开云体育

I use target made by <>. It does schematic, simulation, PCB layout, and is affordable.

ST

On Tue, 02 May 2006 02:09:27 +0200, Roy J. Tellason <rtellason@...> wrote:

Yes...


What platform did you make that software for?

atmel i think.

ST

On Monday 01 May 2006 10:14 pm, rtstofer wrote:

The other day I mentioned my owl with the head moved by a servo.
Well, it works pretty well but it is not as mechanically smooth as I
would like.

So, I have fitted a 42mm stepper motor rated 3.15V @ 1A (per energized
winding I suppose). I intend to move the motor 30 steps either side
of 'center' and take about 3 seconds to do it. A total of 120 steps
or about 40 steps per second. I don't know if I will bother with
velocity ramping.

Hmm. I hadn't really thought that most of those smaller steppers I have on
hand here would be of all that much use, but... :-)

Wandering the Internet I notice two distinct ways of energizing the
windings for full steps: energize only one winding at a time or
energize two adjacent windings at a time and keep the rotor locked
between windings.

For my purposes, with a low inertia load, wouldn't just a single
energized winding work well? I'm only thinking of full steps (because
I don't have enough PWM pins) and I don't need much torque.

Yes, I would tend to think so. I've been reading all sorts of stuff on
steppers (and then falling into the whole CNC thing too :-) for a while now,
perhaps as long as a couple of years or so, after realizing how big and
heavy that box of steppers I had was turning out to be.

Since I don't need detent torque either, is there any reason to not shut off
all of the windings when the system is idle?

Seems to me that the most you gain from doubling up on the energized windings
like that is more torque (and of course some finer positioning too, but...).
I forget if it was Ian Harries' pages or maybe that was in Jones on Steppers,
both of which I'd highly recommend if you haven't read 'em yet.

I know I could use one of the stepper drivers we bought earlier but I don't
think this application is worth the effort. Four MOSFETs ought to do it.

Yes. I was actually originally planning to use salvaged bipolars here but
since I recently acquired a number of MOSFETs too, I may just have a go at
making an H-bridge or 3 out of them.

Since the model operates on 9V, I will use a couple of 6 ohm 10 watt forcing
resistors (I think; I may just drop the voltage somehow).

Volts will get you speed, and amps will get you torque... :-)

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

On Monday 01 May 2006 08:42 pm, rtstofer wrote:

--- In Electronics_101@..., "Roy J. Tellason"
<rtellason@...> wrote:

On Monday 01 May 2006 12:48 pm, Stefan Trethan wrote:

On Mon, 01 May 2006 18:39:33 +0200, rtstofer <rstofer@...> wrote:

Among other things, if you build a software state machine to track the
changes, debouncing will be automatic. Sure, you may bobble between A
is high, B is high back and forth with A is low, B is high (or A is
high, B is low) (in other words both sides of the transition) but it
doesn't matter because only one line is changing states - you wont go
from A is high, B is high to A is low, B is low.

You aren't transitioning far enough to upset the count or miss a
detent position. But you can detect the difference between increase
and decrease.

Yes, even I managed to make the software for a encoder of this type
work, and that says something!
Good thinking really that quadrature stuff...

Yes...

What platform did you make that software for?

You may find the code in avrlib useful in designing this type of
interface:

Rather than downloading the whole mess, which would be a bit slow on dialup,
I went to the online html documentation link, and selected encoder.c and
encoder.h and downloaded the documentation and source pages for both of
those. I hope that's what you were referring to. :-) The encoder.h source
in particular has a nice explanation in there showing waveforms and such, and
explains just how it is that they deal with processing the inputs from the
device.

I know nothing at all about these processor chips, but I can read c well
enough to see what they're doing there, which is pretty nifty from what I
see so far.

The avrlib implementation is fully interrupt driven from both input
phases and works on a variety of AVR devices. It is written in C.
Depending on the size of the AVR device, more than one encoder can be
connected.

