K- 160 tach reading error.
 

Hello all, I'm having a perplexing repeatable tach reading error with my K-160 when actuating the elevators on my F- 15. It only happens with the elevators; I can move all the other control surfaces all at the same time with no problems. If I unplug one of the elevators I have no problems, it doesn't matter which I unplug; only when both elevators are plugged in do I get the tach reading error.

I thought maybe the ECU was too close to my PowerBox Mercury, so I moved it with no luck. Then I thought maybe the sensor wires were too close to the servo leads so I rerouted them outside if the airplane with no luck whatsoever. Even with the ECU and wires completely outside if the airframe I'm still getting tach errors.

Also it doesn't seem to matter if I have only one rx battery or both plugged in or the turbine battery plugged in or not.

Any advice?

https://youtu.be/OF5m7ARLl44 Addendum: she used to have a K-120G (xicoy ECU) and didn't have an issue like this. None of my other xicoy ECU equipped KT turbines have similar issues either.

Thanks

Luge

The New KingTech ECU requires at least 6V for the GSU to function properly. We have found that some on-board switches are drawing a fully charged 6.6V battery down to 4V or even lower in some cases. If you are using a voltage regulator, make sure you have it set to at least 6V. If you are not using a Regulator, bypass your switches, plug a 6.6V battery directly into the receiver and see if the problem still exists. You probably have a larger, more power hungry servo on the elevators than the other surfaces. When you move the elevators, it is draining the battery well below 6 V and that is why the GSU is acting that way. Let us know what you find.

Dirk

Thank you for the response Dirk

I did some more testing yesterday. I fully charged my Rx packs and found they were half charged (two 2s 3000mah Lipo). My PowerBox is set to regulate to 7.4v as I'm running HV servos; since the PowerBox only has the option for 7.4 or 5.9 and the ECU needs a minimum of 6v, it's now my only option with my current set up.

With two fully charged batteries everything was a- okay. If I powered down one battery the issue would return. If the batteries are only half charged then even with both turned on the issue would persist. I kept a watchful eye on the regulated voltage as you had mentioned the 6v threshold. What I found was that as soon as the voltage dropped below 7 volts it would start exhibiting the noted behavior.

The last thing I want is for a tach error to shut down my engine in flight, especially if one of my two Rx batteries happens to fail or if I want to fly more than once between charges, or if the power consumption in the air is high enough even with everything perfect to momentarily dip the voltage below the 7 volt threshold.

What are my options? I could, and maybe should, get new, better, receiver packs; but even then with a 7v threshold it seems like the error could still occur. Would it be feasible to separate the signal lead on the Rx in on the ECU and run a dedicated battery? Not ideal since it would add weight.

Thank you

Luge,

Only the GSU is requiring a higher power demand while it is plugged in, as it has a mini processor for the LCD screen and utility functions to work. It is not going to affect how the turbine runs. You can unplug the GSU and go fly with no issues. The ECU commands how the turbine runs, not the GSU.

Dirk

Yes Dirk, I understand that I could disconnect the GSU. For my own reasons I chose to mount it in the aircraft.

However, that's not the issue at hand. The issue is the tach anomaly. The GSU is the only tool I have to read the turbine stats; so I have to rely upon what it says. Are you saying that the GSU is solely at fault and not the ECU or turbine sensor?

I would not say that the GSU is the faulty problem, nor the ECU or RPM board at this time. We have encountered this before, and have found the customer was using a switch with poor continuity that caused severe voltage drop to the to the system. Maybe your power box is not performing to spec under a load? I read what you wrote above, the question I will ask is, did you put a Volt meter to the throttle lead at the ECU, and get a static voltage reading, and then move the elevators,control surfaces and take another reading? The GSU requires a steady voltage to power the unit. If the power drops, the GSU processor will not function properly and will display what you are seeing. If you are getting the same voltage readings statically and under a load, I would suggest sending it back to us to be checked out. If you are getting big voltage drops, I would suggest finding the power drain in your system.


Dirk

My touch screen GSU won't turn on when the airplane's power is turned on, even though it's plugged in. However, if I then unplug the GSU and plug it back in, it WILL turn on. Any idea what this problem is? Is it related to the above power issues and the tach? Also, the pull down menus work poorly. Same power issue?

I had the same problem at Kentucky on a new build I did. It is 100% power related like you said. Also the plane flew fine and it appears to only affect the GSU and does not affect the ECU and the RPM of the engine. I did many flights without any issues.

I have not seen this problem. Sounds like a bad GSU. I have seen a GSU unit go bad. Try and call Barry or Dirk and see how to proceed.

Problem is solved, or at least understood. See this recent link, post #2:
http://www.rcuniverse.com/forum/king...1#post12353739

Dirk, just wanted to let you know for full understanding,(and I know this is resolved) that a Power Box Mercury uses a soft switch, there should be no switch induced voltage drop on that setup.

The only reason for a regulator anymore is either the receiver, or servos are spec'd to 6V. But a switch to LIFE (from LIPO) usually puts the voltage down in the safe range. Eliminate the regulator. I've used 6V servos for years with no regulator, no problem. Each case is different though. Any switch that drops 2.4V alone has no business being on a turbine jet, but the warning is good to have as it's part of the education and being informed process. These are not park flyers. The builder needs to take responsibility to engineer his components in a competent way. Sometimes cost can be a reason people make decisions, but that can't compromise safety.

Interesting, my GSU showed exactly the same thing as the video constantly even with no movement of any surface. The voltage was regulated to 5.6v-5.7v via a Powerbox Sensor Switch.

I will try switching to 7.4v instead.

If you could adjust to 6V should take care of it, but 7.4 wont' hurt it either.

Regards,
Barry