>>You probably need more filtering on the servo power/gnd pins.
>>Also, it's possible you need filtering on the signal pin too,
>>and maybe /Mclr on the PIC.>
>
>I'll buy that.  You're probably right about the signal pin not being used
>for high current draw, but I'm not sure how much that signal pin draws,
>either.  Could you surmise why is it more susceptible to resets when the
>battery voltage drops from 5.45 down to 5.10?


Drew,

AFAIK, it is only a few mA - plenty of boards use uC pins bare to
drive the servo signal pin. Some kind of electronic speed controller
in there.

As far as your batt voltage, are you driving the PIC straight off
the batt, or do you have a v.reg in there? If the latter, you may be
experiencing v.reg dropout at the lower batt voltages.

Also, I think you should be able to get away with powering the servo
at ~6v or so, with only 5v from the uC on the signal pin.
=======


>When you say "more filtering," do you mean "at least some filtering"? :)  I
>have none anywhere, really, except for a bypass cap on the power/gnd PIC
>pins.  The servo power/gnd pins are shared with the receiver's power supply
>pins.  I'm kind of "branching off" of the line from the receiver to the
>servo.


I popped the case on my Futaba S3003 servo a couple of weeks ago,
and it has a little hi-speed dc motor with a multi-gear speed reducer
in there, but the pcb is all smt and hard to tell what/if the filtering
is. The motor draws ~500 mA, and these lo-V, hi-I motors tend to be
very noisy. For my Tamiya motor geartrain - similar motor to the servo
- I found that a series RC snubber across the motor contacts worked
fairly well - R = 15 - 100 ohms, C = 0.047 - 0.1 uf or so.

Fig 7.19 in Mobile Robots by Jones/Flynn shows a servo hacked for
"continuous" ops - they show a small electrolytic across the motor
terminals, with resistors from the terminals to the metal case.

However, with my Tamiya geartrain, I am using an h-bridge with
PWM speed control, and I found that a bare cap actually produced
worse noise than the snubber described above. Difference is
continuous d.c. versus PWM chopping.

- danM
==============

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads