[NSRCA-discussion] regulators

[J.Oddino]

Bob, Ed, et al,
First of all, the Jaccio (say Jackie O) regulator does not regulate at no
load.  The i4C must put a slight load on it or you would see the full
battery voltage at no load.  So the real drop you measured is about .18
volts from the idle current condition.  This is made up of droop in the
regulator and loss in the wiring.  The regulator drop is spec'd at .2 volts
at 5 amps so it is proportionately less at 1.5 amps.  The regulator is a
servo so it must have an error between commanded value and output to set the
"gain".  Gain is defined as output divided by commanded input.  We'd like it
to be one, but we'd end up with an oscillator or a regulator with a very
slow response time.  I tried a design where I sensed the voltage on the
receiver buss instead of internally in the regulator and had a terrible time
keeping it from oscillating.  The idea was to eliminate the drop between the
regulator and the receiver buss but I decided it wasn't worth it.
There have been countless discussions about wiring losses and these are
significant in IMAC and other giant scale type models.  I don't believe we
need to worry about it in pattern planes but maybe we could provide quicker
elevator response in snaps for guys like Dave L would do everything they can
to get high speed and high torque.  Higher voltage at the servo is the
easiest way to get that result.  Someday maybe I'll try to measure the
voltage at the servo during flight.
I totally agree with Ed that you are still better off with a Lithium pack
and one regulator instead of a five cell NiMH pack and no regulator, because
even though you don't have perfect regulation at the servo, it is consistent
from flight to flight as the pack discharges.

Jim O


----- Original Message ----- 
From: "Ed Alt" <ed_alt at hotmail.com>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, December 06, 2006 7:37 AM
Subject: Re: [NSRCA-discussion] regulators


> Bob:
> The regulator is probably doing just fine. Every regulator that's out
there
> for use in our models has one thing in common.  They regulate the voltage
> output at the point that the regulator is physically connected to.  They
> can't "see" the actual voltage at the end of the wires where your servos
> are. They can only see it at the point where the pins leave the regulator
IC
> package.  What is happening is that a voltage drop is developing across
all
> of the wiring in between the regulator and the load where you are
measuring.
> The voltage drop is calculated by E=IR, where voltage is E, current is I
and
> R is resistance.
>
> There are two ways to accomplish regulation at the load.  One is to have a
> remote sense design to the voltage regulator system, which actually takes
> the true voltage at the point where the load connects and feeds that back
to
> the regulator, to permit the regulator to compensate for the losses in the
> wiring. In practice, this would not work for our application, since the
load
> varies at each servo, so if servo 1 is drawing a bunch of current and thus
> experiencing a lower voltage, the other servos actually don't see a
voltage
> as low as the one drawing the load. So if you boosted the regulator
voltage
> to make servo #1 happy, the others would see a higher voltage.  The end
> result is that the voltage would be all over the place on the high side,
> which is not desireable.
>
> The other thing you could do is just place a regulator at each servo.  Jim
> Oddino could tell you more about it, since he has this setup flying, but
> it's a perfectly good method if you don't mind doing the wiring up at the
> end of each extension. It has several benefits, some minor drawbacks,
> overall it's a cool idea.  Believe it or not, even though you are seeing
> this effect of wiring resistance, you are still better off with the one
> regulator that you have.  It is taking away the effect of the battery's
> internal resistance and all of the wiring in between it and the battery,
so
> the servos are in fact getting a more constant supply than they otherwise
> would.
>
> Ed
>
> ----- Original Message -----
> From: "Robert Mairs" <robertm at sssnet.com>
> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> Sent: Wednesday, December 06, 2006 7:53 AM
> Subject: [NSRCA-discussion] regulators
>
> > I've got a Jaico that regulates to 6.11 volts.   Using a 480 mah TP
lipo,
> > and the Jaico, I got the following.
> >
> > no load, 6.11v
> > 500mah load, 5.72v
> > 1A load, 5.63v
> > 1.5A load, 5.54v
> >
> > Just with the battery, no regulator I get
> >
> > no load, 8.2v
> > 500mah, 7.84v
> > 1A, 7.51v
> > 1.5A, 7.2v
> >
> > I don't understand.  Why doesn't the regulated voltage stay at 6.11v
with
> > a
> > load?  I always thought using a regulator was supposed to give you a
> > constant voltage so the servos reaction would always be the same, yet it
> > acts just like a battery,  just not as great a drop off it seems.
> >
> >
> > _______________________________________________
> > NSRCA-discussion mailing list
> > NSRCA-discussion at lists.nsrca.org
> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> >
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.15.9/573 - Release Date: 12/5/2006
4:07 PM
>
>