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Thread: Electronics Gurus - Read Here

  1. #1
    FLAC Gutter's Avatar
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    Electronics Gurus - Read Here

    Our car stereo got jacked last night and I'd like to add a little surveillance. I'm wiring up a homemade video security system and need a little help. I bought a light with a motion detector and opened it up. I connected the power from a small camera to the switch inside the motion detector so that when the light comes on, the camera powers on as well. Easy enough.

    Here's the tougher part. I need to record only when the camera comes on. I'm thinking of setting up a linux PVR as opposed to a VCR, but either way, I'm not quite sure how to hook that up. A simple relay wouldn't work because in both cases I would need a momentary connection to simulate a keystroke or record button being pressed. And I need a second momentary connection when the circuit opens.

    As simply as possible, how would you do this?

  2. #2
    FLAC shakes's Avatar
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    the switch on the motion detector could also trigger the relay to power the PVR ... then you can build a momentary pulse circuit to "press record" for 1sec or so 5 secs after the pvr is powered up.

    the easiest way I know to do this sort of delayed momentary pulse would be either with a PIC or a BASIC STAMP.
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    Raw Wave hijinks21's Avatar
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    you gotta think like the criminal. If you see a car with a camera in it and one without a camera.. which one are you taking. I'm taking the one with the camera in it.

    Chances are you're not gonna get a good picture of him anyway.. a good one can take out a HU in seconds.
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  4. #4
    Raw Wave
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    Probably the easiest way is to connect the + supply of the camera to a parallel port...lets just assume its +5V for now. The standard parallel port have 5 inputs, so you can use any one of them.

    http://www.infonewsindia.com/pinout/#6A


    Then just read the parallel port if the +5V is on or not...that is the camera being on or not. A small software then act to it acordingly, I think girder does it.

    You should be able to use the serial port for this also, just make sure you provide the correct "HIGH/LOW" voltage level to the serial port. Even use the joystick button if you wish, the input is easily acessible from the gameport.


    If you did go for the momentary action...Im assuming you are trying to simulate a keystroke. Its alittle awkward connecting things to a keyboard though.

  5. #5
    FLAC Gutter's Avatar
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    The camera will be placed next to the light in front of my driveway. The idea is that during the night when the motion detector functions (it only operates when it's dark), the camera will come on with it. The idea is to then trigger a PVR or VCR inside the house that will record the video.

    So it may not prevent the actual theft, but at least there's a chance of tracking the cockgobbler down. Something I can hand to the police.

    Thanks shakes, I was hoping there was a simpler way that I wasn't thinking of. I've never worked with STAMPs and PICs before, so I guess I'll need to do a little edumacatin. Didn't someone on here build a momentary pulse circuit to trigger an ATX motherboard? Time to do a little searching.

    Very smart, Rickey. Only problem is that it's 110vAC, and not 5vDC. I suppose I could add in a AT power supply that is powered on with the camera and then sends the 5vDC to the parallel port of the PVR. Hmm, this might be possible after all.

  6. #6
    Raw Wave
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    The idea is to then trigger a PVR or VCR inside the house that will record the video.

    If you were more specific then I would have said :

    Look for 555 timers configured as monostable, stick a relay at the output. Then use the relay contacts as your "button press"

  7. #7
    Raw Wave
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    now you say its 110 V AC

  8. #8
    FLAC Gutter's Avatar
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    The parallel port idea seems to be the simplest. I can modify some open source PVR software pretty easily to get it to record when it gets a signal from LPT1.

    According to this:
    http://www.electro-tech-online.com/v...?p=27194#27194

    I just need a <560ohm resistor, probably an LED so I know when the unit is functioning, and a relay that's triggered with power is applied. Awesome.

    Edit: Even simpler! Modify the software to record as soon as a video signal is detected. The hardware side might be simpler, but the software may be a little complicated. I've never worked with the TV inputs on video cards.

  9. #9
    Raw Wave
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    I just need a <560ohm resistor, probably an LED so I know when the unit is functioning,

    You dont really need the resistor as you are allowed to earth the input directly to the parallel port ground, but stick one if you want anyway.

    With the LED to indicate its on, not sure where you gonna get your supply to do this. Also how does your relay get activated? If you already knew how to get the signals you needed then I cant see it not working, just a matter of programming the software side of it.

    Good luck

  10. #10
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    I've seen various software out there that will only record when it detects motion in the frame, so you would not have to worry about external triggers, etc. if you record in software.

    Unfortunately I don't have any links, but if you can search for "webcam" or something like that. It's possible that you'll find some good stuff.

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