problem with controlling a servo

Started by Michael Bloom January 2, 2009
hi, I pulled out my old BX24 to play with controlling a servo, and I am
having some problems with it. I have a both a regular analog servo and
a new digital servo, both are micro 9 gram servos. When I send a
single position PWM to the servo it moves to that position OK, but when
I try to have it move through a range of positions it messes up and
just jumps around between two positions. Even using the sample
servo.bas that has it move from 10 mS to 20 mS, that comes with with
the BX24 documentation, it still doesn't work right. I have hooked up
the BX24 to a scope and it is generating the correct signal but when I
plug in the servo it acts like the bx24 is resetting itself. Anyone
have any clue or suggestions.

Thanks,
Michael
Problem solved, I was under powering the system with just 220mA, once
I put the servo on its own power supply at 550mA it works just fine.

Thanks,
Michael
--- In b..., "Michael Bloom"
wrote:
>
> hi, I pulled out my old BX24 to play with controlling a servo, and
I am
> having some problems with it. I have a both a regular analog servo
and
> a new digital servo, both are micro 9 gram servos. When I send a
> single position PWM to the servo it moves to that position OK, but
when
> I try to have it move through a range of positions it messes up and
> just jumps around between two positions. Even using the sample
> servo.bas that has it move from 10 mS to 20 mS, that comes with
with
> the BX24 documentation, it still doesn't work right. I have hooked
up
> the BX24 to a scope and it is generating the correct signal but
when I
> plug in the servo it acts like the bx24 is resetting itself.
Anyone
> have any clue or suggestions.
>
> Thanks,
> Michael
>

> ... servo on its own power supply...

Very common problem, and the common solution. An archive search of
"servo reset" would've found that several times.
Tom

Is the servo running from the same power supply? The digital servo
may take more current and cause the BX24 to reset.
David

--- In b..., "Michael Bloom"
wrote:
>
> hi, I pulled out my old BX24 to play with controlling a servo, and
I am
> having some problems with it. I have a both a regular analog servo
and
> a new digital servo, both are micro 9 gram servos. When I send a
> single position PWM to the servo it moves to that position OK, but
when
> I try to have it move through a range of positions it messes up and
> just jumps around between two positions. Even using the sample
> servo.bas that has it move from 10 mS to 20 mS, that comes with
with
> the BX24 documentation, it still doesn't work right. I have hooked
up
> the BX24 to a scope and it is generating the correct signal but
when I
> plug in the servo it acts like the bx24 is resetting itself.
Anyone
> have any clue or suggestions.
>
> Thanks,
> Michael
>

I had a similar issue once... I turned out the power supply does not
produce enough current for both the BX24 and the servo. (approx .5a)

And while I could control 1 servo most of the time if it wasnt under
load. Any kind of load or other items also drawing current would
cause the power supply to go into thermal shutdown. Basically turning
off and then restarting a sec or 2 later.

Basically.... your servo power should come from a different source.