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POS-12 incorrect output

FlyDave

FlyDave

Active Member
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Hi all,

We installed the PH Aviation PHA-01 flap motor today. I had also purchased a RAC POS-12 to drive a flap widget on my Dynon HDX.
In addition to the 2 wires to power the motor there were 3 wires not connected to anything and marked GREEN, ORANGE and BLUE....Bingo!
With the flap motor and POS-12 installed we wired everything up. The motor works fine, is quieter and has internal power limiting at the end of travel.
I configured the POS-12 in the HDX but from FLAPS UP to about 20 deg I don't get a change in voltage on the HDX and the widget doesn't change until I get to 20 deg. From 20 deg to full flaps I get a constant change. See the attached images. I have not verified the change with a volt meter at the POS-12 yet.
I didn't do the wiring from the motor location to the HDX. But this seems to me that the POS-12 is failing in the first ~1/4" of arm travel.
Thoughts?

Dave

Flaps 20.pngFlaps 30.pngFlaps 40.pngFlaps UP.pngFlaps widget.png
 
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If the PHA-01 has 3 position wires, can they be connected directly to the Dynon without using the RAC POS-12 Position Sensor?
 
The POS-12 output is nothing more than a variable resistance that changes with the position of the slide.
If an ohm meter shows a changing resistance through the full travel range of the slide, you then have either a wiring problem or a calibration procedure problem.
Though I have seen instances where in the first initial amount of travel of the slide, the resistance didn’t change. Adjusting the sensor linkage so that the full travel range was not being used when the flap motor moved from full up to full down, solved the issue.
 
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rvbuilder2002 said:
The POS-12 output is nothing more than a variable resistance that changes with the position of the slide.
If an ohm meter shows a changing resistance through the full travel range of the slide, you then have either a wiring problem or a calibration procedure problem.
Though I have seen instances where in the first initial amount of travel of the slide, the resistance didn’t change. Adjusting the sensor linkage so that the full travel range was not being used when the flap motor moved from full up to full down, solved the issue.
Click to expand...
This is exactly what I'm doing. Shortening the required throw and moving it to and section that produces a chance in voltage.
 
Should be linear but isn’t. Might be wired wrong. Put ohm meter on three wires and put flaps in 20*. A to B should be 5 or 10k. B to A should be 5 or 10k. A to C should be somewhere in the middle. B to C should be 5 or 10k minus the A to C number. Then A goes to reference power, C goes to ground and B goes to the io port input. You can flip a and c to get 0 volts at up and 5 volts at 40*. It may be setup to work that way.
 
I tested the POS-12 and it reads from 0 - 5K ohms as it should. I checked the wiring from the panel and found that the orange wire was supplying 12v, not 5v from the Dynon EMS. I emailed Dynon and they said that this would cause the output to the widget I experienced. I have an avionics shop doing a few other things on Wednesday morning and they will change this wire to the appropriate output on the Dynon EMS.
Thanks to all that responded!

Dave
 
We changed the orange power connector from a 12v bus to the 5v Dynon supply and the trim indicator works as it should with full travel on the POS-12.
Also, the new PH Aviation motor is faster - now less than 4 seconds for full deployment where the old motor took a full 5 seconds. The limit switches on either end are nice as well.
When I flew today I got my first "flap overspeed" warning ;)
 
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