805kitbuilder

My Feedback: (15)

So yesterday I was flying my 3D hobby shop when I lost all signal followed by losing the entire plane (total loss) The plane was just built and was running quality equipment. Motor - Turnigy Aerodrive xp 900, with a Castle Phoenix Ice 75, Spektrum AR7000 with 4 cell lipo battery. I shook it off and decided to fly the other plane I brought . Shortly in to the flight this one too lost signal. I was luckyas this was a high wing decathlon and I was able to bring it in. I recently changed my Spektrum radio battery to a lipo but had flown with it several times with no issues. I have thought about putting in the original battery back in but have serious concerns that this may not be what caused the brown outs. I dont want to risk another plane, or possibly people until this issue has been resolved Has anybody run in to this problem? If so ,was it radio problem? The radio is less than 8 months old.
Thanks for any input

BuschBarber

My Feedback: (2)

Are you certain you experienced a Brownout? Did you have any Blinking Light on the Rx indicating a Power Loss to the Rx? The Throttle did not go to Idle?

BarracudaHockey

My Feedback: (11)

I'd be more inclined to take a look at the transmitter antenna connection at the RF board.

JIMF14D

How do you bring a plane in if you have lost signal? You had no control and then got control back?

805kitbuilder

My Feedback: (15)

The 3D Hobby shop that crashed went in and out of signal. I made a hard turn to bring it back when the signal was lost again. It rolled over and went straight down. Thedecathlonbegan to have the same problem but signal came back long enough to put it on the ground. The decathlon is a nitro plane, the motor went to idle at signal loss then came back up to 3/4 throttle where i had the stick on the radio. As soon as the signal came back I did a slow flat turn back in to the runway where I was able to put it down safely

JIMF14D

Sounds like a real bummer day for sure. Brown out is a low voltage condition where the Rx works and then does not etc. So a good battery system check is in order for sure.

Signal loss is a different thing as far as Iunderstand it. Signal loss should cause the system to go to fail safe which it sounds like the glow model did but who knows for sure.

Jim D.

805kitbuilder

My Feedback: (15)

In trying to do some research I came across this on the Spektrum website.

Recently Horizon Hobby Service Department discovered a software issue in DX7 transmitters with HA002J, HR003J, HR004J, HR005J, HR006J, HR007J, HR008J or HR009J Product IDs (PIDs) and FCC ID: BRWDAMTX11.

It says that there is a problem when trying to model match (bind) model 11-20 and that there is a software updateavailablethrough Horizon hobby. Transmitter must be sent to them and all the info is on there site
http://www.spektrumrc.com/Products/S...ProdId=SPM2710

The 2 models I had issues with yesterday were #11 and #14

Jezmo

Call and talk to Horizon. According to what I was told DX7 radios are damaged by the LiPo battery and must be sent back for repairs. The DX7 doesn't work with LiPo voltage. It's simply too high.

At our field, the radio would go bad after changing the battery type for those that did so. The radio would work for a short period, sometimes hours, sometimes days, but would then start cutting out. I never did change mine but after others had problems, I did call and was advised not to use a Lipo in my DX7 due to the potential for failure.

BuschBarber

My Feedback: (2)

http://www.jethobby.com.sg/cgi-bin/e...17&idx=1&gid=4

I have been using 3cell 2500mah LiPo Tx batteries in both of my JR 9303's, for over 4 years, without issue. You can install inexpensive diodes, from Radio Shack, to drop the voltage, if you are afraid of the higher voltage. You can also use LiFe Tx batteries as their voltage is lower. I charge my Tx once a month and the charge only takes less than 30 min.

Jezmo

All I know is Horizon says not to use LiPo's in the DX7 as it will cause damage. I am only repeating what the big folks say at Horizon. It may not fit into everyones liking but thems the facts.

On a more technical note it appears the cause of the failure is the LM2397ES linear voltage regulator getting too hot with the additional voltage from the LiPo. I have read that other electronics may also get damaged when the reg fails. I do agree that if you take precautions to reduce the voltage "seen" by the transmitter then it "should" be OK.

P.S. Rich, I have read the JR's don't have the issue with LiPo's like the DX7.

BuschBarber

My Feedback: (2)

Thanks!! Jezmo!! As you say, the Voltage is the main concern. I think that the LiFe is a good choice in that case. Some of the newer model transmitters are LiPo compatible.

rmh

Does mfgr making an exclusively 2.4 radio , use other than a 4.8 tx battery?
If so, why?

BuschBarber

My Feedback: (2)

Up until the last couple of years, most RC transmitters used 8 cell 9.6v NiCad or NiMh batteries. Some of the newer transmitter models use a lower voltage. The Spektrum DX8 and Hitec Aurora 9 in particular. They also have options for LiPo Tx batteries. I am sure there are others.

Jezmo

What Rich said.

rmh

I really expect to see the higher voltage tx go the way of other older electronics -

tacx

My Feedback: (1)

mx,
Your original post says you are using a AR7000 with a 4 cell lipo?? Are you using a 4 cell lipo to power your RX?? If so thats about 16.8 volts on a full charge!!!

Or did I miss something?

BarracudaHockey

My Feedback: (11)

He also says Castle Ice 75a Speed Controller, I'm guessing he's using the BEC.

fizzwater2

My Feedback: (61)

The 9303, especially if you are using module based 9303's with the Spektrum module, is likely to be a completely different animal than the DX7. I believe in the DX7 that the regulated voltage (3.3v) is supplied to the whole radio, including the RF part. The 9303 module based I believe supplies battery voltage direct to the module connector, without the internal regulator. The internal regulator in the 9303 most likely provides power for the encoder / processor and runs at 5 volts (again, I'm surmising, I don't want to take apart my 9303..)

Just for grins - let's say the two radios both consume about 300 ma of current. Let's further assume the RF section takes about 100ma, the encoder/processor the other 200. So for the 9303 (module based) you have 200ma through the regulator, the DX7 you'd have all 300 ma through the regulator.

With a NiMh or NiCd battery, the NOMINAL voltage is 9.6V. With 200 ma of current going through the linear 5V regulator, there's 0.92 watts of heat in the regulator to get rid of. Not a terribly large amount. At 11.1V NOMINAL from a 3S Lipo, there would be 1.22 Watts - again, not a huge increase in power to dissipate in the regulator. (power dissipated in the regulator is the difference between the input voltage and the output voltage, multiplied by the current. (eg. (9.6V-5V)x.2A = 0.92W). The greater the difference in input and output voltage, the greater the power dissipated.

Now - for instance, assume the DX7 has a 3.3V regulator, and all 300ma of current pass through the regulator. With a 9.6V NOMINAL NIMH battery, there is 1.89 watts of power dissipation in the regulator. At 11.1V, 2.34Watts, nearly 25% more heat ((11.1V-3.3V)*0.3A)=2.34W. Starting to get to be quite a bit for a surface mount regulator that depends on the PC board for heatsinking. No wonder the folks at Horizon don't recommend LiPo for transmitters.

The 9.9V NOMINAL LiFe battery would be about 1.98W of power to dissipate in the DX7 regulator, and while it's higher, it's not a 25% increase.

Please note that all of the above numbers are based on some ballpark estimates that should be at least close, and NOMINAL tx battery voltages just for comparison purposes. I don't claim that I've measured actual current and calculated dissipation - just pointing out that the 11.1V LiPo can indeed stress a regulator.