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help designing triggering device for underwater camera

Discussion in 'General Electronics Discussion' started by white_chev, Aug 8, 2016.

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  1. white_chev

    white_chev

    15
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    Aug 8, 2016
    Hi there. I am hoping someone can help me with a project. I acquired an old underwater camera that was used on ROV's in the oil and gas industry. I need to make some sort of tethered triggering device that will allow me to trigger the camera shutter from the surface of the water. I have an underwater cable that connects to the correct terminal on the camera itself. Originally this cable would have attached to the ROV directly and the camera shutter would have been triggered through the ROV remote control.

    Here are the technical details from the manual re: the shutter:


    3.1.3 SHUTTER

    When the trigger input line is pulled down, the bistable latch comprised of cross coupled nand gates is set resulting in the positive excursion of the input to monostable IC2. This monostable produces a positive pulse on pin 6 of IC2. This in turn turns on the shutter drive transistor effectively connecting the shutter solenoid across the 3300 microfarad capacitor C2 which has been charged to 16 volts. As the capacitor discharges, the solenoid current decreases down to a steady state value determined by its series connections with 2.7 ohm resistor, the drive transistor, and the two IN5392 diodes.

    As the shutter solenoid operates, the shutter contacts close, firing the sronge and also resetting the monostable via pin 3. Because of the short time taken to operate the contacts, the monostable's nominal 50 ms output pulse is shortened to approximately 15 ms by the reset of action on pin 3 of IC2.




    I have no real experience with electronics and would appreciate any insight or suggestions. The trigger will be operated high and dry from a boat. It could take any form- a button, plunger, etc. It doesn't need to be pretty just functional.



    Thanks in advance,




    Chris
     
  2. white_chev

    white_chev

    15
    1
    Aug 8, 2016
    Just adding other relevant information:




    3.1 CIRCUIT THEORY (reference Schematic B-378-40)

    The camera circuity is divided into two basic control functions: motor controls and shutter control. All circuity with the exception of the optical film sensor is located on a single P.C. board mounted on the rear end cap of the camera. The film advance sensor is located on a small board on the bottom of the camera. Access to the boards can be achieved by disassembly of the unit as shown in Figure 2-1

    3.1.1 POWER


    Power for the camera is supplied from an internal 9 volt alkaline battery. Power for the shutter and film advance motor are taken directly from the battery while power for the logic and control circuitry is buggered through a diode a 33 microfarad capacitor.

    C1, pines 1, 2, and 3, along with C1 and R1 comprise an RC oscillator which drives transistors Q1 and Q2 to produce -7 volt supply for C2. This allows the shutter solenoid to be pulsed with 16 volts giving the necessary drive for proper operation.
     
  3. shrtrnd

    shrtrnd

    3,827
    524
    Jan 15, 2010
    Your long and detailed description is pretty good.
    Any possibility you can get a schematic from the manufacturer, or on-line, or anything on the manual you're reading
    all this from, that gives a part number, to that IC2?
    If you can display the schematic here, somebody will figure-out your answer.
     
  4. white_chev

    white_chev

    15
    1
    Aug 8, 2016
    Hi shrtnd, thanks for the quick reply. I reached out to the manufacturer but they have not been very helpful because they stopped producing this camera 10+ years ago.

    I photographed the schematic from the manual and have posted it below (direct link- http://content.vickysabourin.com/DSCF4120.JPG)

    This may also be of some use:



    3.1.2 BULKHEAD CONNECTOR PINS


    A four pin underwater mateable connector is used to control the operation of the camera. Pins 1 and 2 are the sunc connections for firing the strobe light. Pin 1 is common, while pin 2 is connected to the strobe's positive lead. Check the strobe polarity as reversing the sync leads will cause faulty camera operation.

    Pins 3 and 4 are the input trigger connections, 3 being common and pin 4 the trigger. To trigger the camera, pin 4 must be shorted to pin 3.



    [​IMG]
     
  5. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Isn't it just a case of shorting pins 3 and 4 with a switch?
    Adam
     
  6. white_chev

    white_chev

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    Aug 8, 2016
    Hi Arouse1973, thanks for the reply. It would be great if it is that simple! I could easily test this- is there any risk to the electronics onside the camera?
     
