Help with circuit layout

Discussion in 'The Projects Forum' started by gumbright, May 22, 2006.

  1. gumbright

    Thread Starter New Member

    May 22, 2006
    4
    0
    I am working on a project and am having a problem figuring out how to get it it work. It is not so much a circuit problem as a logic problem. Here is what I have (this is obviously not intented as a proper circuit diagram, just a quick hack to show the problem):

    [​IMG]

    B/C/E/F represent subcomponents that I have working fine, H/S/O represent the logical goupings of components that need to be activated together. I am using transistor switches as the physical switches will be replaced by a microcontroller at some point in the future. The problem is (as you might have already seen) that when any of the switches are closed, all the compenents get power. I know I could add some diodes to prevent the backflow (I think it would take 4), but it strikes me that there must be some more elegant way that is completely escaping me.

    I would appreciate any ideas, advice, etc. BTW, I am pretty much a beginner, so I apologize of any idiocy in advance. I will be happy to provide any other info or clarification if it would help.

    Thanks
     
  2. gumbright

    Thread Starter New Member

    May 22, 2006
    4
    0
    Oops, I used the wrong transistor symbol on the graphic. Sorry about that. I am using NPNs in the circuit and they work fine (except for the above stated problem, that is).
     
  3. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    You'ld do it with 3 diodes. Why arn't diodes elegant..?
     
  4. gumbright

    Thread Starter New Member

    May 22, 2006
    4
    0
    It just seems to me to be a brute force approach. It is patching the problem rather than fixing it. But perhaps that is a completely rational approach in circuit design. That is one reason I wanted to ask others, as this is just my second project. My background is in software development where I have found that a brute force approach is often not the right answer, so that colors my judgement.

    I take it you mean the diodes would need to be on EO, SF, & FO?

    Thanks for the reply

    Guy
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    Isolation diodes are perfectly reasonable to use when trying to use separate input lines. DTL logic would never have functioned without them.
     
  6. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Actually, 4 diodes... sorry, you were right the first time...
    *bangs head against wall* ;)
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    A diode is the very soul of elegance. No active component is more basic. The long history of the diode adds dignity.

    Brute force is the purview of relays, contactors, and switches.

    B)
     
  8. gumbright

    Thread Starter New Member

    May 22, 2006
    4
    0
    I have my circuit completed and behaving as desired. Thanks all for your help. :)
     
Loading...