S
Stephen Ramsay
 Jan 1, 1970
 0
I'm going to reveal the extreme depths of my ignorance here, but I just
can't get my head around schematic diagrams and I'm hoping someone can
help.
I'm an absolute newbie. I've read Forrest Mimms and several other books
designed for beginners. I know what the various circuit symbols mean,
and I understand (at least in a preliminary way) what the various
components do. I also think I understand the ohm's law, and the various
rules governing series and parallel circuits. It suspect, however, that
I don't understand these things fully, and that this is part of the
problem.
All the books I have start out by describing lots of closed circuits.
In each case, the circuit has a battery. The lines in the diagram lead
from the positive terminal of the battery, through several components
(resistors, diodes, lamps, whatever), and return to the negative
terminal. All of this seems to make total sense.
However, each book, at a certain point in the explanation, abandons this
format and moves (without warning) to a schematic like the one I've
crudely described below  that is, there's a voltage in, a voltage
out, and a number of ground symbols. In other words, the circuit
isn't "connected" in the way the earlier ones were. I'm having a lot
of trouble understanding how to read even these simple circuits, which
means, of course, that the more complicated ones in magazines are
entirely illegible.
+V

/
\
/
\

>V out
 
v 
 \
 /
v \
 /
 
v 
 
 
= =
[I'm sure I'm not doing this right. The little "v"s are represent three
diodes in series. It's the first circuit example in Mimms on p. 101]
Now, let me try to walk through my muddled thinking on what's going on
here, and see if someone can tell me where I'm making the big conceptual
errors.
1. What do those ground symbols mean? Well, they're supposed to be
connected, so let me imagine that they're connected to each other, and
that they're further connected to the negative terminal of the battery.
Now, ground, if I understand it correctly, is the point at zero voltage.
2. But what is "zero voltage?" If voltage is analogous to pressure,
then zero pressure might mean that electrons are flowing in an unimpeded
manner. No, that's got to be wrong, because that sounds like
resistance. Perhaps it means that the voltage drop across the entire
circuit goes from 12 volts at the positive terminal of the battery to
zero volts at the point indicated as ground. I'm sure I'm confused,
because voltage doesn't "go" anywhere. Perhaps now I'm confusing it
with current.
3. What if there was a wire connecting the positive terminal to the
negative terminal and nothing else. Where would the "zero voltage"
point be in that case? Perhaps it would be the case that the wire
itself is zero voltage and that the voltage rating (say, 9v) is the drop
*across" the battery itself. Hmm.
4. What to do with V out? Well, it has to be connected in some way to
the rest of the circuit (or, presumably, to another circuit that's
connected to this one). Mimms indicates that the voltage at that point
is n x 0.6 volts. Okay, I think I get that. The diodes are adding
voltage in 0.6 increments. But what is that wire connected to? If we
connect it to ground, it seems like we'll have a situation in which the
n x 0.6 voltage is connected to this mysterious "zero voltage."
5. Perhaps we could imagine that the n x 0.6 voltage is connected to
some load that is in series with the ground point. The load "uses it
up" so that the voltage returns to zero. Okay, that has just got to be
wrong. I'm still thinking of voltage as if it's resistance.
As you can see, I'm utterly confused. And I have a sense that my
confusion is borne of fundamental misunderstanding. I would really
appreciate it if some kind soul would take the time to show me the error
of my ways. I feel like I'm not going to get anywhere until I sort this
out.
Steve
can't get my head around schematic diagrams and I'm hoping someone can
help.
I'm an absolute newbie. I've read Forrest Mimms and several other books
designed for beginners. I know what the various circuit symbols mean,
and I understand (at least in a preliminary way) what the various
components do. I also think I understand the ohm's law, and the various
rules governing series and parallel circuits. It suspect, however, that
I don't understand these things fully, and that this is part of the
problem.
All the books I have start out by describing lots of closed circuits.
In each case, the circuit has a battery. The lines in the diagram lead
from the positive terminal of the battery, through several components
(resistors, diodes, lamps, whatever), and return to the negative
terminal. All of this seems to make total sense.
However, each book, at a certain point in the explanation, abandons this
format and moves (without warning) to a schematic like the one I've
crudely described below  that is, there's a voltage in, a voltage
out, and a number of ground symbols. In other words, the circuit
isn't "connected" in the way the earlier ones were. I'm having a lot
of trouble understanding how to read even these simple circuits, which
means, of course, that the more complicated ones in magazines are
entirely illegible.
+V

/
\
/
\

>V out
 
v 
 \
 /
v \
 /
 
v 
 
 
= =
[I'm sure I'm not doing this right. The little "v"s are represent three
diodes in series. It's the first circuit example in Mimms on p. 101]
Now, let me try to walk through my muddled thinking on what's going on
here, and see if someone can tell me where I'm making the big conceptual
errors.
1. What do those ground symbols mean? Well, they're supposed to be
connected, so let me imagine that they're connected to each other, and
that they're further connected to the negative terminal of the battery.
Now, ground, if I understand it correctly, is the point at zero voltage.
2. But what is "zero voltage?" If voltage is analogous to pressure,
then zero pressure might mean that electrons are flowing in an unimpeded
manner. No, that's got to be wrong, because that sounds like
resistance. Perhaps it means that the voltage drop across the entire
circuit goes from 12 volts at the positive terminal of the battery to
zero volts at the point indicated as ground. I'm sure I'm confused,
because voltage doesn't "go" anywhere. Perhaps now I'm confusing it
with current.
3. What if there was a wire connecting the positive terminal to the
negative terminal and nothing else. Where would the "zero voltage"
point be in that case? Perhaps it would be the case that the wire
itself is zero voltage and that the voltage rating (say, 9v) is the drop
*across" the battery itself. Hmm.
4. What to do with V out? Well, it has to be connected in some way to
the rest of the circuit (or, presumably, to another circuit that's
connected to this one). Mimms indicates that the voltage at that point
is n x 0.6 volts. Okay, I think I get that. The diodes are adding
voltage in 0.6 increments. But what is that wire connected to? If we
connect it to ground, it seems like we'll have a situation in which the
n x 0.6 voltage is connected to this mysterious "zero voltage."
5. Perhaps we could imagine that the n x 0.6 voltage is connected to
some load that is in series with the ground point. The load "uses it
up" so that the voltage returns to zero. Okay, that has just got to be
wrong. I'm still thinking of voltage as if it's resistance.
As you can see, I'm utterly confused. And I have a sense that my
confusion is borne of fundamental misunderstanding. I would really
appreciate it if some kind soul would take the time to show me the error
of my ways. I feel like I'm not going to get anywhere until I sort this
out.
Steve