supplying servo power directly off a battery

[TacoCrawler]

So I'm a tad confused after reading all these "How to" articles.

So the yellow wire is the signal wire for the RX ?
Doesn't it require the ground wire too ?
I'm trying to wire up a 3 wire servo - GRND- and POS+ and the yellow SIGNAL wire.
From my RX leading to the servo powering directly off my 4S Lipo.
I realize the POS+ needs be removed from the RX plug.
But I need this RX ground wire to ground for the Lipo battery as well ?
Assuming the RX needs this too ?
Do I simply splice into the RX's ground wire inserting it into a FST plug and feed it from both POS+ and NEG- of the Lipo battery that way ?
I have a pass through Deans plug with a female JST plug/pigtail.
Was contemplating using a BEC or voltage regulator to limit the voltage (if need be) off a 4S Lipo.
I need to have the capability to switch from 3S to 4S Lipo batteries.
I'm trying to supply the servo with a constant 12.6 volts.
Yes I realize I likely explained it all backwards.

But I think I have the basic understanding down ?

 

[Ots]

Usually we plug the battery into an electronic speed control (ESC) in the case of an RC car. The ESC has a three-wire lead and connector to plug into the 'Throttle" receptacle of the receiver.

This powers the receiver. The output voltage of the ESC should fall into the acceptable voltage range of the receiver. This information is available with the literature that came with the ESC and the receiver or can be found on-line.

The servo's three-wire lead and connector then plug into the appropriate receptacle on the receiver. "Steering" for a servo that will control steering, etc. The output voltage from the receiver should fall into the acceptable voltage range of the servo. This information should have come with the servo or can be found on-line.

Always note the proper polarity when plugging into the receiver. It's usually marked on the receiver as "+," "-" and a symbol for the signal wire (often a square wave).

If there are any voltage incompatibilities they should be resolved before powering.

Hope this helps.

 

[TacoCrawler]

This servo cannot draw power from the the ESC through the RX.
The ESC's BEC voltage will be too low.
The servo's voltage supply must be 12.6 volts. Not the ESC's internal 5.0-6.0 voltage.
Power must be supplied by the primary Lipo battery, directly to the servo.
I don't really need to know how the system works.
I am aware of that generally.

What I need to know is about the install of how this servo goes, regarding
its wiring input to the RX and if both the signal/ground are utilized in the RX ?
I realize that the power (POS+) wire must be disabled (removed).
(And if so) is the servo's ground wire split between the RX and the servo's Lipo battery voltage supply / wiring ?
I'll assume the POS+ lead (from the servo) needs go to the Lipo battery but I'll require a negative - as well.
Can the negative wire leading to/thru the RX be shared for both the RX and power supply ? (battery)

 

[ferp420]

the servo only needs 1 ground wire the receiver only needs a signal wire
your direct power servo should have 2 separate leads the receiver plug that sometimes has a ground also but I sent needed
the other lead should have a jst plug with power and ground
if you got the version with 3wires I'm sorry lol but it should have came with a adaptor already wired right
the issue is the 3 wire units with the adapter seem to glitch hard with some set ups and I don't know of any fixes for that other than a different radio

 

[Ots]

This servo cannot draw power from the the ESC through the RX.
The ESC's BEC voltage will be too low.
The servo's voltage supply must be 12.6 volts. Not the ESC's internal 5.0-6.0 voltage.
Power must be supplied by the primary Lipo battery, directly to the servo.
I don't really need to know how the system works.
I am aware of that generally.

What I need to know is about the install of how this servo goes, regarding
its wiring input to the RX and if both the signal/ground are utilized in the RX ?
I realize that the power (POS+) wire must be disabled (removed).
(And if so) is the servo's ground wire split between the RX and the servo's Lipo battery voltage supply / wiring ?
I'll assume the POS+ lead (from the servo) needs go to the Lipo battery but I'll require a negative - as well.
Can the negative wire leading to/thru the RX be shared for both the RX and power supply ? (battery)

Sorry for trying to be helpful. I guess I misunderstood your question.

