EMS "CONTACT" inputs anomally

[kurtfly]

Dynon,

Can you please explain why I am experiencing this?

I just received my EMS-220 module back from Dynon after repairs.  The board was replaced per Dynon write up.  So I think I basically have a new EMS.  I performed the Software update to 15.0.4, network configure and loaded the .SFG and .DFG files.

I discovered that when the system voltage is above ~14.2 volts the EMS will display all sensors as RED "X's". I isolated problem to the 3 "Contact" inputs i have configured for my landing gear DOWN indicator. Disconnecting any one of these and the EMS starts displaying good data.

I have C37-p10, p20, and p21 configured as a contact input.  Each of these are spliced off of the Green Gear Down lamps. These are all 14V lamps. 14Volt system.

The install manual says you can input up to 15 Vdc on these and up to 30V momentarily.

I corrected this problem by installing a 10k Ohm resistor in series on each of these contact inputs.  But I am curious why this board is different than my previous one.

Thanks,

 

[Dynon]

Do ALL of the sensors go to red Xes? Or just the contacts?

 

[kurtfly]

All the sensor's indicate "X". even the Tach and MP.

 

[dynonsupport]

Are you sure tach goes red X? MAP makes sense, tach does not.

Is it also true that if you have 2/3 contacts at 14+V, it's OK, but only if all 3 are above it's an issue?

Knowing these will help us look at what might be different.

 

[kurtfly]

The way I troubleshot this was I connected a bench adjustable power supply to the alternator output line and adjusted the power supply for 14.4 Volts.  I pulled circuit breakers and when I pulled my Landing Gear Control breaker the problem cleared. The only thing I have SV connected to Landing Gear Control is the Down Locked lamps. In this configuration, I unplugged one at a time and in every case the problem cleared.  Then re-plugged it in and problem returned.  Did this one at a time.

The 10K resistor dropped the voltage approximately to 6V with 14.4V bus.

I am pretty sure the tack also "X"d out but I could be wrong.

I flew for an hour today for the 1st time with this new EMS.  Everything looks good!

Kurt

 

[kurtfly]

Dynon,

Any new info on what had changed with the "Contact" inputs?

Kurt

 

[Dynon]

Sorry - I thought you had the issue solved. As far as I know currently, nothing changed in the way the contacts are handled in any recent update. What's your current status?

 

[kurtfly]

I currently must have 10 K resistors in series with my 3 landing gear contacts. With the full 14V signals going to the "Contact" inputs the engine status displays all "X"'s, only when all 3 are above 14V. With the 10 K resistors inline the voltage is reduced and it works OK. This started with the new EMS module I received from Dynon and/or when upgraded from 15.0.3 to 15.0.4

There is definitely something different. My previous module handled the 14V contacts without any problems. Does the EMS go into some kinda "protection mode" or is something driven into saturation?

 

[vlittle]

I don't think that overdriving the EMS inputs is good design practice. I use isolation diodes with the anodes connected to the EMS, like shown in the link.

http://www.vx-aviation.com/sprocket/photos/panel_elec/schematics/EMS.pdf

Vern

 

[kurtfly]

i agree the diodes will accomplish the same thing. In the diode case the contact input will rise to the pull up voltage at high input, and when signal is low it will lower to the forward bias level of the diode approximately .7 Volts.

I was just interested if Dynon had changed the design in this area. My previous EMS module handled to full 14+ volts with no problem. Just curious. I am sure someone else will experience this and be pulling their hair out.

 

[N82rb]

i had the same issue with my pitot heat contact, however, it would only happen when i was pulling above 20 amps from the alternator. i put a 10k current limiting resistor in and the problem, as did yours, went away. i think it is a current issue within the circuit
.

bob burns
RV-4 N82RB

 

[bbtapb]

Don't those inputs all have 5v pull-ups? You need to pull them down (to ground) not try to measure if they go above 5v.

 

[kurtfly]

The un-energized lamp serves as the pull down. One side of lamp is connected to ground. If I remove the lamp or it burns open it will "pull up" and show as a "Green-Down" indication.