Unstable 555 monostable timers

Discussion in 'General Electronics Chat' started by cberkins, Jun 10, 2012.

  1. cberkins

    Thread Starter New Member

    Dec 6, 2011
    I want to use a 555 to trigger a 1 second rotation of a DC motor. I can get one LM555 timer to function properly but have half a dozen timers that will trigger and run only as long as the neg voltage is present but not allow the duration to run after the trigger is applied. Several of the 555's are new. Is there something I'm missiing in the standard one shot circuit or do I need to try multiple timers until I find ones that will actually work as advertised? Do I need to set up a voltage divider to create a ground rather than +/- voltage to make it work?
  2. Wendy


    Mar 24, 2008
    This was neither feedback nor a suggestion, so I have moved it to a more appropriate forum.
  3. #12


    Nov 30, 2010
    555 timers have a good reputation ie, they usually work.
    If you posted a drawing of what you've made, we might be able to see what can be improved.