RLC Timer

Discussion in 'General Electronics Chat' started by Ambassador, Jun 13, 2014.

  1. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Can any here post a reference to a one [1] minute timer circuit schematic that uses only passive RLC components?

    If not a one [1] minute timer, then any close span of time would be useful.
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
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    Can you use a solid state relay?

    What is the load?
     
  3. wayneh

    Expert

    Sep 9, 2010
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    Maybe such a thing is already out there, but without looking, the request made me think of my "ring tester", which is designed to ring a coil to test it for inductance. The tester sends a pulse and then watches for (and counts) the peaks of the damped LC oscillation. It would be a small thing (easy for me to say) to adapt that to a clock application.

    That said, in my case the pulses were generated by a 555, so there would be no need to add the complexity of LC ringing in order to build a clock. I suppose you could trigger pulses with some other arrangement.

    It's worth noting that the LC will not oscillate for more than about a second before it needs a fresh ping. There's always an R in the RLC. I suppose a big L and a big C could give you a minute of ringing.
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Your question needs a lot of work.
    What is the application?
    What power is available for the timer?
    Is there a load to be switched by the timer, or just some kind of indication?
    What starts the timer?

    ak
     
  5. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Thank you - you folks are quick!

    inwo,
    Regarding "Can you use a solid state relay?" - no.

    Regarding "What is the load?" - the circuit's output terminals need only provide some sort of indication.
    AnalogKid,
    Regarding "What power is available for the timer?" - a 12V dc battery source.

    Regarding "Is there a load to be switched by the timer, or just some kind of indication?" - just an indication.

    Regarding "What starts the timer?" - a physical switch.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    Why do you need an inductor (?), just use an RC timer.
     
  7. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    crutschow,

    Regarding "Why do you need an inductor (?), just use an RC timer." - that would be okay.
     
  8. crutschow

    Expert

    Mar 14, 2008
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    So an R of 100k ohm in series with a 270 microfarad capacitor to ground will charge up to 89% of the applied voltage or 10.7V in 60 seconds after the 12V is applied to the circuit.

    But you need something to determine when that voltage is reached. Don't see how you can do that with only passive components. :confused:
     
  9. LETITROLL

    Member

    Oct 9, 2013
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    I guess using transistors is necessary for an astable timer , they will act as chargers and dischargers .

    Impossible to make an active application using only passive components .
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    What type of indicator is allowed?

    A meter, led, neon? Relays are out! How about fuse, zener, scr, mov?

    There are chemical indicators. LCDs and the little test strips on batteries.

    Give us something to work with.:D
     
  11. inwo

    Well-Known Member

    Nov 7, 2013
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    With led and zener.
    Discharge not shown.
    If zener not allowed triple R1.
    If led not allowed, guess you'll have to use a cat.:D

    It works surprisingly well!
    Couple seconds turn on ramp.

    [​IMG]
     
    absf likes this.
  12. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Regarding "What type of indicator is allowed ... Give us something to work with" - okay, any small dc motor.
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
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    Ok, so a motor is allowed but not a relay or transistor to control it...:confused:

    Next question. Why the limitations?

    As you may guess. I'm stumped.:D
     
  14. wayneh

    Expert

    Sep 9, 2010
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    +1

    What are we doing? You started off wanting an LC timer, so I assumed there was some un-stated requirement to use an inductor. What other un-stated rules do we not know about?
     
  15. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Regarding "... started off wanting an LC timer ..." - the post references a timer that uses only passive components like RLC components.

    The small dc motor was suggested because inwo made the good point "What type of indicator is allowed ... Give us something to work with."
     
  16. LETITROLL

    Member

    Oct 9, 2013
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    Is that some extinct style of posting in forums :D
     
  17. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Incidentally, the RLC timer circuit is to be fashioned as would have been possible before semiconductor materials were available.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    Relays were available since forever.:D Why no relays?
     
  19. Ambassador

    Thread Starter New Member

    Jun 13, 2014
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    Relays that are not based upon semiconductor materials are okay.
    (Sorry about that)
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Finally we know what we are looking for.
    Values may be off a little. Made R 1/10 of coil resistance.
     
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