Quick question on 555 Timer use.

Discussion in 'The Projects Forum' started by Chavez91, Jul 24, 2013.

  1. Chavez91

    Thread Starter New Member

    Jul 22, 2013
    2
    0
    I'm trying to use a 555 timer to generate a constant signal of 100Hz at a 97% Duty Cycle. Its also using a 12v input and output.

    Is the 555 a good choice for this, or are their better easier options out there for trying to accomplish this?
     
  2. donpetru

    Active Member

    Nov 14, 2008
    186
    25
    If is only one frequency then I recommend you use a microcontroller that you can better control the duty cycle.
    For example, an MCU Attiny13V can do this and cost less than 1$. The software I can do for free in few minutes. So, if you decide to call for a solution to the MCU, then tell me and I help you with the software.

    For programming Atmel MCU I recommend PonyProg solution:

    Schematic PonyProg use serial port:
    http://www.lancos.com/siprogsch.html

    and PonyProg software:
    http://www.lancos.com/ppwin95.html
     
    Last edited: Jul 24, 2013
  3. WBahn

    Moderator

    Mar 31, 2012
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    The 555 is probably a reasonable choice. You have a period of 10ms with an short portion of 300μs. Those are pretty comfortable numbers. It's been long enough since I worked with a 555 that I don't remember if the classic astable output has duty cycles more than 50% or less than 50%, but that is easily taken care of with an inverter on the output.

    Now, whether the 555 is a better way to go compared to a cheap MCU, well that depends on the application, what kind of performance you need, how many you are going to make, how fast you need to get it up and running, what tools you have available to you, and so on and so on.
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    You can use CD 4093 chip and get a 50/50duty cycle using one gate. And uses less current,voltage. cd4093
     
    Last edited: Jul 24, 2013
  5. Wendy

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    Mar 24, 2008
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  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  7. wayneh

    Expert

    Sep 9, 2010
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    Yes, depending on what you mean by "constant". The 555 and its timing components will drift a bit, especially with temperature. You'd never notice if you're flashing an LED but it won't work for tuning an instrument or running a clock. (You'd use a quartz crystal oscillator for those.)
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    C1 = 1μF, R1 = 12k, R2 = 1.2k, calculates to 91.67% duty cycle at 100 Hz.
     
    Last edited: Jul 24, 2013
  9. WBahn

    Moderator

    Mar 31, 2012
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    So? He's not trying to get a 50% duty cycle, but rather a 97% duty cycle.
     
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