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250 Class Electric Helicopters 250 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 06-06-2015, 10:11 AM   #1 (permalink)
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Default Brown out or signal loss?

Hi.

I need your help with something please.

During flight my 250 looses power and control for a split second, but I immediately regain power and control. After landing the satellite led flashes as well as all the led's on the 3GX.

If I disconnect power to the esc and reconnect it the satellite led is solid but all the led's on the 3GX still flashes and it does not initialize.

When disconnecting and reconnecting the battery again all works as it should.

What I need to know is, is this a sign of a brown out on the ecs or just signal loss?

Thanks,
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Old 06-06-2015, 01:44 PM   #2 (permalink)
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Morne, that is a brown out. If it is signal loss only, then only the sat will flash. The 3GX also flashing shows that is has reset.
If you still have the original Align ESC remove it and hit it with a 10lb hammer. That will fix it.
Then fit a Talon 15.
The align built in BEC is crappy. My 250 had its first crash ever on flight #97 due to esc failure. The Talon now has in excess of 170 flights.
Remember if you are running V5 on your 3GX it will work you servos harder which in turn causes more current draw.
The problems you are having with your 250 lately may very well all be directly related to your align esc and built in bec. The symptoms certainly all concur.
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Old 06-06-2015, 10:27 PM   #3 (permalink)
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Quote:
Originally Posted by TR450ZS View Post
Morne, that is a brown out. If it is signal loss only, then only the sat will flash. The 3GX also flashing shows that is has reset.
The RX doesn't flash due to signal loss. It means the receiver hit a low voltage cutoff and it triggered a reset. You can lose signal all day long and the lights won't flash (you can check this by turning off your transmitter anytime and leaving the RX powered [although you might want to try this on a receiver that isn't hooked up to anything]).

I do agree that the internal BEC is likely the culprit. It only commands 2 amps max and I doubt it was ever intended to run digitals, but if you can turn down the refresh rate on the servos down to 50 Hz then they should draw a little less current, although I don't have exact figures you can expect.
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Old 06-07-2015, 12:02 AM   #4 (permalink)
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Thanks for the replies.

Allan I knew you were going to say that.

If it is a brown out, would the 3GX not initialize after power is restored?

I did a bench test and by disconnecting the satellite and then reconnecting it I could duplicate the results. This makes me think it is a faulty satellite cable.
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Old 06-07-2015, 12:54 AM   #5 (permalink)
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Let me guess. Not using a Futaba. Right.
You got a JR or spek...etc. The 250 is a beltdrive. Mega static. Get back on google and you will find what to do. Ground strap, full 2x rx's, maybe capacitor, maybe seperate bec. Good luck.
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Old 06-07-2015, 02:37 AM   #6 (permalink)
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It is a DFC PRO with TT drive. Radio is Spektrum and he has one sat connected directly to the 3GX. With this setup, if you get a brief signal loss while flying, then the sat will be flashing when you land.
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TREX 250 PRO,Talon15, GPRO, Zeal ----TREX 500 EFL PRO, GPRO, RAILS ----2x TREX 450PRO V2, 1xGPRO&1xBRAIN, Talon35, RAIL , Zeal ---- SAVOX powered TREX500 EFL in Roban scale UH1-N ---- TREX 600 EFL PRO, GPRO, RAILS ---- DX9 ----
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Old 06-07-2015, 07:28 AM   #7 (permalink)
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I've had static problems before in my bigger machines. Usually all that happens is the controls blanking out for a few milliseconds and it comes right back on when the rpm drops (the field collapses or dissipates) or the link reestablishes itself.

When you have a power failure then it will take a while for the FBL unit to reinitialize if it even had time before it hits the ground, if it even reinitializes at all (they usually have to sit flat and level for a while)

I bet it's the internal BEC dropping out under load causing the issue.
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Old 06-07-2015, 07:34 AM   #8 (permalink)
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What ESC are you running on there? If its the stock Align one its known to cause problems, especially if you're using satellites.
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Old 06-07-2015, 07:45 AM   #9 (permalink)
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Quote:
Originally Posted by TR450ZS View Post
With this setup, if you get a brief signal loss while flying, then the sat will be flashing when you land.
I'm not sure you understand what the blinking lights mean.

