Pulse Width Modulation and independence
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Posts: 46,084
Hi there, my problem is I need to run a continuous PWM command,
whose' DUTY variable is calculated based on logic/program I created.
But, the PWM must be ran uninterrupted, and so therefore while the
program is calculating the appropriate DUTY cycle, the PWM command is
not being run. I need some kind of soution that involves a PWM
command running independandtly.
Short of purchasing another stamp to handle a continuous PWM command,
does anybody have any ideas?
whose' DUTY variable is calculated based on logic/program I created.
But, the PWM must be ran uninterrupted, and so therefore while the
program is calculating the appropriate DUTY cycle, the PWM command is
not being run. I need some kind of soution that involves a PWM
command running independandtly.
Short of purchasing another stamp to handle a continuous PWM command,
does anybody have any ideas?
Comments
You need an independent PWM controller. There are many of them out there. I
am using a Parallax PWMPAL on a robot, and it works great. One of the nice
features is that it fits underneath the Stamp, and so consumes no real
estate and requires no external connections. The down side is that certain
pins on the Stamp HAVE to be dedicated to the PWMPAL, which could be a
problem in an existing design.
Jonathan
www.madlabs.info
Original Message
From: "viper3558" <viper3558@y...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, April 21, 2004 9:30 AM
Subject: [noparse][[/noparse]basicstamps] Pulse Width Modulation and independence
> Hi there, my problem is I need to run a continuous PWM command,
> whose' DUTY variable is calculated based on logic/program I created.
> But, the PWM must be ran uninterrupted, and so therefore while the
> program is calculating the appropriate DUTY cycle, the PWM command is
> not being run. I need some kind of soution that involves a PWM
> command running independandtly.
>
> Short of purchasing another stamp to handle a continuous PWM command,
> does anybody have any ideas?
>
>
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
> Yahoo! Groups Links
>
>
>
>
>
>
ken
=================================
Hi there, my problem is I need to run a continuous PWM command,
whose' DUTY variable is calculated based on logic/program I created.
But, the PWM must be ran uninterrupted, and so therefore while the
program is calculating the appropriate DUTY cycle, the PWM command is
not being run. I need some kind of soution that involves a PWM
command running independandtly.
Short of purchasing another stamp to handle a continuous PWM command,
does anybody have any ideas?
[noparse][[/noparse]Non-text portions of this message have been removed]
-Viper
--- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> I think Al Williams has a PAK? that will run a continuous PWM
>
> ken
> =================================
> Hi there, my problem is I need to run a continuous PWM command,
> whose' DUTY variable is calculated based on logic/program I
created.
> But, the PWM must be ran uninterrupted, and so therefore while the
> program is calculating the appropriate DUTY cycle, the PWM command
is
> not being run. I need some kind of soution that involves a PWM
> command running independandtly.
>
> Short of purchasing another stamp to handle a continuous PWM
command,
> does anybody have any ideas?
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
-Viper
--- In basicstamps@yahoogroups.com, "Jonathan Peakall"
<jpeakall@p...> wrote:
> Viper,
>
> You need an independent PWM controller. There are many of them out
there. I
> am using a Parallax PWMPAL on a robot, and it works great. One of
the nice
> features is that it fits underneath the Stamp, and so consumes no
real
> estate and requires no external connections. The down side is that
certain
> pins on the Stamp HAVE to be dedicated to the PWMPAL, which could
be a
> problem in an existing design.
>
> Jonathan
>
> www.madlabs.info
>
>
Original Message
> From: "viper3558" <viper3558@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Wednesday, April 21, 2004 9:30 AM
> Subject: [noparse][[/noparse]basicstamps] Pulse Width Modulation and independence
>
>
> > Hi there, my problem is I need to run a continuous PWM command,
> > whose' DUTY variable is calculated based on logic/program I
created.
> > But, the PWM must be ran uninterrupted, and so therefore while the
> > program is calculating the appropriate DUTY cycle, the PWM
command is
> > not being run. I need some kind of soution that involves a PWM
> > command running independandtly.
> >
> > Short of purchasing another stamp to handle a continuous PWM
command,
> > does anybody have any ideas?
> >
> >
> >
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
full-time PWM. The PAK-VIII can also be coaxed into making very
high-resolution PWM among other things (most people use them to drive RC
servos, it seems).
