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Blocking Diodes

Discussion in 'General Electronics Discussion' started by Sudden, May 1, 2011.

  1. Sudden

    Sudden

    9
    0
    Apr 27, 2011
    Hi,
    How do I calculate the correct blocking diode?
    I am trying to stop voltage going to a DC socket when it is not in use and to a battery set when a power adaptor is plugged into the dc socket . I am using a dc voltage of 9.6 with 1A current. This for a PMR Radio converted to amateur radio use.
     
  2. davenn

    davenn Moderator

    13,107
    1,696
    Sep 5, 2009
    Hi there also a ham radio op this way :)

    I am trying to figure out your meaning. draw a pic and post it with the various bits to the puzzle and how / when they need to be connected :)

    Dave
     
  3. Sudden

    Sudden

    9
    0
    Apr 27, 2011
    Hi Davenn,
    I have put together a diagram for my small project. As you can see no input socket is shown this because I can’t find a suitable symbol for it.
    The battery shown within the blue square can be taken off of the radio and if left disconnected then the terminals of the battery and radio are exposed to touch. My idea is to leave the battery on the radio but disconnected from the radio when using the power adapter via the dc socket otherwise the battery and the adapter will both supply voltage at the same time.
    The diodes will block voltage from the battery going to the socket and voltage from the socket going to the battery.
     

    Attached Files:

  4. duke37

    duke37

    5,155
    694
    Jan 9, 2011
    The diodes in the negative leads are not needed and in fact are the wrong way round and will stop the circuit working.
     
  5. davenn

    davenn Moderator

    13,107
    1,696
    Sep 5, 2009
    Agreed, take out the 2 negative lead diodes, not needed
    But that still doesnt disconnect the battery from the radio when the main supply is used. A relay across the main supply with NC contacts would keep the battery in cct till the main supply and relay was energised. Then the NC contact would open and disconnect the battery.


    [​IMG]

    see how that suits ya :)

    cheers
    Dave
    VK2TDN
     

    Attached Files:

    Last edited: May 3, 2011
  6. Sudden

    Sudden

    9
    0
    Apr 27, 2011
    Hi Davenn,
    I will look into that idea. It might come down to lack of space to fit the relay.
    Sudden
     
  7. davenn

    davenn Moderator

    13,107
    1,696
    Sep 5, 2009
    :) there are some VERY small relays available have a look around :)

    Dave
     
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