Spektrum receivers JUST SHUT DOWN!!!

[HoverOver]

I just reported a major problem with my new Spektrum receivers (transmitter?). If after reading this post, I'm wondering if others are experiencing the same and if you've found resolution???

Anyway, here's my story - see if you can relate...

The SHORT Version:
Power cuts off (i.e. receiver shuts down) during flight. I have repeated the problem several times with two different Receivers in two different helicopters...
Transmitter: X9303
Helicopter / Receiver #1) T-Rex 450SE with AR7000
Helicopter / Receiver #2: T-Rex 600 CF (electric) with R921 receiver (came with X9303)
RESULT: Helicopters drop out of air with ZERO input control!!! Yesterday, the T-Rex 450 SE dropped from 25+feet during a climb-out. It landed on right skid with tremendous force breaking just about everything. This helicopter was PERFECT!!! I estimate $500+ in damage! I am not happy

The LONG Version (or at least the rest of the story):
My original thought was that it "could" have been the ESC cut-off setting as the battery was getting low. I am sure this was not the problem now, however, for several reasons:

• REASON #1) I use a low voltage warning alarm (on the 450 SE) which has an audible and visual warning system preventing me from running my batteries too low in the first place. It did NOT do this with my 7202 TX and R790 RX.

• REASON #2) It did the same thing on my T-Rex 600 (Brand new - just completed) which had a brand new fresh battery (thunder power 5000mAh) and freshly charged Align 1200mAh BEC battery powering the receiver. Fortunately I was only a few feet up and just hovering when it sent my 600 back to earth!!!!!!

• REASON #3) Yesterday it did it to my T-REX 450SE during flight when it had more than half of it's charge left (I verified this by re-charging my LiPo and documenting the amount of MaH's it took).

• REASON #4) Ironically, I was listening to the "All Things That Fly" pod-cast today (dated 10/22/07, Titled "ATTF #21 - It's your Canopy!") which can be downloaded from the following website: http://insideheli.libsyn.com/
I strongly recommend you listen to it starting at 35:00 minutes into the pod-cast. That is where they talk about what appears to be a similar, if not identical situation.

In any event, I recently sold ALL my old radio equipment in anticipation of the arrival of my X9303 / 2.4 GHZ stuff and spent a fortune!!! DID I MAKE THE WRONG DECISION? Who will pay for my T-Rex 450?

I'm a long time loyal customer but I'm gunna need some attention on this one - SOON!

[DavidH]

Sounds to me like a power problem to the receivers. When the power gets too low on the 2.4 ghz receivers. They go into a mode trying to rebind to the transmitter. During this time there is no signal between the receiver and transmitter that can be used to control the model.
http://www.spektrumrc.com/Articles/Article.aspx?ArticleID=1683

This could be what happened. There is several reported incidences of this happening on the forums. So it would be best to check the power supply to the receiver. What may have been fine using another system, may not be enough when using the 2,4 setup.

David

[PTFlyer]

check this thread out.......

http://www.rcuniverse.com/forum/m_3742089/tm.htm

you might want to try one of these........6 bucks..cheap insurance....
http://www.rchobbies.net/index.php?main_page=product_info&products_id=10718

[DavidH]

You can get a capacitor at Radio shack for less than a $1. That is all the device in the link is a capacitor.

David

[HoverOver]

Hi Fellas, thanks for your responses....

I do not use a separate BEC in the T-Rex 450 but do in the T-Rex 600. I suppose it is "possible that in a hard pullout (on the 450) the current drops enough to cause the rx to shut down - but then why did it do it when I was just hovering? More importantly, why it does it do it on the 600 which DOES have a separate power source for the rx (i.e. BEC). I understand the question and it would certainly be one of the first considerations but keep in mind I had the exact same setup but with the JR R790 RX with NO problems.

If I was sure it would prevent a "shut-down", I would invest into a separate BEC/power source (and add more weight) but I am not. I am seeing this problem more and more in these forums... I've considered the static issue but see that many people have taken all the grounding precautions from isolation, re-location and even letting their receivers "dangle" below the heli - all without conclusive results. I'm at a loss here. Did I get lured into something that is over-hyped here? Did I make a mistake? Have any more ideas?

By the way, I did purchase a couple of capacitors and will give that a try. My question is: If this is an inherent problem with these transmitters, why no mention of it when they sold them to me (for a price of $900+)??? Why not include the capacitors?

I read through numerous forums and see references to the same kind of comments I am getting about the low power and static. I'm more of the mind that I am concerned with regards to why this would be happening with the AR7000 (and the R921) when it didn't happen with the JR R790 with the exact same setups (I did use a R790 in the 600 before I got the R921)... Seems like it might be a manufacturing / design flaw... I am trying to keep my emotions in check here because my true sentiments are lining up with the multitudes of other [disgruntled] Spektrum customers in the forums. I have this question posted in rcuniverse and runryder and am seeing some angry responses.

I'll let you know if I learn something but am anxious to see if someone else knows something.

Thanks, Mike

[HoverOver]

Hey David,
Can you tell me more specifically about the capacitor I could pick up at Radioshack? I am assuming I would just solder on a jr receiver pack connector to it.
Thanks, Mike

[tailStrike]

I was attacked by a guys R60 after he lost a radio link on his 2nd day of flying after installing a spektrum module in his Tx. I'm not sure what the cause was and haven't really been able to talk to him to see what the status of his Rx pack was before the flight. I have been using a DX7 on my 50 and park fliers for a few months now w/ no issues, but I'm a little more uneasy about the setup.

I think a redundant power supply solution might be worth considering.

HoverOver, there is a post in that thread that reveals what the capacitor is:
http://www.rcuniverse.com/forum/fb.asp?m=3747606

[bullaculla]

I have never had a problem with my 450SE or either of my 600s.
450 is stock and using the 6100, and my 600s are using ar7000, one is using the align 6amp regulator and the other one which is on 10s is using the medusa 3.5 amp BEC.

which regulator are you using with the 600 and with what servos? Some have been having problems with the 3amp reg and high draw servos.

[HoverOver]

I was attacked by a guys R60 after he lost a radio link on his 2nd day of flying after installing a spektrum module in his Tx. I'm not sure what the cause was and haven't really been able to talk to him to see what the status of his Rx pack was before the flight. I have been using a DX7 on my 50 and park fliers for a few months now w/ no issues, but I'm a little more uneasy about the setup.

I think a redundant power supply solution might be worth considering.

HoverOver, there is a post in that thread that reveals what the capacitor is:
http://www.rcuniverse.com/forum/fb.asp?m=3747606

How would you set up a redundant power supply on a small bird like the T-Rex 450? Plug an additional battery into an open receiver slot? What battery? Or are you suggesting the Spektrum voltage protector (i.e. capacitor) will accomplish this?

I was asking about the capacitor specifics so I would be sure to get the right thing from Radio Shack.
Thanks

[HoverOver]

I have never had a problem with my 450SE or either of my 600s.
450 is stock and using the 6100, and my 600s are using ar7000, one is using the align 6amp regulator and the other one which is on 10s is using the medusa 3.5 amp BEC.

which regulator are you using with the 600 and with what servos? Some have been having problems with the 3amp reg and high draw servos.

I am using the stock align setup (i.e. Align RCE-B3X BEC with Align 1200 mAh 7.4 V battery) with Hi-Tec HS6965HB Digital Servos for Cyclic and the Logitech 6100 on the tail. Keep in mind, however, that this is happening on a full charge babying it into a gentle hover about 5 feet off the ground. Its not like I'm slamming in hard aileron and elevator!!! I can't imagine it is an overdraw - or even a power supply issue. It's like it glitches, but unlike the old system which would just come back on as soon as the glitch passed, it just shuts down!

As "in to" this hobby as I have gotten in the last couple of years, I'm now regretting the "upgrades", including purchasing the T-Rex 600. I'm a Firefighter with a family and a house. It was a bit of a stretch to spend this kind of money on this in the first place. I should have put the money into my daughter's college fund!!!

[tailStrike]

How would you set up a redundant power supply on a small bird like the T-Rex 450? Plug an additional battery into an open receiver slot? What battery? Or are you suggesting the Spektrum voltage protector (i.e. capacitor) will accomplish this?
Meant the redundant supply might be worth considering on my 50...I guess I wasn't clear. Obviously not practical on a 450.

I was asking about the capacitor specifics so I would be sure to get the right thing from Radio Shack.
Thanks

Got ya, that's why I put a link to that post that discussed that - I have no idea if a 10V 100uF is appropriate or not, as I'm no electronics expert, but 10V sounds kinda high. Anyone more knowledgeable know if this will actually cause a 10V to be sent to the Rx, or is that just the max the capacitor will reach? I don't see how it could reach a 10V level if it was only receiving 5V, but again I took physics for non-majors and didn't study too much on the electronics portion :).

