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Loss of signal DX7/6100

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Old 03-08-2008, 08:33 PM
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BobbyGee
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Default Loss of signal DX7/6100

I just lost my foamy Mapgpie AP aerial photography plane into a tree - it still sits 50 feet up with no way to get to it.

I was about 5 minutes into a flight with fresh charged Lipo 3s 2100 and a fresh charge on the TX. Plane was about 75-100 feet high some 450 to 500 feet away from me.

All of a sudden it noses down. Up elevator - no response. Power down, full power - no response. Everything went dead. Nothing left to do but watch it nose down across a creek into the trees on private acreage and listen for the crunch.

Has anyone had similar experiences with the DX7/6100 combo?

It is very unlikely that this is a low voltage issue. I can't look at any of the components since I can't get the blasted plane out of the tree.

Any ideas as to what could have happened? No glitches leading up to it. Just a total loss of signal.

Thanks,

BobbyG
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Old 03-08-2008, 09:08 PM
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Ken6PPC
 
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Default RE: Loss of signal DX7/6100

Sorry to hear of the loss of your plane. We've all been there, and it really sucks.

Sounds like your battery either shorted out or came unplugged to me.

In any case, you have my sympathy.
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Old 03-08-2008, 10:49 PM
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Default RE: Loss of signal DX7/6100


ORIGINAL: Ken6PPC

Sorry to hear of the loss of your plane. We've all been there, and it really sucks.

Sounds like your battery either shorted out or came unplugged to me.

In any case, you have my sympathy.


Thanks, Ken. Those are a couple of things that have occured to me.

Unplugged is unlikely- it's Deans plugs and it's not easy to pull them apart even when I want to. Short is always a possibility.

Maybe the wind will blow it out of that tree before the elements turn everything to trash ... I'd like to rescue my motor, servos and camera at the very least. I don't think I can trust that ESC battery or after this. Or the receiver.

BobbyG

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Old 03-09-2008, 10:02 AM
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Zeeb
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Default RE: Loss of signal DX7/6100

ORIGINAL: BobbyGee


ORIGINAL: Ken6PPC

Sorry to hear of the loss of your plane. We've all been there, and it really sucks.

Sounds like your battery either shorted out or came unplugged to me.

In any case, you have my sympathy.


Thanks, Ken. Those are a couple of things that have occured to me.

Unplugged is unlikely- it's Deans plugs and it's not easy to pull them apart even when I want to. Short is always a possibility.

Maybe the wind will blow it out of that tree before the elements turn everything to trash ... I'd like to rescue my motor, servos and camera at the very least. I don't think I can trust that ESC battery or after this. Or the receiver.

BobbyG


While it is really difficult to try and figure out what went wrong when you can't access the carnage, I'll venture a guess and it's based on reports of failures I've seen since watching these forums.

Most of the early failures of the Spektrum systems, and to a large extent those occuring now, were related to electrical power. Those in glow/gas models had issues with either small or high impedence battery packs causing a voltage drop and the rx shuts down. Most of the failures in electrically powered models seems to have been related to either battery packs or more commonly, the BEC circuit of the ESC's...

BEC's have been a issue for some time and is the reason the large model guys ran separate radio batteries. Two problems are associated with the BEC circuit; that part of the ESC wasn't really intended as a power supply circuit, it just happened to be available and easily adapted. Then there is the issue of quality control and the difficulty in comparing one manufacturer's products to another since the ratings/specs are different. The big issue with BEC's is that most to this point have used linear regulators which cut the voltage from the batteries via resistance. That creates heat and the hotter the BEC gets, the more resistance it has up to the point where it can no longer support the radio/servo requirements, or it fails outright. There are now ESC's coming out, and separate BEC's which use a stepping regulator which doesn't have the heat issues associated with a linear regulator and seems to be working much better with the more voltage sensitive SS systems.

Long story to support your conclusion of not trusting either the battery or the ESC should you manage to retrieve them. I would not suspect the rx, but after a crash it should be checked out before using it again.

Oh, one other possibility that I forgot to address; you camera system. Is it a 2.4GHz or did you happen to opt for one of the 900MHz models? It is possible for the tx of the camera system to "swamp" the rx of the flight control system if it's too close, doesn't have a ground plane, or possibly something in that system which had previously been working had an issue causing the flight control rx to be affected?

As for problems with a DX7 and an AR6100; I've not had any problems with my 6100 rx's using either my DX7 or the X9303. We have a club member who's got an electrically powered Cub with a camera system, but he uses a DX7 with an AR7000 rx which has a satellite rx and which is as far away from the camera tx as he can put it. The camera system is a 900MHz model he ordered specifically due to concerns about a camera system on 2.4GHz possibly affecting the flight control system. So far he's not had any problems and the system is really interesting to fly with...

But this is also JMHO...[8D]
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Old 03-09-2008, 06:45 PM
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Default RE: Loss of signal DX7/6100


ORIGINAL: Zeeb

ORIGINAL: BobbyGee


ORIGINAL: Ken6PPC

Sorry to hear of the loss of your plane. We've all been there, and it really sucks.

Sounds like your battery either shorted out or came unplugged to me.

In any case, you have my sympathy.


Thanks, Ken. Those are a couple of things that have occured to me.

Unplugged is unlikely- it's Deans plugs and it's not easy to pull them apart even when I want to. Short is always a possibility.

Maybe the wind will blow it out of that tree before the elements turn everything to trash ... I'd like to rescue my motor, servos and camera at the very least. I don't think I can trust that ESC battery or after this. Or the receiver.

BobbyG

Oh, one other possibility that I forgot to address; you camera system. Is it a 2.4GHz or did you happen to opt for one of the 900MHz models? It is possible for the tx of the camera system to "swamp" the rx of the flight control system if it's too close, doesn't have a ground plane, or possibly something in that system which had previously been working had an issue causing the flight control rx to be affected?


Thanks much for an expansive and thorough response, Zeeb!

I am reading that BEC's might be the weak link in all of this.

As to my camera, it's not a live video downlink. It's a small digital rigged with a switch to trigger from an empty channel via the 3-way switch. It does receive power from the Rx - but we're talking about a small digital that uses 2 AAA batteries - all of a 2.4v load and low amps. It was set to triggger once every 3 seconds.

In other words, the camera would not have been a source of frequency interference. It's also not a source of high current draw. I would typically do flights of 15 - 20 minutes and then see all of 750-850 mA go into a 3S 2100 LiPo pack in order to get back to full charge.

Thanks!

BobbyG

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Old 03-11-2008, 06:21 PM
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Default RE: Loss of signal DX7/6100

The CC BECs tell you not to run 4 servos when on 3 cell 11.1 volt.batts. Found out the hard way. Not the fault of the Spektrum, would have happened with any rcvr. Everything shut right off. After the ESC cooled off, everything worked fine. Went to 3 servos and everything was fine.
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