Servo does not move

[ruijc]

Greetings,

i've found a program to move a servo ( left and right ).

Did some minor modifications ( lcd pinouts ) and programmed my pic 16f84A.

However the servo does not move !

The LCD displays the position OK and the buttons work OK but there is no movement from the servo.
With an ohmeter i cannot sense any voltage also.

Is there something wrong with the program ?
Any ideas ?

This is the program:

pos var word ' Servo position
servo1 var PORTB.4 ' Alias servo pin

Low servo1 ' Servo output low
PORTB = 0 ' PORTB lines low to read buttons
TRISB = $fe ' Enable first button row
Pause 100 ' Wait for LCD to startup
Gosub center ' Center servo

mainloop:
If PORTB.5 = 1 Then
Gosub left
Endif
If PORTB.2 = 1 Then
Gosub center
Endif
If PORTB.6 = 1 Then
Gosub right
Endif

servo1 = 1 ' Start servo pulse
Pauseus 1000 + pos ' Delay for servo pulse high time
servo1 = 0 ' End servo pulse
Pause 16 ' Servo update rate about 60Hz
Goto mainloop ' Do it all forever

left:
If pos < 2000 Then
pos = pos + 1
GoSub display ' Display new position on LCD
Endif
Return

right:
If pos > 1000 Then
pos = pos - 1
GoSub display ' Display new position on LCD
Endif
Return

center:
pos = 1500
GoSub display ' Display new position on LCD
Return

display:
Lcdout $fe, 1, "Position = ", #pos
Return

end

thanks

[HenrikOlsson]

Hi,
You have the servo on portB.4 but then you do

TRISB = $fe ' Enable first button row

Which sets that pin to input. So when you do:

servo1 = 1 ' Start servo pulse
Pauseus 1000 + pos ' Delay for servo pulse high time
servo1 = 0 ' End servo pulse
Pause 16 ' Servo update rate about 60Hz
Goto mainloop ' Do it all forever

PortB.4 won't go high since it's set to be an input.

Either change your servo1 = 1 to HIGH servo1 and servo1 = 0 to LOW servo1 or make sure that PortB.4 is setup as an output.

/Henrik Olsson.

[ruijc]

that's it !

i missed that !

thanks . it's working fine now.

.

[ruijc]

I have all things working and changed the code to be more complete.

But still having some issues.

I've noticed that the value for the servo to be centered the pos must be 400 ( even with the original code )

for far left the value must be 1300

but for far right 0 is not enough.

i've tryed this but doesnt work...

right:
If pos > -100 Then
pos = pos - 10
Endif
servo1 = 1
Pauseus 1000 + pos
servo1 = 0
Pause 16 ' Servo update rate about 60Hz
Return

any ideas ?
and why arent the original values working for me ? I've seen many servo programs and all have the same values for center.

thanks

[Acetronics2]

Hi, Ruijc

I think you are "mixing" and misunderstanding some servo parameters here ...

so, before going further ... what is your servo model and brand ??? and what is your radio set ???

Alain

[ruijc]

Hi Alain,

thanks for your help.

i'm currently using a futaba's S148 servo.

My idea is to test any futaba and hitec servos ( digital and analog ).


.