Strange Occurance During Trim Installation

[daveg]

I connected my Ray Allen aileron and elevator trim servos per your suggestion to another poster where I have both the Ray Allen indicators and Dynon D180 reading trim position.  The instruction was to tie a GP input into the green wire.  All works well until I actuate the elevator trim motor to the full down position.  As the trim gets near the end of its travel, all thermocouple readings go nuts.  The odd EGT's and CHT's go to -1F.  The even EGT's go to around 1400F and the even CHT's go to around 1700F.  When I actuate the trim motor back up, the temperature readings go back to normal.

What's going on here?

Thanks,

Dave Gallagher
Zenith 601XL, Jabiru 3300 and Dynon D180 in final assembly process.

 

[dynonsupport]

The voltage that the trim sensor is putting into the GP input is either less than 0V or greater than 5V. This will mess up lots of stuff inside the EMS while this voltage is out of range. This must mean the Ray Allen display unit puts more than 5V into the sender.

Unfortunately, this means that you can't have the Ray Allen and the Dynon EMS hooked up at the same time. You'll need to choose one. Sorry we didn't know this beforehand.

 

[annken100]

The white wire with green stripe from the ray allen servo which connects to the LED indicator goes from 0.225 volts to 1.52 volts. The voltage never exceeds 5 VDC and doesn't go negative. This should work just fine with the Dynon GP inputs.

Do you have the analog or digital trim indicators?

Ken

 

[daveg]

Ken,

I had the needle type indicators. Per Ray Allen, they see up to 6 VDC. This 6 volts is what tripped up the D180. I have since removed the connection between the two.

Thanks,

Dave

 

[annken100]

Hi Dave,

You can use a resistor in series with the wire going to the Dynon gp input. You should be able to find a resistor value that will prevent the voltage from exceeding 5 volts. I would start with a 1 meg ohm resistor and go from there. If voltage keeps exceeding 5 volts add more resistance. Radio Shack sells resistor assortment packs that are pretty reasonable in price.

Ken

 

[josok]

Sorry Annken, bad advice. You assume that the internal resistance of the input is linear, and not voltage dependant, and that the output of the RayA would not be load dependant. That's most probably not true.
Maybe it's possible to provide stabilised 5 V to the RayA stuff and still have it work properly? There are 5 V stabiliser DCtoDC transformers available from the shelf.

Regards,

Jos

 

[uk_figs]

Did anyone get the Ray Allen trim indicator piggyback approach to work? I just hooked it up as per the previous post (green wire to the GP input) and both Ray Allen indicators went to the full deflection position and there was no trim indication on the EMS. GP inputs were set to elev and ail trim, sensor type was 1 (not changeable).
Ray Allen position indicators would not change position with trim movement.

 

[Brantel]

Sorry, but there is no easy way to use both the Dynon and the stock indicators at the same time. This screws up the bias of the indicator like you have seen.

There is a way to make it work but you would need something to go in between your parallel connection to the indicator that would be of really high impedance in order to not screw up the bias of the indicator. I suppose you could use an op amp to do this and use the op amp output to drive the Dynon.

That brings up a question for Dynon. What is the GP input impedance? Apparently it is low enough to mess with the bias of the RA indicators.....