Help on programming PSC

fleurdelis158

Greetings.

I'm new to this programming stuff of Basic Stamp. I need some help in programming two servos to make my robot move forward (or backward). I'm using BS2p24 microcontroller and Board of Education Rev C. I also use the Parallax Servo Controller (#28023). I've tried to program it but all i can do is making the servo rotating in the same direction. I know that in order to make the robot move forward (or backward), one servo must rotate clockwise and the other must rotate counterclockwise, but i really don't know how. What position should i put in my program?(GWS servos are used). Which command should I use?

allanlane5

Usually, a pulse of 1.5 mSec, repeated every 20 mSec, makes a modified servo (modified so it will rotate continuosly) 'stand still'. Pulses of more than 1.5 mSec make it rotate one way, and less than 1.5 mSec rotate the other.

For a BS2, "PULSOUT ServoPin1, 750" will generate a 1.5 mSec pulse (since that's 750 * 2 uSec). Some people use
"PULSOUT ServoPin1, 500", and "Pulsout ServoPin2, 1000" to get a 1 mSec (spin one way) and 2 mSec (spin the other way) pulse. Then you need a "Pause 20" before doing it again.

fleurdelis158

i'm using this program but i don't think it's right..the servos rotate in the same direction..how can i fix this?

' {$STAMP BS2p}
' {$PBASIC 2.5}

ch VAR Byte
ch2 VAR Byte
pw VAR Word
pw2 VAR Word
ra VAR Byte
Sdat CON 15
baud CON 396
i VAR Byte
ra = 7
ch = 14
ch2= 15

FOR i=1 TO 10
pw = 1240
pw2= 1240
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch, ra, pw.LOWBYTE, pw.HIGHBYTE, CR]
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch2, ra, pw2.LOWBYTE, pw2.HIGHBYTE, CR]
PAUSE 500

pw = 260
pw2= 260
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch, ra, pw.LOWBYTE, pw.HIGHBYTE, CR]
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch2, ra, pw2.LOWBYTE, pw2.HIGHBYTE, CR]
PAUSE 500
NEXT
END

Chris Savage

You're using the same pulse values for both servos...You should try lowering one to 500 and see if the servo goes the other way as it should.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

fleurdelis158

Thanks for the reply..

Anyway, I've tried lowering the pulses of one of the servo to 500.but its still not working.does it has anything to do with the potentiometer inside the servo?

Pengatom

FOR i=1 TO 10
pw = 1240   <-- change this to 260
pw2= 1240
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch, ra, pw.LOWBYTE, pw.HIGHBYTE, CR]
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch2, ra, pw2.LOWBYTE, pw2.HIGHBYTE, CR]
PAUSE 500

pw = 260    <-- and this to 1240
pw2= 260
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch, ra, pw.LOWBYTE, pw.HIGHBYTE, CR]
SEROUT Sdat, 1021,[noparse][[/noparse]"!SC", ch2, ra, pw2.LOWBYTE, pw2.HIGHBYTE, CR]
PAUSE 500

If you change it like this, the servos should go seperate ways
Don't know if the FOR loop is working though?

Pengatom

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1 + 1 = 10· |· 4 + 4 = 10· |· 5 + 5 = 10· |· 8 + 8 = 10

Chris Savage

Have the servos been centered?· If you send them a 750 pulse do they still turn?

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Chris Savage
Parallax Tech Support
csavage@parallax.com