Servo not reaching full travel

[ruijc]

Hi all,

skimask,

i'm not really sure if the servo moves equally to both sides because it will depend on where the center is.
In my program the center is at pos = 700

The servo never came to the point of hitting it's internal stops and "keeping the motor running" ( if you know what i mean )

I can increase the pos value but the servo stops when reaching pos +- 1300.

I think that the minimum value could be the key here...i mean...the min value is 25...can i go lower than this ( minus ) ???

Jumper,

I did not opened the servo yet.

BrianT,

My servos do not have the center adjustment screw. Were did you see this ? I have never seen this in any of my servos ( hitec, futaba, digital/analog ).

About the pulsout method...i tryed once that but for some reason it didnt worked as well as my code above...will try it again though

.

[BrianT]

Not all servos have a centre adjustment. To check, remove the philips head screw that holds the servo arm on. Look down the hole in the splined shaft that holds the servo arm. If your servo has a centre adjustment, you will see a very small flat blade screwdriver slot. That is the centre adjustment.

HTH
Brian

[skimask]

Hi all,
i'm not really sure if the servo moves equally to both sides because it will depend on where the center is.
In my program the center is at pos = 700

Put a mark on the servo horn and eyeball it.

The servo never came to the point of hitting it's internal stops and "keeping the motor running" ( if you know what i mean )

Stalling perhaps?

I can increase the pos value but the servo stops when reaching pos +- 1300.
I think that the minimum value could be the key here...i mean...the min value is 25...can i go lower than this ( minus ) ???

Somehow, I think you're Oscillator and you're DEFINE's don't match up. Grab an LED, and try a simple one second per flash LED flasher type thing and see what happens.
I still get the feeling that you're a magnitude or two off the mark here.
The servo stopping at 1300, tells me that if your oscillator was off by a factor of 2, that the 1300 might actually be 2600. A pulse width of 2.6ms on a servo is 'off the scale' at one end by quite a bit, I don't think it's completely unreasonable that you'd be hitting a stop there rather than around 2-2.1 ms like it should be.

And another thing...You also said that your center is 700.
Well, 700 (.7ms) x 2 = 1400 (1.4ms) ....pretty close to 1500 (1.5ms) dontcha think!

Double check your oscillator settings, frequency, code, etc.etc.etc. I'm sticking with that theory for now....in the absense of better information of course...

[ruijc]

skimask ,


just a note:
When i say the center is pos = 700 means that it's 1700 (pauseus 1000+pos ) which is equal to say 1.7ms, right ? ( pretty close to those 1.5ms ).

About the osc you are right because i already did some work there. I started with a define for a 4mhz speed and ended at a 3 mhz define ( with a define osc 3 i got closer to the real thing )

this is because i noticed that using define osc 3 i could get more travel with the lower limit ( pos = 25 ) rather than with define osc 4

.

[Jumper]

Hi

DEFINE OSC 4

you must use capital letters in the define line.

/me

[ruijc]

Opps...i did not knew that

Does that mean that if i use like :

DEFINE osc 3

it will not work ?

shouldnt pbp recognize it anyway ?

.

[Jumper]

All definitions must be in UPPER CASE .... or the compiler MAY not recognize them.

This goes for the entire DEFINE STATEMENT. It has to be exactly as stated in the PBP manual or ....... but I guess the warning in the manual about this has to be for a reason.

I have not spent any time to figure out what if this and what if that. I just stick to the manual and spend my time with writing the code instead.


shouldnt pbp recognize it anyway ? - May or may not...

I really don't know but I am sure DEFINE OSC 3 will do the job.

/me

[skimask]

When i say the center is pos = 700 means that it's 1700 (pauseus 1000+pos ) which is equal to say 1.7ms, right ? ( pretty close to those 1.5ms ).

Ok, that makes a bit more sense now...

About the osc you are right because i already did some work there. I started with a define for a 4mhz speed and ended at a 3 mhz define ( with a define osc 3 i got closer to the real thing )

You do realize that DEFINE OSC 3 doesn't really define 3Mhz, it's actually 3.58Mhz, (14.31818 / 4, for use with colorburst crystals, which used to be dirt cheap and easy to find and accurate).

[ruijc]

Thanks for the warning Jumper,

i have to be more carefull with that from now on

skimask,

i've checked my pbp manual and you are right. Osc 3 is really 3.58 Mhz.

I will try with lower speeds...maybe using the internal oscilators and see what happens

.

[skimask]

skimask,
i've checked my pbp manual and you are right. Osc 3 is really 3.58 Mhz.
I will try with lower speeds...maybe using the internal oscilators and see what happens
.

That's the thing...you shouldn't have to do that.
I can run servo's just as happily running 48mhz on the 18F4550 as I can at 4mhz on the same PIC, same program, same everything, just a different DEFINE OSC at the beginning.
You've got something else going on that's preventing you from doing so.
Port not set right, interrupt's bugging something, register not set up right or something...

And if I remember right, I don't think I've seen your FULL code yet...just fragments.
That doesn't work so good.
Time and time again, somebody says, 'well, the problem can't be over there, 'cause that's got nothing to do with anything over here'.
Well, guess what.....the problem was over there because it had everything to do with all of it over here in one way or the other...

If you run the servo to an endpoint (at least an endpoint that you've found using the PIC and it's software), how much farther (if any) can you make it move after removing power by manually turning it?

[ruijc]

skimask ,

the full code with settings is in my 2nd post.

I ran the program again and moved the servo to the far right and then i moved it with my fingers and yes...it moved a bit more !

this means that it can move a bit more to the right but it's limited with the low 25 ( 1025 ms ).

To the left it goes all the way !

This also means that center is not where i though it was .

.