Ace GT5 causing ESC to get HOT and servos to twitch like crazy

[d2tw4all]

Hi guys,
I'm having trouble setting up my mini titan with the FBL conversion and the GT5. Got the head all together and installed and now I'm trying to get the GT5 going and it's scaring me, I'm using 3 HS-65HB servos for swash and an HS-81MG for the tail. I don't fly 3D at this point and I saw another thread where someone was using this configuration on a GT5 FBL mini titan without any problems. I have everything bound through a spektrum Sat to my DX8, didn't have any problems there, and I set up the basic config for swash etc, but when I plug in all my servos and it turns on, they all buzz pretty bad and none of them will center on their own, it's weird all the servos seem to respond to my inputs but stay at the extremes, they don't follow my stick movements except outwards if that makes sense, and I noticed after fiddling with it for a minute or so that the ESC was getting HOT which since the motor isn't even connected tells me the BEC is pulling a LOT of juice. Anyone have any ideas? I haven't switched anything from the defaults except set the swash to 120, radio to spektrum and bound, and the servo frequency is 166. I'd love some advice here because the manual is useless and I have no experience with FBL and 120 degree helis... HELP!

Tom

[gwright]

I have three ideas on this, first one I think has about a 98% chance of being the culprit, the other two are about 1% ea.

First one, which I think is the issue, is that your cyclic trims are not centered. The flybarless systems are sort of a "fly by wire" system. The stick and trims on the transmitter simply tell the unit the rate at which you want rotation about an axis. The flybarless unit senses the rate it's experiencing, compares it to the rate you are commanding, and calculates where to put the servo to achieve that. If the stick and trims are dead center its being told not to move and it doesn't. If one or more trims are off center, even the slightest bit, like one beep,.. then it thinks you are commanding a rotation about that axis so it does it's thing and moves the servo(s), compares the rate your commanding to the rate it's sensing, and feeds in more if they don't agree. So with even one click of trim it will move the servo to the extreme since it's sitting stationary on the ground. It's simply doing what your telling it to do. The transmitter is telling it to rotate, it senses it's not rotating so it feeds in an input,.. and it's still not rotating so it feeds in more. It eventually hits the endpoint of servo movement. Since you haven't got the endpoints adjusted yet for no binding, it's hitting the max movement and binding, drawing lots of current and heating the BEC , which is in your speed control

Second idea is that you may have either intentionally or unintentionally adjusted the sensor calibration settings on one or more of the axis so the sensor thinks it's moving when it's not leading to the above situation. These calibration numbers should never be touched. There is a post somewhere on this forum about adjusting them if you mess them up, but not sure exactly where at the moment.

Third idea is that your transmitter sticks aren't exactly centering every time, leading to the first situation. This is a common issue with a specific brand of radio. You can put them on a scope and see that they never truly center in exactly the same spot every time. This is not a terminal issue, as you can increase the stick deadbands in the gt5 to accomodate that inconsistency.

[d2tw4all]

Thanks for the reply, I'm assuming this is Gary Wright, I read your detailed writeup on FBL systems last night while trying to figure out the problem, so I guess I'm talking to the right person!!! I'm using a Spektrum DX8 for my tx and all trims are at zero, I started with a new model for this and even reset it just to ensure things were starting from scratch. That being the case, I'm guessing it must be number 2 perhaps but have no idea how to check for this. I absolutely clicked some things that I have no idea what they are by mistake when I first turned on the GT5 and was trying to select the radio, and I know there was a number that got changed that I thought I changed back. I'll have to see if I can find the post on how to recalibrate the unit. Let me know if the DX8 is known for centering issues, I've never had problems with any of my AS3X birds or myriad of planes with it. Thanks again for the help, this is very frustrating and I'm glad I noticed the hot ESC or it might have cost me a speed controller!

Tom

[NitroAl]

Before you fry your servos you should drop the servo frequency to 50 or 60hz for the servos you listed and that may cure the hot speedy situation at the same time. If your speedy is still cooking then you may have to tweak the throttle end points or calabrate the the throttle range in the speedys own setup. If the throttle is one or two points into the range the FET gates could be open just enough load up but not start the motor! The Standard TT speedy supplied with the Mini Titan is rather delicate and prone to let out it's smoke if not set up just right!

If you want to see the cyclic servos follow the sticks like you would on a flybar heli then simply enter the servo travel adjust menu and select a servo!

