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Help with electronics terms

I'm having a bit of difficulty understanding the following terms:

A "pull up resistor".

[But then I have a bit of a problem when folk say they have "added a
load" to a circuit, with a resistor, when I would have said (in my
logic) that a restriction had been added.
But then like the optimist/pessimist dichotomy, it depends whether you
are thinking of the resistor added across a short circuit, or an open
circuit.]

And "bit-banged serial" which I assume refers to a serial port on a
Pic(axe) or similar processor.

Thanks for any clarification, jack
 
Jack,

I wouldn't try to limit yourself with the way people label
technologies. If those labels (words) meant something, you wouldn't
be looking for a solution for your own project.

They can't do anything more with what they've been provided, so if you
need to create something, don't depend on the limiting boundaries set
forth by those who have accomplished done one thing or another.

Over the next 20 years, resistors of every make will go completely
extinct, including those previously designed to work with positronic
PCs. What are you trying to build?
 
Jack,

I wouldn't try to limit yourself with the way people label
technologies. If those labels (words) meant something, you wouldn't
be looking for a solution for your own project.

They can't do anything more with what they've been provided, so if you
need to create something, don't depend on the limiting boundaries set
forth by those who have accomplished done one thing or another.

Over the next 20 years, resistors of every make will go completely
extinct, including those previously designed to work with positronic
PCs. What are you trying to build?

G'day, Peerdom.
I'm mainly trying to learn. I was once accused of reinventing the
wheel -- no, come to think of it, I've been told that several times.
Many years ago I started making a pedal radio out of a car generator.
Still have the bits. One day I may get it chrome plated and mount it
on a jarrah plinth :)
At around the same time, I did a course in programming an old CP/M
computer with Pascal to do a simple accounting job. I was told not to
be silly and to buy an accounting package off the shelf. I thought it
was a much more practical effort than my overpaid seniors' effort in
writing a similar program in FORTRAN on an old IBM mainframe using
punch cards!
The only bottom line to all of this wasted effort was that the big
boss had some warped idea that anything that came out of a dot matrix
printer was gospel. Oh, well!.

I'm again reinventing the wheel, but hopefully learning a lot along
the way (again).
I want to program picaxe microcontrollers to do all sorts of neat
things, and especially datalogging of various measurements and perhaps
a keyless front door lock, and maybe a controller for an electric
wheelchair.
For the moment, I will stick with electrons and the various methods of
impeding and encouraging their flow, but thanks for your advice, jack
 
E

Eeyore

Jan 1, 1970
0
I'm having a bit of difficulty understanding the following terms:

A "pull up resistor".
http://en.wikipedia.org/wiki/Pull-up_resistor


[But then I have a bit of a problem when folk say they have "added a
load" to a circuit, with a resistor, when I would have said (in my
logic) that a restriction had been added.
But then like the optimist/pessimist dichotomy, it depends whether you
are thinking of the resistor added across a short circuit, or an open
circuit.]

And "bit-banged serial" which I assume refers to a serial port on a
Pic(axe) or similar processor.

A serial port handles one bit of data at a time by definition being only 'one
bit wide'.

The banging refers to handling that port, or making any general purpose I/O
behave like a serial port, typically in low-level software (although it need
not be) written yourself rather than letting relevent hardware ( a UART for
example which may be on-chip) handle it for example.
http://en.wikipedia.org/wiki/Uart

Graham
 
B

Bob Masta

Jan 1, 1970
0
I'm having a bit of difficulty understanding the following terms:

A "pull up resistor".

This is needed on the output of an "open collector" (or "open drain",
etc) type logic gate. Consider the output stage to be a simple switch
with one side connected to ground and the other side connected to
the output pin. The pull-up goes between the output pin and the
power rail, so that the pin will go high when the switch is open.
When the switch is closed, the pin is effectively shorted to ground
so the output voltage is zero (and current flows through the pull-up).
[But then I have a bit of a problem when folk say they have "added a
load" to a circuit, with a resistor, when I would have said (in my
logic) that a restriction had been added.
But then like the optimist/pessimist dichotomy, it depends whether you
are thinking of the resistor added across a short circuit, or an open
circuit.]

And "bit-banged serial" which I assume refers to a serial port on a
Pic(axe) or similar processor.

This means that the serial port operation is done by careful
programming of the processor (to get the timig right, etc), as
opposed to having a separate chip or circuit within the processor
that is dedicated to take care of all the serial port stuff.
The dedicated port frees up the processor, allowing
it to do something else than babysit the port, so it's handy
to have... but of course costs more in dollars and watts.

Best regards,


Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
J

John Popelish

Jan 1, 1970
0
I'm having a bit of difficulty understanding the following terms:

A "pull up resistor".

[But then I have a bit of a problem when folk say they have "added a
load" to a circuit, with a resistor, when I would have said (in my
logic) that a restriction had been added.

When you add a resistor to a circuit, there are generally
two possibilities as to how it is related to the signal
path. The resistor can be added in series with the path, or
in parallel to it (making an additional branch). Pull up
resistors produce a parallel branch of a signal path to a
positive supply, to provide a tendency for the signal
voltage to head toward the positive supply, when all other
influences (like an open collector transistor that pulls the
signal line to ground, when the transistor turns on) turn
off. It provides a default, no drive situation, voltage.
But then like the optimist/pessimist dichotomy, it depends whether you
are thinking of the resistor added across a short circuit, or an open
circuit.]

And "bit-banged serial" which I assume refers to a serial port on a
Pic(axe) or similar processor.

Serial communications involve timing bit states so that they
follow one another at the baud rate. Programming a port
line to produce a serial output is pretty simple, with only
a per character permission (handshaking) scheme that
controls it. But receiving a serial stream involves syncing
to the bit timing to the leading edge of the start bit of
each character (in the case of asynchronous serial), and
this is usually done with a resolution of 1/16th of the bit
time. Writing code that does this process is called bit
banging. The alternative is to use hardware that performs
all these tasks, automatically, leaving your processor free
to do other things, with just an occasional character move
into or out of the hardware.
 
R

Rich Grise

Jan 1, 1970
0
I'm having a bit of difficulty understanding the following terms:

A "pull up resistor".

Eeyore got this one pretty good.
[But then I have a bit of a problem when folk say they have "added a
load" to a circuit, with a resistor, when I would have said (in my
logic) that a restriction had been added.
But then like the optimist/pessimist dichotomy, it depends whether you
are thinking of the resistor added across a short circuit, or an open
circuit.]

Think of it as adding a conductance in parallel with whatever the output
is. Conductance, being the reciprocal of resistance, means there's "more
load" with _less_ resistance across the output terminals.

Typically, "more load" means more current output.
And "bit-banged serial" which I assume refers to a serial port on a
Pic(axe) or similar processor.

Like Eeyore said, it's just emulating a UART in software/firmware.

Hope This Helps!
Rich
 
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