That's interesting too -- would that depend on how many interrupt inputs you
had available or how fast the chip in question could handle one and therefore
be likely to be able to deal with more than one?

I know *nothing* about these parts -- is there any place in particular where
you could point me to that would get me going? I'm familiar with a bunch of
way earlier chips, stuff like the 8080, 8085, z80, 68xx, 65xx, and similar,
but just haven't kept up. (Like I *really* need another thing on my plate,
which is already pretty full. :-)

That said, the overall state transitions can be coded in any language
but the idea of using interrupt inputs is a good one. It is not
possible to determine when a phase change may occur.

Yeah, I looked at that bit in the header file and it made immediate sense to
me. Not a bad approach at all. I'll have to look it over and study it in
some detail and see how they're handling the rest of it besides the input...

I don't always use avrlib but I have been know to parphrase the code.
Even convert it to an ARM processor.

I don't know about those, either.

A while back I thought that maybe I oughta start catching up on this newer
stuff. So I subscribed to the piclist. But there was way too much OT stuff
in there even after I'd supposedly configured their end to not send me all
that stuff... So I gave up on that list. Maybe one of these days I'll run
across a better (more focused) source of info.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

Does anybody know of any cheap or low cost circuit design software
like Electronics Workbench or simular. I would like to get back into
electronics design circuits and such see what I have missed the last
ten years. Any suggestions would be helpful.

Tom

The other day I mentioned my owl with the head moved by a servo.
Well, it works pretty well but it is not as mechanically smooth as I
would like.

So, I have fitted a 42mm stepper motor rated 3.15V @ 1A (per energized
winding I suppose). I intend to move the motor 30 steps either side
of 'center' and take about 3 seconds to do it. A total of 120 steps
or about 40 steps per second. I don't know if I will bother with
velocity ramping.

Wandering the Internet I notice two distinct ways of energizing the
windings for full steps: energize only one winding at a time or
energize two adjacent windings at a time and keep the rotor locked
between windings.

For my purposes, with a low inertia load, wouldn't just a single
energized winding work well? I'm only thinking of full steps (because
I don't have enough PWM pins) and I don't need much torque.

Since I don't need detent torque either, is there any reason to not
shut off all of the windings when the system is idle?

I know I could use one of the stepper drivers we bought earlier but I
don't think this application is worth the effort. Four MOSFETs ought
to do it. Since the model operates on 9V, I will use a couple of 6
ohm 10 watt forcing resistors (I think; I may just drop the voltage
somehow).

Richard

--- In Electronics_101@..., "Roy J. Tellason"
<rtellason@...> wrote:

On Monday 01 May 2006 12:48 pm, Stefan Trethan wrote:

On Mon, 01 May 2006 18:39:33 +0200, rtstofer <rstofer@...> wrote:

Among other things, if you build a software state machine to

track the

changes, debouncing will be automatic. Sure, you may bobble

between A

is high, B is high back and forth with A is low, B is high (or A is
high, B is low) (in other words both sides of the transition) but it
doesn't matter because only one line is changing states - you

wont go

from A is high, B is high to A is low, B is low.

You aren't transitioning far enough to upset the count or miss a
detent position. But you can detect the difference between increase
and decrease.

Yes, even I managed to make the software for a encoder of this

type work,

and that says something!
Good thinking really that quadrature stuff...

Yes...

What platform did you make that software for?

You may find the code in avrlib useful in designing this type of
interface:

The avrlib implementation is fully interrupt driven from both input
phases and works on a variety of AVR devices. It is written in C.
Depending on the size of the AVR device, more than one encoder can be
connected.

That said, the overall state transitions can be coded in any language
but the idea of using interrupt inputs is a good one. It is not
possible to determine when a phase change may occur.

I don't always use avrlib but I have been know to parphrase the code.
Even convert it to an ARM processor.

