What does this arrow in the circuit mean?

Discussion in 'General Electronics Chat' started by Rohit400, Aug 1, 2012.

  1. Rohit400

    Thread Starter New Member

    Aug 1, 2012
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    Hi guys!, im very new when it comes to building circuits, and i don't really know much. so i thought what a better way to learn circuits then to get my feet wet by "just" building a circuit.
    so the problem is i don't know what the arrow means. the arrows is going from the C5 to the Inductor L1 (is this a inductor? b/c it doesnt look like a resistor)

    does this arrow mean that the C5 connects to the L1 ?

    Thx guys
     
    Last edited: Aug 1, 2012
  2. jwilk13

    Member

    Jun 15, 2011
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    Looks like it might be a variable inductor with C5 connected to the "wiper".
     
  3. SteveHow

    Member

    Jul 2, 2012
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    What does your parts list say it is ? Have you got a parts list for the other components. Capacitor Values, Resistor Values, etc.
     
  4. Rohit400

    Thread Starter New Member

    Aug 1, 2012
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    jwilk13 i dont think its a variable inductor because it only have 2 terminals
    stevehow the partslist calls it L1 - 4 turns + 1 jumper
     
  5. SteveHow

    Member

    Jul 2, 2012
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    I have to agree with jwilk13, Variable Inductor with C5 Connected to the Wiper. Hence it must have 3 Terminals.
     
  6. Rohit400

    Thread Starter New Member

    Aug 1, 2012
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    i think the parts list that i got is wrong, um guys is there any way to connect the c5 to the 2 terminal inductor ?

    also what does it mean when it says the jumper
     
  7. BMorse

    Senior Member

    Sep 26, 2009
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    It is an inductor (according to the circuit it is labeled L1), with a center tap.... must have to be a home made inductor with a center tap wire for tuning.....
     
  8. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    It's definitely a variable inductor. The 'wiper' might just be a wire you have to rest on it. Do you have pictures of the inductor you have? Also, was this a kit? Did it come with an inductor, or did you just find an inductor and assume it would work?

    You should just be able to "tap" it with a piece of wire. That piece of wire will act as the wiper.
     
  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I would agree with the center tap, but in that case it should have a dot or something showing that it's connected permanently to the coil. In this case, however, it's an arrow, signifying it can move. Hence it's a variable inductor, even if you need to physically pick up and move a wire on the coil to tune it.
     
  10. Rohit400

    Thread Starter New Member

    Aug 1, 2012
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    yes it was a kit, it came with the inductor and all the parts necessary for the kit. the inductor that came with the kit was of this kind http://tinyurl.com/d6ojzan

    except it has only 4 turns, and the outer is coated with plastic

    can you explain the tapping process please. do i just strip all the plastic from the inductor and connect the jumper from c5 anywhere on the inductor?
     
  11. wmodavis

    Well-Known Member

    Oct 23, 2010
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    variable!.................................
     
  12. BMorse

    Senior Member

    Sep 26, 2009
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    Thats pretty much what I meant ;)..... its not fixed and moveable for tuning purposes..... reminds me of an old Fox hole radio I built as a kid with a toilet paper roll for the core of the inductor which was attached to a razor blade, and a piece of pencil lead was used as a tap, when you slide it across the razor, you can tune it to different stations....:D
     
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  13. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I thought the pencil lead and razor blade acted as the cat-whisker diode....? I always tapped my radios directly on the toilet paper tube coil.
     
    Last edited: Aug 1, 2012
  14. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Quite unusual to vary the inductance of a tiny RF inductor with a wiper contact. If it was an inductor with a core you could adjust the core position. If it is an air coil (which it probably is) you can adjust it once to tune the circuit (and then solder the C5 wire directly to the coil) but it cannot be meant to constantly being adjusted...
     
  15. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    I didn't usually have a tuning cap on mine--it was just the most basic coil and diode. Tuning capacitors were somewhat hard to come by.

    [​IMG]
     
  16. BMorse

    Senior Member

    Sep 26, 2009
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    The way I remember it (this was nearly 25 to 30 years ago, yes, I'm THAT old! ), you had to have the blade laying on its side with one side of the circuit connected to it, and have the pencil lead attached to a safety pin, that acted as a spring, so when you press down on the "spring" it slides the lead across the face of the blade..... I don't remember if i tuned it on the blade or the tube coil.... now I am gonna have to look it up, you got me curious :rolleyes:
     
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  17. DerStrom8

    Well-Known Member

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    Yup, that sounds right. If I remember correctly, the razor blade had to be slightly rusty. The pencil lead had to be moved across the face of the blade in order for it to make contact with just the right rusty spot to create a decent diode. Once there, it would operate correctly and you could tune it by adjusting the antenna tap on the coil. That's how I remember it, anyway. I could, of course, be wrong ;)
     
  18. BMorse

    Senior Member

    Sep 26, 2009
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  19. vk6zgo

    Active Member

    Jul 21, 2012
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    I'd say that is exactly what you do.In other words,it is"adjust on test".
    Once you get the best position,you solder it in place.
    My guess is that the kit assumes you can get away with connecting C5 to the top of the coil & get away with it.
     
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