PBASIC: Run Motors Simultaneously

lewisg

Hi, everyone!

I am trying to run two motors simultaneously, but I can't figure out the code.

I am using BASIC Stamp Editor, PBASIC 2.5, and a Parallax Stamps In Class Homework Board.

Thanks!

$WMc%

lewisg

The Stamps just like most computers, Can only do one thing at a time. But they run really fast and appear to run things simultaneously.

If You'll post some code, I/WE can help You make both motors run.

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The Truth is out there············___$WMc%___···························· BoogerWoods, FL. USA

Franklin

You are going to need more than the stamp to drive your motors and depending on what you want them to do you could opt for a smart motor driver that would run the motors without tying up the stamps processing power.

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- Stephen

Mike Green

It depends on what kind of motors you're trying to drive. If you're using servos, they use intermittent control pulses and the Stamp can briefly do other things while a servo is between control pulses (like controlling a 2nd servo and reading a few sensors). If you're using stepper motors, you should be able to interleave two stepper motors' windings' pulses. If you're using a DC motor with an H-Bridge, you need some external PWM driver. Something as simple as a 555 timer with a digital pot controlling the on-time would be adequate.

In all cases, you can buy external motor controllers that take much of the burden off the Stamp and allow it to handle sensors, make decisions, and set the state of whatever motors you're using.

lewisg

This is the code

a VAR Word
FOR a = 0 TO 100
PULSOUT 14,280
NEXT
b VAR Word
FOR b = 0 TO 100
PULSOUT 14,1280
NEXT
c VAR Word
FOR c = 0 TO 200
PULSOUT 14,790
NEXT
d VAR Word
FOR d = 0 TO 100
PULSOUT 15,280
NEXT
e VAR Word
FOR e = 0 TO 100
PULSOUT 15,1280
NEXT
f VAR Word
FOR f = 0 TO 200
PULSOUT 15,790
NEXT
END

erco

a VAR byte' a<255
FOR a = 0 TO 100
PULSOUT 14,280
pulsout 15,280' send 2 pulses together
pause 10' full wait is 20 ms
NEXT
FOR a = 0 TO 100' reuse a
PULSOUT 14,1280
pulsout 15,280
pause 10
NEXT
FOR a = 0 TO 200
PULSOUT 14,790
PULSOUT 15,790
pause 10
next
end

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·"If you build it, they will come."

W9GFO

lewisg said...
This is the code

a VAR Word
FOR a = 0 TO 100
PULSOUT 14,280
NEXT
b VAR Word
FOR b = 0 TO 100
PULSOUT 14,1280
NEXT
c VAR Word
FOR c = 0 TO 200
PULSOUT 14,790
NEXT
d VAR Word
FOR d = 0 TO 100
PULSOUT 15,280
NEXT
e VAR Word
FOR e = 0 TO 100
PULSOUT 15,1280
NEXT
f VAR Word
FOR f = 0 TO 200
PULSOUT 15,790
NEXT
END

It appears that the motors you are talking about are continuous rotation servos. If so there are a couple problems. The first is that there are no PAUSE statements. Your FOR..NEXT loop will execute many times faster than the servos need the pulses - they expect a pulse once every 20mS (50 times a second). Second, there is no reason why you cannot follow one PULSOUT with another inside each loop - both motors will be running at the same time with one receiving the PULSOUT command a tiny fraction of a second after the other. In most cases this would not be detectable.

a VAR Byte          ' only use Word variables if you need values greater than 255, and it can be reused - don't need a new one for each loop

FOR a = 0 TO 100
PULSOUT 14, 280     ' takes about 1/4 mS for the command and 1/2 mS for the pulse length total ~ .750mS
PULSOUT 15, 280     ' another ~ .750 mS
PAUSE 18            ' The other lines of code use up a small amount of time so I use PAUSE 18 to keep the pulses close to every 20mS - because that's just the way I am. 
NEXT                ' PAUSE 20 would be fine but be sure to reduce once you add more code within the loop or the servos may start stuttering

FOR a = 0 TO 100
PULSOUT 14, 1280    ' takes about 1/4 mS for the command and 2.5 mS for the pulse length total ~ 2.750mS
PULSOUT 15, 1280    ' another ~ 2.750mS
PAUSE 14            ' 20.000mS - (2 * 2.750mS) = 14.500mS round down to account for execution time of FOR..NEXT
NEXT

FOR a = 0 TO 200
PULSOUT 14, 790     ' takes about 1/4 mS for the command and 1.5 mS for the pulse length total ~ 1.750mS
PULSOUT 15, 790     ' another ~ 1.750mS
PAUSE 16
NEXT

END

Just like erco said! But with formatting

One thing to add, if they are servos and they will always move together, simply tie both signal lines to just one pin. Then they truly will be getting the pulse at exactly the same moment.

Rich H

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The Simple Servo Tester, a kit from Gadget Gangster.

Post Edited (W9GFO) : 1/11/2010 8:07:53 PM GMT

lewisg

Thank you all soooo much, I fianally got the code to work
Thanks Again
lewisg