Richard

On Monday 01 May 2006 12:48 pm, Stefan Trethan wrote:

On Mon, 01 May 2006 18:39:33 +0200, rtstofer <rstofer@...> wrote:

Among other things, if you build a software state machine to track the
changes, debouncing will be automatic. Sure, you may bobble between A
is high, B is high back and forth with A is low, B is high (or A is
high, B is low) (in other words both sides of the transition) but it
doesn't matter because only one line is changing states - you wont go
from A is high, B is high to A is low, B is low.

You aren't transitioning far enough to upset the count or miss a
detent position. But you can detect the difference between increase
and decrease.

Yes, even I managed to make the software for a encoder of this type work,
and that says something!
Good thinking really that quadrature stuff...

Yes...

What platform did you make that software for?

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

One thing to watch out for is asymetrical speed--the
open collector drivers have different rise times
relative to the fall times. This may matter for SPI
communication at the higher speeds.

But, open collector outputs are pretty hardy, and easy
enough to replace if abused. They also afford cheap
fast voltage conversion, going higher/lower in I/O
voltage levels.

On the input side, often a simple series resistor will
suffice. Alot of IC's that I've seen state that an
input can be overdriven by up to 30mA into the pin--so
a 1k resistor will get up to 30V protection! This
works by using the ESD structures in (most) IC's to
clamp that pin voltage to +/- a diode drop of either
supply.

Now, I've done this; but others have recommended to
not depend upon the ESD structures for DC
currents--they are meant for short duration overload
conditions, not continous "abuse". They would
recommmend using external diodes and the same series
resistor. Your choice.

Me, on a board I once used series 2.2k resistors with
220pF caps to ground (high noise enviroment) to drive
a 74HCT541 buffer. The drivers were TTL, and I use
CMOS as a rule of thumb. Worked well, and ended a
long standing failure mode (damage to downstream
IC's). No diodes. The only thing I had to watch out
for was rise/fall times; HC and HCT devices will show
a spike in ICC for slow switching speeds due to both
transistors being on, unless if it is a Schotkey input
type.

Shawn

--- lcdpublishing <lcdpublishing@...> wrote:

Hi Guys,

I will be making a small I/O board for some AVRs.
As the inputs
should be pretty straight forward, I am not overly
worried about
them at the present (most of them will be switched
to ground).

However, for the outputs, I don't yet know what I
will be connecting
to them. It could be any of the following:
Mosfets, Relays, LEDs,
etc.

I have some experience with the ULN2803 and being
that I am familiar
with it, I want to use it again. But, that doesn't
expand my
knowledge much either - which is bad.

I would like both the inputs and outputs to be
fairly robust, but
certainly don't want to build them like a tank
either.

So, if you all have some suggestions, I am all ears.
But, as usual,
I am very much on my 'learners permit' :-)

Chris

Shawn Upton, KB1CKT

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around

Hi Guys,

I will be making a small I/O board for some AVRs. As the inputs
should be pretty straight forward, I am not overly worried about
them at the present (most of them will be switched to ground).

However, for the outputs, I don't yet know what I will be connecting
to them. It could be any of the following: Mosfets, Relays, LEDs,
etc.

I have some experience with the ULN2803 and being that I am familiar
with it, I want to use it again. But, that doesn't expand my
knowledge much either - which is bad.

I would like both the inputs and outputs to be fairly robust, but
certainly don't want to build them like a tank either.

So, if you all have some suggestions, I am all ears. But, as usual,
I am very much on my 'learners permit' :-)

Chris

Thanks buddy! I was off by a couple - it's capital U

Chris



--- In Electronics_101@..., Robert Hedan
<robert.hedan@...> wrote:

Chris,



Robert
:)

-----Message d'origine-----
De : Electronics_101@...
[mailto:Electronics_101@...] De la part de

lcdpublishing

Envoyé : mai 1 2006 15:52
? : Electronics_101@...
Objet : [Electronics_101] Re: SPI interfacing - How long can
external connections be?


That is somewhat what I plan to do. However, if storage worked

on

my scope - this would all be much easier to see! I guess I

could

get a series of identical characters passing between the two

chips.