 

[TacoCrawler]

I appreciate your input.
But it just wasn't helpful to my inquiry.

I do not have a second power input wire/plug to supply power to this servo.
I only have a 3 wire feed from this servo unless I can figure out the proper
wiring to feed the RX and supply this servo with power directly off the 4S Lipo battery.
I know it can be done, but I'm just not quite sure on how the wiring is.
I know the signal from this servo needs to go to the RX.
I just don't know for sure about the negative wire coming from the servo.
And whether that can share the same ground as the RX.

I really don't want to have to purchase a different servo that has a separate power in lead.
But I will if I must !?
Or if no one can help me in understanding this ?

I know it has been done before.
And I will likely attempt this on my own.
I just wanted some verification before making my attempt.
I'd rather not fry my electronics when attempting this process !

 

[TacoCrawler]

I also need to locate or purchase an in-line Deans plug with two JST female plug ends, with 3-4" of wire on each.
To feed power directly from my Lipo battery.
So far I can only find a single female JST plug, per each Deans in-line plug.
and this would mean a super long extension to reach my Lipo battery.

 

[nightcrawler48]

I believe powering the servo from a dedicated LiPo is the same as powering from a dedicated BEC. The yellow/white signal wire plugs in to the steering channel on the RX. The positive (red) and ground (black) wires are removed from the servo JST plug. The positive (red) and ground (black) of the servo need to be in their own female JST plug. This plug is plugged in to a male JST plug from the BEC or direct power LiPo. In most cases this will work. However, there have been posts here from members who had to add a ground wire to the JST that is plugged in to the RX. I've looked but can't seem to find any of those posts. Maybe someone can have better luck finding them for you.

I use the signal wire (yellow/white) plugged in to the RX with direct power from a BEC on all my RCs and haven't had any issues. I have a variety of servos I use - Hitec, Savox, and a few cheap servos as well. I'm usually at 6V or 7.4V so I don't know if there might be an issue with 12V.

Just out of curiosity, why do you need 2 JST plugs on your Deans passthrough plug?

 

[Panther6834]

The easiest...and, possibly best...way to go about what you're doing is to use a Holmes Hobbies Receiver Bypass Harness. He makes them for single, as well as dual, servos...and, he makes them with, and without, auxiliary power outputs.

Additionally, when using them, there's NO need to cut ANY wires. When you cut a wire...for example, the + wire, then you've just eliminated the ability to use that servo in another vehicle, powered by a receiver. Essentially, the harness "protects" the servo's wiring. Check them out here:

https://www.amainhobbies.com/search?cID=&s=holmes+hobbies+receiver+bypass


~ More peace, love, laughter, & kindness would make the world a MUCH better place

 

[TacoCrawler]

I believe powering the servo from a dedicated LiPo is the same as powering from a dedicated BEC. The yellow/white signal wire plugs in to the steering channel on the RX. The positive (red) and ground (black) wires are removed from the servo JST plug. The positive (red) and ground (black) of the servo need to be in their own female JST plug. This plug is plugged in to a male JST plug from the BEC or direct power LiPo. In most cases this will work. However, there have been posts here from members who had to add a ground wire to the JST that is plugged in to the RX. I've looked but can't seem to find any of those posts. Maybe someone can have better luck finding them for you.

I use the signal wire (yellow/white) plugged in to the RX with direct power from a BEC on all my RCs and haven't had any issues. I have a variety of servos I use - Hitec, Savox, and a few cheap servos as well. I'm usually at 6V or 7.4V so I don't know if there might be an issue with 12V.

Just out of curiosity, why do you need 2 JST plugs on your Deans passthrough plug?

The signal wire carries no voltage. And the POS+ and the negative would be removed from the servo wire as well. The RX will likely be powered/ground at the plug for channel 2 ?

