> Folks,
>
> I'm lost here, I have a CCTV video lens that has a mechanized iris. 
> The lens I'm using is the DC type (not the one that uses the video 
> signal). It has 4 wires: Control (-), Control (+), Drive (+) and Drive 
> (-). The lens manual says that maximum voltage is 6V while 0.5V closes 
> the iris and 4V opens the iris. I'm attaching a schematic cut from the 
> lens manual if that helps.
>
> My question is: how can I control that iris by myself? Yesterday I 
> tryed plugging 5V to drive+ and GND to drive- and nothing happened (I 
> added a current limiting resistor in series just in case).
>
> Anyone have a clue on how to control this lens? If I have a 5V psu, 
> just a pot is enough to control it?

The iris is meant to be operated in closed circuit with AGC signal. You 
want to operate it open circuit, so you can drive it with a control 
current. Try a constant current generator with a LM317L and a 
potentiometer. The action will be sticky and not linear. You want the 
maximum set current to be about 30mA.

Peter

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist