[NSRCA-discussion] berg 7 channel Rx

[John Pavlick]

Sure. The time integration creates the effect of higher output power. The
maximum torque IS a function of the mechanical limitations of the servo but
the effective output power (torque) is dependant on the signal applied over
time. No torque is generated when the servo is not supplied with a pulse. By
increasing the rate at which the servo receives pulses, power will be
generated more frequently. The resolution will not increase at a higher
pulse rate, however because the original servo pulse is generated at a 50Hz
frame rate in the Tx encoder. You are simply applying this pulse twice per
frame at the 100Hz rate. To double the resolution you would need to double
the original frame rate to 100Hz. That is generated by the transmitter, not
the receiver. Think about it. Oops, it looks like I need another beer...

John Pavlick
http://www.idseng.com


> -----Original Message-----
> From: nsrca-discussion-bounces at lists.nsrca.org
> [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Ed Alt
> Sent: Wednesday, September 13, 2006 11:49 PM
> To: nsrca-discussion at lists.nsrca.org
> Subject: Re: [NSRCA-discussion] berg 7 channel Rx
>
>
> Basically, the way our standard servos work is that they trigger
> a one shot
> on every pulse received.  The output of the one shot is a pulse
> of opposite
> polarity to the input pulse whose width is controlled by the feedback pot
> position  (corresponds to the servo arm position).  These two pulses are
> summed and if any error signal exists (if they don't match
> exactly in pulse
> width), the error signal is stretched (made wider) and amplified to drive
> the motor in one direction or the other to resolve the error signal.
>
> The electronics are "dumb" in a standard servo and within certain timing
> limits, you should be able to increase the effective output torque by
> increasing the sampling rate of the pulses that are fed to it.  I
> don't know
> that it would be exactly double, but it should go up.  This is
> because the
> motor is not driven at 100% duty cycle when it's running, i.e.,
> it receives
> a train of stretched pulses, but not a pure DC voltage level.
>
> Ed
>
>
> >From: "Fred Huber" <fhhuber at clearwire.com>
> >Reply-To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
> >To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> >Subject: Re: [NSRCA-discussion] berg 7 channel Rx
> >Date: Wed, 13 Sep 2006 22:16:11 -0500
> >
> >Max output torque of a servo is a function of battery supplied
> voltage, the
> >motor in the servo and the gear ratio.
> >
> >Changing the signal line frequency will not alter the servo
> output torque.
> >
> >Also.. max torque of a servo can sometimes be a GEAR TRAIN limit.
> >otherwise it would be impossible to strip a sevo gear in flight.
>  No change
> >to the voltage supplied is going to alter the strength of the
> gears in the
> >servo.
> >
> >It may effectively increase the servo resolution and thus sensitivity to
> >being off center, but it will not increase its available torque.
> >
> >It MAY have the servo circuit apply more power at a smaller
> deviation from
> >"demanded" position...  But that is an effect of resolution.
> >
> >So.. it may apply full torque available at half the deviation
> from demanded
> >position... (may be what you MEANT to say...)
> >
> >Note that using a dual-inverter "glitch buster"
> >http://www.uoguelph.ca/~antoon/gadgets/noiserx.htm (especially
> with Futabe
> >127 DF RX's) will boost the signal line from the RX output (appx
> 3.8 v for
> >the Futaba 127 when using 4.8 v NiCd pack) to full RX pack
> voltage.  This
> >can increase effective resolution. (especially with long servo leads)
> >The circuit is INTENDED to filter interference from long leads... and it
> >works.  The side effect is almost as good as the intended purpose.
> >
> >  If you can find the chip to make the circuit... I'm having trouble
> >finding the DIP (.10 inch pin spacing) I got some .05 in pin spacing
> >chips... which are going to be harder than heck to solder into
> the circuit,
> >but should do the job.

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