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Thread: Time-delay circuit...

  1. #1
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    Default Time-delay circuit...

    (OK - I know I posted a similar thread in another section...)

    Do any of you folks use a time-delay circuit and/or relay to turn on the lasers in your projector, and if so, would you be willing to post details here?

    I would like to go ahead and wire mine to meet all the CDRH requirements during initial construction.

    Thanks!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  2. #2
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    Default

    I know this is obvious and im not trying to insult ya but a 555 would do. Some CNIs use one and its output is ANDed with the ttl signal to keep the laser off for about 5-10 seconds after power up.
    Obviously you need to be a little more inventive with an analogue laser but its not crazy hard.

    Rob
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  3. #3
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    Default

    Hey Stuka! Do a google search for either "monostable multivibrator" or "bistable multivibrator." Either configuration can be built with a 555 timer, a capacitor and a few resistors. Depending on how you want the delay timer to work, you will either be building one of the two configurations above.

  4. #4
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    Thanks guys - I don't know WHY I didn't think about using a 555 timer to begin with!

    (Definitely one of those DUH moments )

    Randy
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  5. #5
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    Default

    A "Time Delay Relay" would be an easy way of accomplishing this, and that's how NEO-NEON does it. Many of these operate off of AC power, and delay the AC power from going further into the projector. Seems like an easy way to go...

    Bill

  6. #6
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    randy-

    the laser has a delay circuit built in. plug in and i believe its about a 6 second delay.

    -Marc
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  7. #7
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    An off-the-shelf time-delay relay sounds easy enough - I may have to give that a try.

    Thanks!

    Randy
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  8. #8
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    If you want to make an analog signal time delay, there are some interesting chips out there that were designed for audio, collectively called "bucket brigade" chips. They are a series of capacitors that hold an analog voltage charge. When the clock ticks, the last one dumps to the output and each one in the line before it dumps it's charge to the next one. These things were all the rage back in the day. They were the core of many time delay audio effects like echo, flanging, chorus, etc. If you set them up correctly, you can achieve almost no distortion. Take a look at the SAD-1024. It's a dual 512 stage serial analog delay. Radio Shack used to sell them!

    James.

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