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Old Dec 22, 2012, 05:22 AM
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beenflying's Avatar
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Originally Posted by Dr.M View Post
I'm using a CC Phoenix 75A internal BEC (5A); no capacitor...

I don't think it's brown out for multiple reasons:
- I had control at all times; a reboot of the ZYX takes at least 8-10 seconds.
- The Rx indicator would've blinked if it detected a brown out, and the ESC would've flinched.
- Both flying incidents happened in a gentle stationary hover, so minimal load on the BEC.
- I ran the heli on the ground (no main blades) full speed and wiggling all servos at once - no problems

On the other hand, I've also purposely zapped the gyro with static and that tail twitch and swash tilt is very reproducible. The strange thing is the entire heli is grounded - nose to tail electrical continuity...

I suspect some other electrical glitch, perhaps an intermittent short inside the box or along the wiring. I opened up the gyro and inspected it carefully - nothing out of the ordinary. As a precaution I reinforced the Rx wires with liquid electrical tape and added some more padding to potential contact points between the case and the PCB.

I'm stumped
The CC ESC's internal BEC is one of the worst for brownouts due to peak loads. It may not be low enough to reset the Rx and the gyro may have a fast boot mechanism, when it detects a brownout, as opposed to a power up. My advise is to try the capacitor. I use them in most of my helis.

bionicbone, if it was a coding bug, we would all be having the problem. I'm flying 4 ZYX's and one CX-3X1000 (crossflashed), with no problems.
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Old Dec 22, 2012, 06:43 AM
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Originally Posted by beenflying View Post
bionicbone, if it was a coding bug, we would all be having the problem. I'm flying 4 ZYX's and one CX-3X1000 (crossflashed), with no problems.
I would generally agree with this statement.

Is there any worth in flashing the "known to work" firmware download using the link from page 1? OK, I know I'm a skeptic but who knows what sub versions of code are used in production.

But you are probably correct about using a cap, it would never provide enough power to cover a full brown out but would generally smooth out the power line and as long as the reverse current into the Rx is not an issue it should help.

Kev
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Old Dec 22, 2012, 08:16 AM
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Originally Posted by pitchp View Post
sounds like your CX-ZYX is really prone to ESD. perhaps buy a Tarot ZYX-S might be a better solution??
But the CX has a full metal jacket, whereas the ZYX is plastic - so surely more likely to suffer ESD issues.
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Old Dec 22, 2012, 11:24 AM
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I agree, the cap is a good idea and can't hurt. In fact, I do run one one my other zyx bird.

I've also seen the graphs with the CC ESC BEC dipping voltage under load, but the dips were 0.2-0.3V and I run mine at 6V. I would not think this was a problem.

I'll simulate a brown out later tonight to see what happens.

Thanks everyone for your input.
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Old Dec 22, 2012, 12:14 PM
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What you are describing is very like the "hits" I have seen when connecting/ disconnecting the hand programmer. My working assumption is that is caused by a static discharge causing the RAM area holding the unitialization data to be corrupted since it can be "reset" without cycling power by toggling the aux channel several times to trigger a re-initialize.

It does sound like static
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Old Dec 22, 2012, 03:40 PM
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I guess a thorough dousing with anti-static silicone is in order...
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Old Dec 22, 2012, 04:06 PM
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Originally Posted by 2Doggs View Post
But the CX has a full metal jacket, whereas the ZYX is plastic - so surely more likely to suffer ESD issues.
If the case isn't grounded it can work against you, by allowing the static to jump from the case to the closest component on the circuit board.

In the case of the Align 3GX (with a conductive chromed lid), it was traveling down the LED light tubes, where the lid went down very close to the board. All some had to do was touch the lid of the 3GX to get it to reset. With the 3GX if you were lucky it would just reset and work again very quickly. If you were unlucky it would reinitialize the entire NV ram (all settings).

bionicbone, the firmware on that link is the firmware I'm using in all of my gyros, so it certainly couldn't hurt.

About the capacitor, this comment on RPP Hobbies site is interesting:
Quote:
This is a capacitor that plugs into an open slot of a receiver. When used it will help even out voltage spikes that can cause signal dropouts/brownouts when high power servos such as the Hitec 7940 are used. In many cases, RPP Hobby has found that the use of this capacitor can eliminate the need for an external BEC.
http://www.rpphobby.com/product_p/spm1600.htm
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Old Dec 22, 2012, 04:49 PM
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Originally Posted by Dr.M View Post
I agree, the cap is a good idea and can't hurt. In fact, I do run one one my other zyx bird.

I've also seen the graphs with the CC ESC BEC dipping voltage under load, but the dips were 0.2-0.3V and I run mine at 6V. I would not think this was a problem.

I'll simulate a brown out later tonight to see what happens.

Thanks everyone for your input.
I've put a scope on the CC and the power out isn't very clean (with varying load). Personally, I think and old inefficient non-switching regulator may be better than these (cheap) switching regulators considering the sensitive electronics we use now days.

Caps will help though.

Merry Christmas,
Ken
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Old Dec 22, 2012, 04:49 PM
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Brown out testing

Test conditions: used a 4-cell NiCd Rx pack almost depleted. The Rx pack has two leads, one was plugged into a voltage monitor/charger, the other plugged into a free Rx port. I wiggled all sticks until bad stuff started to happen, then started the charger to increase voltage.

