Two-speed idea #2:   I like Dan's diagram.   to replace the speed control, how about using ARINC 429 label 206 for IAS, repeat the data for that label into an micro controller for 10$ and have it switch out to the relay along with some time damping to handle airspeed oscillations.  Maybe upgrade that idea by sending the output as PWM directly to the trim motor so that trim speed follows a table of IAS.   I'm guessing all this is doable for cheap parts, it avoids opening the pitot system and avoids the Ray Allen speed controller and relay.
Paul
Legacy
On 2013-04-02, at 6:46 PM, Dan Ballin <dballin@gmail.com> wrote:

> I