Because I need to power an LED light bar at 7.4 V and I need to power the servo at 12.6 v. Don't have concern though as I have/and will utilize two separate adjustable voltage regulators to obtain the necessary voltage for each individual component.
At least it works out as such in my mind !?

The easiest...and, possibly best...way to go about what you're doing is to use a Holmes Hobbies Receiver Bypass Harness. He makes them for single, as well as dual, servos...and, he makes them with, and without, auxiliary power outputs.


Additionally, when using them, there's NO need to cut ANY wires. When you cut a wire...for example, the + wire, then you've just eliminated the ability to use that servo in another vehicle, powered by a receiver. Essentially, the harness "protects" the servo's wiring. Check them out here:

https://www.amainhobbies.com/search?cID=&s=holmes+hobbies+receiver+bypass


~ More peace, love, laughter, & kindness would make the world a MUCH better place

That's a good idea if it works. I'll have to check that product out.
Though I'm still trying to figure out how the ESC supplies voltage to the RX ?
The ESC's POS+/NEG- is feed into the RX supplying the voltage from the ESC's internal BEC through CH 2 ? Makes sense to me I'll suppose.

So why would I need this HH's by-pass thingy ?
I'll need the servo's POS+/NEG- wires to draw voltage directly from the Lipo battery ?
Not sure that by-pass will allow me the voltage I need for my servo ?
Definately can't push 12.6 volts through that RX !

 

[Panther6834]

The bypass takes the power directly from the battery, to the servo (and, if you get one of the "accessory plug" versions, to the always-on accessory plugged into that. The servo (and accessory, if applicable) receive the same voltage output by the battery. The negative & signal wires provide the signal connection to the servo, while simultaneously preventing power (ie. the positive wire) racing the servo from the receiver. As I said, NO wires are cut...none need to be, as the bypass harness takes care of that.

At the same time, programming the ESC's BEC, whatever other accessories are plugged into the receiver, from Ch3 on up, will receive whatever voltage you programed the BEC for.

And, yes, the harness DOES work. The C3 vehicle I took to Scale Nats in 2020 had 4WS. In setting up the vehicle, I used the dual bypass harness, which powered the front & rear servos from the battery...although, as I was using 3S, and the servos only needed 7.4V, I ran the power through an external BEC, programed to 7.4V. In other words, the chain went from the battery to the external BEC, to the bypass harness, to the two servos. On the Rx end of the servos, the front was on Ch2, and the rear on Ch3. At the same time, with the same battery plugged into the ESC, I programed the ESC's BEC to 6V, and had the winch on Ch4, with individually-controlled lights on Ch5-8.

With this setup, the servos received 7.4V, and the lights, winch, and receiver all received 6V...and, NO wires had to be cut/pulled. The closest 'exception' was the removal of a small portion of the ESC's + & - wiring jacket, close to the ESC, to solder the external BEC. EVERYTHING else became "plug & play" (well, except programming the external BEC for 7.4V...but, that's quick & simple to do).


~ More peace, love, laughter, & kindness would make the world a MUCH better place

 

[TacoCrawler]

I'm going to try and use the HH's by-pass thingy and see it works for me.
Not really sure how it hooks up but does it come with instructions ?
Or are they only on HH's website ?
Order purchased !

 

[Panther6834]

I'm going to try and use the HH's by-pass thingy and see it works for me.

Not really sure how it hooks up but does it come with instructions ?

Or are they only on HH's website ?

Order purchased !

I gave you the link to order from Amain. As for how everyone is connected, I don't remember if instructions were included...but, when you look at it, you'll see it's easy to figure out. If you ordered the version with auxiliary connection, and if I remember correctly, the one you plug the servo into is clearly labeled "Servo", and the other is labeled "Aux"...I think.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

 

[TacoCrawler]

I gave you the link to order from Amain. As for how everyone is connected, I don't remember if instructions were included...but, when you look at it, you'll see it's easy to figure out. If you ordered the version with auxiliary connection, and if I remember correctly, the one you plug the servo into is clearly labeled "Servo", and the other is labeled "Aux"...I think.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

Well the part I ordered clearly has two auxiliary plugs and a servo plug.
I'll hope I can make sense of it !?
Can I use adjustable voltage regulators or must they be BEC's ?
I'm not really sure what's the difference !?

