Running 6v RX with 7.4v steering using what I already have.

[RichardA]

Hi, Newbie post, please could anyone knowledgeable about rc electrics have a look at these diagrams I've made and advise me if what i want to do is going to work or not. The first is my current electrical setup on my TRX4 (stock with traxxas 6v BEC and 25kg steering servo running at 6v). The second is how I think it will work when i fit a HW1080 ESC using the internal BEC at 7.4v to power the steering servo and using the 6v BEC to power the Rx and other servos. My goal is to have separate 6v for the Rx running the diff and 2sp servos, 7.4v for steering and 11.1v for winch / lights / sound accessories. I've read that the ground wires as well as the signal wires must remain to prevent 'ground loop noise' interfering with the signal. I have little electrical knowledge so any advice would be appreciated.
Existing wiring diagram - https://www.dropbox.com/s/kezsmj7w0585r08/TRX4 Existing Wiring.jpg?dl=0
Proposed wiring diagram - https://www.dropbox.com/s/6wewwaitahisw5m/TRX4 Proposed Wiring.jpg?dl=0

 

[Topher Builds]

IMO I’d ditch the traxxas BEC, set the 1080 at 6.0v to power everything else, and then use something like this to power your steering servo

https://www.amainhobbies.com/heyok-performance-no-brainer-bec-heynbradj/p521836

 

[HumboldtEF]

I agree with Topher.

I'll also add that running just 2 different voltages will simplify things otherwise with 3 you'll need 2 BEC's & bypass adapters. Try to match the winch and steering servo voltage wise, there are servos that can handle 12V or you can undervolt your winch.

 

[jwilson2899]

Count me as a 3rd to run an external BEC for your steering servo, and leave the Hobbywing at 6V. This is what I do on my SCX10.3 and it works great. You will want a bypass like the Holmes Hobbies one if you don’t use the BEC that Topher linked to. The one Topher lined will take care of the bypass for you.

 

[Inspector86]

First, Welcome to RCC!

Same here, ditch the Traxxas 2260 BEC it is not programmable, run the HW1080 at 6v to power the receiver and shift servos, install a CC 10a BEC with a HH By-pass adapter to power the steering servo at 7.4v.

HH by-pass adapter:
https://holmeshobbies.com/electronics-and-wiring/wiring-and-wiring-accessories/holmes-hobbies-rx-bypass-adapter.html

CC 10a BEC:
https://holmeshobbies.com/electronics-and-wiring/becs-and-voltage-regulators/castle-creations-bec-10a.html

 

[RichardA]

Hi,
Thanks for the advice it's much appreciated.
I'm going to ditch the traxxas BEC, i've never understood the way it connects as its different to all other BEC's i've looked at.
My winch is one i built from the original traxxas 2075x steering servo by desoldering the circuit board and removing the potentiometer and limit pin so its basically a motor with gears on it, I run that through a HeyOK Performance winch/lights remote at 11.1v 3s, it deadlifts my 11 lb truck with ease. It has no fine control except full spool out / spool in, but its cheap and works or cheaply replaceable when it breaks.
I should of ordered the external BEC from Al direct at HeyOK in Canada when i got the winch/lights remote...oh well another 3 week wait for parts (i'm from the UK)...
Can any of you guys recommend a reasonably priced 7.4v or 12v steering servo i'm using a HD Power 25kg 6.6v one (at 6v) currently.
Again thanks
Richard

 

[RichardA]

Thanks inspector i've got a lot better answers to this question here than on the facebook groups...
i'll look at the CC BEC as well but i may stay brand faithful to Al at HeyOk :ror:
thanks for the advice

 

[Inspector86]

Yeah I have stopped going to fakebook or instacrap groups for anything. There is just far too much mis-information or just flat out intentionally false info there. I have several HeyOk bits here and there, good stuff. Here's another option for you, I'm running a Savox 1230SG steering servo which is rated at 500 oz in at 6v which eliminates the need for a 7.4v power source. With the HW1080 set to 6v it powers everything without any issues and a BEC is just added insurance.

 

[Count0Interrupt]

Just want to add that voltage is just one of two things you need to consider. HW1080 internal BEC can only supply 3A continuously. There's a very good chance any high torque servo will exceed that amperage easily. So while running your servo off HW1080 @ 6V works fine, you probably are not getting the full torque since the BEC can't supply the necessary current.

 

[RichardA]

Cheers guys, so i think ideally stick with 6v for the rx and 3 mini servos from the internal hw1080 BEC (3a). Then get a 7.4v steering servo and say a 7.4v 10a BEC just for that servo with a HH bypass connector or similar. My winch / lights / sound etc run off 3s 11.1v direct from the battery leads switched remotely by the HeyOK controller "thumbsup"

 

[nowinaminite]

I'm not sure if using 2s is an option but I saw this simple mod to run a servo straight from the battery with just a few connectors over on RCgroups by bill_delong

It's important to only have the + coming from the lipo balance connector or you can get glitching.

It depends on your servo being able to handle a fully charged 8.4v lipo too but most 7.4v servos are advertised as being compatible with 2s lipo/6s NIMH and both exceed 7.4v when fresh. I've even run towerpro mg996rs at 8.4v with no worries so an actual high voltage sevro should be fine.

You have to power up the ESC/RC before you plug the servo in too so that it has a signal when it turns on. Otherwise, the servo can veer off to one side.