APM 3.5 Mini Tricopter no tail servo movement

Ted Conowal

Ted Conowal

Member
Anybody with experience in APM Tri copters? I'm sure this has been asked before, but I really need to get this thing off the ground.

I'm set to go except one thing. My Tri Copter has no yaw servo movement. The signal seems to have no pass through. The motors spin up with the throttle, and adjust in different attitudes, but no tail servo. I have no where to begin, and need suggestions.

It has power supplied from a separate step-down converter to the tail servo, and retracts. I am running an FRSKY module in a football 9C with a FRSKY D8R-XP in CPPM mode


Is there a way to check the firmware while connected to make sure it is tri copter firmware?
It seems that when you select the frame type in MP, the tri copter frame is mixed with a whole bunch of others kind of generally...

I am suspecting that the tri copter firmware is not going into my board, which might explain no tail servo movement. (maybe)


Any suggestions?

Thanks
Ted
 

crayfellow

crayfellow

Member
No need to specifically choose tricopter (assuming you installed tricopter firmware in the vehicle wizard initially), just make sure in the frame type you have chosen the "X" family as opposed to the "+" since "X" includes tricopters.
Keep in mind that it will not move the servo unless the motors are under power, which makes sense since the servo has no reason to move when the craft is not flying. So if you haven't tried it, spin up the motors just a bit and try moving your yaw stick.

Is your servo on channel 7 on your APM? And just to make sure have you tried moving the servo with a servo tester, taking power from the same supply you will be using in flight? If you don't have a servo tester, you could use a channel on your receiver directly, just to make sure the plumbing is generally working.

APM Copter is really great for tri's, you will have a lot of fun!
 
Last edited by a moderator:

Ted Conowal

Ted Conowal

Member
Thank you for responding. Your response has cleared up some questions I had.

My tail servo plugged into ch7 on receiver, and the servo is powered by and external step-down converter, plugged into the balance plug of a 14V lipo.
The motors arm, I have no warnings. The servo has proper voltage.

I found this on the APM Tricopter wiki, but it seems it is a bit vague.
I believe this page is the issue.

I wish there were clear, concise directions to solve this problem on the wiki. It seems that this problem has been over looked, or most likely people like Quads, and other frame types better. No biggie, I like Tricopters for their maneuverability.

I suspect these settings are in the advanced parameters, correct?

Can you make sense of them? If so can you explain it to me?

Wiki Link to info below..
http://copter.ardupilot.com/wiki/tricopter/


APM_2_5_MOTORS_TRI

1 Copter 3.3 (and higher)

2 Copter 3.2.1 (and earlier)

Copter 3.3 (and higher)

MOT_YAW_SV_MIN: yaw servo’s lowest PWM value before binding occurs.
MOT_YAW_SV_MAX: yaw servo’s highest PWM value before binding occurs.
MOT_YAW_SV_TRIM: yaw servo’s PWM value close to what is required to keep the tail from spinning.
MOT_YAW_SV_REV: yaw servo’s reverse setting. +1 = servo moves in default direction, -1 to reverse direction of movement.


Copter 3.2.1 (and earlier)

RC7_MIN: yaw servo’s lowest PWM value before binding occurs.
RC7_MAX: yaw servo’s highest PWM value before binding occurs.
RC7_TRIM: yaw servo’s PWM value close to what is required to keep the tail from spinning.
RC7_REV: yaw servo’s reverse setting. +1 = servo moves in default direction, -1 to reverse direction of movement.
 

crayfellow

crayfellow

Member
Wait, if you have the servo on ch7 on your receiver that may be your issue. You want it plugged into ch7 on the APM! Same place as the ESC's since to the APM it's just another one of the signals it's using to control the copter.


Sent from my iPhone using Tapatalk
 

crayfellow

crayfellow

Member
Btw yes, tricopters are awesome! What are you using for your yaw tilt mechanism? What ESC's?


Sent from my iPhone using Tapatalk
 


crayfellow

crayfellow

Member
Ok then I would just start the vehicle wizard again so you have fresh firmware, rc calibration, etc. then see where we stand. I can share info from my setup too if you need to compare APM configs.


Sent from my iPhone using Tapatalk
 


crayfellow

crayfellow

Member
Those ESC's have BEC circuits onboard so one of them is perfectly well suited to powering your servo. Pull out just the red wire from two of the ESC servo plugs that go into your APM, but leave one of them. This will supply 5V to your APM servo rail. Then, simply plug your servo into ch7 on the APM, every wire, and there is no need for your separate regulator. If you have all the ESC red wires plugged in, then separate Vcc and Gnd going to the servo from a dedicated regulator, that may well be giving you trouble. You already have the BEC's; you might as well use one! This also serves as backup power for APM in case your power module fails.


