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Electronics Looking for Circuit Training/Boxing timer schematic

Discussion in 'Modding' started by jgrade, 3 Oct 2007.

  1. jgrade

    jgrade What's a Dremel?

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    I am looking for a schematic for making a timer that is used for circuit training or boxing training etc. Here is the cycle I am looking for. This does not need any input, but to reset the timer to the beginning.

    Start
    2 1/2 minutes - Light green led/lamp, sound buzzer momentarily
    1/2 minute - Light yellow led/lamp, sound buzzer momentarily
    1/2 minute - Light red led/lamp, sound buzzer momentarily
    reset timer(s) start sequence over

    I m thinking a 555 (or multiples). I could use a stamp but did not want to invest too much in what seems to be a simple project.

    Any help would be greatly appreciated.
     
  2. const_

    const_ What's a Dremel?

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    its a simple project why not making it simpler by using a microcontroller ? you will not invest much take the pic12f635 for example, costs less than 2$ on top of that a few analog components that you are going buy anyways.
     
  3. cpemma

    cpemma Ecky thump

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    You've got 7 equal intervals in total; use a 30-second 555 astable clocking a 4017, taking outputs 1-5, 6, 7, reset after the full cycle. For the short buzz, the 4017 output to the light switcher also (through steering diodes) starts a second 555 monostable connected to the buzzer.

    Light side
     
    Last edited: 8 Oct 2007
  4. jgrade

    jgrade What's a Dremel?

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    const_: I am just not familiar with pics. I have been using stamps for a few years, but don't want to spend the money for a stamp.

    cpemma: I will look into that. I am confused about the second 555 monostable.

    Hope to fumble a schematic for you guys to look over soon.

    Thanks for the help.
     
  5. cpemma

    cpemma Ecky thump

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    The circuit needed is one which gives a short (timed) buzz even if the operating switch/button is held closed, so the start of the 30 seconds for which the lamp is lit sets it going for, say, only 1 second or less.
     
  6. jgrade

    jgrade What's a Dremel?

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    That is what I thought. Thanks again. Here is the first attempt at the circuit without the buzzer. I used the divide by 10 for the first 5 counts to eliminate using diodes. Please be kind, this is first attempt. I am not EE I just play one on TV.

    [​IMG]

    Note: The schematic program i used could not jump over the connection at pin 8. Pin 6 and reset do not connect to pin 8. This is a crude attempt to jump over the connection.
     
  7. jgrade

    jgrade What's a Dremel?

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    Well the circuit works as expected (although I did not have a 10nF cap to test the timing). Now for for the monostable 555.

    cpemma, you mentioned steering diodes. I think I know what you are talking about, but could I use the LED's as steering diodes, or is the bias reversed? How would they be connected?
     
  8. cpemma

    cpemma Ecky thump

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    On the Bill Bowden traffic lights circuit I linked, the 1N914 diodes are used to connect a block of 4017 outputs together so if any one of them is 'high' that light is activated. Technically they're OR gates so if Q0 .OR. Q1 .OR. Q2, etc are high the cathodes' junction point is high, but if Q0 is high there's no short to the low Q1-Q4.

    In your case Q0-Q4 would have diodes on each to a common point to give a 150s green, then Q5 alone (no diode needed) for 30s yellow, then Q6 alone for 30s red.

    Without the 555 and buzzer sections, and simplified lights,

    [​IMG]
     
  9. jgrade

    jgrade What's a Dremel?

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    Yes thank you. I have seen this circuit and a variation that help me greatly. I used cout instead of a bunch of diodes since I need exactly half the count thats where my confusion came in. I will try to add the second 555 this afternoon and see how it works.

    I think I found a big problem with my math and the values for R1, R2 and C1. I want the 555 to pulse every 30 seconds. Either I am over thinking this or I have too few brain cells left to make the calculation For some reason I have the 555 running at 30Hz which is NOT 30 seconds. I found a great calculator at Doctronics that helps calculate the values for astable and monostable. Please help. At what frequency would I need the 555 running to equal 30 seconds. I am thinking .3Hz

    Thanks again for the help.
     
    Last edited: 27 Oct 2007
  10. cpemma

    cpemma Ecky thump

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    0.03Hz. Another good calculator here. In theory, 47uF, 330k and 300k will be close, but due to the wide tolerance on capacitors a variable resistor (470k pot) will be needed instead of the 300k. The 'on' and 'off' times don't need to be equal.

    If you want the times to be accurate, a crystal-controlled timer and frequency-divider chain (eg, CMOS4060B) would be better and not much more complex or expensive. Even without a crystal, the 4060B would make a better clock as a low-value, more stable, film capacitor can be used. See here.
     
  11. jgrade

    jgrade What's a Dremel?

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    Thanks again. Of course .03 would be 30 seconds. I am a little more awake now then the last post. The timing is not critical enough to need a crystal.

    I was thinking and reading about the monostable circuit for the buzzer. I think I have a problem attaching it to the out of the 4017. Everything I have read says the the signal in must be shorter then the signal out. In this case I would have about 20 seconds ON time which would be too long. How can I connect the 555 to the 4017? The monostable circuit would be ON for about 2 seconds.
     
  12. fat-tony

    fat-tony What's a Dremel?

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    Just to point out, since this seems to be missed.

    f = 1/30 seconds = 0.03333 repeating Hz, not 0.03 Hz.
     

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