Servo direct to battery

[papabash]

Hey guys, I did a search for this, and checked the stickies, but the 2 posts I found weren't much help. I'm needing to hook my servo directly to my battery (7.4 volt lipo, 7.4 volt servo) to avoid having to run a BEC. Can someone please tell me how to do this? I am a visual learner, so wiring diagrams would be a tremendous help, electronics just isn't my strong point.
Thanks for your help!

 

[EGRESSor]

just servo + to battery +
servo - to battery -
signal to receiver

 

[papabash]

Sounds simple even for me. :mrgreen:
Thanks!

 

[winkscrawler]

The best way I know how to do this is by using a servo extension. Plug the servo into the extension and then on the other side of the extension you cut the negative and positive wires near the extension end. The signal wire remains and you plug that end into the receiver. The negative and positive leads are then soldered onto your male end deans plug and you are done. Hope that helps. Sorry I dont have a pic available but you should be able to follow my directions.

 

[Trubble]

My Helicopter LiPos (2S-500mAh) use the small red JST-BEC style connectors, so I just pulled the red wire from the ESC's receiver plug, and plugged my heli battery straight into my receiver. Certainly gave the stock servo a LOT of snap! But remember, a fully charged LiPo is over 8 volts, you really still should have a BEC to try and keep the volts regulated to around seven, even with a HV servo. Last time I had the battery hooked up like this, I went and really got my servo worked up, temp gun read 212°.** It'd be a shame to see someone waste a nice servo 'cause they wouldn't spend @$20ish.

Also remember servos (and BECs) don't have voltage cutoffs to protect your LiPos. (and they do indeed draw power just sitting idle) If you don't already have a device for checking the battery's voltage at the balance tap (ex. Hyperion's EOS Sentry, I think TCS has one by Yeah Racing, too), might want to get one and use it often. Unplug your LiPo(s) whenever you're not running.


Edit: ** Keep in mind that to get some temp in my servo, my crawler was on a stand, just turning the wheels left & right, nearly zero resistance. I imagine if you got a front tire wedged and used the servo to lift the truck's rear in order to get unstuck, you could really spike the amp draw, and build some pretty significant heat pretty quick. High voltage is fun, just gotta take some precautions.

 

[papabash]

But remember, a fully charged LiPo is over 8 volts, you really still should have a BEC to try and keep the volts regulated to around seven.
Good point, I hadn't thought of that.......

It'd be a shame to see someone waste a nice servo 'cause they wouldn't spend @$20ish.
I have 3 brand new BEC's on the shelf, the only reason I want to avoid using one is lack of space in my new mini build.

If you don't already have a device for checking the battery's voltage at the balance tap (ex. Hyperion's EOS Sentry, I think TCS has one by Yeah Racing, too), might want to get one and use it often.

Have one. "thumbsup"

Unplug your LiPo(s) whenever you're not running.
I do, that's why all my rigs have the power switch removed.

Thanks for your reply! "thumbsup"

 

[EGRESSor]

a 2s servo should work with a full charged 2s lipo (8.4V)

i used a Hitec 7980 and 7950 in my xr10 and hyperion mini 2s servo in the mrc
all powered by 2s lipo

 

[papabash]

Good to know, thanks!

 

[Manning]

My servo/rx power lead comes off the battery leads, but at the esc solder points to keep things marginally cleaner.

My rx can handle the higher voltage, some cant.

 

[holycaveman]

I tried this last night and it did not work. Any ideas?

For some reason I am thinking there is more to it?

Thanks

Ps. I am running 2 2s packs in series. + and - of one 2s pack to servo. Yellow signal wire from servo to reciever.

 

[Charlie-III]

I tried this last night and it did not work. Any ideas?

For some reason I am thinking there is more to it?

Thanks

Ps. I am running 2 2s packs in series. + and - of one 2s pack to servo. Yellow signal wire from servo to reciever.

That should be all you need. The black or brown servo wire to battery -, the red or orange servo wire to battery +, the white or yellow servo wire to steering channel on the RX (pin away from RX edge of the 3 pins for that channel).

 

[holycaveman]

Alright.

I hooked t up again. Made certain with a volt meter I was getting voltage to the servo through the 2s lipo.

Yellow wire plugged in the reciever no 1 port.

Absolutely nothing at all.

Took off the battery, put the red/black back in the servo plug. Plugged in to port one on the rx and servo works just fine.


What am I missing:x

Thanks

 

[holycaveman]

That should be all you need. The black or brown servo wire to battery -, the red or orange servo wire to battery +, the white or yellow servo wire to steering channel on the RX (center pin of the 3 pins for that channel).

Are you saying the yellow wire should be in the center pin slot?

Mine is where it was origiinally, to the right pin.

 

[holycaveman]

I mean left pin....

 

[holycaveman]

I think I figured it out.

The servo signal wire has to share a common ground.

If you run a completely seperate battery to the servo then you need to leave the black wire in with the signal wire.

If you are running the same battery for everything then you can let the signal wire go by itself.

What I was doing is thinking since I have two 2 cells I would just run one to the servo. But its not a two cell any longer, its part of a 4 cell circut.

So if I would try and run a ground with the yellow I would actually be reversing the polarity because in a 4s lipo the negative runs to the positive right where I split it.


So unfortunately I will have to get a bec to regulate the 14vlts coming out of the 2 two sells.

Are we having fun yet!!

All this and I hope I am wrong.

 

[Charlie-III]

Are you saying the yellow wire should be in the center pin slot?

Mine is where it was origiinally, to the right pin.

My bad, I was at work with no servo.
The signal is furthest away from the edge of the RX.

 

[ClassicGMJunkie]

yep cavey sounds like you tried it with a "floating" ground, and not a common ground. I totally forgot that issue as well. i'm sure that will save others from the boggle when they do the same.

 

[holycaveman]

yep cavey sounds like you tried it with a "floating" ground, and not a common ground. I totally forgot that issue as well. i'm sure that will save others from the boggle when they do the same.

Yep, and I just confirmed it.

Instead of running a split 4s I ran just one 2s with the positive/negative to the servo and to the esc. Yellow wire to the rec just like before. Except this time everything worked perfectly.

Also I realized how much better 2s crawls than 4s. Those hh 45turns I just bought are awesome!

So I am just going to run one 2s battery that's bridged to both the esc and servo. Notice a huge power gain running the battery directly to the servo.