Servo troubles.

[Glenn]

This should do nothing more than swing the servo back and forth, from endpoint to endpoint. It'll probably hang up for a bit at the endpoints and might even move too fast or jerk around a bit trying to catch up to the program.
If it doesn't, you've got something else going on.
It all boils down to breaking it down to it's simplest form and building it back up again.
Try it and report back...

Well, it swings the servoarm to one endpoint, stops for a while, then all the way to the other endpoint (or near it anyway) and directly start to go back again and repeats everything.

Its not a very smooth movement but it looks ok.

[skimask]

Well, it swings the servoarm to one endpoint, stops for a while, then all the way to the other endpoint (or near it anyway) and directly start to go back again and repeats everything.

Its not a very smooth movement but it looks ok.

Ok, that's good...at least you know stuff is working.

Now take the program and modify it to 'pull the endpoints' in a bit until you get to the actual endpoints.
When it 'stops for awhile', the program is probably trying to drive the servo past it's endpoints. The program goes to 0ms pulse width, but the servo can only actually drive to a 1ms pulse width, actually it'll probably drive farther than that, a lot farther, just not all the way to zero, or by the same token, won't drive all the way to 2.55 ms pulse width.

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4
temp var byte
main:
        for temp = 100 to 200
        pulsout portb.0, temp
	pause 17 'try lower numbers until it starts acting even stupider than it's acting now
        next temp
        for temp = 200 to 100 step -1
        pulsout portb.0, temp
        pause 18 'try lower numbers until it starts acting even stupider than it's acting now
        next temp
        goto main
END

Decrease the 100 until it starts pausing at one end (meaning the PIC is trying to over-drive the servo) and increase the 200 until it starts pausing at the other end (again, meaning the PIC is trying to over-drive the servo in the other direction).

[Acetronics2]

Hi, Glenn

This one Should run

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_ON,PROTECT_OFF
DEFINE OSC 4

CMCON = 7 ' Disable comparators

PORTA = %00000011
PORTB = 0

TRISA = %00000011
TRISB = 0

'Use b1 to hold pulse width variable for servo 1

b1 var byte

'initialize variables
b1 = 150

low portb.0		' put the servoport low.
main:

        low portb.0
	pulsout portb.0, b1		'send current servo 1 position out
	if porta.0 = 0 then left1	'check for pressed switch 0
	if porta.1 = 0 then right1	'check for pressed switch 1

bugtrap:

        if b1 > 150 then
               b1 = b1 - 1

        else
               if b1 < 150 then b1 = b1 + 1
              
        endif
        pause 18 : goto main

left1: 
         IF porta.1 = 0 Then bugtrap
         b1 = b1 + 1 
         if b1 > 199 then max1
         Pause 8 : goto main

right1:  
           IF Porta.0 = 0 Then bugtrap
           b1 = b1 - 1 
           if b1 < 100 then min1
           Pause 8 : goto main

max1:  b1 = 100 : goto main ; jump to other side

min1:  b1 = 200 : goto main ; jump to other side

END

and do not forget : courtesy SKI !!!

Alain

[Glenn]

Hi, Glenn

This one Should run

Well, it kind of works, the servo stands still until I touch the switch, but it moves in very strange ways, I'll try to adjust the values a bit and see if it changes anything.

But it sure looks like the comparators was the problem, great!

[Acetronics2]

Well, it kind of works, the servo stands still until I touch the switch,

Looks it should be in the 1500µs position ...

but it moves in very strange ways, I'll try to adjust the values a bit and see if it changes anything.

should reach slowly one end, then RUN to the other end, then slowly to the other end , Then RUN ...

WHILE pushing a button

and going back to center if buttonS realeased ... or both buttons pushed.

But it sure looks like the comparators was the problem, great!

Alain

[Glenn]

Decrease the 100 until it starts pausing at one end (meaning the PIC is trying to over-drive the servo) and increase the 200 until it starts pausing at the other end (again, meaning the PIC is trying to over-drive the servo in the other direction).

Well, as you said before the values depends on which servo I use, I settled for the servo that I'm going to use (the brand new china-made) and with that 75 and 255 seem to be the correct values, however, when its 255, its still not at the endpioint, its a few mm more left. ..However this doesnt matter.

[skimask]

however, when its 255, its still not at the endpioint, its a few mm more left. ..However this doesnt matter.

Change your BYTE variable to a WORD variable and you'll be able to go beyond 2.55 ms. But that sounds a bit goofy since a 2.55ms pulse width is out of spec for most servo's. But hey, if it works for you, go with it...

[Acetronics2]

Hi, SKI

The maximum I ever reached is 250 µs to 2600 µs ... with a Futaba S3001 or a Robbe RS100 ...

not linear at all between 250 and 600µs !!!

regards
Alain

[Acetronics2]

Hi, Glenn

I Think I've found what looks "strange" to you ...

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_ON,PROTECT_OFF
DEFINE OSC 4

CMCON = 7 ' Disable comparators

PORTA = %00000011
PORTB = 0

TRISA = %00000011
TRISB = 0

'Use b1 to hold pulse width variable for servo 1

b1 var WORD

'initialize variables
b1 = 150 << 4

low portb.0		' put the servoport low.
main:

        low portb.0
	pulsout portb.0, ( b1 >> 4 )	'send current servo 1 position out
	if porta.0 = 0 then left1	'check for pressed switch 0
	if porta.1 = 0 then right1	'check for pressed switch 1

bugtrap:

        if b1 > ( 150 << 4 ) then
               b1 = b1 - 1

        else
               if b1 < ( 150 << 4 ) then b1 = b1 + 1
              
        endif
        pause 18 : goto main

left1: 
         IF porta.1 = 0 Then bugtrap
         b1 = b1 + 1 
         if b1 > ( 3199 ) then max1
         Pause 8 : goto main

right1:  
           IF Porta.0 = 0 Then bugtrap
           b1 = b1 - 1 
           if b1 < ( 1601 ) then min1
           Pause 8 : goto main

max1:  b1 = ( 100 << 4 ) : goto main ; jump to other side

min1:  b1 = ( 200 << 4 ) : goto main ; jump to other side

END

This is not the "perfect movement" ... but the maximum to get from this coding style.

Alain

PS : Question : Why multiply b1 per 16 ( << 4 ) and divide it per 16 ( >> 4 ) when outputting the pulse.
The answer to last trouble is here !!!