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Subject: Re: [LML] Re: Change the speed of the ROC servo  for trim
From: Colyn Case <colyncase@earthlink.net>
In-Reply-To: <list-5001360@logan.com>
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Paul,

I see.   I don't know anything about that PreciseFlight box.
I have 24v power and 12v trim servos if that is what you mean.
I do know that the way the trutrak auto-trim box works is that it has a =
set of relays in it.  When it's dis-engaged the manual trim signal is a =
pass-through.  When it's engaged the manual trim sources are totally =
disconnected and it's feeding it's own power to the servos.  There's a =
control on the auto-trim to control The servo speed is controlled by the =
length of the power interval (much longer than pwm pulses).   We talked =
about putting a speed control between the servo and the auto-trim.   =
That doesn't work they way they have it set up.   Also, and very =
unfortunately, they don't provide an input for the trim power.

If you actually figure out a way to limit the auto-trim speed external =
to the auto-trim box, let me know.  ....or maybe you have done that =
already?

Colyn

On Jun 2, 2011, at 8:28 AM, Paul Miller wrote:

> We're on the same page Colyn but I've got a weird setup.  A 24v buss =
and 12v servos.  The trim box is something made by PreciseFlight with no =
wiring diagram and no response from the firm.  Lancair Avionics put it =
in.  I presume I could feed that box with 12v and see what happens.  =
Then the TruTrak feeds the autotrim module which was just upgraded for =
free by TruTrak (thanks) to handle the unplanned 24v that seems to go to =
the pitch trim in many aircraft (source:TruTrak).  The pitch trim output =
from the Precise Box goes to a 200k pot and is also in series with the =
autotrim also has a variable speed adjustment, probably another pot.
>=20
> As I said in a past post, I'll put an airspeed switch coupled with a =
PWM output to feed the RAC pitch trim servo and get rid of all the pots.
>=20
> On 5/31/2011 9:33 AM, Colyn Case wrote:
>> Paul,
>> I would say the added value is more exposure.
>> I'm not sure they designed the speed control to have a 28V input.   I =
think they would expect you to put their 28v ->12v converter in.   The =
latter may also be just a resistor but the point is they worked out all =
the power dissipation requirements etc.
>>=20
>=20
> --
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