Regards,
Al Williams
AWC
http://www.awce.com/pak5.htm
Original Message
From: smartdim@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=8BhfaH6ctTtoG0A0S_RjyPz_Ax9ocs0pPmbvtOsLA32zQP8AWofa_0EyS_pHcc-_cu-v78fm]smartdim@a...[/url
Sent: Wednesday, April 21, 2004 7:58 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Pulse Width Modulation and independence
I think Al Williams has a PAK? that will run a continuous PWM
ken
=================================
Hi there, my problem is I need to run a continuous PWM command,
whose' DUTY variable is calculated based on logic/program I created.
But, the PWM must be ran uninterrupted, and so therefore while the
program is calculating the appropriate DUTY cycle, the PWM command is
not being run. I need some kind of soution that involves a PWM
command running independandtly.
Short of purchasing another stamp to handle a continuous PWM command,
does anybody have any ideas?
[noparse][[/noparse]Non-text portions of this message have been removed]
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Yahoo! Groups Links
PIC co-processors to help people with the
BS2. He calls each different co-processor
a "PAK". Thus you have the PAK-I, PAK-II,
etc. Each one fulfills a different purpose.
I believe the PAK-8 is the PWM PAK. The
problem with PWM is some chip has to sit there,
generating a Pulse-Width Modulated signal
continuously to drive electric motors. The
PWM signal lets you speed up and slow down
the motor.
Since the BS2 is a single-tasking beast, it
can only PWM one channel at a time -- which is
a pain when you want to control two or more
motors. Thus, the PAK-8 is controlled by a
BS2, and it then controls the motor speeds.
--- In basicstamps@yahoogroups.com, "viper3558" <viper3558@y...>
wrote:
> What's a PAK and who is Al Williams?
>
> -Viper
>
> --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > I think Al Williams has a PAK? that will run a continuous PWM
> >
> > ken
> > =================================
> > Hi there, my problem is I need to run a continuous PWM command,
> > whose' DUTY variable is calculated based on logic/program I
> created.
> > But, the PWM must be ran uninterrupted, and so therefore while
the
> > program is calculating the appropriate DUTY cycle, the PWM
command
> is
> > not being run. I need some kind of soution that involves a PWM
> > command running independandtly.
> >
> > Short of purchasing another stamp to handle a continuous PWM
> command,
> > does anybody have any ideas?
> >
> >
> > [noparse][[/noparse]Non-text portions of this message have been removed]
wrote:
> What's a PAK and who is Al Williams?
>
> -Viper
I'm sure Al will offer more details, but he has written a few books
on micro controllers as well as his current book on how to make home-
brew circuit boards.
He has developed what could be called support chips for the Stamp (as
well as some other microcontollers)
The PAC-(x) is a support chip that is really a separate
microcontroller that runs in the background.
The Stamp can look at all sorts of things, then tell the PAC-(x) to
run one of the output channels of PWM at 43% duty cycle and the PAC
chip will just run a constant PWM while the Stamp is off doing other
things.
Makes for a constant PWM output.
Check out his website
AWC
http://www.awce.com/pak5.htm
He also offers other support chips, here is the listing
http://www.al-williams.com/compare.htm
oh yeah, he posts a "Stamp Project of the Month" on here one or near
the first of the month. A Free project if you want to experiment.
I have no affiliation with Al, except to say I'm a satisfied customer.
Dave
wrote:
> Hi there, my problem is I need to run a continuous PWM command,
> whose' DUTY variable is calculated based on logic/program I
created.
> But, the PWM must be ran uninterrupted, and so therefore while the
> program is calculating the appropriate DUTY cycle, the PWM command
is
> not being run. I need some kind of soution that involves a PWM
> command running independandtly.
>
> Short of purchasing another stamp to handle a continuous PWM
command,
> does anybody have any ideas?
This will just be a variation on some of the other posts suggesting
an external PWM controller. If cheap and dirty is important, try one
or more TL507 a/d converter chips which have a mode of operation
where they give a very satisfactory PWM output when given an analog
voltage in.
What you do is use a stamp PWM out with a slightly larger than
normal filter capacitor to give a voltage input to the 507. The
voltage will remain stable while your stamp goes to do other things.
See "The Forrest Mims Engineer's Notebook" from Radio Shack. If its
not available, e-mail me directly and I'll send you some notes.
Tom Sisk