INPUT with three legs - mine only has two...

Discussion in 'General Electronics Chat' started by Alichino, Sep 9, 2016.

  1. Alichino

    Thread Starter New Member

    Feb 20, 2012
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    0
    Hello,

    On many circuit designs the INPUT has three legs:

    [​IMG]

    But the input socket I've got has only two legs, one of which I connect to ground. In the image above, the other leg would go down the path with the capacitor.
    Where and how do I connect the battery...?
     
  2. jpanhalt

    Expert

    Jan 18, 2008
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    What is your input signal?

    As drawn, the capacitor provides AC coupling to whatever in the plug is connected to that ring. And with the assumptions in the next paragraph, it blocks any DC.

    That design MAY be meant to act as a DC switch in addition to the AC input mentioned above.. In other words, it can be used to turn the device on or off. For that to work with the jack configuration you show, the barrel and second ring from the tip need to be connected in the plug and the device and plug need a common ground. That seems unusual to me. When I have used a plug as a switch, I have done it differently.

    On the other hand, the ring connected to the negative battery terminal may simply be providing access to that terminal to whatever is connected to the plug.

    As for how to connect the battery, you need to show us the rest of the relevant circuit or decide whether you want the plug to act as a switch.

    John
     
  3. Alichino

    Thread Starter New Member

    Feb 20, 2012
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    0
    Hmm here is the image:

    upload_2016-9-9_12-39-50.png
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    It depends on what the circuit is.
     
  5. jpanhalt

    Expert

    Jan 18, 2008
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    @Moderators
    @ScottWang
    @DickCappels

    Why was my response to the other (earlier) version of this thread deleted? I then reported the later-posted duplicate thread, which is the thread you retained. Please find my post and restore it to this thread.

    John
     
  6. jpanhalt

    Expert

    Jan 18, 2008
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    As I pointed out earlier, that configuration suggests that the barrel and second ring perform the function of an on/off switch. The first ring and capacitor block DC from either an input or output. If that function is not needed, then you connect the single ring or tip as if it were the second ring.

    John
     
  7. Alichino

    Thread Starter New Member

    Feb 20, 2012
    7
    0
    Hi John,

    Hmm I don't really understand the tech linguo (what are the rings?), as I am a total beginner here... Could you re-explain this to me, like to a 5-year-old...?

    Here is an example circuit:

    [​IMG]

    I'm trying to build something like this on a breadboard. I've got two leads in the input socket: one goes to the ground, which is one of the side columns on the breadboard, and the other one goes in any one of the 5 pin rows, where the capacitor is also connected. Where does the '-' terminal of the battery go...?