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Old Feb 20, 2015, 12:37 PM
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United States, KS, Olathe
Joined Jan 2015
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Help!
Y cabling servos causes brown out

Help!

I feel like I am missing something very simple, but it is causing me to bang my head against the wall.

I purchased two AXN Floater Jets for my father and I to re-learn RC planes, eventually getting into FPV. During construction of the first AXN, we were just wrapping up and had a brown out / freak out during the final servo to rx wiring. During the build, we tested each electronic piece as we glued them into place, they all worked fine. Anyhow, here is what is going on:

- when the two aileron servos are Y connected and power is plugged in, the servos immediately go into a bind and the esc will reset. It acts as though a ground and power are touching. I am using the factory y cable supplied with the plane.

Since this started, I have done the following to troubleshoot:

- I have used a different rx (from my unbuilt plane)
- I have used a different y cable (from my unbuilt plane)
- I have used two different servos (from my unbuilt plane)
- I have created my own Y cable (3 red, 3 black, 3 white connected)

In each attempt above, when the two servos are Y connected, it Browns Out.

Further testing:

- I can connect each servo independently to the RX on a different channel and they work fine!
- I have removed all other servos from the test (just using the two aileron or two uninstalled servos on the bench with the RX).
- I am powering everything through my lipo and esc, using the bec into the RX. Everything works fine, until I introduce the y cable for two servos into one channel.

Equipment used:
- Turnigy 50090m servos
- v8fr-ii receiver
- Taranis x9d Plus TX
- Turnigy AE25A ESC.

I am completely lost at this point... Any help would be extremely appreciated.

Mike
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Old Feb 20, 2015, 01:50 PM
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Letchworth, Great Britain (UK)
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Since you've done so many substitutions, and always get the same result, it's really a puzzle. Have you tried plugging the Y-leaded servos into a different channel in the receiver, just to see what happens? And have you been able to measure the BEC output voltage and current while this is happening?
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Old Feb 20, 2015, 03:38 PM
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USA, GA, Marietta
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Quote:
Originally Posted by ZenOhSix View Post
Help!

I feel like I am missing something very simple, but it is causing me to bang my head against the wall.

I purchased two AXN Floater Jets for my father and I to re-learn RC planes, eventually getting into FPV. During construction of the first AXN, we were just wrapping up and had a brown out / freak out during the final servo to rx wiring. During the build, we tested each electronic piece as we glued them into place, they all worked fine. Anyhow, here is what is going on:

- when the two aileron servos are Y connected and power is plugged in, the servos immediately go into a bind and the esc will reset.

Please define "bind" and ESC reset. Do you mean the servos travel to one end and stop? What about the ESC reset? What does it do? Can you measure the BEC voltage? Have you tried using a seperate RX battery rather than the BEC in the ESC?

It acts as though a ground and power are touching. I am using the factory y cable supplied with the plane.

Since this started, I have done the following to troubleshoot:

- I have used a different rx (from my unbuilt plane)
- I have used a different y cable (from my unbuilt plane)
- I have used two different servos (from my unbuilt plane)
- I have created my own Y cable (3 red, 3 black, 3 white connected)

In each attempt above, when the two servos are Y connected, it Browns Out.

Further testing:

- I can connect each servo independently to the RX on a different channel and they work fine!
- I have removed all other servos from the test (just using the two aileron or two uninstalled servos on the bench with the RX).
- I am powering everything through my lipo and esc, using the bec into the RX. Everything works fine, until I introduce the y cable for two servos into one channel.

You have changed everything except the ESC. Give that a try. (Grasping at straws here ).

What happens if only one servo is connected to the "Y" cable? No servos? (more straws ).


Equipment used:
- Turnigy 50090m servos
- v8fr-ii receiver
- Taranis x9d Plus TX
- Turnigy AE25A ESC.

I am completely lost at this point... Any help would be extremely appreciated.

Mike
A final thought/question. What battery are you using? Fully charged? If you have a wattmeter what does it telll you (voltage and current)?

