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From: firstname.lastname@example.org (Bill Allison)
Subject: Re: Help - Power mosfets - difficult load
Date: 29 Oct 2002 00:55:19 -0800
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 29 Oct 2002 08:55:19 GMT
"Phil Allison" wrote in message news:...
> "Bill Allison" wrote in message
> > Phil
> > "Phil Allison" wrote:
> > >
> > > ** I don't think you have any idea what a glitch is. It may last
> > > 1/10 of a second - not enough to barely move a servo but enough to
> > > fets.
> > Your idea of what a glitch is corresponds to the last generation of RC
> > kit, when servo positions were transmitted in PPM frames modulated
> > onto the rf and got to the servo more or less directly (via receiver
> > and demultiplexer). Signal reception quality would affect pulse width,
> > dramatically at the limits of radio range.
> ** Glitching with PPM can occur at any range - other RF signals and
> electrical noises do the job beautifully.
Yep - I think that's exactly what i just said - the limit of radio
range, i.e the point at which outputs to the servo are degraded
dramatically, obviously can be anything between zero and a 1 mile
depending on the amount and nature of the interfering signals. That's
why PPM is not used nowadays in any situation where control
reliability is paramount.
> > For the last time - modern microcontrolled RC receivers DO NOT rely on
> > quality of rf link. The pulses output to the servo are generated
> > locally. The pulse width defaults to that defined by the fail-safe
> > rules programmed into the receiver by the operator. When an error free
> > PCM data stream is received via the fm rf link the pulse-width
> > generated is then that commanded. (That's the simplistic version,
> > there's somewhat more sophistication than that). Not a single frame
> > deviates from that behaviour.
> ** When the PCM data stream becomes corrupted a brief clitch can be
> produced as the software recognises the error - you would need a CRO so see
> it on the PPM signal - or your fets will let you know.
Phil that's absolutely not the case. An uninterrupted stream of good
pulses to the servo is guaranteed by the program code in the receiver
decoder's microcontroller section - and is verifiable by CRO
> . . . . .............. Phil
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