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Old Jun 28, 2016, 06:22 AM
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Smaller Twin running both BECs?

Built a smaller twin motored plane for FPV. Had and may be having some issues with brownout. Initially I would launch and as I moved the control surfaces one motor would cut out. Needless to say the plane flew sluggish with the motor with the active ESC being reset.

I put on a 2200uf capacitor on an empty receiver port and it seemed to solve the issue. Did have an intermittent loss of control on the last flight resulting in a crash.

Has anyone considered running a two motored plane with both 5 volt power supplies active? I have one clipped off. I realize that both are probably not the same voltage so one would supply the current unless it sagged when the lower voltage 5 volt power supply might take over.

Perhaps in the turn I was doing I somehow got binding of the controls overloading the bec.
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Old Jun 28, 2016, 06:42 AM
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What ESCs are you using, and what are the specs of their BECs? If they're linear BECs you can usually connect them together without any problem. You won't get double the amps capability, but maybe 60% more than a single one.

You can connect two switching BECs provided you put a diode in line with each one so that it won't "back-feed" into the other. An elegant way to achieve this is to use a twin Schottky diode (less voltage drop than a regular diode) and is described in this thread.

But, from your description, of one motor cutting out, it doesn't sound like a "brown-out" to me -- that would result in temporary complete loss of control. I have read recently of instances where some "alternative" receivers are unable to put out a strong enough signal to control two ESCs Y-leaded into a single channel. If that's the issue, connecting one motor to the throttle channel and the other to an AUX channel that's mixed 100% with the throttle channel is the usual solution. It may also simply be that your battery is too small or too old to supply the amps for two motors, and one ESC is hitting lvc before the other one does.

Let us know what your radio equipment is as well, and someone may have a more-specific answer.
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Old Jun 28, 2016, 07:01 AM
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There are no Y cables I'm flying the plane on 2 10amp 1amp BEC simon speed controllers. 4 3.7 gram servos as in the picture.

The combined motors draw 9 amps max and I am flying them at about 4amps. New 1ah 3s battery.

My plan will be to hook up the power wire to the second ESC.

I run inexpensive components and am looking for a work around.

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Old Jun 28, 2016, 10:10 AM
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I would get a small add on switching BEC. I believe the issue is the 1 amp linear BEC on the speed controllers are overloaded, getting too hot and tripping off, resulting in no power to controls. You could buy ESC with at least a 2 amp linear BEC, or new ESC with a switching BEC, but I think the easiest would be to add a switching BEC.

I used the smaller 1.5 amp DE switching BEC with (4) HS-65 servos and never had a issue.

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Old Jun 28, 2016, 12:47 PM
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Thanks for your answer. I might just do that

Also am considering just running it on 2s.

It's an fpv plane and flies at 70percent.
Just checked bec link. It is $30. That isn't happening, too much money.
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Old Jun 28, 2016, 02:14 PM
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You could probably get one a lot cheaper at Hobby King. Or get a Plush 10 amp ESC, I believe they come with a 2 amp bec, I have used either a 10 or 12 amp Plush and haven't hade any issues.

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Old Jun 28, 2016, 02:14 PM
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Quote:
Originally Posted by basicguy View Post
There are no Y cables I'm flying the plane on 2 10amp 1amp BEC simon speed controllers. . . .
If the two ESCs are plugged into the same channel in the receiver, that's a Y-lead

Is this the ESC you've got? If so, the spec says its BEC output is only 3v, not the more-usual 5v. Maybe that's the root of your problem because not many receivers, or servos, are happy with that low voltage. The spec also suggests that the BECs are linear (i.e. it mentions nothing about "switching" or "SBEC"), so hooking them up together should be okay. But, if they're only delivering 3v it's not going to help much, if at all

Quote:
Originally Posted by basicguy View Post
. . . The combined motors draw 9 amps max and I am flying them at about 4amps. New 1ah 3s battery. . . . .
A 1Ah battery should be good for your combined 9A load, provided it's in good condition.
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Old Jun 28, 2016, 04:43 PM
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Those are the speed controllers. I had not noticed that it said 3v bec. I have tested them one puts out 5.00 and the other 4.96 I tested them under load with a 5ohm resistor caused an immediate reset I decided to wire them in parallel and test with the 5ohm resistor the voltage gradually pulled down and did a reset within a minute.

Did a bench test and they lasted 30 seconds of mid throttle running on 3s.

I would assume that the bec is linear.

Basically speed controllers that don't meet their own standard.

I have been using the HK 10 amp basic with similar sized servos but one motor and never had a problem with them.

Have a pile of plush 10 amp speed controllers from last season that died but not from bad BEC.

My solution will be to contact the banggood and put on less junky speed controllers.

I don't run two controllers on the same channel but set up a mix The buss of course is the same but the signals are discreet. At least that is the way I understand on how computer radios work.

Thanks guys.

Quote:
Originally Posted by abenn View Post
If the two ESCs are plugged into the same channel in the receiver, that's a Y-lead

Is this the ESC you've got? If so, the spec says its BEC output is only 3v, not the more-usual 5v. Maybe that's the root of your problem because not many receivers, or servos, are happy with that low voltage. The spec also suggests that the BECs are linear (i.e. it mentions nothing about "switching" or "SBEC"), so hooking them up together should be okay. But, if they're only delivering 3v it's not going to help much, if at all

A 1Ah battery should be good for your combined 9A load, provided it's in good condition.
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Old Jun 29, 2016, 02:05 AM
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Makes you wonder what manufacturers really mean when they quote the amps capability of their products. Maybe yours can put out 1A, but they should be able to do it -- at least for a limited period -- without the voltage sagging so far as to cause a reset. And running two in parallel with the same load indicates that they can't even achieve half their "rated" output for a reasonable period

Did you try them on 2S to see if the result is the same?
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Old Jun 29, 2016, 06:17 AM
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I didn't try it on 2s after seeing the pathetic performance on 3s.

I installed Turnigy 20 amp speed controllers. With the earlier simonk speed controls the motors didnt track well. With the new speed controllers I still noticed that problem. one motor would speed up more than the other. I played with offset to no avail.

My next check was to do a kv check on my new motors as they didn't track rpm well. Using the drill press test I got one motor at 2540kv and the other 2050kv. They are AX 1806N 2500kv motors. The lower reading motor was probably a mislabeled 2100kv motor.

I had purchased 3 of these 2500kv motors. So decided to test the third, previously installed on another airplane and got 2610. The two higher motors are within 3% of each other, You can still hear the variation in rpm as they go out of sync but at least it should pull more evenly.
I think this twin is a pretty decent aircraft. Sure is giving me teething problems though. Vendors really make things worse.
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