Relay or NPN Transistor? and One or 2 Power Sources?

Discussion in 'The Projects Forum' started by Clexxy, Jul 12, 2014.

  1. Clexxy

    Thread Starter New Member

    Jul 12, 2014
    1
    0
    In the attached JPG, I can't figure out how, once LED C, D, or E switch is closed (via reed-switch) then how to also activate the circuit that has LED-G and the speaker. I may only use one power source, but the circuit that has the LED-G and Speaker should not go above 12 volts total (9 for alarm and 3 for the LED). Otherwise, until one of those additional switches are activated, the usual power will be going through LED-A, and B when the system is activated and at normal status. Thanks for any help or criticism!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Use three diodes from C,D,E to G, or one diode from F to G.
     
  3. eetech00

    Active Member

    Jun 8, 2013
    648
    110
    Hi

    This should do it...

    eT:)
     
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