servo programming

jdnphoto · 2010-09-29 06:36

Can anyone tell me if there is a way of programming a servo to change position by one increment each time through a loop. Example first time through loop pulsout 14, 750 next time through loop pulsout 14, 800 and so on until loop is completed by counting. Thanks for you help.

Mike Green · 2010-09-29 06:59

Sure, use a FOR loop like this:

FOR i = 750 TO 2000 STEP 50
PULSOUT 14,i
PAUSE 20
NEXT i

jdnphoto · 2010-09-29 07:10

I tried something similar and all it did was rotate the servo from 750 to 1000.

Here is part of my program so you can see the total picture. Please look at the "'TILT"

PULSOUT HB25D, 500 + 129 ' FORWARD MOTION
PAUSE 20

PULSOUT HB25H, 500 + 50 ' UP MOTION
PAUSE 20

SEROUT 10, BAUD, ["[E159}"] ' ROTATE
GOSUB CHECKBUSY2
PAUSE 10

CHECKBUSY2:
PAUSE 10
CB_LOOP2:
IF IN8 = 1 THEN CB_LOOP2
PAUSE 100

FOR TiltPrevPosition = 750 TO 1000 STEP 4 'TILT
PULSOUT 15, TiltPrevPosition
NEXT
PAUSE 3000

LOOP UNTIL (COUNTER = 62)

Mike Green · 2010-09-29 07:21

You have to have the PAUSE statement in the loop. A servo expects a control pulse about 50 times a second and cannot respond to pulses more frequent than that. Make the STEP size large enough so the servo moves through its range as quickly as you want even through the pulses (and loop steps) are only occurring 50 times a second.

jdnphoto · 2010-09-29 07:24

Thank you so much I will try that.

erco · 2010-09-29 09:43

Also make sure you have a RETURN at the end of your Checkbusy2 routine. Can't tell from your edited program listing.

jdnphoto · 2010-09-29 12:29

I tried the following code. The servo "tilt" goes through all steps before advancing the main loop. I need it to move (step) 4 then hold this position until the main loop returns to it the next time. Then move (step) 4 hold again and so on.

Routine2:

DEBUG "Routine 2 is running", CR

'

Initialization

DO: LOOP UNTIL HB25D = 1 'Wait for HB25 Power up
LOW HB25D 'Make I/Opin Output/Low
PAUSE 5 'Wait for HB25 to Initialize
PULSOUT HB25D, 750 'Stop Motor 1

'

Initialization HB25H

DO: LOOP UNTIL HB25H = 1 'Wait for HB25 Power up
LOW HB25H 'Make I/Opin Output/Low
PAUSE 5 'Wait for HB25 to Initialize
PULSOUT HB25H, 750 'Stop Motor 2

PAUSE 1000

'

Program Code

UpCounter = 0

DO
UpCounter = UpCounter + 1

PULSOUT HB25D, 500 + 129 'Forward 1/4"
PAUSE 5000

PULSOUT HB25H, 500 + 50 'Up 1/2"
PAUSE 5000

SEROUT 10, baud, ["{E-150}"] 'Rotate
GOSUB checkbusy2
PAUSE 5000

checkbusy2:
PAUSE 10
CB_loop2:
IF IN8 = 1 THEN CB_loop2
PAUSE 100

FOR TiltPrevPosition = 750 TO 1000 STEP 4
PULSOUT Tilt, TiltPrevPosition 'Tilt
PAUSE 5000
NEXT

DEBUG BELL
PAUSE 3000 'Hold for 3 seconds

LOOP UNTIL (UpCounter = 62)

GOSUB Routine3:

Mike Green · 2010-09-29 12:51

Please re-read erco's reply. Your program logic is in trouble and the program will eventually stop working since you have GOSUBs without RETURNs.

Your existing FOR loop won't work particularly well. You have a PAUSE 5000 in the loop which means that the servo will get one control pulse every 5 seconds. That won't work. Servos need control pulses every 20ms or they'll shut themselves off. That causes mechanical jitter and slippage.

I think you need to back up and talk about what your program is supposed to do. Go back to a flowchart or some similar sort of diagram, even a written list of actions and when they occur.

Daniel Harris · 2010-09-29 13:05

Try this:

Routine2:

DEBUG "Routine 2 is running", CR


'------------Initialization----------------------------
DO: LOOP UNTIL HB25D = 1 'Wait for HB25 Power up
LOW HB25D 'Make I/Opin Output/Low
PAUSE 5 'Wait for HB25 to Initialize
PULSOUT HB25D, 750 'Stop Motor 1

'------------Initialization HB25H----------------------------
DO: LOOP UNTIL HB25H = 1 'Wait for HB25 Power up
LOW HB25H 'Make I/Opin Output/Low
PAUSE 5 'Wait for HB25 to Initialize
PULSOUT HB25H, 750 'Stop Motor 2

PAUSE 1000

'------------Program Code-----------------------------
UpCounter = 0

'----------change here --------------
TiltPrevPosition = 750
'----------change here --------------
DO
UpCounter = UpCounter + 1


PULSOUT HB25D, 500 + 129 'Forward 1/4"
PAUSE 5000

PULSOUT HB25H, 500 + 50 'Up 1/2"
PAUSE 5000

SEROUT 10, baud, ["{E-150}"] 'Rotate
GOSUB checkbusy2
PAUSE 5000

checkbusy2:
PAUSE 10
CB_loop2:
IF IN8 = 1 THEN CB_loop2
PAUSE 100

'----------change here --------------
PULSOUT Tilt, TiltPrevPosition 'Tilt

TiltPrevPosition = TiltPrevPosition + 4
'----------change here --------------


DEBUG BELL
PAUSE 3000 'Hold for 3 seconds

LOOP UNTIL (UpCounter = 62)

GOSUB Routine3:

servo programming

Comments