 

[TacoCrawler]

I need these two adj. regulators because I have to supply two different voltages.
One for the servo @ 12.6v and one to my light bar @ 7.4v.
I'll have to hope this will work for me ?

Sorry that I did not use your AMAIN link.
I did not see that until I'd already placed the order with HH's.
And figured I'd just buy it from the source anyway.

 

[Panther6834]

No worries about the link. It was just an Amain search. I assume you'll be powering the vehicle with a 3S pack. Power the servo, through the bypass harness, directly from the 3S. As for powering other things (lightbar, winch, etc), program the ESC's BEC for 7.4V, and pay those accessories from the Rx. Simple.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

 

[TacoCrawler]

No worries about the link. It was just an Amain search. I assume you'll be powering the vehicle with a 3S pack. Power the servo, through the bypass harness, directly from the 3S. As for powering other things (lightbar, winch, etc), program the ESC's BEC for 7.4V, and pay those accessories from the Rx. Simple.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

I have 3s Lipos but I would hope to utilize my 4s Lipos on this.
If it can handle the difference in voltage ?
I usually run 3 or 4s Lipo batteries.
I say batteries because I run two wired parallel.

 

[TacoCrawler]

No worries about the link. It was just an Amain search. I assume you'll be powering the vehicle with a 3S pack. Power the servo, through the bypass harness, directly from the 3S. As for powering other things (lightbar, winch, etc), program the ESC's BEC for 7.4V, and pay those accessories from the Rx. Simple.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

I'm purdy sure my RX or ESC are not programable regarding their BEC voltage values.
Maybe but I'm not aware, nor capable of doing that.
This is going on an RTR with what I presume is cheaply made (costs) electronics.
It's for my SCX6 RTR.
And if it can be programed I'm not aware nor capable of doing that.
I would utilize my adjustable voltage regulators for any voltage changes or requirements.
I swear, but it seems like this has not been done before ?
As there seems to be little documentation on this subject ?
Of course that can't be true ! But it seems so from my stand point.
I'll just hope I can make this happen.

All I know is the RX will at least will require a signal and ground wires.
And the Lipo battery connection will need the same.
I'm assuming they can both share a common ground.
So I would likely need to splice into the ground- entering the RX on CH 1 ?
Or maybe the HH's by-pass resolves that for me ?
I guess I really don't know until I get into this and make an attempt at it ?

definitely not getting the skinny answers I was hoping I'd get from here.
Generic answers are helping me very little.
Except in spending my money on a not so sure resolve :?:

I suppose years back I'd just figure it out on my own.
But not so much these days.

 

[ferp420]

john from Holmes hobbies who pioneered the direct power servo did a write up on them and he telks about those adapters too and goes in to the who and why of it all
basically though the servo needs to be rewired to a 4 wire instead of a 3 wire
I have one like that a 3 wire 16.8v servo that I tried the adapter on and it glitched like mad the truck was un drivable works fine on 4.8v from the receiver but it's week lol so I'm gonna experiment with it and try running it with only the signal wire going to the rx if that doesn't work I'll try adding another ground wire if that still dosent work it will end up in a different rig maybe as a shift servo

you shouldn't need a ground to the rx if there is one from the servo to the battery in theory you can just run the signal wire to the rx like castle and hobby wing dose with there auxiliary wires but I haven't tried it yet I had planned too I can post up next week if it works I'll post in my 1/6 ranger build thread if that doesn't work you can try the hh adapter but those only work for some esc/radio combos

what brand servo are you running ?

 

[ferp420]

you could always contact John directly through this site or since you just bought one of his adapters from his site I'm sure you could get some help from them directly as well
if you contact him here dont expect a reply right away but he might be willing to take more time and explain things in a bit more details here maybe lol