When you enter the "set servo centre" menu and select a servo all the servos will centre and stay there untill you exit this menu.
Tip-While you can move the cyclic stick(s) and the cyclic servos will remain centered the same can not be said for the rudder! Whe you enter this menu the rudder servo will centre but if you move the rudder stick the servo will move but will not centre again with the stick so set up the servo horn before you touch the stick!

[d2tw4all]

I'm so glad there are people here watching these threads who know what they are talking about. Can you tell me how to change the frequency for the servos to 60hz I couldn't find that on the GT5. Also I think Gary is correct in his number 2, when I first powered on the unit and was looking for the radio setting I think I changed one of the X,Y,Z presets for the sensors so now I have to calibrate. I did find this thread:

https://www.helifreak.com/showthread...343454&page=37

Post 365 seems to describe the process so I guess I'll have to give that a try and get all 3 to go from 0 to 89.

Definitely appreciate any further advice especially on setting up for these analog servos. All my previous helis were either old school 90 degree setups or came prebuild/preconfigured (blade msrx, mcpx, 130x) so I definitely don't have some fundamental heli skills on the build/calibration side. Looking to learn though!!!

Tom

[d2tw4all]

I think something is wrong with this GT5. I've been looking at the config for the sensors and I think I have X spot on, Y I didn't need to touch, but Z is behaving weird. When at rest it slowly counts up a degree every second or so, none of the others do that, is this normal?

Tom

[d2tw4all]

Ok I've made some progress, I found where you can change the frequency of the servos and dropped them all down to 60hz from 166, THAT made them all stop twitching for sure. I assume I should do that for all of them even the tail? Once I did that the ESC is getting warm but not super hot like before. Also the Z started behaving once I power cycled a couple of times and now I think I have them all pretty close to 0 when level and 89 when at 90 degrees. It's not 100 percent perfect all the time but it looks pretty close, hopefully it's enough that I can make some progress. Not sure what to do next but I'll do some more reading and try to figure things out. I assume I need to center the servos and then put on the servo arms and get the head so that it's the correct pitch. I'd love it if someone had any step by step instructions on how to do that though as this is all new to me...

Tom

[d2tw4all]

I'ts behaving much better now, and I've gotten the servos I think pretty close to where they should be, however now I'm trying to figure out how to get them all going in the right direction. I've gotten the left and right aileron servos going in the correct direction, so left aileron the left servo goes down and the right goes up, and vice versa, and the elevator servo goes down when I give down elevator, however the left and right aileron servos don't go up when I give down elevator they also go down with the elevator servo! How do I reverse this?

Tom

[d2tw4all]

More progress, I figured out the servo issue with direction, after looking at the back of the GT5 manual I see it says NOT to reverse the servos EXCEPT to ensure pitch is going in the correct direction, and then do the rest of the servo reversing on the TX. I used that as a guideline and now things appear to be moving in the correct direction. HOWEVER I notice that when I am in the servo centering menu so the servos move proportionally everything looks good, travel looks good at least for a starting point, etc. however when I exit out to the normal mode, the travel is MUCH further and it's going way too far... I'm stuck for now unless I read something more, hopefully Gary or someone can give me advice on how to continue. At least I feel like I've made progress though!

[gwright]

set your endpoints in the servo menu so that there is no binding when in the programming screens and moving full deflection. Default is 250 (always wonder why they don't just go 0-100, but it's 0-250, guess it's finer resolution ). This takes several minutes as you have to adjust both a and b for each of the three cyclic servos, and they should all be the same. When I end up with the correct movement (right servo arm length) I usually end up in the 180 to 250 range. Again, all 6 numbers (each endpoint for the three servos) should be the same. When you get this setup you shouldn't see binding when out of programming mode. Oh, there is a setting in the tools menu to increase the time the unit will stay in programming mode without touching anything. Something like 25 or 50 is the default and it will go to 250 seconds if I remember correctly. I set mine to 250 because sometimes I'm in programming mode to adjust cyclic ranges (set with transmitter ATV's) and I'm in there a while with the pitch guage and messing with the radio. It's annoying when it automatically goes out of programming mode. This is sort of like the "screen saver timer" on a pc.

[d2tw4all]

Thanks for the reply Gary, that 25 secs got old quick so I maxed that a couple nights ago after reading your flybarless article. I'll have to play with endpoints, all of this is very new to me unfortunately so I'm flying blind.