There is an internal 3.3V buck regulator that uses the line voltage (usually between 4.8V and 8.4V) to power the receive section of the satellite or receiver itself. When the total line voltage drops below a threshold of the buck voltage regulator, the receiver initializes an internal reset or reboot. Usually this takes a few milliseconds until the voltage goes back up or the power comes back on. The comparator circuit will be able to tell that it's out of sync with the transmitter's master clock pulse until the capacitor discharges (this can take several minutes if the RX unpowered). Once the capacitor discharges, the RX will come on without the blinking lights, but again, this could take several to tens of seconds to happen.

Proof of concept is to turn on the radio and receiver. Now unplug the RX, wait a second or two, plug it back in. The lights will flash. You can leave the RX off for however long you want and turn it back on and the lights won't stop flashing until you turn off the TX and it selects two new channels to operate on. This is because the blinking lights are pointing out a power interruption, not a signal loss.

Now turn off the TX and the RX and then back on again to establish a new link. Leaving the RX, now turn off the radio instead... you will observe no blinking lights. Turn the TX back on. Still no blinking lights. You can even stir the sticks while powering the TX on and off and you can see how quickly it reestablishes the RF link (It's actually incredibly fast).
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Old 06-09-2015, 02:14 AM   #10 (permalink)
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Just some feedback.

I swopped out the satellite receiver cable and tested it on the bench and in flight.

10 packs later and it did not happen again, this leads me to believe that the cable got damaged when I did some other work on my heli.

In conclusion.
It was neither signal loss nor a brown out, but power loss to the receiver due to a faulty cable.

Thanks again for everyone's reply.
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Old 06-09-2015, 02:49 AM   #11 (permalink)
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such an easy fix. Glad it's sorted
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TREX 250 PRO,Talon15, GPRO, Zeal ----TREX 500 EFL PRO, GPRO, RAILS ----2x TREX 450PRO V2, 1xGPRO&1xBRAIN, Talon35, RAIL , Zeal ---- SAVOX powered TREX500 EFL in Roban scale UH1-N ---- TREX 600 EFL PRO, GPRO, RAILS ---- DX9 ----
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Old 06-09-2015, 06:07 PM   #12 (permalink)
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I've had that happen. I actually had the sat port go bad on one of my AR7200BXs. Cost me a set of 690 blades in the process.
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Old 06-10-2015, 07:30 PM   #13 (permalink)
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Quote:
Originally Posted by skunkworx View Post
I'm not sure you understand what the blinking lights mean.

There is an internal 3.3V buck regulator that uses the line voltage (usually between 4.8V and 8.4V) to power the receive section of the satellite or receiver itself. When the total line voltage drops below a threshold of the buck voltage regulator, the receiver initializes an internal reset or reboot. Usually this takes a few milliseconds until the voltage goes back up or the power comes back on. The comparator circuit will be able to tell that it's out of sync with the transmitter's master clock pulse until the capacitor discharges (this can take several minutes if the RX unpowered). Once the capacitor discharges, the RX will come on without the blinking lights, but again, this could take several to tens of seconds to happen.

Proof of concept is to turn on the radio and receiver. Now unplug the RX, wait a second or two, plug it back in. The lights will flash. You can leave the RX off for however long you want and turn it back on and the lights won't stop flashing until you turn off the TX and it selects two new channels to operate on. This is because the blinking lights are pointing out a power interruption, not a signal loss.

Now turn off the TX and the RX and then back on again to establish a new link. Leaving the RX, now turn off the radio instead... you will observe no blinking lights. Turn the TX back on. Still no blinking lights. You can even stir the sticks while powering the TX on and off and you can see how quickly it reestablishes the RF link (It's actually incredibly fast).
The above is only true if you are using DSM2. If you are using DSMx, the LEDs DO NOT blink to indicate a brown out. The receiver will reconnect after the brownout but the LED will come back on steady.

