millisecond timer

Discussion in 'The Projects Forum' started by gremlin, Oct 26, 2011.

  1. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    has anyone got a simple circuit for a delay on timer to switch a optocoupler on with an ajustable delay from sao .001 sec to maybe 1 sec

    any thoughts would be greatfully recieved

    thanks

    gremlin
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What is your supply voltage? If it's low-voltage DC, you could use a 555 timer and some parts.
     
  3. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    hi i can use any supply voltage so long as it will triger a optoisolator i would like to use 9v from a AA battery pack but could go to 12v if needed
    the idea is to trigger a TIP120 transistor via the optoisolator

    the timing delay i was hoping to use a pottentiometer maybe two one caurse one fine ajustment

    i have had a quick look at some 555 circuites on the net and this great site but canot find any with millisecond delay

    thank you

    gremlin
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Something like the attached should work for you.

    It has a range a bit wider than you specified, but that's necessary due to tolerances in resistors/capacitors.

    I didn't show caps across the Vcc/GND terminals of the 555 timer; but you need an 0.1uF/100nF ceramic or poly metal film and a 1uF or larger aluminum electrolytic.
     
  5. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    many thanks sgtwookie for your time and help i will give that a go tommorow on some breadboard

    one thing i forgot to say was that it will be trigered by a microphone so a single pulse for a millisecond or so when it hears a bang
    then wait the pre set time and fire a 12v dc solenoid via the tip120 transistor it would be nice too for it to only fire once untill a reset button is pressed, the mic will have a simple pre amp so the threshold can be ajusted

    thank you again

    regards

    gremlin
     
    Last edited: Oct 26, 2011
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Oh, silly me - I thought you wanted an astable instead of a monostable. That's a different circuit, but it'll have similarities. I really don't know why I posted an astable configuration.

    Do you have the preamp for the mic built already, and is it working?
     
  7. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    hi no i dont have the pre amp done as yet but i have a simple circuit to copy from a vellerman mono pre amp kit
    thank you once again

    gremlin
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    What is the Velleman kit number?
     
  9. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    Hi Sgtwookie
    the kit # is
    K1803 Universal Mono Pre-Amplifier

    http://www.maplin.co.uk/k1803-universal-mono-pre-amplifier-2921

    thanks

    i hope to make somthink that will hear the sound of a bang wait the elapsed time of the set duration in milliseconds, then fire a 12v solenoid once via a TIP120 transistor
    and not fire again till re-armed and a bang is heared again to start the process off again

    thank you

    gremlin
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Can't view the assembly PDF at the moment, but Velleman's page for the kit is here:
    http://www.velleman.eu/products/view/?country=be&lang=en&id=8897

    Just so you know; that project uses a 741 opamp which has rather poor performance and requires at least 9v to operate. You would be much better off using almost any other voltage-feedback opamp.
     
  11. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    hi sgtwookie yes i managed to see the 741 from the pic on the supliers website,
    i dont mind that it is crude and requires 9+ volts as i have 12v available from the battery pack i am going to use on the solenoid,
    it does not matter as i am only looking to get a response from a microphone detecting a bang from a droped item etc so no real audio application is required,

    i was hoping that someone may have a simple circuit etc as i was looking at having to use a arduino micro to do what i wanted , but did not want all the addition of the periferals to run the arduino crystals etc etc
    i was hoping for same simple 2 or three chips and some capacitors resistors etc

    thank you for your kind assistance

    regards

    gremlin
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    After the delay time is elapsed, how long do you want the TIP120 transistor turned on?

    If it's a relay or solenoid, it will take a LONG time to respond. You would likely have to have it on for at least 100mS.
     
  13. gremlin

    Thread Starter New Member

    Jul 22, 2010
    19
    2
    hi yes i would gues 250 Ms to be on the safe side
    thanks

    gremlin
     
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