BEC question

[Bob Abell 2Participant @bobabell2]

Let’s have a recap

[Bob Abell 2Participant @bobabell2]

I would like to settle a nagging question, please…..

With the BEC system, the power to the reciever is sent down the servo leads?

The receiver has two throttle leads and a rudder lead

One throttle lead has the middle wire cut….This leaves two leads with power to the receiver ?

Is this correct?

Bob

[ashley needhamParticipant @ashleyneedham69188]

Almost. Yes the BEC battery supply is fed down a servo lead.

I am assuming you mean that you have THREE leads into the receiver. One rudder, two throttle?

The BEC power will be coming down one of the ESC leads. If you have two ESC leads, one needs to have the centre wire cut.

.. The rudder servo lead does not supply power so can be discounted from the issue.

This leaves us with the two leads into the RX from the ESC`s, ONE of which has the centre wire disabled.

I hope I have interpreted your question correctly.

Ashley

[Bob Abell 2Participant @bobabell2]

You are right of course, Ashley

I had forgotten about that!

So it was just a silly question….Sorry chaps

Bob

[ashley needhamParticipant @ashleyneedham69188]

Theres nothing wrong with getting it right, if you know what I mean. It is very easy to think you have got something, but in reality you have it all mucked up! ESPECIALLY when posts meander on a bit.

Ashley

[Bob Abell 2Participant @bobabell2]

Thank you, Ashley

While you are still there….The BEC comes down the uncut lead along with the throttle signals?

That's a bit tricky?

Bob

[ashley needhamParticipant @ashleyneedham69188]

Nope, In a nutshell, the signal is on the outer wires only, the centre one supplies the BEC.

The must be more to it than that, but thats the practicality of it. The issue of having more than one BEC supply coming down two leads has to do with the "other"issues, but again we dont need to know that.

You are probably not the only one struggling with this, and you should continue to ask away until we hit on the right explanation, ie, the one that you fully understand. There is nothing wrong with alternative explanations.

I wonder if DM has a nice drawing to illustrate this, picture paints a fahzand werds etc etc

Ashley

[Bob Abell 2Participant @bobabell2]

I believe the battery, on non BEC systems, can be plugged into any of the servo slots

ie….Not just in the slot marked…" B "

Bob

[Colin BishopModerator @colinbishop34627]

Dave Milbourn has an article on BEC's in the forthcoming August issue of the magazine with several nice diagrams which you can all cut out and pin to your workshop wall or to any convenient parts of your anatomy!

Bob, the BEC from the speed controller supplies power so it is the power lead that needs to be disconnected at the receiver plug. as Ashley says, this is usually the centre lead and just to confirm it is the power lead it will be a RED wire.

Colin

[Bob Abell 2Participant @bobabell2]

What would you say, when referring to an ESC…….This means?…..

………" Absolute short circuit and motor overload protection" mean?

Does it mean it can not be burnt out and that it would switch itself off somehow?

Bob

[Malcolm FraryParticipant @malcolmfrary95515]

Most ESCs nowadays contain a BEC or Battery Eliminator Circuit to provide a nice steady regulated 5 volts to work the receiver and anything plugged into it from the main battery, hence eliminating the need for a receiver battery. The same BEC also powers its own ESCs internal control circuits. When you use a second ESC that also has a BEC, one needs its red (center) wire disconnecting. Not all regulators give the exact same voltage out, and when presented with another voltage, they both try to regulate, argue, and fail miserably, even if its only a very few microvolts difference. The "disconnected" one is, however, still supplying power to its own ESC control circuit.

The short circuit protection means that there is a bit of circuit in there checking by one means or another that whatever is beyond the ESC, if it tries to demand more current than the ESC is capable of supplying, will cause the ESC to stop trying. Just as there are many ways, so they say, of skinning a cat, there are several ways of spotting when too much current is flowing, and several ways of taming it. All have their pros and cons, most do a good job, and I while I think that they are a good thing, I would not rely on it implicitly. Sensible choice of motor and prop and good wiring practice beat any electronic protection. It does not protect against internal faults within the ESC, so a fuse between battery and ESC is still a good idea.

[Bob Abell 2Participant @bobabell2]

Thank you, Malcom

I was only trying to get support for the feeble ESC on Brutus!

See latest cock and bull story, in the Brutus thread

Bob

[Gareth JonesParticipant @garethjones79649]

Bob,

My understanding is that the Mtroniks speed controllers fitted in Brutus have a current limiter circuit, set at some point above the nominal rating of the controller. If you short circuit the output of the controller (the blue and yellow wires) or your motor stalls because the propeller is jammed by weed, or you just have a propeller that is too large and try to run at full throttle, the current limiter will come into play and prevent the speed controller from being destroyed by excessive current. If the fault persists for some time the controller will start to get hot and I believe at that point the controller will switch itself off be means of an internal thermal switch.

As Malcolm says, the ESC can protect itself against some of the faults that a user might experience in operating a model. However it can't protect itself against faults within the controller itself and I dont think it is protected against reversing the polarity of the power supply, ie the red and black leads. Hence it is always wise to fit a fuse between the battery and controller, just in case the controller fails, for whatever reason, or you short out the power supply leads somewhere. Mtroniks recommend a fuse about 5 amps below the maximum rating of the ESC.

I have found, by practical experience in Shemarah that if I connect the main battery connectors the wrong way round the 20 amp fuse blows before the 25 amp ESC is damaged. I hasten to add this was not a deliberate test, just incompetence on my part, but I did learn something from it.

I have had several Mtroniks controllers fail in my models over the years. Even though I usually cut off the Tamiya connector on the power supply leads and fit my own connectors, usually ring tags or an XT60 type, Mtroniks have always replaced the faulty units without question. The information in the first paragraph abovewas gleaned from a discussion I had with one of their technical specialists following an ESC failure.

You mentioned in one of your posts, I think on the Brutus thread, that the 20 amp fuse I fitted had also blown. I did not realise that had happened, did you discover it after I had left? I cannot remember what rating the speed controllers were in Brutus but if they were rated at 10 or 15 amps, it is possible that the current limiter will have begun to take effect when we did the full throttle in the water test on the LH motor and it was drawing about 22 amps.

Gareth

[Bob Abell 2Participant @bobabell2]

Thank you, Gareth

Just got some good news from Howes

The speed controllers are rated at 50amps!…..And they have a built in cutout that switches off and comes back on again, at some point

So we are sailing!

Bob

[captainslogParticipant @captainslog]

why do we use bec in boats anyway? its great for aircraft as it cuts the weight down by eliminitang a reciever pack. but surely in run of the mill boats on a pond that require ballast anyway dont need it? therefor for beginners to the hobby it cuts out all the electrickery questins which will confuse them even more. myself, i have never used bec in a boat and after reading this thread i am more confused about it than i ever was. sorry

[Colin BishopModerator @colinbishop34627]

If you have the current (August) edition of Model Boats you will see that Dave Milbourn has covered the subject pretty definitively in his BEC article. It is pretty simple really!

Colin

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by captainslog on 06/07/2014 20:54:24:

why do we use bec in boats anyway? its great for aircraft as it cuts the weight down by eliminitang a reciever pack. but surely in run of the mill boats on a pond that require ballast anyway dont need it? therefor for beginners to the hobby it cuts out all the electrickery questins which will confuse them even more. myself, i have never used bec in a boat and after reading this thread i am more confused about it than i ever was. sorry

Eliminating the RX battery means one less battery to forget to charge or have go wrong on its own account. Normally, you see that if the model has slowed down, it is time to come in, with a separate RX battery quite often the first indication that the RX battery is too low is that control is lost.

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