Simultaneous Servo Control?
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Posts: 46,084
Is there a limit to how many servos you can be moving simulaneously with
the stamp? what about with a PIC? I was wondering this because I rarely
see code that moves multiples at once and I was wondering if this is
because is not capable... if you can move multiples at once, how many
could you do theoretically?
- Matt
the stamp? what about with a PIC? I was wondering this because I rarely
see code that moves multiples at once and I was wondering if this is
because is not capable... if you can move multiples at once, how many
could you do theoretically?
- Matt
Comments
each servo control signal must be sent one after the other. Also each servo
needs a control signal to be repeateted at a rate of between 50Hz and
20hz(in my limited experiments with Hitec servos), you may be able to go
lower, but useally the torque and smoothness of movement suffers. Assuming
that all servos could be driven with a maximum signal length (2ms), you
could fit 10 individual servo signals into a 20ms space(50hz update rate),
or 25 servos signals into a 50ms space (20hz update rate). This doesn't take
into account the fact that the PULSOUT command itself also takes time just
to execute, which further slows down the process. Also, any other code in
the program would slow down the process still further.
The main techniques to maximise servo numbers are to use a faster Samp like
an SX, use fast and efficient coding in between the servo controlls, and
limit the total amount of roation of the servos so that shorter signals are
needed.
You can also extend the number of servos by using external circuitry.
I don't know about the PIC microcontrollers.
Paul Lugger
>From: Matt Johnson <matt@m...>
>Reply-To: basicstamps@yahoogroups.com
>To: basicstamps@yahoogroups.com
>Subject: [noparse][[/noparse]basicstamps] Simultaneous Servo Control?
>Date: Sun, 14 Jul 2002 21:33:09 -0700 (PDT)
>
>Is there a limit to how many servos you can be moving simulaneously with
>the stamp? what about with a PIC? I was wondering this because I rarely
>see code that moves multiples at once and I was wondering if this is
>because is not capable... if you can move multiples at once, how many
>could you do theoretically?
>
>- Matt
>
>
>
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of application. I am using the PAK8 in an application that requires at least
four independant frequency sources to all run at the same time! The PAK8
parts work perfectly!
AZEASI
mks.niobrara.com/servo1
He has a PIC Assy language program for running 8 at a time.
I have not tried it yet but will in the future.
May even try it in Mbasic Pro.
Original Message
From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=9OpfC0DjhfbbtPY3rULEFm6xJL9r4wKVZMoaJ9oVLIEGkI8Q0dkd5X4Mci6opJouuBIsxofBbTQ]matt@m...[/url
Sent: Monday, July 15, 2002 12:33 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Simultaneous Servo Control?
Is there a limit to how many servos you can be moving simulaneously with
the stamp? what about with a PIC? I was wondering this because I rarely
see code that moves multiples at once and I was wondering if this is
because is not capable... if you can move multiples at once, how many
could you do theoretically?
- Matt
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.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
[noparse][[/noparse]Non-text portions of this message have been removed]
It depends on what you are doing. If all your stamp II is doing
is moving servos your theoretical max (for 20ms rep. rate) is 10
servos. Remember, you don't have to sit there twidling your bits
waiting for the 20ms to be up! I regularly control 3 or more servos
while running a bunch of other robot code. The secret is to break
up your code into behaviors, then further break your behaviors into
state machines that move to new states on subsequent routine entry
points. In this way you can time your code and run your servos in-
between other code execution. If you'd like some examples of this,
check out my site http://www.techtoystoday.com and bonk on the
"my current robots" list. Then bonk on the source code for one of
the Stamp based robots. All my robots run using modified state
machines to implement Brooksian subsumption behavioral programming.
have fun,
DLC
--- In basicstamps@y..., Matt Johnson ?matt@m...? wrote:
? Is there a limit to how many servos you can be moving simulaneously
with
? the stamp? what about with a PIC? I was wondering this because I
rarely
? see code that moves multiples at once and I was wondering if this is
? because is not capable... if you can move multiples at once, how
many
? could you do theoretically?
?
? - Matt