problems with Servo Motors...

[saturnX]

thanks for the replies guys.. i never knew servo motors would do that on start up.. never had it happened before so found it strange. Is it common though?

this is how i have written the pulse to the motor:


Servomotor:
pulsout portb.0, b(0) 'Send current servo 1 position out

pause 5 '5 milisecond delay to generate 50 Hz signal
return 'To servomotors
'-------------------


That's like a standard common way of writting the pulsout code isn't it? Although i might consider separating the power supply to the pic and the servo motor but that is really a strange thing to do and adds more weight to the robot.

@Acetronics
Would u mind if i PM you later on to further discuss this topic related to another project of mine which took forever to complete. Again it deals with servo motors. Let me know.

Cheers guys for the feedback. will have a tweak at the project later on. oh is the Code tags available in the forum? can't seem to get it to work

[Acetronics2]

[QUOTE=saturnX]Servomotor:

pulsout portb.0, b(0) 'Send current servo 1 position out

pause 5 '5 milisecond delay to generate 50 Hz signal
return 'To servomotors
'-------------------


Hi, Saturnix ...

Pause 5 is much too short !!! pulsout is 1 - 2 ms, so pause must be ~18ms for ~ 50 Hz framerate.

Some servos do not like like that at all !!! DANGER !!!

Alain

[picster]

Also, be sure that your pulse widths are within the design specs of the servo - if you use a simple pulsout command with a 4MHz clock, you'll have to some math to figure out your MINIMUM and MAXIMUM widths that you can allow, and then spread that range out over 256 steps.

For example, if your servo specs say 600uS to 2400uS then your pulsout would have to be a MINIMUM of 60 and a MAXIMUM of 240 with a 4MHz clock. Beyond that, you'll start overheating (and grinding the gears of) the servo, pushing it past its mechanical limit. If you look at the range in this example, you have a range of 240-60=180, so you can calculate what you should output as 60+(180n/255) where n is your "real" range of 0-255. Thus for a 'n' of 0, you'll have a pulse width of 600, and for a 'n' of 255, you'll have a result of 2400.

It's probably also a good idea to initialize the pin as LOW, just as a housekeeping measure.

--------------------Picster-----------------