  7. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    In post 4 you mention short pins 3 and 4 together to trigger the camera. Looking at the circuit it will supply a short trigger pulse at the front end. I guess this is how it should work?
    Adam
     
  8. white_chev

    white_chev

    15
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    Aug 8, 2016
    I will try it out and let you know. Thanks again.
     
  9. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Ok, let us know how you get on.
    Adam
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    There is already a TEST push-button switch that is part of the camera circuitry. This switch shorts pins 3 and 4 together when it is pressed. Try pressing this switch to see if there is anything wrong with the circuit before adding a few hundred feet of cable.
     
  11. white_chev

    white_chev

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    Aug 8, 2016
    hello Hevans1944. Thank-you for responding. I have used the test button and the camera operates properly.

    I just tried shorting pins 3 and 4 using a small bit of wire like this-

    [​IMG]

    With the top double connector attached to the camera. No luck. I could not get the camera to operate.

    Any other suggestions? Did I go about shorting the pins correctly?
     
  12. Alec_t

    Alec_t

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    Jul 7, 2015
    Possibly not. It's unclear which contacts on the cable plugs correspond to pins 3 and 4 of the schematic.
     
  13. white_chev

    white_chev

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    Aug 8, 2016
    Hi Alec_t - here is a detail of which connector is which:


    [​IMG]
     
  14. Alec_t

    Alec_t

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    Jul 7, 2015
    Providing all conductors in the cable are intact (have you checked with a meter?), and the contacts on the plugs and sockets are clean, then shorting the contacts that go to pins 3 and 4 should trigger the camera.
     
  15. white_chev

    white_chev

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    Aug 8, 2016
    Hi Alec_t - I can confirm that the conductors in the cable are intact. It is difficult to check the contacts in the socket but I have tried my best to clean them. I am still not able to get the camera to trigger via the cable.

    I hate to be dense, and I appreciate your patience. But can you please confirm that 'shorting the contacts' simply means touching the two contacts together? I do not need to add an additional power supply or anything else? Somehow it seems strange to me that the power from that little 9-volt battery could travel 200 meters up a tether be shorted.

    I may be grasping at straws here but I am hoping there is some other piece of the puzzle!
     
  16. white_chev

    white_chev

    15
    1
    Aug 8, 2016
    I wonder if the part in bold below may be the problem-

    3.1.2 BULKHEAD CONNECTOR PINS


    A four pin underwater mateable connector is used to control the operation of the camera. Pins 1 and 2 are the sunc connections for firing the strobe light. Pin 1 is common, while pin 2 is connected to the strobe's positive lead. Check the strobe polarity as reversing the sync leads will cause faulty camera operation.

    Pins 3 and 4 are the input trigger connections, 3 being common and pin 4 the trigger. To trigger the camera, pin 4 must be shorted to pin 3.




    The camera is designed to be used with strobe lighting. I wonder if the problem is that I am not using it with strobe lighting. Is there some relationship between having "pin 2 connected to the strobe's positive lead" and the camera operating properly?
     
  17. Alec_t

    Alec_t

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    834
    Jul 7, 2015
    Nothing else. Just bridging the two contacts on that lower plug with a piece of wire should do it. If it doesn't, then it looks like there's a problem with the camera [Edit: or its connector].
     
    Last edited: Aug 9, 2016
  18. Alec_t

    Alec_t

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    834
    Jul 7, 2015
    The schematic indicates that leaving the strobe disconnected won't affect the camera triggering.
    Check with your meter that pins 1 and 3 show permanent connectivity with the cable connected.
     
  19. white_chev

    white_chev

    15
    1
    Aug 8, 2016
    Alec_t thanks again for your help. I will check with my meter later and report back.
     
  20. white_chev

    white_chev

    15
    1
    Aug 8, 2016
    Alec_t - both cables show continuity so they seem to be in good shape. When I have the cable attached to the camera I can't get any of the pins to show continuity in any combination.

    I am curious if the connectors inside the female end of the connector (the connector attached to the camera itself) are dirty. Could this be a realistic problem? I am not sure the best way to clean them since they are embedded in rubber. I read that some connector cleaners can damage rubber. Maybe I should try alcohol?
     
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