RadioBanter - View Single Post - Hi-Q RF filters, anyone?

July 29th 03, 01:55 AM

"Paul Burridge" wrote in message
...
On Mon, 28 Jul 2003 13:20:27 GMT, (John Crighton)
wrote:

The rich guy is stunting around and decides to buzz
me at low level about 20 feet above the ground.
His model flies over me and then nose dives into
the ground near by. I could here his servos twitching
away as I walked past the wreckage.
After I retrieved my model and switched off my
transmitter, I stopped by the little gathering at the
wreck site. The rich guy was operating his servos OK
and scratching his head. " I spend thousands on
my model and that ******* John Crighton comes
here every weekend with 50 dollars worth of homebuilt
junk and flies. It just isn't fair." "Moan...grumble..moan."
I didn't try to explain that his receiver got swamped. His
mates put the crash down to pilot error at low level, and
that was that.

John, what in your experience causes this 'servo-twitching'? I've
observed it myself at close hand many times. The last time it
happened, we cured it by isolating the die-cast box the rx was mounted
in from the chassis. I still can't figure out why this worked, as I'd
have thought grounding it *ought* to solve the problem. But in this
instance, grounding it *created* the problem and isolating it solved
it! Sometimes when I see those servos behaving like they've got a mind
of their own it almost makes me believe in the supernatural.

R/C servos are EXTREMELY sensitive to trash on the power supply leads.
Grounding the box probably coupled some trash into the ground lead to the
servo.

I don't know what you have in your system, but I'd start by investing in a
few small 250 uF (nominal) capacitors and put them directly across the servo
supply leads. Use Y-harnesses to hook them in if you don't feel like
modifying a cable.