Read: 3G Servo Bus Concern

[syn90]

So after reading lindahls post above, I am really concerned about my setup. I didn't realize that the 3G had an internal regualtor? That doesn't make any sense, the output of the 3G to the servos should be what is seen by the input, otherwise you can't even run an HV setup because the 3G unit would always be limiting voltage to your cyclic servos? WTF is going on here? Can anyone else confirm there is a built in regulator in the 3G that limits voltage output to the cyclic servos? If this is true, I am going to get really pissed off and rip those things off my birds this weekend and sit tight for a total G. All this stuff is really starting to boil my pot, especially align's response which doesn't really address anything but merely indicate there is a problem. Well guess what, we already knew there was a problem, we want resolution damn it!

[HiroboFreak]

I'm running a 7100R & 2s LiPo.

When I tested my 3G on the bench I was getting pack voltage (8.4v) to the cyclic servos, & 5.2v to the rudder circuit.

I haven't had a problem with any brownouts, but after reading this thread I am now pulling power for 2 of the 3 cyclic servos direct from the Rx, which has now made future servo removal no longer a simple task.

If all is confirmed to be OK I will go back to the standard setup.
The pros are running it in stock form with no issues & they push the model & servos a hell of a lot harder than I do!

I will wait to hear what Align has to say about this.

[lindahl]

Originally Posted by syn90

It would be nice to hear some more details from lindahl. Was there a regualtor causing the 6.11 volt output at the 3G, or was that the voltage that was also seen at the output of his receiver/aileron connector. If it is and he is running straight off a 2 cell lipo, then that lipo is already .2 volts over discharged and most likely junk. This is why we need more details as things aren't adding up.

The lipo was not fully charged, It had 8.14V without load. The pack is a new Zippy 2s2p 3600mah 20C. The only regulator i use is the built in for the tail servo on 5.1V. The rest goes unregulated.

The output on the receiver connector was also 8.14V. Just as the lipo.

Somewhere it disappeared 2.03V in the FL760 unit.

[syn90]

I am going to test mine when I get home, but Hirobofreak's results are what I would expect, the output of the 3G should be what the input is seeing. I'm glad to see your post hirobofreak, it's helped to calm me down.

Lindahl,
Hirobofreak's post helps to further solidify that something doesn't sound right with your 3G unit even before the voltage dropped and the unit shut down, you should have been seeing pretty close to pack voltage on the output, I believe you said something like 8.14 volts.

[lindahl]

Originally Posted by HiroboFreak

When I tested my 3G on the bench I was getting pack voltage (8.4v) to the cyclic servos, & 5.2v to the rudder circuit.

Well pack volt was 8.14 but i was far away from that. I wonder why. Do you use the short or long sensor cable?

[OnTheSnap]

There is mass confusion going on here.

The 3g unit simply buses the input voltage from the RX connection on Aileron to the servo outputs. There is no regulator between the RX input rail and the servo output rail. There is just a solid copper connection.

Tapping off this connection, there is a small regulator that feeds the 3g microprocessor. This is the voltage I'm concerned about. If the voltage at th 3g inputs falls below say 4.5V, then the 3g microprocessor may see a voltage that is too low and then fail to operate correctly.

If you measure 8V at the 3g input, but 6V at the servo output, the PCB in the 3G unit is fried. Meaning, the copper etch has been damaged severely and there was probably some magic smoke.

[HiroboFreak]

Originally Posted by lindahl

Well pack volt was 8.14 but i was far away from that. I wonder why. Do you use the short or long sensor cable?

I use the long cable, but I don't see what that has to do with output voltage.

[harryboe]

Originally Posted by Leon Luke

I have been informed by Align that some problems in the 3G have been traced to low voltages under load when using 4 cell nicad receiver packs, when voltage drops below 4.5.

If that's true than i'm really concerned now !
4.5 V ! in this case every standard 5V BEC set-up will potentially fail. Including the T450 and T500 ???

Maybe they refer to the voltage of the nicad pack and the brownout limit is much lower ???

[Bert Kammerer]

Hello guys,

Just my observation. I firmly believe that the single wire has nothing to do with the cause of the issues that some people are having. I have hundreds of flights on two units, one running Align DS-610's and the other one running JR 8717HV's (both on full unregulated 2 cell lipos). I have never had a problem, In addition, I remember back when I received my first prototype T-Rex 700, I was using a JR heavy duty switch with a Spektrum AR9000 receiver, the switch was soldered to a 2s lipo, if you have seen those switches, you know how thin of a wire they have (servo wire), that single wire was powering the entire helicopter, not just the cyclic servos, but everything (throttle servo, governor, cyclic servos, gyro, tail servo, etc.) and I never had a problem then either. Keep in mind, the 3G system can cause the servos to draw peaks of 12 amps, but that only happens for a fraction of a second every now and then throughout the flight, the average current is usually 3 amps or less.

