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.
>
> 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.
>
> 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.
>>
>
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