I believe letter N was the one that adds up to 01010101 binary.

If

I can get a repeating pattern it should be pretty easy to watch

and

compare - I hope :-)

Chris

Chris,



Robert
:)

That is somewhat what I plan to do. However, if storage worked on
my scope - this would all be much easier to see! I guess I could
get a series of identical characters passing between the two chips.
I believe letter N was the one that adds up to 01010101 binary. If
I can get a repeating pattern it should be pretty easy to watch and
compare - I hope :-)

Chris


--- In Electronics_101@..., Robert Hedan
<robert.hedan@...> wrote:

I have a suggestion:

- try with a short wire, note results on scope.
- try with a very long wire, compare results on scope with short

wire

results.

If it matches, hurray!

Robert
:)

-----Message d'origine-----
De : Electronics_101@...
[mailto:Electronics_101@...] De la part de

lcdpublishing

Envoyé : mai 1 2006 10:48
? : Electronics_101@...
Objet : [Electronics_101] Re: SPI interfacing - How long can
external connections be?


Roy, I will do when I get the cable in that I plan on using for
this. By chance, can you give me a hint as to what sort of good

and

bad things I should be looking for?

Right now, my technique on the scope is more or less, if I see

two

horizontal lines - spaced apart at the voltage and duration I

think

they should be - I am happy.

Chris

I have a suggestion:

- try with a short wire, note results on scope.
- try with a very long wire, compare results on scope with short wire
results.

If it matches, hurray!

Robert
:)

--- In Electronics_101@..., "lcdpublishing"
<lcdpublishing@...> wrote:

Thanks! That makes sense. Now I just need to decide how I want to
interpret that in the AVR. Right now I can do it both ways easily
(getting 96 counts per rev and 24 counts per rev).

I just know that there will be times when I don't want it to jump a
couple extra steps when the switch settles into a detent. That's when
it will be best to have it count 24 per rev.

I do like that quadrature signal system though - it's neat and
somewhat easy to understand (even for this dummy)

Chris

Implicit in all this is the fact that you don't want to push the
button unless the switch is in the detent position. I think you still
have 24 positions per rotation and the fact that there are 4
transitions between positions is simply a software issue.

Richard

Thanks! That makes sense. Now I just need to decide how I want to
interpret that in the AVR. Right now I can do it both ways easily
(getting 96 counts per rev and 24 counts per rev).

I just know that there will be times when I don't want it to jump a
couple extra steps when the switch settles into a detent. That's when
it will be best to have it count 24 per rev.

I do like that quadrature signal system though - it's neat and
somewhat easy to understand (even for this dummy)

Chris

THanks Richard,

I am 95% sure I got the 232N parts when I ordered the 232cpe parts
from Jameco and they shipped the 232N instead. I don't mind
substitutes, as long as I understand what it is being done to me :-)

CHris

Looks to me like the MAX232N is a Texas Instruments part while the
MAX232CPE is a Maxim part. At least that't the way I found the
datasheets.

No matter, both use 1.0 ufd capacitors. Too bad, the MAX232A uses

0.1

ufd which are much smaller.

I prefer the MAX233 because it doesn't require any charge pump
capacitors. It still requires a decoupling capacitor.

Richard

Facinating Shawn! While some (well, much) of it is over my head at
this time, I get the gist of what you are saying and describing.

I am hoping, (odd someone hopes for problems) that I will see some
of these effects when I get the cable and put a scope on this
signal. It sure would be great to actually "See" and "Measure" the
cause and effects of this sort of thing.

I will have to re-read this post a number of times to gain more from
it. So I may be back at you will questions further down the road.

Thanks!!!!

Chris






--- In Electronics_101@..., Shawn Standfast
<sstandfast@...> wrote:

--- lcdpublishing <lcdpublishing@...> wrote:

Roy, I will do when I get the cable in that I plan
on using for
this. By chance, can you give me a hint as to what
sort of good and
bad things I should be looking for?

