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Trio Pro Pilot Auto Trim - Circuit

cgbag40

Member
This has been covered awhile back, but I'm stumped on a simple circuit and the installation manual hasn't helped (page 78 option 2). The Trio Propilot uses a double pole double throw relay to control the trim motor. One of the relays gets an input from manual hat switch on my infinity grip. The other relay gets the input of the auto trim on the Pro Pilot. There is a bridge rectifier to arbitrate the two input signals from the manual trim and the Propilot so there is only one control at any given time. In my case I am using the IDEC RH-2B cube type DPDT relay and the NTE 5322 bridge rectifier. The circuit drives the DC trim motor in forward and reverse.

pin 1 to Pin 5 on the trio servo pin 4 to pin 6 on the trio servo
pin 5 to hat switch UP - AC bridge pin 8 to hat switch down - AC bridge
pin 9 to trim motor pin 12 trim motor
pin 13 to ground and - bridge pin 14 to + 12 VDC and + bridge

the common on the infinity grip is connected to aircraft +12 VDC

Would someone please provide me guidance on where I've got this wrong?

Carlton
 
A little confusing but I think I can see what you did.
The two wires labeled manual trim must both be connected to power or ground, e.g., if the hat connects the bottom wire to 12 volts it must also connect the top wire to ground. But that doesn’t happen in the stick; the top wire is an open circuit when the hat connects the bottom wire.
I’m also concerned about feeding 12 volts into the common wire. Does this affect any other stick buttons? Finally, the relatively small switches in the stick may be pushing their current limits when driving a trim motor. (Not sure about this).
All these issues can be dealt with by having ‘nose up’ control a relay which switches between ground and 12 volts, and a second relay controlled by ‘nose down’. The outputs from these two relays would then be the two wires shown coming from ‘manual trim’ in the Trio manual.
There are other ways of doing this. I use two double pole double throw relays instead of the bridge rectifier and relay shown in the Trio manual.
 
Carlton,

I sent you an email with a couple pictures of the doodad that used to do what you are trying to recreate. It is a Radio Shack 275206 DPDT relay with a 2907 transistor potted on top of it.
 
schematic

Here is the solutions I was able to glean from our peers. Posted here for those who follow behind us

Carlton
 

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Here is the solutions I was able to glean from our peers. Posted here for those who follow behind us

Carlton

One of the great features of the Trio trim controller is its built- in speed control. e.g., on my -10, full trim speed is about right (or maybe even a bit slow) for landing and takeoff, but way too fast for fine adjustments in cruise. The Trio allows you to program max trim speed below, say, 90 kias (you choose), and progressively slower trim speeds as the airplane goes faster. It does this with pulse width modulation (‘PWM’). Unfortunately this does not lend itself well to operating a relay - the relay probably has enough inductance that it will just stay on between the pulses. I don’t think your circuit will work.
 
Trio Auto Trim

One of the great features of the Trio trim controller is its built- in speed control. e.g., on my -10, full trim speed is about right (or maybe even a bit slow) for landing and takeoff, but way too fast for fine adjustments in cruise. The Trio allows you to program max trim speed below, say, 90 kias (you choose), and progressively slower trim speeds as the airplane goes faster. It does this with pulse width modulation (‘PWM’). Unfortunately this does not lend itself well to operating a relay - the relay probably has enough inductance that it will just stay on between the pulses. I don’t think your circuit will work.

I agree Bob. There is a diagram in the Trio install manual showing how to simply do it using a 1 x DPDT relay & bridge rectifier diode - it’s simple & it works. I mount the diode/relay combo in a ‘jiffy’ box with a male dsub connector. That way you can remove it easily IF you need to troubleshoot an ‘issue’.
I’ve lost count of the number of setups done this way & never had any problems - it just works as expected.
Making it simple is always the best option IMO.;)
 
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