[DavidH]

Mike,
The specs for the capacitor are on the one that Spektrum sells.
http://www.horizonhobby.com/Products/Zoom.aspx?ProdID=SPM1600

It is a 4700uf 10V capacitor +105c operating temp. make sure it is +105c and NOT +85c as the top temp
Radial style eletrolyctic
It is made by Topcon. They are located in Taiwan.

There is plenty of companies that make capacitors of the same specs. They range in price from 50 cents to $2. You can get them at any shop that sells electronic compontents.
[url]http://www.digikey.com/?gclid=CP7cy7fSqo8CFQukHgodrwY7Kg[/url

Digikey above is one online to get some from. The above capacitors are used on computer motherboards also, so a computer repair shop will probably have them also.

Also the JR 790 receiver you mentioned using earlier. That receiver probably did not react to low voltage drops the same as the 2.4 ghz. The 2.4 ghz drops voltage below a certain level and it trys to rebind with the transmitter.

David

[HoverOver]

Hi Guys,
Just received an email back from Castle Creations. His response seems to agree with the low-voltage theory. Here was his response (take special note of the word "ANY":

Mike,

The problem here is not with the Phoenix ESC but the Spektrum receiver. They have a know issue in that they shut down with almost any fluctuation with input voltage. When they turn back on, they have to rebind with the transmitter and usually a crash occurs within this interval. The onboard BEC design in ESCS has not changed in the last 10 years and in our case uses two linear regulators in parallel. The voltage from these is relatively stable but they can allow small voltage changes to the receiver under heavy servo load. There really is no reason why Spektrum receivers are sensitive to this; it is simply a design flaw. No other receiver is sensitive to these normal voltage changes. By the way, a regular MiMh receiver pack’s voltage supply is much more unstable than that from a linear regulator.

Currently the best solution for running Spektrum receivers is to disable the onboard BEC on the ESC by pulling the red wire between the ESC and receiver and use a separate switching regulator BEC such as the Castle BEC. Switching regulators are capable of supplying very close to constant voltage. This works around the internal voltage regulation design flaw in Spektrum receivers.


--
Bernie Wolfard
Product Support Supervisor
Castle Creations
235 S Kansas Ave
Olathe, KS 66061
913-390-6939 Ext 123

[DavidH]

Well don't know that I agree with the ANY flucutation of voltage part. Because even using a battery hooked directly to the receiver. The voltage is going to fluctuate as the servos move to operate the controls. Not hard to see that, just put a voltmeter hooked to the receiver and start working the controls. A regulator setup is going to provide a more constant voltage setup. Thou it will also fluctuate some, just not as much as a battery only setup.

David

[HoverOver]

David I agree! I'm working all the forums on this issue to speed the process and here was a response I got (with my response back) on RCUniverse:

HIS RESPONSE:
Well I'm glad you are gaining ground. but I question the word " flaw" in other words it's not our fault but theirs. I think his statement "not changed in 10 years' says much more. Maybe it's time for them to catch up with the times. If radio systems improve other companies must keep up. They are right in that the 72's could handle brown outs better. If they want to keep their market they will have to improve the product to meet the demands of the new radios.

MY RESPONSE:
I agree with the sentiments "It's not our fault, its theirs" is a common [poor] excuse (the computer industry is notorious for it). That being said, however, is creating a product that is more vulnerable to power fluctuations better or worse than last year's technology that wasn't?

Just food for thought.

[RCHeliJim]

There really is no reason why Spektrum receivers are sensitive to this; it is simply a design flaw. No other receiver is sensitive to these normal voltage changes.

Thats really not smart on CCs part to say. First off, there are documented cases of about all the 2.4Ghz stuff experiencing these brownouts due to RX voltage issues - they are all quite sensitive to voltage when compared to 72Mhz stuff. Go over to RCGroups and take a look at the XPS threads - there are a few crashes from this very thing with their stuff as well. You are moving to a mini-computer in your recevier when you go to 2.4, with that change comes a change in power requirements. Other receivers are prone to this and the response you got from CC is plain false..... just my opinion of course.

