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Author Topic: ESC witha BEC and a RX with a BEC  (Read 2972 times)

roycv

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ESC witha BEC and a RX with a BEC
« on: June 20, 2015, 08:00:48 AM »

Hi all, I have a Chinese cheap esc with a switch, I am not sure what the switch does. 

Does it turn the esc on and off or the BEC on and off.

What happens is I turn on Tx,  switch on ESC switch and get 3 beeps and it all works.
I have what seemed like a nice setup but forgot that the Rx had a BEC in it.
 
After about an hour the rudder servo cooked and is kaput now.  The RX is still working but not sure of the Rx BEC circuit, but I do have a spare Rx.
 I am running on 40M AM and all my Rx's are BEC

I am currently finding what works etc using 27M non BEC Rx.

Do I have to cut or withdraw the red wire from the ESC Rx connector? 
If I do this I do not see how the Rx will get any power to run its' own BEC.  I do not know how to disable the Rx BEC.
All responses appreciated.
Roy
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barriew

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Re: ESC witha BEC and a RX with a BEC
« Reply #1 on: June 20, 2015, 09:07:45 AM »

The receiver BEC just means that you can feed it with more than 4.8 - 5 volts, and it will only output 5 volts to servos etc connected to it. The BEC in the ESC supplies 5 volts to the receiver, so you don't need a separate receiver battery.


Barrie
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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #2 on: June 20, 2015, 09:34:03 AM »

The switch turns the receiver on and off if you are using the speed controller's BEC to power the system.
The only things plugged into the receiver should be the ESC and the rudder servo. Don't connect anything to the receiver's "Batt" socket.
If you have a voltmeter it would be a good idea to measure the voltage across the +ve and -ve pins of the receiver output. It should be within a whisker of 5.0v - in which case it wasn't excess voltage which killed your servo. The fact that it took an hour to die rather suggests that it was overloaded so check that the rudder is free to rotate in both directions without binding or tightening up. The connections to the servo disc and tiller arm should also be free to rotate without being sloppy. If those connections are OK then we have to assume that there was a sudden failure of a component inside it or a wire came lose etc.
If the motor isn't burned out then 'dead' servos can come in handy as motor/gearbox combos for things like radar sweep arms or small winches, so don't bin it!
DM
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malcolmfrary

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Re: ESC witha BEC and a RX with a BEC
« Reply #3 on: June 20, 2015, 10:11:14 AM »

I have used crippled servos as parts mines for ages, but, a few days ago the magic smoke came out of one.  I tried the motor with a battery and it rotated slowly.  Measuring the resistance, it was 0.1 ohms.  Normally I would expect to see about 10+ ohms.  Just goes to show that one problem can create more.
I have seen a few adverts on fleabay for ESCs that say they have a 6 volt BEC.  Without buying one and testing there is no telling whether the 6 is a fact or casual typing by the seller.  From what I have seen of BEC RXs, the BEC lives between the "batt" connection and the rest of the system.  Any higher voltage being applied via the other connections will not be regulated, and will get fed to everything.  If whatever is plugged in there is designed with a 5 volt max in mind, things will fail.  If they are getting more power and being caused to work harder than intended, again, they will fail.
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #4 on: June 20, 2015, 10:53:58 AM »

Hi all, thanks for the responses.
The rudder is nice and free to turn and there is no binding in the connection.

I have now checked the failed esc on a 27M non bec Rx.  This is not working as an esc, and it is not delivering any voltage to the Rx to enable a rudder servo (new one) to move.  You have to switch to on position for the Rx to work.
When a working esc is switched on there are 3 tones, with the failed ones there is just one beep.

When sorting out the problem at home I connected a similar esc in place of the failed one which I had used else where and now this does not work with the same symptoms as the first one.

I am curently with a 27M setup and no smells!

The rudder servo was a very powerful one but did not have much work to do.  I have now fitted a standard one.

The start of the problem was after coming off the lake and running very well.  I was checking duration and original motor current in bath was 4.5 -5 amps.  The batteriy is a 3300mAh 7.2 volts driving a vintage Hectoperm with interference capacitors fitted (3 off).

I was quite pleased with the first trip on the lake.  I decided to test everything, brought the boat in and changed to a new battery, the boat went off at speed got 20 yards out and stopped.
Boat drifted in fortunately.
On getting home and testing I do not think the rudder servo made the 2nd. ESC fail as I checked the failed servo on the 27m rig and it did not work but after disconnecting the Rx was still working.

I am on my 3rd. and last esc and am loathe to go back to 40M bec Rx in case it all happens again.
Does anyone else run an ESC with BEC and a Rx with bec?
 
I remember in the dim and distant past I had a boat with a frizzled wire, I changed to a non bec esc and no more problems.

I have to pass the model boat back to its' owners this afternoon hence the hurry on my part.
kind regards Roy

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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #5 on: June 20, 2015, 12:05:12 PM »

Your reply isn't clear on one point; did you have anything plugged into the receiver besides the speed controller and the rudder servo?
DM
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #6 on: June 20, 2015, 01:04:06 PM »

Hi Inertia, there was nothing else plugged in when checking esc except a working servo. This was a test for if esc was supplying battery power, which it was not.

By the way I plugged in an old gold Hitec esc into another Hitec bec Rx and with drive battery connected I had to use a separate 4.8 volt battery pack to get it to work.  I thought the bec would take power from the drive battery
regards Roy
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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #7 on: June 20, 2015, 01:32:13 PM »

Roy

You're not having a great deal of luck are you, m'duck? My advice would be to ignore the BEC in the receiver; to disable the BEC in the ESC by removing the red wire from the plug (See diagram here - http://www.action-electronics.co.uk/wd.php - Scroll down the list to "Disabling BEC ESCs"), and use your separate 4-cell battery pack to power the receiver.

