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Re: HOWTO control auto-iris lens?

From: Rob Cruickshank   robcruicsympatico.ca
Date: Sun, 24 Jul 2005 12:33:39 -0700

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Most of the security-type cameras I've seen have an iris that is controlled by a galavanometer. This is pretty much like an analog meter movement. Like a meter, it reacts to current, rather than voltage. So you may damage it by applying straight DC, although the ones I've used seem pretty tough. What you want is a resistor in series with your voltage- try a 50 k pot for starters. once you find a resistance value that opens the lens to where you want at 5v, you can solder in a fixed resistor, (or leave the pot in so you can adjust it)
The video DC jack is proably for systems that allow the camera to be powered by the video line, very common in closed circuit stuff, but I'm not 100% sure.

arjen wrote:

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hi list


i have a lens here, that has electronically controllled zoom and focus.
and a connection for the iris to be controlled by the camera.

i would however like to control the iris myself, or rather fix the iris at certain point, so that the image the camera produces is always the same, and not influenced by light.

i want to use this for precise color-/motion-tracking

does anyone know how to control the iris?

i discovered that feeding the iris just power, starting around 5 Volts, it completely opens, which in our case is enough.
the camera has a power connection for the lens, which is perfect since we then don't have to provide seperate power for the lens.

the (much newer) camera has a connection that is supposed to ouput 9Volt power, and a control-signal, either control voltage or something called "Video DC" (what's that?)

but when Video DC is turned of on the camera, it outputs a 12.5 Volts power, when it's turned of, the power supplied from that output drops to around 3 Volts, which is just to little for the iris to open.
but i don't know if the iris will also work on 12 Volts.. or will i break it with a too high voltage?

so my questions are:
- will the iris work on 12 Volts
- is there a way to control the iris by a simple control-voltage signal
- what the @$#& is Video DC?


tkasnhs
arri


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--


Rob Cruickshank

email: robcruic(at)sympatico.ca
web: robcruickshank.net 


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