help me design an audio based camera controller circuit

Discussion in 'The Projects Forum' started by mehmehmeh, Mar 19, 2011.

  1. mehmehmeh

    Thread Starter New Member

    Mar 19, 2011
    5
    0
    Hi, I'm new to the forum and hobby. I would greatly appreciate it if I could get some held designing this circuit or pointed in the right direction.

    short version:
    I want to build a controller box with a audio headphone input and a camera output. The controller would function as follows: when sound is heard on the right audio channel of the headphone input it will close the focus circuit to the camera. When sound is heard on the left channel it will close the shutter circuit. A constant tone in the left input channel would hold the shutter output circuit closed.

    long version:
    I've been looking into building a dslr intervalometer and a hdr bulb bracket controller for a dslr camera.

    I looked at the arduino and ti msp430 launchpad platforms but I worry about my programing and circuit design/building skills. There is also the very nice open camera controller project that uses a Nintendo DS to control the camera, but the cable interface looks complex to build and a second hand pre assembled cable is going for £85 on the forum.

    I think I came up with an idea that should be a simple and cheap circuit to build, and would not require any programing.

    I was looking at some of the microphone flash triggers (1, 2) for high speed photography and thought the circuit could be adapted for interval timing or bracketing. (also note I can't fully understand schematic diagrams (I don't know all the symbols), but I get a rough idea how it works from the descriptions)

    So I want to build a controller box with a audio headphone input and a camera output. The controller would function as follows: when sound is heard on the right audio channel of the headphone input it will close the focus circuit to the camera. When sound is heard on the left channel it will close the shutter circuit. A constant tone in the left input channel would hold the shutter output circuit closed.

    This way you could hook the controller to say a mp3 player with a audio track that would take a picture every 2 seconds (a short tone on the left audio channel every 2 seconds) or a bracketing sequence in bulb mode (1/4 sec , 1/2 sec , 1 sec, 2 sec, 4 sec exposure sequence would be heard as a 1/4 sec tone, Silent Interval (SI), 1/2 sec tone, SI, 1 sec tone, SI, 2 sec, SI, 4 sec)

    You could have many different audio tracks stored on a mp3 player for different interval times or brackets. A playlist with a bracket audio track and a short silent track on repeat would result in a interval timed bracketing sequence.

    I want to use optocouplers/optoislators to keep the camera electronics separate from the controller electronics. Also want to have led indicator lights for the two output circuits for debugging/testing.

    canon camera remote pinout is as follows
    1 - ground
    2 - focus
    3 - shutter

    shorting pin 2 to 1 focuses the camera, shorting pin 3 to 1 will take a picture. Use of different cables would allow the controller to interface with multiple makes/models of cameras.
     
  2. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Unique approach. What is the purpose of sound, as opposed to a programmed timer? What real world application are you considering?
     
  3. mehmehmeh

    Thread Starter New Member

    Mar 19, 2011
    5
    0
    i figured by using sound, i can have a library of different intervals stored on a mp3 player. The mp3 player would serve as the control interface for the camera. Playing back different files through the controller would allow me to change the interval and also allow for bulb bracketing (taking different exposure lengths in sequence). Using the controller would allow me to make time lapse video, and do HDR photography with a easy to use visual interface (the mp3 player)

    I haven't done any circuit design before so this should also be a simple circuit to execute. Looks like I need to feed each audio channel through an op-amp then i can signal the optocoupler. Not sure what I need to do to also turn on the indicator LED lights (only want to send specific voltage to LEDs right? )
     
    Last edited: Mar 19, 2011
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Will the sound be heard or will it only be fed to the controller?
    Do you need more than one signal from the sound sequence?

    Bertus
     
  5. mehmehmeh

    Thread Starter New Member

    Mar 19, 2011
    5
    0
    sound does not need to be heard, I figure the controller will just have a 3.5mm input which will connect to an audio source like a mp3 player. Just need to get two control signals out of it, so that should be achieved using stereo sound and two sound detector circuits (one for each channel)
     
    Last edited: Mar 19, 2011
  6. bribri

    Member

    Feb 20, 2011
    133
    5
    something like this might work:
    http://www.eleccircuit.com/sound-operated-switch-by-bc109/

    (i think that this is the design i used quite some time ago)
    the input was adapted for line-level audio instead of a mic.
    if i remember rightly, tones needed to be above 1KHz is order to hold the switch down properly.

    a relay as in this design should provide all the isolation you need no?

    but maybe it would just be easier to use a dual opamp, 2 LEDS, 2 relays, and a few passive components.

    i guess you want to run this from a battery?
     
  7. mehmehmeh

    Thread Starter New Member

    Mar 19, 2011
    5
    0
    yes battery operated, and should fit it into something small like an altoids container.

    relays will provide enough isolation


    just to reiterate the basic goals:
    controller with 3.5mm stereo audio input jack.
    Loud noise on left channel input -> turn on led1 (close relay1)
    Loud noise on right channel input-> turn on led2 (close relay2)
    left and right channels should be independent of each other
    when a sound activates one of the leds, the led should stay on and be constant for the duration of the sound (close corresponding relay for duration)

    I will be generating the audio files for the controller on my pc, encoding them and storing them on a mp3 player, they don't need to sound like anything in particular as long as the controller works
     
  8. mehmehmeh

    Thread Starter New Member

    Mar 19, 2011
    5
    0

    how would you change the referenced circuit to accept line level rather than use a mic? also would there be changes to resistors if running this off 5v?

    i found this circuit it looks like it compares first then amplifies the signal?
     
  9. bribri

    Member

    Feb 20, 2011
    133
    5
    i probably used an "L-pad" made from 2 resistors. (was a long time ago)
    looking at it now, i guess that it's a bit overkill if you're using a line level input from a mp3 player headphone output.

    it's really a bit out of my league to say.
    if it was me, the first things i'd look at altering in case of it not working with 5 volts would be the 22k, 10k, and 470k values close to the diodes. perhaps the 2.2k connected to the LED also?
    but i rightly don't know actually.


    the transistor amplifies the microphone signal. the opamp... yeah, i guess it just outputs Vdd when its input goes above half of Vdd...
    ...sorry, i'm a novice here... hopefully someone who really knows what's going on here will chime in...
    if you decide to go with this design, i suspect that you can skip the transistor and use the other side of the LM358 instead.
     
    Last edited: Mar 21, 2011
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