Need help - Vibration Circuit Design

Discussion in 'General Electronics Chat' started by sdas86, Aug 26, 2015.

  1. sdas86

    Thread Starter New Member

    Mar 18, 2015
    26
    0
    Dear all,
    I would like to create a circuit which can detect vibration for 15 seconds then only output a signal pulse to LED. The LED will then ON for 10 seconds and turn off if no more vibration.

    I have been trying using 555 timers but I can only make the LED turn on 10 seconds but can't do the 15 seconds timing.

    My circuit block diagram:
    Vibration Sensor ----> 555 timer ----> LED (On for 10 seconds, this is set by 555 timer RC timing)

    This circuit is unable to do the first part "detect vibration for 15 seconds then only output a signal pulse".
    I am creating this circuit to monitor machine vibration to see what is causing the vibration. Any idea how to do this?

    Thanks.
     
  2. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    Vibration sensor>fixed gain precision rectifier>clipping circuit>Integrator>comparator>555 in resettable monostable configuration
     
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    You haven't provided the specification for the vibration sensor so it's not possible to provide a definitive answer.

    Another approach would be to count the pulses (assuming that it produces pulses) from the vibration sensor within a given time-frame.

    A 4017 decade counter (to count the pulses) and a pair of 555 timers (one to set the time-frame and the other to provide the output pulse) may be all you need.
     
  4. sdas86

    Thread Starter New Member

    Mar 18, 2015
    26
    0
  5. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    Summary: 3.3V-5V = Vcc
    Eo normally zero.
    Activity > square output to Vcc, in this case, +4.4V
    Any clue as to the vibration frequency?
    At least 1 per second? Power line frequency?
    50 Hz, 60 Hz, something higher?
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    This could be a bit more tricky than it first appears. Three questions:

    1. What does "vibration for 15 seconds" mean? If there is vibration for 1 second, then 13 seconds of no vibration, then vibration for 1 second, does this count as 15 seconds of vibration? Or does the vibration have to be constant throughout the 15 seconds to trigger the LED?

    2. Once the LED is triggered, what happens if there is no vibration for 8 seconds, then some vibration at the 9th second? Does the LED reset for another 10 seconds of brightness?

    3. After the LED turns off, how long does the system need to wait before detecting vibration again?

    ak
     
    absf likes this.
  7. sdas86

    Thread Starter New Member

    Mar 18, 2015
    26
    0
    Not sure about this.

    1. Constant vibration for 15 seconds. If 1 seconds vibration, it does not count. Need to be 15 seconds continuous.
    2. LED will light up for 10 seconds. If no more vibration, LED will turn off. If the vibration continuously 15 seconds -> 20 seconds -> 30 seconds... LED will continue light up.
    3. Continuously.

    Any idea?
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,981
    3,712
    @sdas86

    Here

    1) the vibration sensor enables the 555 timer to pulse 1Hz when the sensor is active
    2) vibration sensor also enables the CD4516
    3) the 555 outputs to the CD4516 (4-bit counter) , the cd4516 counts the pulses
    4) when the cd4516 gets to 15, all four pins will be high.
    5) when all four cd4516 pins are high, The 4-input AND gate will go high
    6) the AND gate activates the mosfet and lights the LED (or sounds a Sonalert buzzer).

    7) the MOSFET is latched by the two diodes so it will not turn off until the vibration sensor turns off

    8) When the vibration sensor turns off, the 555 is held in reset and the counter is reset


    The end.

    image.jpg
     
    Last edited: Aug 27, 2015
    Sinus23, sdas86 and absf like this.
  9. sdas86

    Thread Starter New Member

    Mar 18, 2015
    26
    0
    Hi,
    Thanks for this circuit. I would like to ask, is it possible to change from 15 seconds to maybe 10 seconds or maybe 1 minutes or any other period for the vibration? We might need to change the 15 seconds to other time to tune it.

    Thanks.
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,981
    3,712
    Yes, change the 100k resistor on the far left to a 1M potentiometer (audio taper). You will still get 15 pulses of the 555 timer but it will change from 1 Hz to a faster or slower pulse rate.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,981
    3,712
    Note: the drawing was updated. The cd4516 needs a positive pulse to reset (transistor added to invert) and OP asked for potentiometer to make activation time adjustable.
     
    absf likes this.
  12. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    First pass at a vibration indicator with adjustable delay and indicator times. I don't like large electrolytic capacitors in timers, so I went with a higher freq oscillator and prescalers. The timer increment value is 5 seconds. To eliminate a +/- 5 second ambiguity in one timer I had to have independent prescalers. As shown the delay time is 20 seconds and the alarm time is 10 seconds. Both are adjustable by moving to different 4017 outputs.

    There are many possible logic interactions among the timers and the input, and this circuit handles one set of them based on the early posts. If the VIB input still is high when the alarm timer ends, the LED stays on until the VIB input goes low. If the VIB input goes low and then high again during an alarm timer period, the delay timer resets and restarts but the alarm timer continues through its period. This means that when the alarm timer ends and the LED goes off, it might not be off for a full delay timer period because the delay timer has been running a new cycle while the alarm timer finishes the old cycle.

    Another possibility (with a logic change) is that whenever the alarm timer ends it resets the whole system. In this case, even if the VIB input is high and the delay timer is running, it is restarted for a full delay period. This assures that there is a full delay period off time in the LED between alarm events.

    ak
    VibAlarm-1-ch.gif
     
    Last edited: Aug 28, 2015
    absf and Alec_t like this.
  13. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    All I did was read the specifications and post them here to save other people time.
    And, yes, it seems clear that you are not sure about the specifications.
     
  14. Colin55

    Member

    Aug 27, 2015
    191
    19
    You just need a the vibration sensor and an 8 pin PIC chip and nothing else.
     
  15. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,981
    3,712
    No, he would need to learn about I/O ports, timers and interrupts, registers for variables, how to address and change the I/O, timers, interupts, ... in code, the format of code, possibly a lesson in converting his needs into a logical series of programming steps, how to install the microchip IDE, how to create a project, how to compile and debug a project, how to get the final .hex file onto the 8-pin PIC chip. Yes, it is all a valuable lesson but so is learning to crawl before trying to run.
     
    cmartinez likes this.
  16. Colin55

    Member

    Aug 27, 2015
    191
    19
    I didn't say it would be easy, I just said the circuit would be simple.
    This thing would take me about an hour to produce and I would NEVER go back to using discrete components for anything that requires a number of building blocks.
     
  17. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,981
    3,712
    Different work, different things to learn. Both have their places. I do both as well.

    The PIC option requires a bigger investment in tools (programmer) and time (learning curve). Saves board space and allows redesigns without moving a wire. My guess of the OPs skills, I think discrete is a good place for him to learn.
     
  18. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    If the people just needs a way to spend 1 week to finish his job, but you show him the way may take 10 weeks or longer to reach the target?

    If someone willing to learn or already had the conception of uC then what you said may save the time, otherwise sometimes may leading him to the jungle and can't find the way to come back.
     
Loading...