Results: the CX-ZYX will brown out around 3.44V (this pretty much means it's not the BEC). The aftermath of a brown out depended on how long it took for voltage to be restored at operating levels:
1. Fast: no reset, everything returns to normal operation with no loss of control. Swashplate level.
2. Medium: temporary loss of control (feels like a hiccup). All activity returns to normal when voltage is brought back up; the gyro does not reset. Swashplate level
3.Long: complete loss of control, gyro resets (all leds blink), then fails to initialize (blinking blue led). There's no response from any of the servos, or any other input. Swashplate is frozen in an odd position, cyclic servos buzz, tail servo unpowered. A power cycling is required to restore normal operation.

Bonus testing: I also wanted to see what happened if voltage was maintained at marginal levels for a longer period of time. I set and maintained the input to the system at 3.44-3.45 V. All servos were randomly twitching. There was still response to inputs, but the swash was not level and tail servo wanted to be at the fore extreme (ccw pro). Stick inputs resulted in correct response, but upon release, the servos returned to the previous behavior. Increasing voltage above 4V returned the gyro to normal operation (Swashplate level, tail centered).
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Old Dec 22, 2012, 05:09 PM
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conclusion???
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Old Dec 22, 2012, 05:18 PM
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Quote:
Originally Posted by pitchp View Post
conclusion???
The symptoms on my Protos are not consistent with brown out, rather this

Quote:
Originally Posted by teamdavey View Post
What you are describing is very like the "hits" I have seen when connecting/ disconnecting the hand programmer. My working assumption is that is caused by a static discharge causing the RAM area holding the unitialization data to be corrupted since it can be "reset" without cycling power by toggling the aux channel several times to trigger a re-initialize.

It does sound like static
Which is unfortunate, since there is nothing else to ground on that bird...
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Old Dec 22, 2012, 05:25 PM
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Do you have a spare tarot zyx-s? just to try if you get the same problems?? just a thought
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Old Dec 22, 2012, 06:38 PM
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Quote:
Originally Posted by Dr.M View Post
Test conditions: used a 4-cell NiCd Rx pack almost depleted. The Rx pack has two leads, one was plugged into a voltage monitor/charger, the other plugged into a free Rx port. I wiggled all sticks until bad stuff started to happen, then started the charger to increase voltage.

Results: the CX-ZYX will brown out around 3.44V (this pretty much means it's not the BEC). The aftermath of a brown out depended on how long it took for voltage to be restored at operating levels:
1. Fast: no reset, everything returns to normal operation with no loss of control. Swashplate level.
2. Medium: temporary loss of control (feels like a hiccup). All activity returns to normal when voltage is brought back up; the gyro does not reset. Swashplate level
3.Long: complete loss of control, gyro resets (all leds blink), then fails to initialize (blinking blue led). There's no response from any of the servos, or any other input. Swashplate is frozen in an odd position, cyclic servos buzz, tail servo unpowered. A power cycling is required to restore normal operation.

Bonus testing: I also wanted to see what happened if voltage was maintained at marginal levels for a longer period of time. I set and maintained the input to the system at 3.44-3.45 V. All servos were randomly twitching. There was still response to inputs, but the swash was not level and tail servo wanted to be at the fore extreme (ccw pro). Stick inputs resulted in correct response, but upon release, the servos returned to the previous behavior. Increasing voltage above 4V returned the gyro to normal operation (Swashplate level, tail centered).
Thanks for sharing this, Dr.M.

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Originally Posted by Dr.M View Post
Which is unfortunate, since there is nothing else to ground on that bird...
What about grounding the case of the gyro?
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Old Dec 22, 2012, 07:21 PM
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Originally Posted by beenflying View Post
Thanks for sharing this, Dr.M.


What about grounding the case of the gyro?
It's worth a try. Though I don't think it will help, since the ESD pulse most likely travels to the gyro PCB via one of the wires...
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Old Dec 23, 2012, 12:03 AM
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Originally Posted by Dr.M View Post
It's worth a try. Though I don't think it will help, since the ESD pulse most likely travels to the gyro PCB via one of the wires...
beengflying, I have done gyro case grounding and it didn't help.

I think that voltage variations and instability, apart from the CX-ZYX will also affect the RX.
I have landed my 450 twice with full left cyclic, due to a stuck right cyclic servo
and I was also experiencing frequent random tail kicks of more than 90 degrees.

Grounding barely helped healing these symptoms, but installing a boost capacitor was the solution.
I have not experienced any problem afterwards after hundrends of flights, without any grounding. (*)

Lets keep in mind that the capacitor, apart from eliminating voltage variations,
it also acts as a shortcut for any unwanted ac signal appearing in the voltage powering
the RX and the CX-ZYX. And any ESD produces a broad range of unwanted high ac frequencies.

I tend to adopt the thinking, that ESD symtoms can be partially eliminated by grounding,
since electric charges are produced in all the rotating parts of the heli.
My experience shows that together with any grounding to prevent ES buildup,
one should protect the electronics against the Discharges with a capacitor near the RX and CX-ZYX.
This capacitor(C), together with the toroid inductor(L) placed near the plug from the BEC,
constitute a LC filter which "tries" to keep a steady current and a steady voltage powering the RX and the FBL unit.


(*) Fellows at the field have done the same with great results, protecting their
Spektrum and JR RXs. Those with Futaba RXs haven't experienced any of
those problems ... It seems that somehow Futaba does a better job protecting their RX from bad supply voltage ...
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