Sent from my iPhone using Tapatalk
 

Ted Conowal

Ted Conowal

Member
Hello, Cray
Well, first of all of the esc's power leads are folded back on each other, and not used at all. I did this because of all of the stuff I have read about powering issues to the APM boards. I do not remember what I did with the grounds though. I will have to check. I like to keep everything looped in ground together, and run filters, and ferrite rings to the video system to keep out any un wanted noise.

The board itself is powered by the APM power module, which also powers the 3DR Telemetry radio. I could tap one of the esc's, if I needed to, but I think it is un necessary. I will keep your suggestion in mind.
Remember that the motors are spinning up, and I have full arming, and throttle control, which indicates that the esc's are receiving a signal form the board. No issues there.

When I first powered this thing up after all of the wiring was done, (checking for magic smoke) the servo did move to a neutral position. This tells me that for some reason in the newest Tri copter firmware, the RC-7 setting is nulled, but I am going to test the servo again anyway to make sure it is not fried or something.

Another guy I know on the APM forum told me that he just plugged his board in, and up loaded Tri firmware, and his worked first thing. Go figure...Wish I was that lucky...

I am slowly narrowing in on the problem. Like I said, I believe it is in RC_7.

I also have to set up RC_5 as this channel has my retracts on it.

The power, and the ground for the separate step down circuit is grounded and powered to the lipo battery itself, via the balance plug. I do not think there is a better ground
icon_e_wink.gif
I have put a multi meter on the servo power supply, and there is no issue there. Running a strong 6V
Here is where I am going to start.

RC7_MIN: = 1100
RC7_MAX: = 1900
RC7_TRIM: = 1500
RC7_REV: -1 or 1

What are your settings for RC_7?

One thing for sure is I have a tutorial for the "auto tune" setup in APM, which I am certainly going to do once it is in the air. I have heard it is essential for a Tri, as they are a little "twerky" It really smooths them out.

I can't wait to fly this thing. I have two more in the works. A Hobbyking C-3, and an RC Explorer with some secret mods that will make it super fast...
icon_eek.gif


Once again, thank you for responding, I will get back to you.View attachment 25662 View attachment 25663 View attachment 25664

Sure I could just put a flip Mega 3.5 board in this one, but then that would be giving up.
 

Attachments

  • Tri3.jpg
    Tri3.jpg
    136.9 KB · Views: 560
  • Tri2.jpg
    Tri2.jpg
    126.5 KB · Views: 492
  • Tri1.jpg
    Tri1.jpg
    101.8 KB · Views: 456

crayfellow

crayfellow

Member
looks neat! Yes, don't give up. Why don't you just try putting the servo on one of the motor outputs (1, 2, or 4) to see if it moves when you throttle up or do an APM motor test? It should move.

Believe it or not I am flying my tri on stock settings, it's been far too windy to get a good autotune so I'll do it when it calms down.

I will check my RC_7 settings but I have not touched them so they will be whatever is stock (likely 1100-1900 and 1500 trim, as yours). and even if yours were way off, you should get "some" servo movement, but again, only when the motors are under power.

Have you centered the servo already and just tested it quickly with a servo tester or a spare channel on your receiver?
 

Ted Conowal

Ted Conowal

Member
Yes, I will try that for sure.
I am going to try everything I can. The signal is already coming off the board, so what do I have to loose just hooking up the power, and the ground to the rail to see if it works. The problem with that is that This is a Mini APM, and the wires are small, small, small. They are also encased in mesh. I do have a spare set, that I can rig quickly.
I haven't the chance to get into RC_7 either as I am 51 with a 4 year old daughter, running me around. LOL just put her to bed a couple hrs ago, and have been hacking away on my laptop, and surfing goodluckbuy website for new arrivalsLOL

Here is a video of the C-3
https://m.youtube.com/watch?v=VbIhP509FA8&rdm=1bmd58451&client=mv-google

And if you like very "unique" Tricopter frames as I do, you will like this site. They are the company that makes the C-3 for hobby King. You can see the resemblance to the "red" one on their website. Give the website time to load, it is a bazillion miles away in China.
I will get back to you when I make the changes.
http://www.rc-today.com/simpleshop/index.php?route=common/home
Cheers
Ted
 

crayfellow

crayfellow

Member
I really doubt your RC_7 is messed up. If you see the yaw channel moving in RC Calibration screen and you are plugged into channel 7 on the APM you should be good there.

Fun! Yeah, ours is a Flitetest Electrohub frame with SunnySky 980kv's and 9" APC props; the kids wrote their names on each of the wooden arms. Well one kid didn't get to but she can't write yet. Ours are 1, 3, 7, and 8 so trust me I know the feeling!
 

