Yoshizen's Blog

F-Aperture / Iris Control

Sigma Zoom(1)A09A4248-001

As I wrote in the previous posts, I have recycled rear element of the

broken Zoom lenses to use for the macro photography.  Both of them were

Canon EF type lens which has an electronically controlled Diaphragm / Iris.

Electronic Iris has an advantage, they  only needs electronic connection,

not a rigid mechanical connection though, this electronics is not just a cable.

Sigma Zoom(3)A09A4531—– If the recycled lens was maintained

all the electronics as before, Iris could 

be controlled by the camera side. 

But when the lens was stripped down

to Iris and its Pulse motor,  it is

necessary to create a driving circuit 

for the motor. = And this Pulse motor

needs to have a specific alternating pulse.  

So that a Pulse generator and a 

Full-bridge driver would be needed.

Sigma Zoom(2)A09A4525

Electronics is a funny phenomena.  It can be elaborated to have Hi-Tech

sophistication but in the same time it still works in a very primitive way.

= Such as the Electro-Magnetic device could be as sophisticated as HDD, still,

if you wind a wire around an iron nail and connect it to the battery, it would

work as an Electro-Magnet and pull the other iron pieces. 

To drive such pulse-motor, there are many IC chips in the market though

most of them are for higher voltage.  I needed to make it using discreet

components = as long as it generates alternating pulses, the Iris works.

(The original driving circuit has a PWM = Pulse-Width-Modulation for

smooth and quiet operation, but here better not ask too much)

The photo above is a circuit to open-close the Iris in the cannibalized

rear element from a Sigma Zoom lens.   (Can drive Canon’s  as well !)   

(Circuit was too simple, I didn’t even bothered to use Prototyping Beloboard

—– just soldered together. = as long as it works, good enough to test)


From the test, I found the circuit was just enough = no frill, bare minimum.

(Ideally the F-Aperture value indicator may be needed though, in practice,

I may not need more than “Fully open for focus — close down for shooting”

= I decided to put only  two switches, open and close. ~ ~ ~ When the building

work progressed, I’ll show the new photos.  🙂


PS:   WP noticed me, this is not only my 602nd Post but this is also the

Anniversary of 5 years  on blogging. —– gosh.  😀



5 Responses

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  1. […] is the up-date of the post with the same title […]

  2. Kendro said, on August 4, 2014 at 03:07

    Hi there, I’d like to ask if the iris stepper motor you used is a 2-phase one? Is it also okay to you if I ask for the schematic? Thanks.

    • yoshizen said, on August 4, 2014 at 03:35

      It was a motor in the lens and a Bipolar Two-phases type, it’s mean the Drive Current has to be from the Full Bridge Drive Circuit. (so-called H drive)
      And to drive this full bridge, it is necessary to connect clock generator (or multi vibrator such as common 555).
      You can Google [Full Bridge Drive Circuit] using discrete transistor easily and 555 Multi Vibrateor too.
      Good luck.

      • Kendro said, on August 4, 2014 at 07:07

        Hi thank you for the reply! I’m slowly learning about the H-bridge circuit and how to operate the 2-phase stepper motor. One question, I see a single battery (approx 1.5v) in your picture, but I’d still like to confirm if how many volts are you running the stepper motor with? And would 3.3v or 5v damage the motor?

        • yoshizen said, on August 4, 2014 at 09:56

          Most of those Hi-tech cameras were powered by 6 ~ 7.2V Lithium battery =
          Naturally the Iris Motor works on this voltage.
          The Battery in the photo was 2 X 3V Lithium Battery.
          (But not necessary all the parts in a camera would be happy with 5~7V connected straight.
          = current could be regulated such as by PMW control, and the power was connected
          only very short moment. If the motor was connected to the battery direct long time, it
          might be over heated and burnt out.)

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