Tom

[webb1john]

Hello Tom. If you haven't figured out your problem yet, I believe I have the answer. In your swash menu, you have your servo signal speed set at 166 Hz. This is fine for newer high signal speed systems and tail servo's, but not for an old school work horse like the Hitec servo or a speed control with older firmware. You need to lower this setting to 50Hz as this is the old school standard. When you change you swash setting it will also change your throttle signal to 50 Hz. The tail setting is separate.
EXAMPLE: If you we're to change to High frame rate high speed servos and ran an older firmware ESC, You would still have to run your swash signal speed at the old standard because that's what the ESC needs.

You should have no more overheated ESC or twitching servos. Please let us know if this worked for you.

John Webb

[Bladecpnitro]

I had a similar problem with my FB Heli and a CC 10 amp BEC solved the problem. Apparently there wasn't enough power available to the servos once I installed a Futaba GY 520 gyro.

[d2tw4all]

Shelved this project for a while but now that I have a bunch of FBL helis I'm looking at this again. I believe I have made progress with the setup and have pretty much gotten things squared away, but a few things I need help with. I have the pitch setup in the GT5 to 90 and with that I'm getting +-11 degrees of pitch or so with 0 at center. I have no idea how much pitch there should be though and now I'm at the point in the instructions where you set ATV's and pitch ranges for cyclic which I'm assuming means how much additional pitch gets added for aileron/elevator but I'm not certain. I have a DX8 tx. Anybody out there who can break it down for me a little bit?

Tom

[Bladecpnitro]

Gary Wright said in his setup instructions that if your between 90 and 127 in the pitch menu on the Gt-5 and 70 - 100 on your cyclic ATV's and getting desired pitch your good to go. 11 or 12 +/- should be good I think.

Also he said that 7 degrees is a good place to start on aileron and elevator, he likes 9/9 on his big Nitro heli's.


Check Elevator Pitch -

At center stick looking at the side of the helicopter, with the blades 90 degrees to the boom looking strait at you, push the elevator stick all the way forward and hold it there to check what elevator pitch you have with your gauge. If its too much reduce it with your elevator ATV's in the transmitter, if too little add some to the corresponding elevator ATV. Also get a reading with the elevator stick all the way back and adjust ATV's to get 7 degrees of pitch both directions.

Check Aileron Pitch-

For aileron you point the nose of the heli towards you as well as the blades and check aileron the same way at center stick moving aileron stick full right and left, checking each direction with the pitch gauge. If you have more than 7 degrees reduce the aileron ATV's to get 7 degrees of pitch. You may find you want more later its just a starting point.

Good luck man.

[d2tw4all]

That is very helpful. Are ATV's the same thing as rates?

Tom

[Bladecpnitro]

ATV is an older term that stands for adjustable travel volume which adjusts the amount of distance your servos will travel negative and positive. Mostly they are referred to as end points now. In my DX7 they are the page after sub trim. Gary also recommends using no sub trim in the radio to level the swash are 90 the tail servo. The Gt-5 has trim for that and should be used sparingly. Also set to zero all expo in the GT-5 for swash and tail, use the radio expo 20-40 instead.


He did say that to check aileron and elevator pitch the GT-5 has to be in programming mode so the gyro does not move the blades.
Set the gyro gain switch in your transmitter to 60 and 100, fly it at 60 1st before flipping to 100. That way if anything is wagging terribly you can flip back to 60 right quick.

[d2tw4all]

Ok I'm having an issue with this gyro, I've noticed as I've been setting things up that the servos slowly move to their extremes without any input. Originally I thought maybe it was because I hadn't secured the gyro and they were trying to adjust for odd orientation but I've now mounted the gyro and when I connect the battery and the GT5 initializes, the servos center and if I touch NOTHING they slowly tilt the swash forward and to the left until the servos go to extremes. I can't imagine that this is normal, any ideas?

Tom

[Laurens]

Its normal, the GT5 is trying to correct for something it has seen. But because blades aren't turning, its not getting feedback that its correction is working.

[d2tw4all]

Ok it's weird but I guess I'll just have to see how it goes. I think I have everything setup, I set my pitch for 8 degrees for aileron and elevator using the travel functions, oddly I had to reduce travel on one side and increase travel above 100 for the other to get the pitch even in both directions. Is that normal? I did all of it with collective at center stick and confirmed it started at 0 degrees. Hoping to fly this pig for the first time tomorrow!

Tom