Transmission lines all have four basic properties
inherient to them. They are: 1) resistance 2)
inductance 3) capacitance 4) conductance.

The resistance and inductance are in series with the
load at the other end and the capacitance and
conductance are in parallel with the load. What this
means is that your transmission line will behave as a
filter when a signal is passed along it. This has
several side affects associated with it. I will
discuss these in a moment. First let me digress into
an aside about signals.

According to Fourier, any real signal can be expressed
as a sumation of an infinate combination of sines and
cosines; each with a different frequency and
amplitude. The frequencies of each "component" are
integer multiples of the fundimental frequency. This
is what people are refering to when they talk about
n-th order harmonic frequencies (i.e. the third
harmonic for example). In digital circuits, our
transmission signal is a square wave. Transforming
this into its Fourier series yeilds a combination of
sine waves with odd-numbered multiples of the
fundimental frequency. You don't really need to grasp
this fully right now but it is revelant for your case.

Getting back to the transmission line properties, let
me remind you that a transmission line will behave as
a passive filter when the line lengths get long
enough. This results in two distinct effects on a
signal that is being transmitted on it. 1) Phase
shift 2) Voltage reflection.

PHASE SHIFT -- All passive filters will create some
sort of a phase shift of any AC signal that is passed
through it. Whether or not the shift is positive or
negative will depend upon the frequency of the signal
and the type of filter it passes through. Recall that
our digital square-wave is actually composed of an
infinate combination of sine waves. When this type of
wave is sent along a transmission line the wave can
become "distorted" when it comes out the other end.
This is because the "line filter" has shifted the
phase of some of the square wave's harmonics. So what
you should be looking for on the output end of your
line will be ringing on your transitions and rounding
of your signal edges. If your line is really long, or
poorly constructed, you might even see something that
looks more like an audio signal rather than a
square-wave.

VOLTAGE REFLECTION -- The second characteristic that
must be accounted for is voltage reflection. What
this describes is the fact that that not all power
transmitted on the line will be transfered to the
load. Some of it will be reflected back to the
source. The effect is similar to the one observed
when you take a string and tie one end to a wall and
then take the other end and shake it up and down to
create a wave on the string. When the wave reaches
the wall, the wave "bounces back" towards you. This
is onset by a mismatch in impedances between the
source, transmission line, and load. When the voltage
is reflected back to the source, if the source and
line impedences don't match the wave will then be
reflected back down to the load again. This results
in what is called a "standing wave" and in "ideal"
conditions can continue forever. One effect that can
be caused by this standing wave is if the standing
wave happens to be in phase with the signal at the
load then the voltages add together. This can cause
the voltage across the load to increase greatly. The
same is true at the source. When the standing wave is
in phase with the signal at the source, the voltage at
the source can increase greatly.

The opposite is also true. If the standing wave is
180 degrees out of phase with the signal and the
relative amplitudes of each are similar, then the
signal will in effect be canceled out at the load (or
source depending on which end of the line you're on.)
This is why impedence matching is so important between
the source, line, and load. If the impedences match
then a standing wave will not be seen. What you
should look for to determine if this is happening is
check your voltages. If you have a dramatic increase
or decrease on either side of the line then you
probably need to adjust the length of your line.
Also, check each of the components on either side of
the line. If they are getting hot then that probably
indicates a problem as well.

I forget the exact length, but I believe these effects
start to become noticeable when the length of your
line is 1/100th that of the signal wavelength but I'll
have to look this up to be sure. At your voltages and
frequencies, you will probably have to worry more
about phase shift than voltage reflection but it never
hurts to check for both. Also, the degree in which
these effects are manifested depend upon the type of
transmission line used.

If you want more information on either the Fourier
transform or transmission line properties do a google
search. There is quite a bit of information out there
on both topics.

Hope this helps you find what you are looking for.

Shawn



__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around

--- lcdpublishing <lcdpublishing@...> wrote:

Roy, I will do when I get the cable in that I plan
on using for
this. By chance, can you give me a hint as to what
sort of good and
bad things I should be looking for?

