Wiring BEC directly to servo?

[BobTeagle]

Ok, you guys have convinced me to add an external BEC. Please see below and correct me if I am wrong.

If I wire the BEC directly to the servo, I take only the servo's orange control lead to the reciver and then wire the servo's posi and neg leads directly to the external BEC.

But what about motor fans and LED lights? Since I am bypassing the receiver with the external BEC wired straight to the servo, then I can still take the ESC's internal BEC power wires to the receiver to operate the other devices. Right?

Thanks in advance.."thumbsup"

 

[redsawacs]

Excellent choice, I personally think it is better to straight wire your servo so you dont lose voltage inside the receiver (RX). Not to mention you dont have to worry about killing the rx if you pump too much voltage into it. (some receivers dont like anything over 6-7v.)

Correct. When you straight wire the BEC to the servo, you are putting your battery (bec) voltage into the servo and not the receiver. So, the receiver still needs voltage to run anything and everything else wired into it. So, the ESC voltage will feed that.

Remember, ESC voltage goes into the RX and then the servo gets its power from there. (In normal configuration). So, if you're feeding the servo power from another source, you still need voltage into the RX from somewhere.

In the case where you run the BEC directly into the receiver, you'll have to remove the power wire from the ESC so you do not over volt the RX.

One more thing to mention, in some cases when you wire the BEC directly to the servo, you'll have to run a ground jumper into the receiver on the servo input. I had to do that on my crawler to stop the glitching.

Recap - signal wire from servo into servo port on RX and power leads from servo into BEC...you can make a harness that will make it easier if you dont want to solder the wires together. You will see 3 wires coming from the BEC into your plug but the "signal" wire coming from the BEC is dead.

 

[BobTeagle]

Thanks Redsawacs!

 

[Fordfreak95]

One more thing to mention, in some cases when you wire the BEC directly to the servo, you'll have to run a ground jumper into the receiver on the servo input. I had to do that on my crawler to stop the glitching.

So splice the ground from the BEC out wires? Or grab it from any ground wire and jump it over to the servo RX plug.

 

[Barndog Racing]

I have done this many times on my other cars and for some reason on the XL when I plugged it in it fried the ground wire from the esc to the rx.So then I wired it like castle says because my rx can take up to 9v and that time it fried the ground on the bec and the new ground on the rx,that was with the power wire removed from the esc.Now i'm waiting for the new esc cable to get here to see what the hell is going on.Sorry to hijack but nobody seems to know whats wrong with it I talked with castle twice yesterday.

 

[redsawacs]

I wouldn't consider this a hijack, you're bringing to light a potential issue with wiring in a BEC. My questions would be, what receiver are you using and have you tried using a different one or using that receiver in anything else? Possible bad receiver. The other question is, have you checked the voltage flow through the system? Sounds like you have voltage flowing back through the RX on the ground side.

 

[Barndog Racing]

I have tried the rx with a different esc and it works then I plugged in the servo with no bec and it works fine.I did use the axial esc with no servo and it powered up the car fine .The issue was when I ran the signal with a jumper ground that melted the esc wire.then when I wired it like castle suggests it melted the esc wire and bec ground wire.I also checked the voltage out of each wire with the bec plugged in and its fine.

 

[BobTeagle]

Just to clarify, the ground you are referring to is the negative lead from the servo. Right?

So it would wire as follows:
Signal lead and negative from servo to receiver.
Positive lead and negative from servo to external BEC

And by bypassing the receiver with the positive external BEC wire this allows my esc to power the receiver and the external BEC only powers the servo..

I have a harness made but I wanted to double check. Sorry for redundancy. I am a little shaken by the guy who has fried his electronics.

 

[redsawacs]

Dont let it bother you - Barndog has a defective part somewhere in his system.

Yes, you have it correct...Here is a picture, for reference, of the BEC I installed in my crawler using a quick disconnect harness and wiring it direcly to the servo. Big picture for detail:




I tapped the ground from the servo with a 1" ground wire and plugged it into the open ground port on the steering port of the receiver. Notice the "signal" wire from the BEC goes no where? This is because there is only a + and - coming out of the BEC but they used a "servo plug" to make it easy to plug into the receiver and not mix up the polarity....that "signal wire" is completely inert or unused

 

[Szczerba]

I have done my own setup, as shown above, with servo wire crimpers and plugs.

Get one of these if you want a plug and play (minus BEC soldering to battery lead)

Holmes Hobbies LLC

...

 

[BobTeagle]

THX guys! I made a harness of my own using futaba style connecters for easy disconnection. I have worked in electronics/telecommunications over the years and I am familiar with basic circuits, but I did not want to mess this up. I really appreciate your help!

I really hope this improves servo performance. I have a Savox sa1230mg which has a 6v limit but puts out 500oz of torque at 6v. My Hobbywing 150a esc says it puts out 6v @ 3a but I have had a couple of brown outs. Even with a glicthbuster cap.

The BEC I have is Turnigy SBEC and is rated at 6v @ 5amps

 

[Barndog Racing]

Yes Castle said to send it in so I did.I did get the new esc wire today and plugged it in to the rx with the servo and there are no problems there just an issue with the bec.Looks good guys!I at least got to drive it today to test it all out and adjust toe and camber."thumbsup"

 

[BobTeagle]

Dont let it bother you - Barndog has a defective part somewhere in his system.

Yes, you have it correct...Here is a picture, for reference, of the BEC I installed in my crawler using a quick disconnect harness and wiring it direcly to the servo. Big picture for detail:

I sure do appreciate the help here! I got it all wired up today and it turned out great. Best part is my switch on my ESC is still fuctional.. If you wire per castle's diagram it bypasses the switch.