timmer circuit

Discussion in 'The Projects Forum' started by BMK, Feb 28, 2013.

  1. BMK

    Thread Starter New Member

    Nov 9, 2011
    18
    0
    I’m looking for a simple 555 timer circuit which will activate a relay for four seconds and automatically repeat the same operation every 20 seconds (4 seconds on and 20 seconds off). Once power is applied, the timer will continue to function as stated. I have a 2VDC motor which will run for the four seconds duration. The power supply and relay can be as needed for this project. The circuit will control the motor and in-turn the motor shaft is connected to a rock which appears to be falling onto a model railroad track.
    Thank you for your assistance
    Brian Krupicka - USA
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    What is your supply voltage?

    How much current does the motor draw?

    A relay may be overkill for the application if the motor only needs to spin one direction.
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Here's a quick job to see if it is what you are thinking of...

    [​IMG]
     
  4. BMK

    Thread Starter New Member

    Nov 9, 2011
    18
    0
    Available power supply can be 12DC.

    I am not sure of the current draw on the motor, that is why I wanted to utilize a relay as in interface.


    The circuit looks like that I was looking for.
    Thank you
    Brian
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    if the load is a small hobby motor, you can use a transistor to switch it, or a relay, the advantage of a transistor is silence and no mechanical parts to wear out.

    The 555 will run with the 12VDC for power, just remember to put the 0.1uF cap across V+ and GND, probably in parallel with a 22uF electrolytic cap if this is the same supply the actual train motors are run with (the caps will reduce the noise so the 555 doesn't glitch).

    For the 2.5V motor, were you planning on a separate supply? If so, then the relay does make sense, especially if you already have several in your layout. I'd suggest adding a Schottky diode across the relay coil so the inductive kick of the relay shutting off doesn't hurt the 555. The Diode should be across the relay coil with the stripe pointing away from ground/toward +V.
     
  6. BMK

    Thread Starter New Member

    Nov 9, 2011
    18
    0
    Thank you again for your assistance
    Are you talking about a 2N222 transistor as a drive circuit for the motor. see attached.
    Yes, I have a separate power supply for the hobby motor which draws under .200 amps (estimating at this point).
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    I think you better to measure the current of motor first, otherwise the designs can't get into the point, you can't choose the best parts for it, and it just like a puzzle.
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    I read the original post as a 2 Volt motor, not a 24V motor.

    You may want to stick with the relay if that is what you know, it's simple and straightforward.

    Just remember to but the schottky diode across the coil and you should be good to go. The motor will be isolated from the output of the 555 preventing glitches that way as well.
     
  9. BMK

    Thread Starter New Member

    Nov 9, 2011
    18
    0
    Thank you for your comments and assistance.
    Brian
     
Loading...