Transmission lines all have four basic properties
inherient to them. They are: 1) resistance 2)
inductance 3) capacitance 4) conductance.

The resistance and inductance are in series with the
load at the other end and the capacitance and
conductance are in parallel with the load. What this
means is that your transmission line will behave as a
filter when a signal is passed along it. This has
several side affects associated with it. I will
discuss these in a moment. First let me digress into
an aside about signals.

According to Fourier, any real signal can be expressed
as a sumation of an infinate combination of sines and
cosines; each with a different frequency and
amplitude. The frequencies of each "component" are
integer multiples of the fundimental frequency. This
is what people are refering to when they talk about
n-th order harmonic frequencies (i.e. the third
harmonic for example). In digital circuits, our
transmission signal is a square wave. Transforming
this into its Fourier series yeilds a combination of
sine waves with odd-numbered multiples of the
fundimental frequency. You don't really need to grasp
this fully right now but it is revelant for your case.

Getting back to the transmission line properties, let
me remind you that a transmission line will behave as
a passive filter when the line lengths get long
enough. This results in two distinct effects on a
signal that is being transmitted on it. 1) Phase
shift 2) Voltage reflection.

PHASE SHIFT -- All passive filters will create some
sort of a phase shift of any AC signal that is passed
through it. Whether or not the shift is positive or
negative will depend upon the frequency of the signal
and the type of filter it passes through. Recall that
our digital square-wave is actually composed of an
infinate combination of sine waves. When this type of
wave is sent along a transmission line the wave can
become "distorted" when it comes out the other end.
This is because the "line filter" has shifted the
phase of some of the square wave's harmonics. So what
you should be looking for on the output end of your
line will be ringing on your transitions and rounding
of your signal edges. If your line is really long, or
poorly constructed, you might even see something that
looks more like an audio signal rather than a
square-wave.

VOLTAGE REFLECTION -- The second characteristic that
must be accounted for is voltage reflection. What
this describes is the fact that that not all power
transmitted on the line will be transfered to the
load. Some of it will be reflected back to the
source. The effect is similar to the one observed
when you take a string and tie one end to a wall and
then take the other end and shake it up and down to
create a wave on the string. When the wave reaches
the wall, the wave "bounces back" towards you. This
is onset by a mismatch in impedances between the
source, transmission line, and load. When the voltage
is reflected back to the source, if the source and
line impedences don't match the wave will then be
reflected back down to the load again. This results
in what is called a "standing wave" and in "ideal"
conditions can continue forever. One effect that can
be caused by this standing wave is if the standing
wave happens to be in phase with the signal at the
load then the voltages add together. This can cause
the voltage across the load to increase greatly. The
same is true at the source. When the standing wave is
in phase with the signal at the source, the voltage at
the source can increase greatly.

The opposite is also true. If the standing wave is
180 degrees out of phase with the signal and the
relative amplitudes of each are similar, then the
signal will in effect be canceled out at the load (or
source depending on which end of the line you're on.)
This is why impedence matching is so important between
the source, line, and load. If the impedences match
then a standing wave will not be seen. What you
should look for to determine if this is happening is
check your voltages. If you have a dramatic increase
or decrease on either side of the line then you
probably need to adjust the length of your line.
Also, check each of the components on either side of
the line. If they are getting hot then that probably
indicates a problem as well.

I forget the exact length, but I believe these effects
start to become noticeable when the length of your
line is 1/100th that of the signal wavelength but I'll
have to look this up to be sure. At your voltages and
frequencies, you will probably have to worry more
about phase shift than voltage reflection but it never
hurts to check for both. Also, the degree in which
these effects are manifested depend upon the type of
transmission line used.

If you want more information on either the Fourier
transform or transmission line properties do a google
search. There is quite a bit of information out there
on both topics.

Hope this helps you find what you are looking for.

Shawn



__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around