Glen
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Last edited by ggcrandall1; Feb 20, 2015 at 03:44 PM.
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Old Feb 21, 2015, 02:21 AM
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United States, KS, Olathe
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Thank you for your ideas. I used my second ESC (not connected to the motor) and that solved the problem. The esc on the plane currently is hard wired to the motor (didn't have any bullet connectors when I originally put it in), so I am not sure yet if I will have an issue again once I connect the new esc to the motor again. Yet, I was able to bench test my two additional servos and esc directly with the RX, and it worked perfectly. Once I swapped back to the other ESC that is in the plane - boom... Issue.

I am wondering if the BEC has a bad circuit or something? I tested the voltage on both, and the "bad" esc's bec shows .5v less than the good one (same battery, back to back swap test). So something is off...

Ugh!

Thanks,
Mike
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Old Feb 21, 2015, 02:40 AM
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Letchworth, Great Britain (UK)
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Ahhh ... I missed the fact that you hadn't yet swapped the ESC in your checks

So, yes, looks like the original ESC's BEC is no good. Was the .5v difference under load, or with no load? I would guess it's voltage will sag much further under load, which is causing your receiver to shut down.
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Old Feb 21, 2015, 03:57 AM
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USA, GA, Marietta
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Quote:
Originally Posted by ZenOhSix View Post
Thank you for your ideas. I used my second ESC (not connected to the motor) and that solved the problem. The esc on the plane currently is hard wired to the motor (didn't have any bullet connectors when I originally put it in), so I am not sure yet if I will have an issue again once I connect the new esc to the motor again. Yet, I was able to bench test my two additional servos and esc directly with the RX, and it worked perfectly. Once I swapped back to the other ESC that is in the plane - boom... Issue.

I am wondering if the BEC has a bad circuit or something? I tested the voltage on both, and the "bad" esc's bec shows .5v less than the good one (same battery, back to back swap test). So something is off...

for future reference: It would be better to state both voltages rather than saying one was .5V less. The actural voltages may be meaningfull.

Ugh!

Thanks,
Mike
Most happy you got it sorted out.

Glen
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Old Feb 21, 2015, 05:05 PM
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United States, KS, Olathe
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Ok, still having issues. I have a lot more information now. I have never seen anything like this; need some advise.

As I originally mentioned, I have double of everything and even more batteries and receivers. I have extended the testing, and here is what I found:

- all RXs work.
- All ESCs work.
- ESC output BEC voltage is 5.08v, for a single test battery. This is measured across both Turnigy ESCs (measured at the BEC servo connector,).

Original symptoms are the same. When plugging in a battery, the servos will instantly bind (jumping to full deflection). Start up procedure is typical to normal RC.. Power up the TX (wait 20 seconds) and then plug in the battery to the ESC.

What I have found the problem to be is a charged battery vs. a non charged battery. Simply put, the electronics freak when plugging in a 98% tcs charged battery. Any battery around 70 (need more testing, did some random discharge tests) will work fine. This is where all of the confusion comes into play.

I took a brand new 3s out of the box and it was measured at 50% charge on my HobbyKing watt meter, at something like 11.5v. I took the same model battery out of a new box as well, and charged it to 98% or so. It reads 12.55v or so on the pack. Both BEC output voltages read 5.08v - regardless of battery charge percent.

Plugging in the 90%+ charged battery = instant servo freak and bind
Plugging in the 70% or less charged battery = works perfectly.

Plane outputs 210w at 18 or so amps full throttle. Everything works fine... Except the battery charge percentage. I am using a balancer to charge (have a nice IOS charger) and the watt meter has almost all cells matching (I.e., 1 cell is .01 less than the other two).

So... Help?
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Old Feb 21, 2015, 07:21 PM
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Quote:
Originally Posted by ZenOhSix View Post
Ok, still having issues. I have a lot more information now. I have never seen anything like this; need some advise.

As I originally mentioned, I have double of everything and even more batteries and receivers. I have extended the testing, and here is what I found:

- all RXs work.
- All ESCs work.
- ESC output BEC voltage is 5.08v, for a single test battery. This is measured across both Turnigy ESCs (measured at the BEC servo connector,).