Also, as for the report of servo failures when used with 3G, most of the servos listed (Hitec HS5065MG, Hitec HSG-5084MG, Hyperion DS20FMD, Futaba 9650 and JR DS8231) are 6 volt servos, the use of higher voltage will for sure dramatically decrease the servo's life. Even though these servos might perform OK on high voltage in a flybar helicopter, the use of a flybarless system will make the servos work faster and harder, which can cause premature failure. I have successfully ran Align DS-610 servos on 8 volts, but I don't recommend it because they are for sure not going to last as long as they would otherwise. Another thing to keep in mind is that these servos are being controlled by a gyro, so any vibration in the heli (specially high frequency vibrations that are not seen by the naked eye) can cause the servos to "jerk", this can lead to overheating or damage to the motor. When the servo motors short out, they draw crazy amounts of current causing a voltage drop that can lead to brownouts. Flybar helis do not have the gyro induced corrections to cyclic servos, so they are less prone to vibration induced failure to the servos.

Hope this helps

[panzlflyer]

Somehow I knew it would be our setup fault for their electrical ineptness.
Not to mention they are the only manufacturer of Fbl units that use a single path for power that I can find.
Wish i hadnt sold my Skookum now.

[Ultraviolet]

Bert, The reality is that FBL systems can and do cause the servos to draw a lot of current. Continuing to employ tiny wires to carry fairly large loads is extremely unwise, and in fact negligent.

A responsible design of any kind always takes into consideration a safety factor. This safety factor is not present on the 3G. In fact the 3G appears under designed in this respect.

Companies like Spektrum have modified there designs to include a robust power line, which allows for a factor of safety. This is the responsible and prudent thing to do.

Denying that any issues exist implies a less than honest approach to dealing with the customer, not to mention a potentially lethal result for the end user.

There is nothing wrong with admitting a potential design mistake, and then doing everything in your power to fix it. The scary part is the denial.

How a company deals with issues like this, defines the company.

I am sure what folks are looking for is an official response from Align TW.

[Ultraviolet]

One more point....

What agency approval ( CE, UL, CSA, etc ) has Align been granted that shows the 3G has been tested at current draws that the end user will effectively see. What 3rd party documents show that the 3G is in fact safe to use ?

The purpose of these agency's is to help safegard the consumer from potentially dangerous designs that put profit ahead of safety.

[Bert Kammerer]

Wait a minute guys, I never said it was your "setup fault".

Ultraviolet, I am not implying that an issue does not exist, I simply believe it is not the wires, it could be something else and not necessarily "setup fault". This is the main reason why I for the most part refrain myself from posting in forums. I simply try to chime in with some comments to try and help and I get blamed

As I stated, if the wires are an issue, how come I haven't had a problem? I have logged over a hundred flights with HV servos pulling every bit of 8 volts on very hard 3D. Again, not saying there isn't a problem, I am also not saying that the "wire issue" couldn't be improved, just saying that I haven't had that problem myself, that's all.

[rubbersoul]

haven't had a problem on mine either, 610s on 8v. but this thread convinced me to do something about it so I just did a very simple mod to provide power to the servos direct from the ar7100. all my cyclic servos are now isolated power wise from the 3G.

[OnTheSnap]

Hi Bert!
I think we all agree that a 8V "hv" system is much less likely to have a brownout compared to a 5 or 6V setup.

Can you bench test or fly your rig at 5V? If that worked for 100 flights I'd be convinced you are right.

Btw, I loved ep 2 of Smack Talk. Chicken wing was too funny!

[tcast305]

Originally Posted by Bert Kammerer

Wait a minute guys, I never said it was your "setup fault".

Ultraviolet, I am not implying that an issue does not exist, I simply believe it is not the wires, it could be something else and not necessarily "setup fault". This is the main reason why I for the most part refrain myself from posting in forums. I simply try to chime in with some comments to try and help and I get blamed

As I stated, if the wires are an issue, how come I haven't had a problem? I have logged over a hundred flights with HV servos pulling every bit of 8 volts on very hard 3D. Again, not saying there isn't a problem, I am also not saying that the "wire issue" couldn't be improved, just saying that I haven't had that problem myself, that's all.

Bert,

I don't like post anymore because of that. You try to help and what do you get? Some people tend to forget that this is a hobby.

Thanks.

[Bert Kammerer]

OnTheSnap, I thought guys were complaining about the single wire not having enough to carry that many amps, the amp draw would be significantly lower with 6 volts or even 5 volts. Brownouts are a difference story, I didn't think of that, but this could certainly be the case!

[Ultraviolet]

Originally Posted by tcast305

Bert,

I don't like post anymore because of that. You try to help and what do you get? Some people tend to forget that this is a hobby.

Thanks.

Some people also tend to forget that these helis can seriously injure or kill. The last thing people want is for there heli to hurt someone.

[PlasticHead]

Bert,

I totally understand that you are giving your opinion of the issues and not the Align company position and I respectand appreciate that. As to the single wire power bus I think it could function without failure or issue and still be a bad design. Testing has shown that under load voltage drops to around 4 volts which even if it keeps the servos operating sure isn't what we expect to be pushing through our high end digi servos. We don't want our new $400 dollar electronics to be lowering the performance of our other components. I wonder how well your 700 would fly with you at the controls when your servos are getting a steady reliable diet of 6 volts (or whatever your setup is built to do). Maybe you would want to build a wiring harness as described earlier and tell us with you super human skills if their is a difference in control and feel?

Thanks for participating!

PH

[panzlflyer]

I know Bert didnt design it and as he said he has had many flights on it.
My remarks are not directed at him.
I still think it is foolish to trust a heli to one single wire whether it flies or not.
The fix would have been simple and would not cost more than a few cents.
The system is supposedly plug n play with brief instructions what are us masses to think when it does weird things.