Hi Lindy:

Sometimes when I look at a schematic it makes no sense at all.  But when 
redrawn it becomes completely understandable.
I think that some schematics were drawn on purpose to obfuscate how the 
circuit works or were drawn by a publisher to have a certain width or 
height so they fit their page layout.  I recently was working with one 
of these where the signal flow was like a book, i.e. left to right, down 
a line, left to  right.  For me it's much clearer how it works if it's a 
linear left to right flow.  Also using a lot of ground and Vcc symbols 
removes lines that really have little meaning, leaving the important 
stuff.  Sometimes I use a graphics software to color code schematic 
lines which may help understanding.

The free Express PCB schematic drawing package makes it easy to draw and 
modify a schematic.  It's often handy to make or modify the schematic 
symbol for a component to simplify the schematic.  For example the input 
pins to a PIC might be moved to the left side and the output pins moved 
to the right side, with Vcc on the top and grounded pins at the bottom.  
This is much more understandable than having the pins in the same 
relative location as on the actual part.  For logic parts where there 
are multiple gates, each gate is a seperate component but they all have 
the same ID such as IC4.

Recognize orders of magnitude.  Often part values are chosen so that the 
impedance of the part is either very much higher than the adjacent 
circuitry or very much lower.  Examples would be things like pull up 
resistors or bypass capacitors.  Once you can see these parts you can 
look past them to the more important stuff.

Often the data sheet for a component will have an applications section 
that shows some typical circuits and will have an equation to help in 
selecting a key part.  National Semiconductor is very good at this often 
showing many different application circuits.

My computer has a folder called "data sheets" which has many sub 
folders.  This is very handy both for figuring out existing schematics 
and for designing new ones.  This is one area where the internet has 
made life much easier than ordering hard copies of data sheets.

Have Fun,

Brooke Clarke

-- 
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist