On Tue, 24 Jan 2006, Olin Lathrop wrote:

> Padu wrote:
>> 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).
>
> Did you check that you still had nearly 5V after the current limiting
> resistor?  Do you know what the max current is supposed to be?  How do you
> know the limiting resistor wasn't way to big?

These irises will stick if overdriven. Knocking it lightly will release 
it if stuck. The drive polarity is important. Connecting it straight to 
5V should cause no damage (26mA through the 190 Ohm coil). A single 1.5V 
battery is a safer thing to try to determine the polarity. Attach it 
first one way then the other and see which opens the lens a little. 
Mark this wire (only feed current to the 190 Ohm coil, ignore the 540 
Ohm feedback coil for now). Then make a constant current generator with 
a LM317L and a potentiometer for 30mA f.s. and connect it into the 
circuit (observe the polarity you found before with the 1.5V battery). 
You will need a 9V battery to drive the LM317+iris coil assembly. You 
should be able to set the iris with the potentiometer. Afair you have to 
use a 10kOhm pot in series with 1 KOhm fixed resistor to set a LM317L 
between 3 and 30mA.

Peter
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