Is UBEC required?

by AG Pro | May 14, 2014 | (4) Posted in Tips

Why do we need UBEC ?

Adding UBEC to your electrical system might save you model from an unexpected outcome which may lead to uncontrolled plunge and crash into the ground.

 

 

In the basic electrical system setup of model, the ESC has a built-in BEC. The Li-Po battery is connected to the ESC which will power-up the brushless motor, the radio Rx/receiver and all the servos. Most of the built-in BEC have a limited ability to supply power to the radio Rx/receiver and servos without overheating/glitch. When overheating / glitch occurs, the Rx receiver tends to reboot (restart) itself, leaving you unable to control until the reboot process is completed; usually almost 2 seconds. Sometimes during the reboot process, the servos turn to their max travel and then return to neutral position before you can gain control. This will cause your model to maneuver randomly. Your model is still save when the overheating/glitch happens at high altitude, but you will never know when will it happened.

 

 

Besides the limited ability to supply power, a built-in BEC is commonly a linear type. A switch-mode BEC has a much higher efficiency than a linear type BEC, when using Li-Po battery pack with 4S or more.

  • Linear BEC: a 4S Li-Po battery has a typical voltage of 14.8V, in order to produce BEC output of 5V/1A, the current flow into the BEC is at least 1A, therefore the power on BEC is (14.8V x 1A) = 14.8W. But the useful output power is only (5V x 1A) = 5W, so the efficiency of the BEC is just (5W / 14.8W) x 100% = 33.8%; the remaining power of (14.8W – 5W) = 9.8W is converted to heat energy. This makes the BEC hot and may caused overheating.
  • Switch mode BEC: to produce BEC output of 5V/1A, the current flow into BEC is only 0.38A (actual test data from EMAX UBEC manual). The power on BEC is (14.8V x 0.38A) = 5.6W, therefore the efficiency of the BEC is (5W / 5.6W) x 100% = 89.3%.

 

Therefore, adding UBEC with switch-mode BEC to your system will improve the reliability and performance of the model. There are 2 condition of installing UBEC to the system:

 

1.  The ESC has no built-in BEC.

The UBEC’s input cable is connected to the battery and the output cable to the radio Rx/receiver (batt channel). No change is required in the ESC connection.

 

2.  The ESC has a built-in BEC.

The built-in BEC of the ESC needs to be disabled; remove the red wire from the output cable of the ESC (the three-colours-cable which is connected to the Rx receiver). The UBEC’s input cable can be connected to the same Li-Po batt which is used to power up the ESC. This can be done by connecting the UBEC to the Li-Po batt’s balance plug. The header of the UBEC’s input cable is required to be changed to the proper Li-Po batt’s balance plug header.

 

 

Adding UBEC only adds a couple of grams in weight; in this case EMAX 3A UBEC weights 11 g.

Be safe and confident at your flight.

 

 

D.L. ENGINEERING - The Sky is Home

www.dle-tech.info

support@dle-tech.info

COMMENTS

L3Grasshopper on June 18, 2014
what does UBEC stand for?
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AG Pro on June 19, 2014
BEC stands for Battery Elimination Circuit. UBEC is a stand-alone BEC. Some said it stands for Universal BEC. The UBEC printed manual from EMAX stated that it stands for Ultimate BEC, but there is a PDF manual from EMAX

