How to step thru a number of relays

Discussion in 'General Electronics Chat' started by n4ken, Jul 16, 2010.

  1. n4ken

    Thread Starter New Member

    Jul 16, 2010
    Can any one help with a circuit I've been trying to sort out but have failed miserably :mad:

    What I need is this...

    A number of relays, say 10. When a pulse is applied the first relay latches on.
    When another pulse is applied relay number two latches on and number one un-latches etc etc.

    Any suggestions or links would be greatly appreciated.

    Thanks in advance.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Here is a link to a PDF that describes a 4 bit counter -

    It can easily be made into a Johnson counter. The one that is set makes contacts that let the next relay get energized on the count pulse. When that one picks up, one set of (NC) contacts open and break the current path into the preceding one. You can do a lot with 3 and 4 pole double throw relays.

    Here is a link for counters of all kinds -
  3. SgtWookie


    Jul 17, 2007
    Actually, a CD4017/HEF4017/MC14017 (for up to 16v supplies) or 74xx4017 (5v supply) 5-stage Johnson counter already has 10 outputs, and will step through them, only one output high at a time.

    The outputs could be used to drive something like a ULN2003/ULN2004 or ULN2803/ULN2804 Darlington driver IC (7 and 8 channels, respectively) to sink current from the individual relays' coils.

    You'd have a pretty low parts count that way.

    Note that if you wanted to use a switch for clocking the input, you will need to use an appropriate de-bounce circuit.

    Here is a very good explanation of switch bounce problems, and how to deal with them:
    PackratKing likes this.
  4. n4ken

    Thread Starter New Member

    Jul 16, 2010
    Hi Guys...

    Thanks for your help. I've gone the 4017 route as it does just what I want and requires very little to do it.

    Really appreciate your time and help :D