Time Delay help

Discussion in 'The Projects Forum' started by amperage, Sep 26, 2008.

  1. amperage

    Thread Starter New Member

    Sep 26, 2008
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    Hi this is my first post here and I'm really hoping someone here can help me. Here's the basic layout for what I'm trying to do. I have a 1/8'' mono output line that sends out a signal anytime i connect my reed switch that I have it hooked up to but I want that signal to be delayed but about 1/2 a second or so and I want it to be customizable in case I 1/2 isn't exactly what I want. I know it's possible to do this. I'm assuming I would need to use a 555 Timer circuit but that's about as far as my knowledge base goes. Can someone please help me with this? A schematic would be great or any other help too. If there's already a device like this for purchase from like Radio Shack or something that I'm not aware of that would be cool too.

    -Amperage

    EDIT I've also found this schematic: http://www.electronics-project-design.com/images/timedelaycircuit.gif , but I'm not quite sure how if this is what I need, or if this will work with my 1/8'' mono input or how to use it or how much delay this would provide or how to change the amount of delay it's providing
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
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    Do you want to delay the activation of the reed relay or delay the audio as an echo?
     
  3. amperage

    Thread Starter New Member

    Sep 26, 2008
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    I'm not exactly sure how to answer that correctly. But I'll try and explain it this way.

    Lets say I have the switch hooked up to an LED so that when I connect the switch the LED comes on. I want to connect the switch at the same time I currently am, but I don't want the LED to light up when it normally would, but a split second later.

    EDIT I figure it shouldn't be too hard to construct a circuit where I can plug in my 1/8 mono using a 1/8 female type jack and then run it through some kind of delay circuit where the ouput is just another 1/8 cord that i'll be able to plug into my device
     
    Last edited: Sep 26, 2008
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Here is a link which may help you.

    http://www.eleinmec.com/article.asp?4

    Replace the trigger button, shown on figure 2 on the link, with your reed switch and replace the device with your led. Have in mind that you need to use a resistor in series with the LED to limit its current to a safe value (you have to calculate the resistor value according to your supple voltage and led voltage drop).
    The time delay the timer makes equals: T=1.1*R*C
    If you want to have a variable delay time you can replace R, shown on figure 2 on the link, with a variable resistor (100K) in series with a 1K fixed resistor. Also, use a 0.1uF ceramic capacitor (C).
     
  5. amperage

    Thread Starter New Member

    Sep 26, 2008
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    so looking at Figure 2 all I would need to do is choose the correct values for R and C(actually you say to use a 0.1uF cap so) to get the delay I wanted correct and otherwise build the circuit exactly as shown? Because cool. That looks like exactly what I need to do

    also are you saying(and I'm looking at figure 2 now) that I would need a resistor between pin 3 of the 555 and the device?
     
    Last edited: Sep 26, 2008
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    Yes, in your case the device is the LED. To drive a led you need a resistor in series with it to limit the current through it. Tell us your supply voltage and what led are you going to use as we can tell you the value of the resistor.
     
  7. amperage

    Thread Starter New Member

    Sep 26, 2008
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    well I'm probably going to use a 5 volt source and the device is not actually an LED, I was just using that as an example. I'm actually going to replace the LED with two wires which connect to the male end of a 1/8 mono jack so I can plug it into another device which basically creates a signal on the screen everytime i trigger the switch
     
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