( http://www.rcworld.com.au/media/downloadspdf/E%20MAX%20ELECTRIC%20MOTORS%20ACCES.ESCS%20AND%20LIPOS%20EMAX%20ESC%20%20-%20EMax%20UBEC%20Instructions%20LP%20Dec%2008.pdf ) , it stated that is stands for Universal BEC.
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stay-fun on June 16, 2014
Well, feel the ESC and if it's hot, it may be overheating.
Another thing: do a range check.
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AG Pro on June 18, 2014
I'll add another thing : set the proper "FAILSAFE". This setting is crucial for flight safety, both for the human and the plane. Failsafe program let the user to predefine each channel position or status when the radio Rx does not receive signal from the Tx. Set the motor off, to prevent the model from keep flying away and lost it. Set the elevator up at considerable amount, to prevent the model from plunging down straight to the ground. Set the ailerons to a neutral position (pos 0 ) to let the model to level the flight by itself and not keep on rolling or turning. You may also try your own config. Hope this help. Fly safe and cheers.
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Willster72 on June 30, 2014
I think I understand FailSafe now lol, good answerđź‘Ť
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AG Pro on June 30, 2014
"FAILSAFE" setting may also be implemented for RTH (Return To Home) / RTL (Return To Launch) in an autopilot system. Once the model has flown out of the max range of the radio Tx/Rx, the "FAILSAFE" will be active and it will call the RTH / RTL program to autonomously fly the model back to HOME position by which was preconfigured by the GPS module.
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oldguy on June 17, 2014
Stuffed a lot of FT foamies in the ground with my DX5i. Ms. Claus brought me a DX8 for Christmas last year and haven't lost a plane since. Blamed it on the receivers. Went all the way to a satellite and still had the problems you are having. Bind it to a friends radio and see if the problem goes away.
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AG Pro on June 18, 2014
LOL. If the problem still exist, wait for Christmas to get a better equipment. Cheers!
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srfnmnk on July 1, 2014
Hey oldguy. Did you ever determine if it was the DX5i that was causing the issue? Did you always use the same receiver? If not, how could it be the receiver causing the same issue over and over? What components in a Tx could cause this, the transmitter itself?
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apnewton on June 16, 2014
Excellent information. Many thanks.
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AG Pro on June 18, 2014
Cheers!
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Bladerunnerxrc on June 16, 2014
In the case of an adjustable BEC, Like the Castle Creations BEC, how would you determine an appropriate voltage for 4x9g servos and a receiver?
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AG Pro on June 18, 2014
You should refer to the spec of the servos for the operating voltage. In order to change the output voltage of the BEC, usually the BEC circuit board have a tiny jumper to select the output voltage. But by referring to the user guide from CC, it stated that a Castle Link USB interface is required to change the output voltage (sold separately).
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Mat Dockerty on June 17, 2014
Your voltage doesn't change no matter how many servos you run but the amperage drawn will increase.
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RobertBerrios on June 16, 2014
Interesting. Last weekend I was flying the FT Versa when suddenly the motor shut off and I lost control. I was flying low so i crashed into the ground. I'm not sure if the servos went out also, because i was pulling up on the TX and the wing didn't go down with the nose. When reaching the Versa everything was alright. I had control over the servos and the motor. Maybe a glitch or interference?
Anyway, after changing the battery my brother took the FT Versa back into the sky. Five minutes in, he experienced the same problem as me. The motor shut down, he really lost servo control and he crashed. This time the propeller broke, but the Versa, as always, was fine. (Nice job, Josh) a couple seconds later, the TX had control again.
The setup was a Spektrum DX5e with AR610 and a Plush 30A ESC.
Has anyone else had this problem with the ESC? Is it overheating?
The Esc is placed in the Powerpod underneath the Versa. I haven't had this problem with another FT plane.
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AG Pro on June 18, 2014
The Plush 30A ESC has a linear type built-in BEC. The linear type BEC is less efficient than switch mode BEC; thus producing more heat which may caused overheating. The ESC also has over-heat protection, this will cause the ESC to turn-off.
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Wearyman on June 20, 2014
I have very rarely had an issue with the Plush ESC's internal BEC. I have run my primary FPV plane with a single Plush 30 amp running 7 servos (5 control, 2 for the P&T rig) for several years now without a failure.

It could have had a thermal shutdown though. Is the ESC out where air can flow over it? if not then it may have gotten too hot and shut off to protect itself.
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AG Pro on June 23, 2014
Agree on the air flow. Sometimes the ESC comes with a heatshrink as the casing, you may also cut-off and remove to make some holes to expose the heatsink of the ESC circuit board.

Please do also consider the air temperature during the flight. Obviously, the ESC tends to overheat more often during hot summer day.
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Is UBEC required?