Original symptoms are the same. When plugging in a battery, the servos will instantly bind (jumping to full deflection).

Only the aileron servos as per your first post, or all the servos? Originally it was just the servos conected via a Y cable.

Start up procedure is typical to normal RC.. Power up the TX (wait 20 seconds) and then plug in the battery to the ESC.

What I have found the problem to be is a charged battery vs. a non charged battery. Simply put, the electronics freak when plugging in a 98% tcs charged battery. Any battery around 70 (need more testing, did some random discharge tests) will work fine. This is where all of the confusion comes into play.

I took a brand new 3s out of the box and it was measured at 50% charge on my HobbyKing watt meter, at something like 11.5v. I took the same model battery out of a new box as well, and charged it to 98% or so. It reads 12.55v or so on the pack. Both BEC output voltages read 5.08v - regardless of battery charge percent.

Plugging in the 90%+ charged battery = instant servo freak and bind
Plugging in the 70% or less charged battery = works perfectly.

Plane outputs 210w at 18 or so amps full throttle. Everything works fine... Except the battery charge percentage. I am using a balancer to charge (have a nice IOS charger) and the watt meter has almost all cells matching (I.e., 1 cell is .01 less than the other two).

So... Help?
Another question. A couple of posts ago you said it worked with a different ESC. So have you installed that ESC in the plane?

Another thought. Have you tried disabling the BEC in the ESC and using a receiver battery instead? To disable the BEC, pull the red wire out of the ESC to Rx connector. Connect the Rx battery to any unused servo port on the Rx.

Glen
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Old Feb 21, 2015, 09:17 PM
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Glen,

Thanks for the suggestion. I will try the single RX battery option. In regards to the other equipment, what it comes down to (pure guess, but what I think) is that some equipment has more internal resistance than others, therefore the "upset servos" that would occur, changes a little based on overall battery charge and the amount of gear plugged in.

For example, I can take a fully charged battery and plug in two servos and there is no binding. As soon as I add a 3rd, it will freak. I can change the ESC, battery (as long as it is on the same charge level), RX, and Servos - and have the binding / brown out issue occur. Some gear seems to be more tolerant.

Originally when I thought it was the ESC, I had a bad test because I used a different battery. It is the same model/capacity/etc - just grabbed the wrong one (was 1/2 charged). Yet, after retesting, I find that ESC is a little more tolerant. When I had a battery at 92% charged, one ESC would brown out with all the servos plugged in, while the other one didn't until I gave a lot of fast stick movement, flexing each servo concurrently. Then it bound.

I then charged the battery a tad more (94%) and both ESCs on plug in would brown out.

Just seems odd that total charged capacity is causing the problem?
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Old Feb 22, 2015, 02:16 AM
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Letchworth, Great Britain (UK)
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Battery voltage (i.e. state of charge) could still be indicating that it's a fault with the BEC in your ESC because with a linear BEC then more volts = more heat. Is your BEC voltage being measured with nothing connected and running? You really need to monitor the BEC voltage and current while things are happening, to see what's going on; but at $2.99 per ESC perhaps it's not worth the hassle.

A separate Rx battery, or even a good quality stand-alone BEC, is a good suggestion to confirm whether it's a BEC problem.
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Old Feb 22, 2015, 09:49 AM
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Y-cable may be defective/miswired. Try another one.
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Old Feb 25, 2015, 03:23 AM
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United States, KS, Olathe
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Confirmed; Bad ESC BEC on BOTH units received from HobbyKing.

The ESC is the Turnigy AE-25A Brushless ESC.

I did as recommended here, removing the red power wire from the throttle lead (via an extension cable) from the ESC. I then used a 4.8v battery and powered the X8R RX through another channel. Everything worked perfectly. I swapped out both ESCs and both are confirmed to have issues with a fully charged LIPO battery when using the ESCs BEC.

I ordered two new 30a ESCs to replace these two units. My next step is letting HK know that they have a bad production run (else, it is odd that I have two bad units that were brand new).

Thanks for all of the assistance.

Mike
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