How to isolate camera from circuit?

Discussion in 'The Projects Forum' started by JDR04, May 5, 2011.

  1. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Help! Im new to electronics and want to know how to connect my Canon 30D camera to a simple 555 timer circuit in a safe way so as to prevent any sort of damage to my camera. Is there a way to optically isolate it? I have a spare shutter release cable but do not know how to safely connect it to the circuit?? Any help out there?:confused:
     
  2. CDRIVE

    Senior Member

    Jul 1, 2008
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    A basic Optoisolator should work. The collector and emitter are dry and not committed to any other node.
     
  3. #12

    Expert

    Nov 30, 2010
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    In case you didn't know, optoisolators are available with several output devices, like an NPN transistor, a thyristor, or a few other things. This makes designing much more convenient than it used to be.
     
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  4. CDRIVE

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    The interface will look something like this.
     
  5. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks CDRIVE. Appreciate the schematic. Can I use any other type of optoisolator as the one you suggested seems to be in very short supply in the UK?
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
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    This isn't a critical component. Post the part number of the opto that's available to you.

    BTW, you could also use a plain old NPN Transistor. It won't provide the isolation that the opto does but I don't think you need it anyway.

    EDIT: We have plenty of UK members reading this that will probably tell you what's available in the UK.
     
  7. JDR04

    Thread Starter Active Member

    May 5, 2011
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    I bought a SFH618-2 but I'm having trouble getting it to trigger the camera. I can get an LED to switch on but not the camera. Do you think it has something to do with the part??
     
  8. CDRIVE

    Senior Member

    Jul 1, 2008
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    Did you measure the open circuit voltage at the shutter jack, as I asked? Are we sure that the center pin is positive?
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
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    The 4N30 has a darlington output and a 150mA continuous Ic rating. The SFH618-2 is only 50mA and 150mA with a pulse width <= 1mS.

    I don't think you should have purchased anything until we were sure of your requirements. Is your jack coaxial? Is one of its terminals connected to the cam case? What's the polarity. What's the current requirements?

    I assume that when you use the shutter jack with a push button switch, it works?
     
  10. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi CDRIVE, youre begining to scare me now........ but I've done the following to try and get you the info.

    Canon 30D

    The cable release has three wires in it. Theres no co-axial etc.
    One wire is to GND. The second wire is to FOCUS and the third wire is to SHUTTER. The sequence of them closing contact is; HALF push on shutter button brings the FOCUS and the GND wire into contact with each other. FULL push on the button then brings the FOCUS,GND and SHUTTER wires together in that sequence. Voltages are;
    GND + FOCUS = 4.5Vdc
    GND + Shutter =1.22Vdc
    (GND + FOCUS) together measured to SHUTTER = 3.27Vdc.
    All measurements taken with camera ON.

    Does this help? Thanks for your time again.
     
  11. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I am confused as to what you are isolation and what for. What's wrong with the cable release?
     
  12. CDRIVE

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    Did you read his first post?
     
  13. CDRIVE

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    Good information but you didn't answer this.

     
  14. iONic

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    I did. Seems to make no sense...
     
  15. CDRIVE

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    I didn't find the request odd at all.
     
  16. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi CDRIVE, the push button on the remote does activate the camera. All is well there. Oh yes, I forgot to mention that the Canon 30D doesnt use a jack plug for its remote cable release. Its a three pin type male plug on the camera body and a three pin hole type connection on the cable release end......sorry.(See attachments-Hope I've done it right!)Inside the button housing are three plates connected to the three wires I mentioned. The GND wire is in the middle, the FOCUS wire is on the very top and the SHUTTER wire is on the very bottom. I suppose if you really wanted to, you could make up a stereo type jackplug to extend the cable etc but that's not the purpose of this excercise.

    So, the first action to take a picture is to push the button half way down. This brings the top two plates/wires into contact and the camera FOCUSES. The next action is to then push the button all the way down. This brings the top two plates/wires into contact with the bottom plate/wire which fires the SHUTTER. The common plate/wire in both these actions is the middle plate/wire which equates to GND. Am I making sense?????
    I'm not sure what iONic is on about?
    Thanks for your time again.
    JDR04
     
  17. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Not to stop your progress, but connecting a 555 IC and opto-isolator to a camera does nothing without a purpose. If the purpose is to first focus then to take a picture, then this is a valid reason. I didn't see where you alluded to this. But my question is, doesn't the cable release you have do both these functions?
     
  18. CDRIVE

    Senior Member

    Jul 1, 2008
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    Honestly, you didn't mention anything about focus control until a few posts back. If you need to trip the focus function prior to shutter trigger then you'll want something like two 555's or a dual 555 (556). This issue is putting the cart before the horse though. We first have to get both of these functions to trip by using some basic tests.

    An Ammeter should present a very low resistance to the circuit under test. Because of this you can use it to test the closed circuit current from GND to either Shutter or Focus pins. Placing the neg probe on camera Gnd and the positive probe on either the Shutter pin or Focus pin should be nearly equivalent to closing a switch (shorting) these pins. SOP dictates that you always start your tests with the highest scale available and work your way down. Admittedly, this procedure was more relevant back when everyone was using analog meters, where pinning the meter movement was a very bad thing.
     
  19. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Sorry to mess you around about the AUTOFOCUS, I'll do the measurements and post them for you to check.
     
  20. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi iONic, all I'm trying to achieve is to be able to have the camera trigger at set intervals hence the 555 timer. Youre right, the cable release does do the focusing and the triggering of the shutter but that means I have to physically push the cable release button myself. Hopefully with CDRIVE's help I'll be able to have a circuit control the camera. If you have any suggestions I'd welcome them.
     
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