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Help a noob? Please. BEC, ESC, New Servo for Flux.
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knuckle
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Help a noob? Please. BEC, ESC, New Servo for Flux. - 11.20.2012, 01:34 PM

Confused here. I have an HPI Savage Flux HP. My life was not painful enough, so I decided to get back into RC. I have a Savage Flux HP. I've converted it to TCS 1/5 scale chassis. I'm replacing the servo as it hardly moves the wheels, and I have a $150 JR High Voltage, High Torque 7.4 Volt Servo

Now, I don't know much about electronics. I'm using all the stock electronics. The only difference will be the servo. What I'd like to do, to get the max torque / speed out of the servo is to use a 7.4 Receiver pack.

However since the Flux ESC is now powering the receiver, I'm not sure if I can just hook up a 7.4V 2s Lipo pack to the receiver. Do I need to disconnect the power from the ESC > Receiver first (red wire)?

Can the receiver handle the 7.4 volts? What is the stock voltage that the receiver gets from the ESC. I've emailed Castle, and HPI. No response in 5 days.

Do I need to use a BEC as well? I wish I knew what I was doing.

Any help appreciated.
   
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suicideneil
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11.20.2012, 06:06 PM

Quote:
Originally Posted by knuckle View Post
I wish I knew what I was doing.

Any help appreciated.
It's your lucky day:



The esc outputs 6v to the rx and servo normally, so you would indeed need to use an external BEC to power the servo directly to give it more than that; unless you have a HV rx then you can't just feed more than 6v to it ( and the servo ) otherwise the rx will go pop.

Nice simple wiring though, just grab a cheap rx connector or pig tail to get the extra connector you need ( you can just plug the signal wire and pin directly into the rx, bit it's rather fiddly ).

For a BEC, I would suggest the Castle 6s 10amp BEC- there are others around though it's hard to find one that will output more than 3-5amps and 6v.
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knuckle
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11.20.2012, 07:13 PM

Thanks my question is though, if my servo does 7.4 volts, and you said the Castle BEC in the link, which I have only does 6v max?

The link says it does more.

djustable Output Voltage
4.8V to 9 volts.


So if my servo handles 7.4V, I use the castle link to set the BEC to 7.4 correct? I don't need to disable the BEC on the ESC either right? There's no power going out of it anyhow to the receiver.

I did get a Spectrum radio system, which has a receiver that can handle the higher voltage.

Last edited by knuckle; 11.20.2012 at 07:15 PM.
   
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11.20.2012, 10:46 PM

Yes, use the castle link to adjust the output of the bec.

Since you have a spectrum rx you could just wire it directly to the rx (NO bec) and pull the red wire from the esc. This would be the easiest way.

If you do as suicideneil diagramed you are correct, you leave the red wire from the esc intact.


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knuckle
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11.20.2012, 11:43 PM

Quote:
Originally Posted by _paralyzed_ View Post
Yes, use the castle link to adjust the output of the bec.

Since you have a spectrum rx you could just wire it directly to the rx (NO bec) and pull the red wire from the esc. This would be the easiest way.

If you do as suicideneil diagramed you are correct, you leave the red wire from the esc intact.

Not sure what you mean. You said wire what to the RX?

I'm just wondering why in all the other diagrams I've seen, the wire from the ESC > RX, the red wire removed.

The settings on my ESC are adjustable, but you can't turn the ESC BEC off, the lowest it will go is 5V.

So I'm just wondering if sending 5V to the RX from the ESC, plus the 7.4V from the external BEC will be too much for the receiver.
   
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knuckle
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11.21.2012, 12:49 AM

Guys, in the lower right of this, it's saying not to wire it the way you showed in the diagram?

   
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suicideneil
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11.21.2012, 10:31 AM

Quote:
Originally Posted by knuckle View Post
Guys, in the lower right of this, it's saying not to wire it the way you showed in the diagram?
That applies only if you are using 6s lipo total; if you are using 4-5s, then it's fine.

If you are using 6 lipo however, then just wire the bec to one of the batteries to get power, not both ( like the larger diagram shows ).

