I did find what I think might help us out, and it's a YouTube video that shows a guy controlling a dc-iris off a cctv lens, using a small circuit and a POT.
Now, this circuit is flying over my head... so I was wondering if you could help me out to figure it out.
The YouTube video is called DC Iris Driver Circuit Mockup DC Iris Driver Circuit Mockup.
Here is a screen-shot I took off the video... which isn't much high quality, yet I think it's the best I could come up with.
Any idea what I need to replicate this circuit?
I'm a n00b, yet I can try and draw it up in Fritzing!
My guess is that the drive pins are connected to a small dc motor and you need to drive them them from a small h-bridge. What is the resistance between those pins? The other pins are possibly connected to a sensor that detects the rate of movement. The diagram suggests that they could be connected to an amplifier.
I assume red and green are the drive connections. Try connecting them to a pair of pwm output pins. From each pin also connect a Schottky diode to ground (anode to ground) and another to +5v (cathode to +5v). Type BAT43 or BAT85 would be suitable. Drive the first output low and pwm the other. To adjust the iris the other way, drive the second pin low and pwm the first.
If the iris behaves as you have just described, then you should only need to drive it from one Arduino pin, not 2. Connect red to the digital output pin, and green to ground. Also connect a Schottky diode between the output pin and +5V, cathode to +5V. Leave white and black disconnected.
As 1.5V appears to be sufficient to operate the iris, I further suggest that you connect a series resistor of about 330 ohms between the digital output pin and the red wire, to avoid overdriving the iris.
Thanks for your reply!
I will do those as soon as the Schottky diodes arrive (ordered from eBay China, and ordered from DigiKey... I'm in the USA, so lets see if DikiKey arrives soon!).
When they arrive, I will setup what you say, and report back.
dc42, I tried to visualize your suggested circuit, yet I'm having a hard time even starting with anything.
I just don't have the experience.
Can you give me a little bit more hints?
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Another option/possibility I think I stumbled across is a "resistor ladder".
I do have a bunch of resistors, and I bought an "opamp".
Any idea how I could go about this?
Thank you for your time and help!
EDIT:::::
I thought of using a circuit like the one mentioned on this page.
I do have the RFP30N06LE MOSFET... yet I believe it needs at least 7.0v to "activate" or do something.
So I can't see how to do that.
Although it's doing pretty much what I need (see the video at the bottom of that post).
The mosfet circuit would work, but you don't need it because the current draw of the iris is so low. See attached schematics. The left hand one is my original suggestion, based on the assumption that you needed to apply power one way to open the iris and the other way to close it. The right hand one is my later suggestion, based on your observation that the iris is fully open when energized with 1.5V and fully closed when not energized. I suggest you use one of the PWM pins that is not attached to timer 0 (so not D5 or D6 on a Uno), because I expect you will need to increase the PWM frequency.
Hi, have you completed you project. I am also trying to decode the circuit for controlling dc iris through a pot so that i can further interface it with arduino. Please share information at rajatece@hotmail.com.