Ted Conowal

Ted Conowal

Member
Yeah, it could be, I am going to look at RC_7, then try running it out of the servo rail, checking everything, then if that does not work, I am going to re map it to another output. If that does not work I'm cashing it in, and never using an APM board for a tri again. I have 2 more, and I already switched one out to see if it is the board, to no avail. The new one did the same thing. This is a common problem I see out there with ALL of the APM boards. I know a guy on youtube who says he does not do tri's because of this reason. It seems to just randomly not work on a certain few. Most likely it is a wiring problem, but might not be ....
Wow wish I could have another, but I am to old now. Oh well, she has a cousin the same age LOL
I will let you know what happens, I will take pics too.
Cheers
Ted
 

crayfellow

crayfellow

Member
I have never heard of any problems with tricopters and APM, such as OtherHand. I really think you've got to be missing something still. I'm curious to hear if just taking one of the ESC signals moves the servo. If not, see if the servo works at all from your receiver.

I am assuming now when you go to RC Calibration in Mission Planner that you see the Yaw channel moving when you move the stick?
 

Ted Conowal

Ted Conowal

Member
Yes, all green bars move on the calibration page, and I have tested the servo separately with a servo tester. But now that I think of it, I am Not sure if I actually moved the rudder stick while the motors were running. I cannot recall if I did that. If that is the case, which is going to be the first thing I try, boy, will I look stupid... Egg on the face for sure. But I remember when my father worked for Eastern Airlines, a simple little green landing gear light crashed an L 1011 into the Everglades so...you know how it is, wiring these things will make you cross eyed. And, the wires on the mini apm are very small. Maybe I have to ground the output rail maybe not power it, but ground it for the servo to work. I am going to back track and change a lot of things to find out. its a Scooby Doo mystery now...
 

crayfellow

crayfellow

Member
don't change too many things at once! Keep it simple and try moving rudder with the motors running first. if you saw the servo center when you armed, then there is a signal there.
 

Ted Conowal

Ted Conowal

Member
yes, one of the scenarios I am going to try is going to just simply bypass the step down converter and run it off of the apm board only.
 

Ted Conowal

Ted Conowal

Member
OK Cray,

Its working! Finally!

Now here it is....

I feel good about myself, because I did wire this thing right in the first place.....

First of all, I did not change anything. I kind of thought of what you reminded me of....

" if you saw the servo center when you armed, then there is a signal there."

AND, I heard from two people including yourself ...

"I really doubt your RC_7 is messed up. If you see the yaw channel moving in RC Calibration screen and you are plugged into channel 7 on the APM you should be good there."

Yes, there is signal there, and all of the green bars do move in MP...

What I figured was, If there was signal there, and it moved, that means a BAD intermittent connection somewhere. I was right. It was in two places, not one. The connecter I made for the balance plug didn't quite fit. The connector pins that slip into the balance plug, are slightly smaller, and loose.

I also have a buss where all 3 retracts plug into for one signal, and power/ground to all three, plus the tail servo power, and ground. They are both separated form each other, with separate power sources, but all of the plugs are loose, and are intermittent, at the buss.

Problem solved a simple bad connection. Like I said a faulty green light killed a lot of people in the Everglades.

Now Finally the last check list.

Fix the bad connection,

Balance the props,

Check for the proper motor rotation.

Get the retracts enabled on RC_5

Set the 5 degrees on the tail servo in RC_7

And check for proper direction of travel of the tilt mechanism.

Before I fly FPV...

Orient Icons in Minum OSD

Pull out more hair trying to get 3DR radios communicating.

And tune my WDR camera in the nose.

Thank you Cray for reminding me of a few things, and for just having someone to bounce things off of. I by no means am a Newbie to the RC hobby. I am basically a scratch builder of airplanes, on almost a master skill level having built some pretty complex stuff. But, one thing is for sure, these things have made me learn a new part of the trade. Mostly soldering skills, and trouble shooting FC boards. I almost got out of the hobby a few years ago, because I was bored flying sailplanes on our club trash mound. Then I found FPV. I also fly hang gliders, but with a 4 year old, I do not have the time, nor the desire to risk my body anymore at 51. (aerotowing)


I am a military medical component finisher with gobbs of experience in the aerospace industry. I have worked with all kinds of substrates including carbon fiber, titanium, Kevlar, ect, and have painted parts for the shuttle, and the prototype F-22 Raptor. Not to too my horn LOL
Sometimes these things kick my butt LOL

I will be contacting you with more questions, as I'm sure I will run into more tricopter problems.
 


You must log in or register to reply here.
Top