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New Member, Reinstalling Super Cub LP Electronics: Worried about Power Failure

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New Member, Reinstalling Super Cub LP Electronics: Worried about Power Failure

Old 08-14-2013, 02:50 PM
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brockac12
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Question New Member, Reinstalling Super Cub LP Electronics: Worried about Power Failure

Hello, I'm new to RC Planes and have recently bought a Hobbyzone Super Cub LP RTF. I have learned to fly it quite well, but now I would like to upgrade the electronics, and add ailerons and lights. I'm attempting to understand the Voltage, Amps, and Watts so I can choose all parts myself. I think I'm on the right track, but I am still a beginner.

My main concern is that the BEC is only giving 5V to the Receiver, but the servos and Lights all have a max of 6V. Would this cause a power failure in flight, or would it work at all? Any Suggestions would be helpful!

I created this electronics schematic to visually understand all the parts I will need. Thanks for any comments! (Parts are from Hobbyking.com)

Click image for larger version

Name:	Super Cub Future Wire Schematic.PNG
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Size:	42.2 KB
ID:	170249

Last edited by brockac12; 08-14-2013 at 10:47 PM.
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Old 08-14-2013, 04:12 PM
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Hi and welcome to WF. Looking at your schematic, I'm wondering about your Turnigy(?) 30A ESC. You indicated you're kind of new to the electronics part, so are you aware there are ESC's for brushed motors, and ESC's for brushless? Just asking as your diagram didn't specify it.

If you're going this far, maybe you want to go with a brushless motor. There are many threads on upgrading the legendary SuperCub, here and on other forums. I'm sure there would be plenty of motor suggestions out there.

As far as learning the electronics, you can find some good reading here.
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Old 08-14-2013, 04:43 PM
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brockac12
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xmech2k,

Thanks for your comment! Yes, I am aware that there are ESC's for brushed and brushless motors. I should have specified that the one I mentioned is for Brushed motors.
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Old 08-17-2013, 03:08 PM
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AEAJR
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Originally Posted by brockac12 View Post
Hello, I'm new to RC Planes and have recently bought a Hobbyzone Super Cub LP RTF. I have learned to fly it quite well, but now I would like to upgrade the electronics, and add ailerons and lights. I'm attempting to understand the Voltage, Amps, and Watts so I can choose all parts myself. I think I'm on the right track, but I am still a beginner.

My main concern is that the BEC is only giving 5V to the Receiver, but the servos and Lights all have a max of 6V. Would this cause a power failure in flight, or would it work at all? Any Suggestions would be helpful!

I created this electronics schematic to visually understand all the parts I will need. Thanks for any comments! (Parts are from Hobbyking.com)

Attachment 170249
EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
http://www.wattflyer.com/forums/showthread.php?t=31071

So you issue will be can the BEC put out enough amperage to handle two more servos AND the lights. The answer is ... maybe.

How much current are the light pulling?

I would not be concerned with 4 micro servos and receiver running off a 1 A BEC. however some BEC have different outputs depending on type (linear vs. switching) and the voltage of the battery pack.

As discussed in the e-book above, some BEC are basically using resistance to lower the battery pack voltage to 5V for the servos and receiver. The higher the battery pack voltage the more they heat up and the less they can put out.

So, does your ESC/BEC say it puts out 1A at 11.1V input from the battery pack? Take a look.


If those lights pull less than 50 ma, I would not worry about it. If they are pulling more than 100 ma, then I might be concerned.

hook it up with the 4 servos and test it. Move your servos while providing some resistance to the surfaces. This simulates air loads while in flight. Do this for 10 minutes on the ground with the motor running at idle. If it works OK for 5 minutes you are probably OK.

Now fly it - stay over long grass during the test flight. I expect you will be fine.

NOW hook up the lights. Do the same test at home. Then a test flight over the tall grass.


