Broken disconnect Button wire - warning coming on.

[jaba-who]

I have finally got round to installing the pitch servo in my Jabiru and have a couple of problems.
The second I will post as a separate issue.

First.
I keep getting a Broken Disconnect Wire warning coming on. It seems to happen every 30 secs or maybe every minute.

Checking the wiring - it is intact. WHat's more the button works properly all the time from "hold Down"...turns on the AP properly. Press while APis on and immediately disconnects - both servos go to "Off" on the Dynon screen and stop making their jitters etc.

As far as I can I tell don't actually have a broken wire and the disconnect button is actually working and the alarm system worked fine when I had just one servo.

The most obvious answer is it could be an intermittent open circuit but eliminating all possible sites has not changed the regular but intermittent warnings that come on.
I am running the earth from the disconnect button back to the earth wire on the roll servo and that, as I said worked fine with just the roll servo.

Any hints?

John Martin

 

[dynonsupport]

Re: Broken disconnect Button wire - warning coming

Did you actually install the resistor required to check for a broken wire?

If not, we can't detect this and you need to turn the option off in the EFIS.

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

I'm pretty sure I did. Didn't actually pull the joystick apart to check but I am sure I did. My build notes and diagram say I did.
Also when I couldn't find a cause I opened the menu in the dynon and I had previously set the alarm to "Y". (For now I have disabled it)

I would have thought it would have alarmed before if I had set it to "Y" and didn't have the resistor in place.

So back to the original query. I can't get past the thought that I have a wiring problem but checking seemed to suggest it was OK.

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

Went out and did some further checking today.

I deliberately disconnected the disconnect wire from the pitch servo, (leaving just the roll servo wire disconnect wire connected. ) And despite this the joystick button still turned BOTH servos on and off as if it was connected. (Obviously all other wires still connected)

Should that be the case?
If so, why bother having the extra wire in the circuit diagram.

If not - what could be going on to make the servo work when the button is pushed - with no connection going to it

I turned the alarm parameter back on, but sadly...can't remember what the result was. Didn't write it down. Too many other things rattling round my head :'(

Curiouser and curiouser!

John Martin

 

[dynonsupport]

Re: Broken disconnect Button wire - warning coming

The double connection from the disconnect switch to the servos is for redundancy. As long as we get a message from one servo, we obey it. While disconnect hooks to the servos and does issue a local disconnect command, it also publishes it on the network so other servos can obey it. So you can get away with only one connection, but we don't recommend it.

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

So the fact the buttons are working fine doesn't probably help. Sounds like I should recheck the wiring, again.


The second problem I mentioned is related to radio buzzing/static when I energize the servos (which didn't happen with one servo) See my other topic post for details. Could these two problems be linked?

 

[dynonsupport]

Re: Broken disconnect Button wire - warning coming

Does that happen any time the servos are powered up, or only when they're "engaged"?

Does the new servo run go anywhere near an antenna wire?

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

>Does that happen any time the servos are powered up, or only when they're "engaged"?>

As soon as powered up.  Flipping to engaged doesn't make it either worse or better.

>Does the new servo run go anywhere near an antenna wire?<

Yep. It sits in the fuselage pretty much right next to both antenna cables.

To be honest the problem of the noise is (I think) the radios and their associated peripheral stuff.  I have problems with noise getting into my radios from everything electrical in the aircraft, even my Garmin 296.  Despite two returns of radios to MicroAir for "fixing" and just about overloading the aircraft with filters and ferrite clamshell beads the problems persist.  Although I will admit that the noise from the servos is the worst of them all. Actually can't transmit a clear signal now on the radio whose antenna is nearest the servo.

The noise issue is an aside since I "know" it's not strictly the dynon/servos fault. But I do wonder if the noise and disconnect alarms problem are related.

 

[dynonsupport]

Re: Broken disconnect Button wire - warning coming

I don't think that that the two are connected, but based on what you've said so far, a few things.

One the disconnect warning, I'd look for that resistor connection and see if it's not intermittent in some way. Also, check for the right value of resistor by measuring it with a multimeter.

When not energized, the servos are drawing minimal power, but there is still power/data flowing to and from them. Proximity to the antenna wires could be the culprit, and it sounds like your radio setup is a bit prone to interference. That said, try disconnecting each servo, one at a time, to see if you can narrow it down to a particular servo. Perhaps try physically swapping them (assuming they're the same type of servo) to see if that simple change might help with the noise.

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

I have managed to dramatically damp the noise by putting yet another ferrite clamshell on the loom going to the pitch servo. Funny thing is that the usual advice given about ferrite beads is "Put it as close to the instrument etc as possible". In this case I stretched into the tail of the aircraft with a headset on and found moving the clamshell up and down the line till I found the sweet spot where it really damped the noise. Adding a loop so the loom passed through the clamshell twice almost fixed the noise completely. The clamshell is about 6 inches from the servo.

If I can sort out the general noise issue in the radios a bit better it will be enough to accept it as it is now.


I already did the sequential turning off of servos and it is definitely the rear pitch servo. The servos are not the same (ones a 32 and the other a 42).



I will double check that disconnect resistor and let you know what I find.

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

And now to complicate matters!

Due to our prolonged wet season I finally got to fly the new installation yesterday and found another problem.

When I activate the AP the dynon oil temp reading immediately goes to about 138 degrees (C) and alarms ( in the upper end of the red range for the Jabiru.)

If I turn on the AP servos but don't engage it it is OK and if I don't engage the pitch servo (ie: just engage the roll servo) it's OK.

The change is instantaneous, not a gradual climb or delayed triggering,  (and instantly goes back to normal on turning it off).

Sounds like a wiring/earth problem but in the light of the disconnect switch and the radio noise problem I wonder if that gives a clue to where?

John Martin

 

[jakej]

Re: Broken disconnect Button wire - warning coming

John

The 'clue' is the standard jabby com antenna if you have it - I've had 'issues' with these and the RG58 cable. You are using RG400 ?

Jake J

 

[jaba-who]

Re: Broken disconnect Button wire - warning coming

No, sadly I have RG 58 (I think is the terminology.) But RG 400 is in the pipeline as yet another attempted fix for the radio noise.


Gradually working through fixes though none of the multitude of advised and suggested fixes from anybody for the radio noise has worked so far.

But not sure how, or what that would have to do with my AP servo causing the Dynon to read the oil temp high or the disconnect switch to be read as broken. But I remain eternally surprised at the way things interact in the panel of an aircraft.

JM

 

[jakej]

Re: Broken disconnect Button wire - warning coming

John

I'll give you a call - FYI, I have some of the symptoms you describe in a composite aircraft. Testing frequencies in the lower Mhz eg 118.70 gave good results however in higher frequencies 'warnings' came up eg high oil temp & pressure but using the antenna from number 2 radio resulted in no 'alarms' so I'm about to do an SWR check on #1 antenna.
BTW - it is a dipole type similar to the jabby however the jabby one is poorly made/designed and, IMO, can/will cause you issues unless you use low loss cable and toroids (which the jabby doesn't have).

HTH
Jake J