Dual timer 556

Discussion in 'General Electronics Chat' started by mpcotuong, Oct 31, 2010.

  1. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Hi All,

    I have using the 556 for dual timer but I have the issue that once turn on on the power the second stage auotmatic goes high. Can you please let me know, why the second stage get the out put pin 9 high once connect power? Could you please sugguestion how to prevent the second stage automatic goes high once turn on the power?

    Thanks, for your help

    Kevin
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Are u trying to drive the motor bidirectionally?
     
  3. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Yes, I would like Motor run for 10 second one direction and other 10 second revert direction.

    Thanks,
    Kevin
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    You are triggering the second timer off the output of the first. This strikes me as the weak point. A motor is noisy, matter of fact you should have some protection from inductive kick that isn't there. What is the specs of the motor?

    You also have some unnecessary redundancy, R35 and R40 jumped out to me.

    From what I can see you want the motor to spin in one direction, then in the other for the same amount of time.

    If you want I'll redraw it how I would do it, gotta go get some trick and treat candy before the munchkins and goblins arrive first through.

    I started this post before you posted yours, for what it's worth.
     
    mpcotuong likes this.
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    This isn't related to your question directly, but what is the motor RPM and load?

    Attempting to switch a motor that is going full speed tends to do bad things.

    I'll wait for the resident 555 expert to chime in on this one. --ETA: Too Late.
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Wouldn't it be better to include a relay with a time delay.
    It wud be simple and effective

    The delay pulse can be from a 555. like ON for 10sec & OFF for 10sec. and goes on.
    This pulse can switch the relay on and off. Contacts can be used to reverse the motor
     
  7. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Hi Bill,

    Thanks, for reply. Can you please re draw it?

    You have nice Hollaween :)




     
  8. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    The Motor is 70RPM of 12VDC


     
  9. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Your idea to use reply is good. Can you re draw it?



     
  10. R!f@@

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    Apr 2, 2009
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    It wud take time?
    Do u know how to draw it?
     
  11. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Ok, thanks, Whenever you finish new drawing, please post it here.

    Kevin
     
  12. Wendy

    Moderator

    Mar 24, 2008
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    [​IMG]

    Did I read correctly, you have a 12V Motor (we need current (as in amps) specs) and have 5V powering the 556?

    Quick side lesson on a 555/556. The output at Vcc will be 1.2 to 1.4V less than Vcc. It has to do with the internal schematic of the 555.

    [​IMG]

    So with 5V as Vcc you will get 3.8V max out of the 555.

    Even though you can have 200ma out of a 555, you shouldn't use more than ½ that, 100ma. If you need drivers here is something I came up with a while back.

    [​IMG]
    D1 and D2 (or CR1/CR2) are to prevent shoot through, which can burn up the transistors.

    http://forum.allaboutcircuits.com/picture.php?albumid=26&pictureid=309

    Bill's Index

    My Cookbook

    The 555 Projects

    LEDs, 555s, Flashers, and Light Chasers
     
    Last edited: Oct 31, 2010
  13. thatoneguy

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    Feb 19, 2009
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    That is a gearhead motor, so all of the reduction gears will act as flywheels, causing it to take a moment to actually stop spinning before reversing direction.
     
  14. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Thanks, so much Bill. But I forgot to tell you that my Motor need to run 12VDC. If I apply the diode, will the 556 not goes high at pin 9 once turn on the power?

    Best regards,

    Kevin


     
  15. Wendy

    Moderator

    Mar 24, 2008
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    You didn't forget, but you did put 5VDC on the timers. 5V doesn't drive a 12V motor very well, especially when it is 3.8VDC or less. I'm surprised it works at all.

    The diodes are not in the circuit if you look at it. They only conduct if the motor creates voltage above Vcc or below gnd. They are swamping diodes.
     
  16. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Hi Bill,


    I need the dual delay for 10 second each direction and apply to 12DC motor. Will I need addition of Relay for run 12VDC? Please let me know.

    Thanks,
    Kevin.
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    I've shown you solid state drivers. You didn't mention current (which was asked for). If the motor current is small enough the 556 can drive it directly. If not the drivers I referenced can probably do it.

    The 555 has a voltage range of 4.5 to 15VDC.
     
  18. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Hi Bill,

    The current of Motor is about 1A. I think need the rely or some logic with high current to moce the Motor faster. Please let me know.

    Thanks,
    Kevin
     
  19. Wendy

    Moderator

    Mar 24, 2008
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    Yes, you need the transistor or relay drivers.
     
  20. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Thanks, Bill. How can I connect pin5 and pin9 to relay DPDT? Please let me know the circuit is appreciate alot.

    Kevin
     
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