BTW, as to your diagram: The LVC is part of the ESC, unless you have some special set-up.
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Old 08-17-2013, 04:35 PM
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brockac12
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Originally Posted by AEAJR View Post
EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
http://www.wattflyer.com/forums/showthread.php?t=31071

So you issue will be can the BEC put out enough amperage to handle two more servos AND the lights. The answer is ... maybe.

How much current are the light pulling?

I would not be concerned with 4 micro servos and receiver running off a 1 A BEC. however some BEC have different outputs depending on type (linear vs. switching) and the voltage of the battery pack.

As discussed in the e-book above, some BEC are basically using resistance to lower the battery pack voltage to 5V for the servos and receiver. The higher the battery pack voltage the more they heat up and the less they can put out.

So, does your ESC/BEC say it puts out 1A at 11.1V input from the battery pack? Take a look.


If those lights pull less than 50 ma, I would not worry about it. If they are pulling more than 100 ma, then I might be concerned.

hook it up with the 4 servos and test it. Move your servos while providing some resistance to the surfaces. This simulates air loads while in flight. Do this for 10 minutes on the ground with the motor running at idle. If it works OK for 5 minutes you are probably OK.

Now fly it - stay over long grass during the test flight. I expect you will be fine.

NOW hook up the lights. Do the same test at home. Then a test flight over the tall grass.


BTW, as to your diagram: The LVC is part of the ESC, unless you have some special set-up.

Thanks for that info! The lights pull 30mA. So I think it will be fine.
As for the ESC, all it says is the BEC is 5V/1A, so I guess that means it is only putting out 1A at 5V, not 11.1V. I have ordered the parts, so I'll just have to wait and see if it all works.

Here is an updated Diagram:
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Old 08-17-2013, 06:33 PM
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AEAJR
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The ESC is taking in 11.1 V from the battery. It passes that through to the motor. It steps it down to 5V for the receiver and servos.
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Old 08-17-2013, 07:11 PM
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Originally Posted by brockac12 View Post
Thanks for that info! The lights pull 30mA. So I think it will be fine.
As for the ESC, all it says is the BEC is 5V/1A, so I guess that means it is only putting out 1A at 5V, not 11.1V. I have ordered the parts, so I'll just have to wait and see if it all works.
IMHO you need to get yourself either a better ESC or a separate 'ubec' to supply power to your RC and lights. 1 Amp is very poor and you really need much more if you are running extra stuff like light, even without the lights I'd not trust it on any model of mine.

Look for an ESC that has a 'switching mode' BEC with at least 3-4A output. Or better yet a stands alone ubEC with similar or higher output.

The BEC is the single most critical component on the plane because if it fails to deliver enough power you lose all control.
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Old 08-17-2013, 08:04 PM
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AEAJR
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Originally Posted by JetPlaneFlyer View Post
IMHO you need to get yourself either a better ESC or a separate 'ubec' to supply power to your RC and lights. 1 Amp is very poor and you really need much more if you are running extra stuff like light, even without the lights I'd not trust it on any model of mine.

Look for an ESC that has a 'switching mode' BEC with at least 3-4A output. Or better yet a stands alone ubEC with similar or higher output.

The BEC is the single most critical component on the plane because if it fails to deliver enough power you lose all control.
Not sure what you base that upon. the Super cub is not a fast plane so the pressure on the surfaces is not bad. The Parkzone Radian Pro has 6 servos and a 2.4 receiver and the BEC is 750 mah.

I think he will be fine with the 1A Bec.
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Old 08-17-2013, 08:52 PM
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Where do i get it from?...

Typical max current for a 9-12g analogue servo is 150 mA multiply by four once ailerons are added = 600mA (0.6A). Add the 300mA (0.3A) for the lights and a bit for the receiver itself and you are right up to 1A. Plus and VERY importantly; the rating for linear BEC's is based on 2s operation. On 3s due to higher power dissipation and heat generation the amp limit will be about halved (or less). On a 3s battery the max BEC rating will be 0.5A at the most.

