Simple question about component placement

Discussion in 'General Electronics Chat' started by MrShhh, Jul 10, 2009.

  1. MrShhh

    Thread Starter Member

    Jul 7, 2009
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    Hi,

    Suppose I have +12vdc coming from a regulator and then to a smoothing capacitor. Can power to other components be taken from anywhere on the +12v rail? e.g. is a point just after the reg but before the smoothing cap the same as a point just after the smoothing cap?

    I guess this is pretty simple but it vexes me nonetheless, especially when I think about electron flow traveling the other way round the circuit to conventional current...

    Thankyou :D
     
  2. MrShhh

    Thread Starter Member

    Jul 7, 2009
    24
    0
    Sorry, somehow got this thread in the wrong forum..
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    I have moved it to the General Electronics Chat for you.

    Dave
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Yes, you can pull power off the rail anywhere. Except at high frequencies, the supply rail is the same piece of wire. The capacitor's smoothing action takes place between the regulator and it as much as past the capacitor.
     
  5. MrShhh

    Thread Starter Member

    Jul 7, 2009
    24
    0
    Thankyou v.much beenthere for answering a question that I've wondered about for ages :D I really hoped that was the case as it makes designing pcb's that much easier!
     
  6. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469
    Since you mentioned designing PCBs, some words of caution is in order.

    It's a good idea to place smaller capacitors (1 uf for example), between power and ground, near any component that in utilizing the power rail. Then, certain devices may require larger capacitors near them as well. The spec sheet would tell when this is the case.

    Also, the trace width and length come into play. A thin long trace tends to be more of a problem, and often the power and ground are given an entire board layer of their own. This is a good idea in any professional level board, but hobbyists don't always have this option, since they may make their own two layer board. In such cases those extra capacitors can mean the difference between success and failure.
     
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