Auto control of manual motor-driven iris

[Stupidspencer 0]

I was just reading _NeoRage_'s topic "DC iris control circuit", which almost encompasses what I want to do, but I figured I would start a new topic since I want to do the opposite (and it looks like other members do too).

 

I have several Computar T6Z5710M-CS lenses which provide motorized control of zoom, iris, and aspherical focus. Here is a link to the spec page for this lens: Computar T6Z5710M

 

The lens provides motorized manual iris control via 2 wires: 8vdc (+) and (-). The problem is that it is extremely difficult to set the iris manually. I have to tap the control switch very quickly, and usually pass the optimal light level. 3-4 tries and I can get it just right. Thats 2-3 tries too many.

My cameras have AGC, which certainly makes it easier, but has drawbacks: If iris is a little too open, the image blurs significantly. And if the iris is a little too closed, video noise gets amplified by the AGC making the picture "snowy".

 

So I would like to find a way to connect this 2 wire iris to the auto-iris 4-pin connector so it will work automatically. I realize that lenses utilizing DC auto-iris functionality have 2 more wires (brake +/-) which provide positional feedback to create a closed loop circuit like a servo. What about video iris control? It is my understanding that when the camera is set to this mode, it provides a voltage based on the total light level? That could theoretically be used to create a closed loop with the proper circuitry.

 

Please help me come up with a solution. I am very good with electronics and am not scared to try anything. I print my own PCBs and am an expert solderer. With no formal education in electronics engineering though, I am at a loss as to how to design the circuit needed here.

[Stupidspencer 0]

Well fine then. I will take my question to a forum that is perhaps more appropriate; one geared toward electronic circuit design.