Some questions regarding a servo motor's data sheet.

[selbstdual]

Currently I am using gear wheels to make the 180° servo rotate a shaft 360°.

[selbstdual]

For a better understanding, I uploaded a video: Here: http://rapidshare.com/files/112603057/c.avi.html which is 2 minutes long. You will need the xvid codec aswell as a mp3-codec. You should see that the part moving is almost parallel to the cam when being in position X. In software I tell the program to make the servo turn back to the old position as mentioned. But it doesn't as you can see.

And I would like you to tell me why.

EDIT: OR here if you prefer some service like youtube: http://www.revver.com/video/863645/problem-with-servo/

[malc-c]

It seems more like a code problem than hardware. Can you post the code here and let us try to work out what's happening.

Are you refreshing the pulse width every 20 ms ? Normally you send the 1ms - 2ms pulse width to the servo every 18 - 20 ms so that the servo holds its position and via the feedback pot knows its position. It looks as if the code is not sending the pw every 20ms or that the servo is mis-reading it and losing its starting point, so on each instruction it trys to move 180 but hits the limits and thus results in limited travel.

[selbstdual]

On a 16f628a

@ DEVICE MCLR_OFF
@ DEVICE hs_osc
@ DEVICE wdt_off
@ DEVICE lvp_off
@ DEVICE protect_off

Define OSC 20
INTCON = 0
CMCON = 7
TRISA = 0
TRISB = 0

StepsRotating CON 93
RotatingMin CON 267
RotatingMax CON 1218


Position VAR WORD
PositionBefore VAR WORD
Counter VAR WORD
PositionBefore = 0
LR VAR BYTE
RotatingPos VAR WORD
Movement VAR WORD

ServoMotor VAR PORTB.1

GOSUB RoutineStartingPos

ES:
LR = 1
RotatingPos = RotatingMin
ES_HS: 
ES_HS_Drehung:
WHILE 1 = 1
    IF LR = 1 THEN
        WHILE RotatingPos < RotatingMax
            GOSUB RoutineRotate
            RotatingPos = RotatingPos + StepsRotating           
        WEND
        LR = 0
    ENDIF
    IF LR = 0 THEN
        WHILE RotatingPos > RotatingMin
            GOSUB RoutineRotate
            RotatingPos = RotatingPos - StepsRotating           
        WEND
        LR = 1
    ENDIF 
WEND
END

RoutineRotate:   
    FOR Movement = 0 TO 1000 / 20   
        Low ServoMotor
        Pulsout ServoMotor,RotatingPos
        Pause 20
    NEXT Movement 
    RETURN

RoutineStartingPos:
    FOR Counter = 0 TO 1000 / 20 
        Low ServoMotor
        Pulsout ServoMotor,(RotatingMax+RotatingMin)/2
        Pause 20
    NEXT Counter 
    RETURN

[Acetronics2]

the answer to your "problem" contains ... 1/2*J*Omega^2

with Omega as the second derivative of rotation ...

Ha,ha,ha

You got your fine calculations "into the teeth" ...

LOL !

A "Hong Kong" servo, I suppose ... certainly not a "King Kong" one.

Alain

[selbstdual]

Poor old man.

[Acetronics2]

I had forgotten some false additions in your soft ... but that was not the "non return" reason ...

just leads to bump your mechanical rotation limits ... might be some resulting damages too ... who knows ?

Was a pleasure, Mr Tax Inspector.

Alain