I did some experimenting on DSMx to see how fast the receiver reconnects after a power interruption. It can vary from nearly instantaneously to several seconds. After 750mS of no signal, most ESCs will shut down. They will restart as soon as the signal reappears, but if you have soft start enabled you will be on the ground before you notice it spooling back up.

And another wrinkle..... make dead sure you have a genuine Spektrum satellite receiver. I have two counterfeit sats (purchased off Ebay in non-OEM packaging) and they can take anywhere from zero to infinity to reconnect after a brownout. If your satellite is counterfeit, all bets are off.

Paul
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Old 06-10-2015, 08:48 PM   #14 (permalink)
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Correct, they removed the indicator programming on the DSMX receivers. Probably because there were too many cases of confusion, such as this, that they decided it was better without it (people kept blaming the radio link for their problems when it was a power issue all along). Of course, we could sit here and split hairs over placing blame, but that's not my intent. If there are blinking lights on a Spectrum or DSM/DSM2 receiver then it is a power interruption specifically, not a signal loss.
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Old 06-11-2015, 06:11 AM   #15 (permalink)
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I believe the actual reason the LEDs don't blink on recovery from brownout on DSMx is that there is no way for the software to know that it has experienced a brownout.

On DSM2, if a brownout occurs the receiver will see its transmitter on the same two channels when it recovers. This allows rapid reconnect and also tells the receiver that it was power cycled but the transmitter was not so it flashes its LEDs.

With DSMx, the transmitter frequency is continuously hopping and there is no way for the receiver to detect that it was power cycled but the transmitter was not.

Leastways that is how I understand the DSM2 and DSMx systems. It is too bad that Spektrum doesn't publish a clear, concise troubleshooting guide. There is much mis-information out there that makes post crash investigation very difficult. A clear concise system explanation would also be useful as a guide to what to look for after an incident and BEFORE power is removed.

Paul
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Old 06-12-2015, 01:57 PM   #16 (permalink)
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I can't be 100% certain about it, but my guess is it's an op-amp that triggers the reset. It has nothing to do with the incoming signal or lack thereof (hence my suggestion to try power it all on and turn off the TX and back on again = no blinking lights). The DSMX was probably built without that feature turned on, but the circuitry is (most likely) still there. they use identical hardware and chipsets to do both functions (hence why you can bind them in DSM2 or DSMX mode), so it's simply the protocol that has changed.
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Old 06-12-2015, 02:17 PM   #17 (permalink)
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Quote:
Originally Posted by skunkworx View Post
I can't be 100% certain about it, but my guess is it's an op-amp that triggers the reset. It has nothing to do with the incoming signal or lack thereof (hence my suggestion to try power it all on and turn off the TX and back on again = no blinking lights). The DSMX was probably built without that feature turned on, but the circuitry is (most likely) still there. they use identical hardware and chipsets to do both functions (hence why you can bind them in DSM2 or DSMX mode), so it's simply the protocol that has changed.
A brownout is defined as the receiver rebooting while the transmitter remains powered, so merely monitoring the reset pin isn't sufficient because the uP is in reset on initial powerup as well as following a real brownout. The software can't tell the difference unless it also knows whether the transmitter started from power off.

I don't think the difference in brownout detection / indication between DSM2 and DSMx has much to do with hardware. Like I said earlier, with DSM2 if the receiver loses power and then reboots before it has forgotten the two channels it negotiated with the transmitter (15 seconds?), it will find its transmitter on the same two channels when it reboots. That is how it knows it power cycled but the transmitter did not. If the transmitter also power cycled, it would most likely settle on two different channels.

With DSMx, the transmitter is constantly hopping so that method of brownout detection is not available. My guess is that the reconnect time on DSMx is the length of time it takes for the transmitter to randomly hop to whatever channel the receiver monitors on powerup. At that point, they synchronize and they are off to the races.

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