Electric Shock/Spektrum DX7 failure

[RogerIngarfield]

Hi Guys,
Following some of the great advice I was given on this forum I invested in a little shock flyer to sharpen and build my 3D skills for my 50cc Yak.

I decided on an Precision Aerobatics Electric Shock (with all the hardware they recommend). (PA Thrust 10 outrunner motor, PA Quantum 18 Programmable ESC, PA Lipo pack 11,1V 1000mAh 18-30c, Blue bird micro servos.)
For radios I have a Spektrum DX7 system in my 30% Yak so I installed a Spektrum 'park flyer' mini receiver (model AR 6100) in the Electric Shock.

I have had probably 12 uneventful flights with the plane (which I think is fantastic) and then suddenly, out of the blue, in one flight I lost the radio contact. The plane continued with the control deflections I was inputting, which suggests to me that it was not a case of losing complete contact with the transmitter (in which case the motor would have gone to idle and the controls to neutral).

In spite of, what I thought was, quite a heavy smack on the ground there was no damage to the plane (all credit to the construction) and full radio control was back.
I went home, re- bound the receiver and tried to make the two aerial wires protrude through the wing ribs, thinking there might be an interference factor from the carbon fibre strips near the left aileron servo. ( Try as I may, working through the tiny apertures of the wing ribs I could not get the aerials to extend at 90* angles from the receiver, they were pointing foward and a bit sideways through the wing rib, I think, couldn't see them properly.)

Back at the flying field, I had one 13 minute flight with no issues at all. I changed to my other battery pack and 3 minutes into a second flight I lost control again. This time I wasn't so lucky and the plane hit the ground under power at about a 30 degree angle. The front engine mounting section was broken in few places, the wing attachment plates were broken on one wing and worst of all the spindle on the gutsy little motor was bent. Again as I walked up to the plane, full radio control was back.
I am not sure where to look,
- is it a dodgy receiver that has sporadic, unpredictable 2 second blank spots?
- Is there an issue with that voltage drop in a DX7 that results in a radio black out (the 1000mh pack was fully charged - Hyperion charger)
- could there be a problem with one of my battery packs (it struck me afterwards that I should have noted which pack I was using for both incidents - could this important?)
- Was there interference - can it happen with a DX7 system?
- One possible clue, when I was soldering on the Deans plug onto one of the batteries, I accidently touched both bare wires of the battery with the blade, got a quick little flash of a short, but it seemed to work fine, the charger doesn't pick up any issues with this battery pack. I have had a number of uneventful flights with this pack as it was only recently that I invested in a second pack.

I will appreciate your collective wisdom and experience,
Regards,
Roger.

[mahak213]

Sorry to hear about the plane...

It doesn't sound like a battery problem, more along the lines of radio/receiver. I just had an extreme flight extra go in thanks to a DX7/ar7000, however I was unable to see if I had regained control after it hit because the battery was ejected. Try doing a range check with that receiver and with some others. My system fails the range check at about 25 steps. Also, if you do trace the problem back to the receiver/radio, hurry up and send it back. Spektrum/Horizon didn't seem to care much about my situation and isn't doing anything to speed up the turnaround time (which is about 20 business days...).

Hope you find an easy solution to your problem

[Zeeb]

99% of all problems seen with the Spektrum/JR 2.4GHz systems are rx power related.

This can be caused by batteries, switches, regulators, ESC's especially, wiring, solder joints and so forth.

I'm not sure what you're trying to say about the antennas being at 90 degrees to each other? Do you mean coming straight out of the case? If so, that is the correct setup but they should not be bent as those form a bipole antenna. It's not critical that they be exactly straight but get them as close as possible.

AR-6100 rx's do not have the capability to program what is usually called "failsafe" meaning the controls/servos go to a preset position on signal loss, the only servo/control which will go to a preset position is throttle. All others remain at last commanded position. The neutral settings for initial rx bootup and linking are what is set by the last bind after model setup and those happen if the rx loses power and the power comes back on.

If anything causes the power to the rx to drop below 3.5 volts (called a power brownout), the rx will shut down until power is restored. If the rx has the Quick Connect firmware installed, that takes less than 1/2 second, if that firmware is not installed it will take 2 to 5 seconds to reconnect. If the rx has the Quick Connect firmware, it will also display flashing lights when a power brownout has occured and that feature is very useful in diagnosing power system problems some of which cannot be duplicated on the ground.

There is always the possibility of a radio component causing an issue, but that's pretty rare.

[RogerIngarfield]

Thank you Zeeb, thats a really helpful clue, in fact now I recall on a previous flight I noticed that the orange light on the rX was flashing. (you can see it through the translucent covering on the wing) I couldn't find any reference to that occurence in the manual soI rebound the rx, thinking it might be a binding issue.
So, this means that the rx did have a power loss at some point. There are no switches in the system, just a deans plug connector. Maybe its those solder joints (which I soldered). I will re-solder them.
And that short to the battery, is there anything there? I could see from the amount of charge the two batteries took after the incident that it was the battery I shorted that was on the plane when I lost contact with it.
Good information on the failsafe status on the AR-6100's, I didn't know that.
And yes, I did mean those two antennae on the rx. On the Electric Shock its quite tricky to keep all the servos properly connected and then manouvre the rx into a gap in one of the wing ribs. I was trying to keep the antenna in that same 90* to the rx state. I don't think I got it 100% right, but again, I couldn't find any information that told me that it was critical.
I am going to redo those solder joints and then bench run it on each battery and see if it happens again.

[BoneDoc]

Switch your ESC. I bet that's the issue. I had similar problem too when Spektrum was first out (that was before we knew about the 3.5V reboot).

[dick hanson]

If da lights are flashin
you may be crashin.

[Zeeb]

	Quote: Originally Posted by RogerIngarfield
	Thank you Zeeb, thats a really helpful clue, in fact now I recall on a previous flight I noticed that the orange light on the rX was flashing. (you can see it through the translucent covering on the wing) I couldn't find any reference to that occurence in the manual soI rebound the rx, thinking it might be a binding issue.

Check this link for info on the Quick Connect firmware;

http://www.spektrumrc.com/Articles/A...ArticleID=1855

As BoneDoc indicated, the ESC is probably most suspect in this situation. You really have to be careful on the selection of an ESC in this size model as there are a bunch of them out there which cannot handle 4 servos when running on 3 cell Li-Po batteries. It's a gray area between going tall dollar hardware and getting something that works.

The problem BoneDoc mentioned is where the power brownout issue first surfaced with models very much like the one you have and it's due to the internal BEC (most of which are linear not switching) not being up to the task. The more current it pulls, the hotter it gets and the resistance goes up as it gets hotter causing more voltage drop, a vicious circle.

High current demands from the model can also be caused by binding servos due to linkage issues or servo problems themselves and again you have an issue with the BEC.

An external BEC may be worth considering?????