According to Parkzone the Radian has a 3.5A switch mode BEC in the ESC: http://www.parkzone.com/Products/Def...odID=EFLA1030B Possibly the earlier versions had the lower output BEC that you mention, but if that was the case then PZ must have decided to upgrade it, which tells it's own story.

Anyway, maybe it would be ok, maybe not. Personally the BEC is one component where I prefer to have a generous safety margin built in, but it's free world.



.

Last edited by JetPlaneFlyer; 08-17-2013 at 09:55 PM.
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Old 08-17-2013, 10:07 PM
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AEAJR
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Humm, they upgraded the BEC in the Radian Pro I see. The original BEC in the radian pro was 750 mah. Good move on Parkzone's part. I didn't know.

The lights, as poted by the OP are 30 ma, not 300.

So, you say 4 servos, stalled, will pull 600 mah. 70 for the receiver and 30 for the lights = 700.

Of course that assumes that all 4 servos are stalled, pulling max current and all at the same time. Typical running current is probably closer to 75 mah and not having all the servos at that level all the time. If we assume all 4 are running at that rate that would be 300 (which I think is still high) 70 for the receiver and 30 for the lights is 400 mah, about 80% of the rating of 500 mah you suggest for 3 cell battery.

I still think he will be OK.

But, unless we put a meter and record it in flight, we won't know for sure.

This is the receiver/ESC brick that comes in that SuperCub. No specs
http://www.horizonhobby.com/products...-lp-HBZ7357#t3



Brockac12,

I suggest you do the following. Go to one of the BIG ParkZone Super Cub threads. Provide all the information and ask if anyone has done the upgrades you are planning. See if they had any problems.

JetPlaneFlyer raises some valid points. And while he and I disagree, we are disagreeing on opinions, not facts. We don't really know what those servos are going to draw in flight, we are guessing. And he feels that the BEC won't really deliver 1A on a 3 cell, but he doesn't really know because there are no specs on that ESC/BEC other than what you are reading off the package.

Asking people who have done it will give you a better framework to judge if the BEC can handle the load.
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Old 08-17-2013, 11:18 PM
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Yes, there is certainly some uncertainty in the 'calculation' but as the consequence of an underrated BEC is certain loss of control and crash I prefer to err on the safe side. Especially true these days when ESC's with powerful switching BEC's are availably very cheaply, as are 4-5A uBECs. To be honest even if someone else said they were flying on that set up with no problem I'd still not do it, just not worth the risk IMHO.

The reduction on the output of the linear BEC when operated at 3s or above has a sound basis. In fact I might easily be over-estimating it's capability at 0.5A on 3s, the truth may be closer to 1/4 of it's label rating:

From Dimension Engineering web site:

I have a 3A BEC in my speed control - is that enough?
What is a switching BEC?
It is very common for speed controls to have BECs rated at 2 or 3A. However, what the manufacturers do not tell you is that this rating is only true for an input voltage of 6V. The BEC on your speed control is what engineers call a 'linear voltage regulator'. It works by burning up excess voltage and turning it into heat. The higher the input voltage, the more heat gets produced. If there is too much heat, then the BEC will either fry, or shut down! The result of this is that in real world situations, if you are running a 3S lithium battery pack, your ESC's BEC will only be able to provide about 0.5A before it overheats. At 4S, most ESC manufacturers don't recommend you use the BEC at all, or at best power two small servos. Dimension Engineering's BECs are a different type of voltage regulator - a switching voltage regulator. They do not care very much about what the input voltage is, and as such can provide your servos with their full current rating all the way up to 8S or more.

Last edited by JetPlaneFlyer; 08-17-2013 at 11:34 PM.
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Old 08-18-2013, 01:35 AM
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http://www.headsuphobby.com/Sky-Powe...-BEC-H-100.htm

30 amp esc with switchmode bec, $14.95, brushless motors are cheap and will double your flight times and power.
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