If your rx is capable of more than 6v input however ( hv model ), then you can just do like Harold ( paralyzed ) said and connect the external BEC directly to the rx, set for 7.2v, then remove the small red wire from the escs rx cable to disable the escs built-in bec circuit:



the external bec will power the rx & servo in this case, the esc just sends the signal to control left & right + throttle.
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knuckle
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11.21.2012, 10:56 AM

Man this is getting more confusing by the minute. I went and wired the external BEC as the original diagram here. I'm using two 3S batteries = 6S total.

My servo is 7.4V and my receiver, which is a spectrum, can handle 9.6V
   
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rcs2022
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11.21.2012, 02:36 PM

Had almost similar issue http://www.rc-monster.com/forum/showthread.php?t=31551

Hope you got it solved.
   
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11.21.2012, 09:50 PM

In your original post you stated you were using a separate 2s 7.4v rx pack. I based my recommendations on that.


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knuckle
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11.21.2012, 10:42 PM

I can't f'n get anything right. I hope I don't have to rewire the damn thing. I wired it just like the diagram.

I have 2 packs
3s x 2 = 6s total

I was contemplating a 7.4 receiver pack, but changed my mind. I mean I bought a BEC, might as well use it.

Last edited by knuckle; 11.22.2012 at 12:19 AM.
   
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rcs2022
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11.22.2012, 12:47 AM

Which diagram are you referring to?
   
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11.22.2012, 08:21 PM

   
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11.23.2012, 12:16 AM

OK, both castle BECs are rated to 6S, so connecting the BEC over both batteries is 100% OK. It is also OK to connect to just one battery (the ground side battery).

Now, as for connecting the ESC BEC and the external BEC.

If you just connected the External BEC at 7.4V to the RX AND the ESC BEC to the RX at 5V it WON'T be 12.4V. What will happen is the external bec with try to power the ESC BEC and burn it or BOTH of them out. So you can't connect 2 BECs at a different voltage ever (not really recommended to connect 2 at some voltage either unless you know what you're doing, it has to do with the style of BEC, either switching or not, but that doesn't matter in this case).

So now since you don't want to use the ESC BEC anymore, and you can't just turn it off (standard for ESCs). All you have to do is remove the red wire for the lead going from the ESC to the RX. All that red wire does is give the RX and consequently the servos and anything connected to the RX the 5V. So removing the red wire (or using an extension with no red wire is great since you don't damage anything in case you need to use the ESC BEC again) basically turns off the ESC BEC.

Now the tricky part with your situation comes in with the high voltage servo. If you don't have a high voltage RX you can't run 7.4V to it. In this case you'd use the ESC BEC to power the RX by leaving the red wire connected. But now you can't just connect the external BEC to the RX since it already has voltage. To account for this, you would wire it up as in the first photo shared here.

BUT, since you have a RX that can handle the 7.4V (I DON'T KNOW IF YOU DO, YOU need to verify this yourself). It makes it easier since you can power the RX and servo from the same supply, the 7.4V from the BEC.

And since you have a castle BEC, it's good up to 6S lipo, so you can connect across the whole battery connection.

So, simply wire it up like this (if you have a high voltage RX that can handle the voltage you want the BEC to put out).



Hope I explained enough, please post back with specific questions if you have anymore, vague ones are pretty tough to answer. :D

Edit: Just noticed you said you already wired it like the diagram above me. That is totally fine too. As long as you have a RX that can handle the voltage you want the BEC to put out (sounds like you do). Looks like you're all set! Just make sure that the BEC ground is on the ESC ground as well. I hope my long post at least explained better as to why the wired it is OK.


OFNA Jammin CRT.5e, Savage Flux HP, MBX5Te, SCX10, Multirotors, foam planes

Last edited by brainanator; 11.23.2012 at 12:28 AM.
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rcs2022
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11.23.2012, 12:54 AM

I had the same issue before, just try to wire it up using the two batteries, it worked for me. At the time I didn't understand the term "ground side battery" ensure the negative wired to the bec is the same negative powering the esc.
   
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