HELP! reading schematics

Thread Starter

lancellot07

Joined Jul 2, 2012
17
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..
 

Attachments

MrChips

Joined Oct 2, 2009
30,823
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.
 

panic mode

Joined Oct 10, 2011
2,759
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.
 

panic mode

Joined Oct 10, 2011
2,759
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.
 

DickCappels

Joined Aug 21, 2008
10,187
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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