I think the response you got from Spektrum was closer to the truth, this is the way the hobby is headed - like it or not - and the ESC/regulator makers that do not make better power supplies will be left behind eventually. For example, I run a Thunder Power ESC in my mini titan, it has a 4 or 5 amp SWITCHING BEC inside and it costs the same $$ as a CC unit with the linear regs in them. It has been a flawless ESC with my V1 AR6100 receiver for 100s of flights. I also am running Duralite regulators and packs in all my large helis using the SPektrum gear. Because of this I have not experienced a glitch ever with their equipment, and thats over about a years time with the DX7.

The one flaw I find with the Spektrum/XPS/FASST gear is that they are not advertising the more sensitive power needs enough. All their product literature and boxes should have the warning on them letting consumers know before purchasing that they may need to beef up their flight packs to use this type of equipment. Alot of people are getting this gear and running into trouble due to a lack of info and nothing more, and thats really too bad. I know the websites, forums, and manuals have the warnings - but many guys are not heavy internet users and they miss them.

I do feel bad for the guys having these troubles, but I do not think it is a design flaw - the microprocessors in these 2.4GHz units are MUCH more sensitive to voltage than the 72 Mhz gear, thats just how it is currently. The receiver makers will have a hard time getting around the requirements of the chips used in the receivers, dont you agree? I am quite certain that when there are more FASST units actually in use we will see the same thing from people, but it should be less as time goes by. Since Spektrum was the first 2.4 solution there will be more of these issues and posts, but as we all learn from them you will see less and less of these type of issues come up. I have tried to make my DX7 fail and cannot, the technology is proven - just sensitive ;)

[HoverOver]

This forum thread has generated some very interesting discussion and I am genuinely impressed with the caliber of intelligent and thoughtful input!

Based on what I have read in all three forums I started with regards to this issue, I am concluding (at this point anyway) that it is a power fluctuation issue that is causing the spektrum receivers to shut down. The confusing issue to me was that 1) it appears that there are many different causes (i.e. low battery, too much current draw from servos, ESD, etc...) all with the same net result: a momentary drop in voltage and 2) I have a hard time with coincidences and with this happening to me in two different Helicopters with different setup configurations... well you know what I mean.

I had ordered one of the Spektrum voltage protectors (see here: http://www.rchobbies.net/index.php?main_page=product_info&products_id=10718 )
and might consider trying this. For now, however, I have been invited to send my troubled parts including my broken bird) in to Horizon and they are going to run some bench tests and probably update the firmware, etc. I am grateful for their support and plan to update this thread with the results once I learn more.

Thanks again for all your help. I learned from you and hope to return the favor soon.
Respectfully, Mike

[tailStrike]

So by "fluctuation" we are strictly talking about the voltage dropping below an acceptable level, right? Not so much spikes as from what I remember from watching the propaganda video for the DX7 on their website, the Spektrum Rx's are fairly tolerant to higher voltages (I can't remember the exact number, but 12V comes to mind).

So to sum up what I am reading, the best approach (on nitro birds) is to go w/ a higher cell Rx pack on with a linear regulator to bring it back down to levels suitable for our servos/gyro? Let me clarify why I say higher cell pack - does a regulator do much for drops in voltage? I'm assuming no, which is why I am reasoning that higher voltage packs would be the better route.

Also, I think thusfar we have been saying the Rx goes through the "binding" process after the power loss. That's probably not the correct term to use, since the Spektrum definition of binding is the process for associating a Tx model's guid w/ the Rx. The process occuring during a power loss is probably more like the handshake between the two and the search for the two open 2.4Ghz frequencies.

[bsoder]

I had problems with Spektrum reboots with some cheap servos (Waypoints) - I've got Hitecs in everything now, along with Hyperion ESCs and haven't had problems since.

I could actually cause the lockout with ONE Waypoint servo, just quickly moving it back and forth. With four HS-56's on the same ESC/BEC (Hyperion 20A) I can't make it happen.

[PTFlyer]

Mike,
The specs for the capacitor are on the one that Spektrum sells.
http://www.horizonhobby.com/Products/Zoom.aspx?ProdID=SPM1600

It is a 4700uf 10V capacitor +105c operating temp. make sure it is +105c and NOT +85c as the top temp
Radial style eletrolyctic
It is made by Topcon. They are located in Taiwan.

There is plenty of companies that make capacitors of the same specs. They range in price from 50 cents to $2. You can get them at any shop that sells electronic compontents.
[url]http://www.digikey.com/?gclid=CP7cy7fSqo8CFQukHgodrwY7Kg[/url

Digikey above is one online to get some from. The above capacitors are used on computer motherboards also, so a computer repair shop will probably have them also.

