555 Timer Help please help me

Discussion in 'The Projects Forum' started by memyselfandi, May 22, 2009.

  1. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    I am a newbie to the 555 and I will say that I need some major help. I need to build an automatic playback circuit that plays every 10 minutes but I don't know where to start. I have seen this done but did not see it first hand, Please help me figure this out, I already have the recording module but I need to build the other half that triggers and auto resets every 10 minutes. Thank you in advance.

    JP
    [​IMG]
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    My blogs have several projects, along with theories of operation, that might be of some help. There are several people on this site (including myself) that will draw a schematic for a custom application if we know what you are after. The 555 is one of my bailiwicks (but I'm not alone).

    The 555 Projects

    Bill's Index

    Just describe what you are after as good as you can.

    What is this playback circuit you are talking about? Schematics and pictures really help in this. Do you want to record 10 minutes, send a 1 second reset, or what?
     
    Last edited: May 22, 2009
  3. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    I am working on an advertisment circuit that triggers a pre recorded message to play over a wireless audio transmition signal. I already have the recording circut but i need the timer circuit that makes it all possible, but I also need it to auto reset to trigger every 10 minutes.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    OK, it sounds like you want to have a signal that is 10 minutes off, then one second on. I know I'm repeating myself, but it helps to make things clear. BRB with the basic configuration...

    BTW, take the time to click on the links.

    ******************************
    OK, here is a reference sheet I drew up a while back. You want the oscillator on the bottom.

    [​IMG]

    Going through the math (bear with me)...

    C = 1000µF
    Ra = 1MΩ pot (actual value is 857KΩ, but RC timers are not that exact)
    Rb = 1.5KΩ

    The 555 configuration will be inverted from what you need. Also, use a CMOS 555, either a 7555, or a TLC555 (available from Radio Shack). The capacitor can be a problem, some electrolytics have leakage that can make a design not work. I would bread board this similar to what I've shown on my other experiments.

    [​IMG]

    The 556 also has CMOS equivalents. CMOS versions use incredibly low power, so they will really stretch the battery life.
     
    Last edited: May 22, 2009
  5. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    That sounds about right but I'm hoping it auto resets plus the pre recorded message is about 11 seconds long.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Go through the exact sequence, as if your were writing a computer program, or talking to an idiot (same thing). I'm going out for the evening, so I'll pick this up later. More than likely someone else will have you taken care of. BTW, it is unusual to get a response this quick here, but not that unusual. :D
     
  7. HiProfile

    Member

    Mar 15, 2009
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    Does your audio setup require a short pulse at the beginning (like pressing a button), a long pulse to keep it playing (holding button), or both an input for playing and resetting? If we knew that, we'd be able to help you a lot better.

    If it requires a play and reset trigger, you may want 2 timers. One long in asable mode, and one short timer in monostable mode triggered by the other.
     
  8. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    I need it to hold a button and start the message long enough for the message to end then let go of the button then reset itself to repeat 10 min later.
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
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    When dealing with time durations this long the 555 will perform much better and more accurately if a freq divider like a 7490 is used in conjunction with it. Doing so enables the RC time constant of the 555 to be only 1/10th (10:1) of the needed time. This would have the 555 running astable @ only one output transition per minute. Just a thought.....
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    You need to define the signals a bit tighter. We have no way of knowing what your feeding, or what the requirements are. We can't do it all from this end.

    Here is what I think you are asking for.

    [​IMG]

    The times listed are approximate, and can be tweaked easily. The question is where this is the signal you are looking for?

    HiProfile asked the question, it needs answering. Are you needing a second signal synced to this one for a reset? If so, where does the reset pulse line up with?
     
  11. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    Yes I need it to reset after the playback ends
     
  12. Wendy

    Moderator

    Mar 24, 2008
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    What to reset? This assumes we know your setup, and taint no way we can.

    Are you needing a second signal to reset your sound board?

    Something like this maybe?

    [​IMG]

    This means a 3rd 555 timer if so.
     
    Last edited: May 24, 2009
  13. memyselfandi

    Thread Starter New Member

    May 22, 2009
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    Yes that is exactly what I need to accomplish, but like I said I have never worked with the 555 before. I do appologize for my inconstincies because I dont know the correct words to use. lol
     
  14. Wendy

    Moderator

    Mar 24, 2008
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    You can mix the two groups however. Since we still don't know what the module you're driving looks like Wave Shapper #1 may not work, but then again, it might (and it is a lot simplier). The diodes used are not critical, I gave a range of part numbers by way of example.

    [​IMG]
     
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