As Malcolm Frary will tell you, I hold BECs to be the work of the devil.................

DM
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malcolmfrary

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Re: ESC witha BEC and a RX with a BEC
« Reply #8 on: June 20, 2015, 01:58:42 PM »

Quote
By the way I plugged in an old gold Hitec esc into another Hitec bec Rx and with drive battery connected I had to use a separate 4.8 volt battery pack to get it to work.  I thought the bec would take power from the drive battery
regards Roy
The Hitec gold brick, and any other non-BEC ESC, has no path for the main battery to get to the RX connections, so a separate battery is needed.  The fact that there is a BEC in the RX is neither here nor there, if it doesn't get any volts in, it can't give any volts out.
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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #9 on: June 20, 2015, 02:08:48 PM »

Malc's original posting said to treat the BEC logo on a receiver as decoration. This is more or less what I advised - but far more succinct. You might find the first article on this list helpful. http://www.action-electronics.co.uk/art.php
DM



 
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #10 on: June 20, 2015, 07:18:07 PM »

Hi all, again thanks for your thoughts.  I used to make my own BEC's on veroboard and zener diodes etc.  They still work.  Lately because of more interest towards sailing models I have not done so much 'power boating'. 

As far as the model boat goes I eventually came up with a Hitec gold esc and back to the 40m set up.  The Hitec esc is 10 amp and should cope easily.and a separate 4 cell battery pack.  Seems to work well and is fairly standard.

I read the article, thanks for pointing me at that.
Puzzled with what happened to the servo, it was Chinese, but what is'nt! but just 1 hour of life is a bit tough.  I used an old Futaba one as a replacement.
Thanks all for your interest.
regards Roy
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #11 on: June 22, 2015, 10:13:56 AM »

Hi Malcolm I have been following the other thread on 2 feeds to Rx.
I have been tidying up and testing what works etc.
I checked with 2 different Tx's, the crystals have worked before.  Drive motor battery 7.2 volts.
I am still puzzled as to why everything worked for an hour, I change the drive battery and it runs for a few seconds then fails!

After this and the the initial replacement of radio gear to see what was wrong, the damage is as follows.
All Failed!

2 off 40M AM rx's with BEC
2 off esc with BEC.
1 off servo.

Earlier advice that it does not matter did not work for me.
I think this is too high a price to pay without definite advice on removing the red wire from the ESC.  I do not know whether my esc's were switched ones, which apparently could make a difference.

So I now have 2 Tx's (2 ch AM 40 Mhz) but no rx's.  I have 2 FM 40 Mhz 3 ch sets and numerous rx's.  PLus several 27 Mhz sets which as they do not have bec's now look most appealing!

regards Roy
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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #12 on: June 22, 2015, 10:48:45 AM »

Earlier advice that it does not matter did not work for me.
I think this is too high a price to pay without definite advice on removing the red wire from the ESC.  I do not know whether my esc's were switched ones, which apparently could make a difference.

I can't believe that you have managed to kill all of this equipment by doing nothing wrong, Roy. I'm not sure whether or not you've misunderstood what's already been said  (and lord knows that's plenty) but here is my final offering - in pictures. The top two diagrams show the difference between a switched ESC and and a non-switched one. It is immaterial whether the thing has a linear regulator or a UBEC (switch mode regulator) inside it.
The bottom diagram shows how you can use a voltmeter to test whether or not your ESC is providing a voltage to the receiver. If the ESC has a switch then try it in both positions.
If you fail to get a voltage then the ESC is not BEC-equipped and you need a separate battery pack for the receiver.
If you do get a voltage then the thing has BEC and UNDER NO CIRCUMSTANCES should you connect any other power source directly to the receiver.
As for removing a wire to disable a BEC, you only need to do that if you either have more than one BEC device or another power source connected e.g. a receiver battery pack.
"End of", as they say.
Dave M
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #13 on: June 22, 2015, 11:14:46 AM »

Hi Dave thank you for a comprehensive response.  To my personal chagrin I was an electronics specialist on ancient computers, did not seem to be much help here though!
When I said "switched" in my previous message I did mean switched mode power supply, on thinking about it this is more likely to be in a brushless esc.

But my esc's do have a mechanical switch which has to be in the "on" position for everything to work. 

If I have 2 of these esc's on my receiver what would your advice be?   As I was planning to make a simple model (Glynn Guest push tug) with "tank" control of two paddle wheels.  I am thinking remove one red wire from one esc, is that right?
I think my remaing rx's are all non-bec.

I shall try your advice  as soon as the pollen levels drop,  (this could be a 3 pill day for me!)
.kind regards Roy
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inertia

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Re: ESC witha BEC and a RX with a BEC
« Reply #14 on: June 22, 2015, 11:47:34 AM »

I wouldn't personally use the BEC on either, Roy. It's given you too much grief already! Disconnect the red wire on BOTH and use a separate battery pack for the receiver. That way if you're using two main batteries (one for each of the motors) then you won't be draining one faster than the other.
The alternative is to disable one of the BECs by removing the red wire from its plug.
Like I always say, please yourself.
Dave M
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roycv

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Re: ESC witha BEC and a RX with a BEC
« Reply #15 on: June 22, 2015, 12:46:13 PM »

Thanks Dave most helpful and appreciated.  This is a good place for the good guys, my first stop every day.

I think I shall buy some cheap 27Mhz rx's (no BEC's), as I have enough crystals and Tx's to last me out.
Thanks to all who responded.
Roy
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