Also the JR 790 receiver you mentioned using earlier. That receiver probably did not react to low voltage drops the same as the 2.4 ghz. The 2.4 ghz drops voltage below a certain level and it trys to rebind with the transmitter.

David

I noticed that the spektrum capacitor is a 105c as you state and you say to get one rated at 105c and NOT 85c., I'm wondering why you say to be sure to get a 105c as I think either will work...please enlighten me.....

after reading about capacitors I'm not so sure the 85c might not be the better choice....maybe you or some one else can clear this up for me?

Here is why I am questioning the 105c :

http://www.repairfaq.org/REPAIR/F_captest.html#CAPTEST_016

11. What is ESR and how can it be tested?

ESR (Equivalent Series Resistance) is an important parameter of any capacitor.
It represents the effective resistance resulting from the combination of
wiring, internal connections, plates, and electrolyte (in an electrolytic
capacitor). The ESR affects the performance of tuned circuits (high ESR
reduces the Q factor) and may result in totally incorrect or unstable
operation of devices like switchmode power supplies and deflection circuits
in TVs and monitors. As would be expected, electrolytic capacitors tend to
have a high ESR compared to other types - even when new. However, due to
the electrochemical nature of an electrolytic capacitor, the ESR may indeed
change - and not for the better - with time.



16. Cool electrolytics - temperature rating versus ESR

(From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)).

Electrolytic capacitors like to be kept cool! If there's anything that these
capacitors can't stand, it's heat. It causes them to dry out.

Electrolytic capacitors exist in (at least) two different temperature
ratings: 85 C and 105 C. The latter are obviously more temperature resistant.
Unfortunately they also tend to have a higher ESR than their 85 C counterparts.
So in an application where the heat is due to I^2 * ESR dissipation, the 105 C
type may actually be a *worse* choice! If the heat is due to a nearby hot
heatsink then 105 C is indeed a better choice.

[DavidH]

I would guess the 85c might work also. But there is a reason Spektrum chose the 105c.
The problem that is causing the voltage to fluctuate is amp draw. When amperage is being drawn it creates heat. So I would think that is why they are using the higher heat rated one.The capacitor is just storing energy. In a TV or PC it would make a difference which one was used. But in this application is being used to store energy till needed.


David

[huskynox]

Is this a common problem with the Trex's and 2.4Ghz systems? Have you contacted Align and asked them their opinion?

[kgfly]

There have been many crash investigations now of many kinds of models relating to 2.4GHz Rx. The vast majority have been tracked back to Rx power supply problems. It is not a problem with any particular heli it is a problem of marginal power supply setups that got by OK on FM due to the fast reboot/reacquisition time of FM Rx but are exposed with 2.4GHz Rx. Nor is it necessarily true that the 2.4GHz Rx are more *sensitive* to brownouts, but rather the consequences are different due to the longer reboot/reacquisition times.

Spektrum Rx have to scan the band after rebooting to locate the two channels the Tx is using. Depending upon the ambient noise floor this can take several seconds and this is what leads to the loss of control. XPS Rx can reboot/reacquire in under 100ms so long as the Tx has not been turned off.

IMO the capacitor is unlikely to help much as it stores only a tiny amount of energy compared to the loads on a heli from all the servos. Since in many cases the problem is the integrated BEC sagging due to load and or going into thermal shutdown, a few ms of backup from the cap won't help. The solution, as mentioned, is to use an appropriate external *switching* BEC that won't overheat or sag for the loads on your heli.

For a TRex450 or similar the DimensionEngineering SportBEC is ideal and well proven.

If you are interested to see just how poorly NiXx Rx packs, regulators and BECs can perform look at the test results here: http://www.archeli.com.au/cobra/showthread.php?t=112551

[bsoder]

The solution, as mentioned, is to use an appropriate external *switching* BEC that won't overheat or sag for the loads on your heli.

Bet we're going to see more and more ESCs with switching BECs specifically because of this problem. I'm using the Hyperion 35A ESC, it has a 4A switching BEC built in.

[Old Sloppy]

I would guess the 85c might work also. But there is a reason Spektrum chose the 105c.
The problem that is causing the voltage to fluctuate is amp draw. When amperage is being drawn it creates heat. So I would think that is why they are using the higher heat rated one.


David

The tempature goes up over time.

85c will work for shorter flights, 105c has a bigger safety cushion.

Harry