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HELP! reading schematics

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Discussion in 'The Projects Forum' started by lancellot07, Jul 16, 2012.

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  1. Jul 16, 2012 #1
    lancellot07

    Thread Starter New Member

    Jul 2, 2012
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    anobody who could help me how to read the schematics. im still a beginner in electronics... there's an attached pic of a schematic ive seen somwere and i dont know the small circles on some of the pins..and other additional questions is on the pic... could you tell me those symbols? thanks in advance..
     
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  2. Jul 16, 2012 #2
    MrChips

    Moderator

    Oct 2, 2009
    19,132
    6,148
    The circles mean the signals are NEGATIVE LOGIC, i.e. it requires a LOW to activate that function.

    K1a etc are most likely connections to a terminal block.

    P1 is a trim pot to preset the frequency of IC1A.

    P2 is the main adjustment for the pulse width of IC1B.

    P3 is a trim adjustment to set the min or max of IC1B.
     
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  3. Jul 16, 2012 #3
    panic mode

    AAC Fanatic!

    Oct 10, 2011
    1,774
    539
    when circle or bubble is touching envelope of the device (box or whatever representing device) then it means that logic is negative (inverted / lookup logic gate NOT).

    when it is on the wire (not touching envelope of the device), it is just terminal or connection.
     
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  4. Jul 16, 2012 #4
    lancellot07

    Thread Starter New Member

    Jul 2, 2012
    17
    0
    meaning ill just connect a wire from pin 10 to ground that will pass through R7.. and pin 4 to ground? am i correct?
     
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  5. Jul 16, 2012 #5
    panic mode

    AAC Fanatic!

    Oct 10, 2011
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    you can ignore bubbles, just wire as if they were not there. so pin 10 of the IC goes to R7 and S2 for example.

    P2 connects to +12V, R9 and P3.

    motor connects to +17V and T2.

    etc.
     
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  6. Jul 16, 2012 #6
    DickCappels

    Moderator

    Aug 21, 2008
    5,749
    1,801
    You have so many diverse replies, some from people who might not have inspected the attached drawing, so I feel one more vote is a good idea.

    As panic mode said, you can ignore the bubbles. They indicated attachment points for some components. In a classic schematic, they would not exist.
     
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