2s powered Servo issues

[losikid]

So, i just hooked up my new savox brushless servo (400+oz), and it seems real nice, smooth and quite compared to my hitecs.

But, with the slightest bit of power to my throttle, it has almost no power.

I'm running 2s direct, yanking power off the male deans plug (2" away from esc)

I'm assuming, my 13.5t sensored brushless is starving my servo.

Any idea's for the best fix? I'm thinking 3s and a BEC...but jrh said he won't have his 3s's for at least 4 weeks...and if i run 3s, i'll be running HMC 1000's

I noticed this before with my 7954, but it had a decent holding power when i was bound up. this savox just gives up.

I've considered trying to put the bec on a 2s and see if it can boost voltage up to 8 volts...but i'm not sure if the cc bec can boost voltage

[AR Fabrication]

Is that 400oz at 6 volts? Sounds to me like you need a BEC. When you give throttle does the motor and servo glitch or is the servo just slow down?

[SMR 510RR]

What is the C rating on your packs?

There is no way that running a BEC will help, direct from the pack has to be the most efficient setup possible. Have you thought about adding a capacitor to help smooth out any drops in voltage?

No a BEC will not boost voltage, input is as high as they will output.

[korn_2956]

A bec can not boost, only limit. I'd get a bec and if that doesn't fix it then throw in a 3s. But the bec alone should work unless your lipo is junk.

[losikid]

Originally Posted by Track Rat

Is that 400oz at 6 volts? Sounds to me like you need a BEC. When you give throttle does the motor and servo glitch or is the servo just slow down?

at 2s (7.4 volts), i'm running direct lipo to my servo...al the bec may have done is boost it to higher voltage...but, after some searching and coming back to this thread, its not a buck/boost regulator

When i give it throttle, the servo dies completely. Strong as hell when not moving or moving on flat ground. minute i hit the wall and give my motor a load, it dies

Originally Posted by SMR 510RR

What is the C rating on your packs?

There is no way that running a BEC will help, direct from the pack has to be the most efficient setup possible. Have you thought about adding a capacitor to help smooth out any drops in voltage?

No a BEC will not boost voltage, input is as high as they will output.

25c, gens ace, ran my 7955 and 7954 just fine...when my motor was under heavy load they were weak, but they still had some juice...this brushless savox 2270 almost just dies, no control at all of the servo.

Originally Posted by korn_2956

A bec can not boost, only limit. I'd get a bec and if that doesn't fix it then throw in a 3s. But the bec alone should work unless your lipo is junk.

I just got done wiring a a bec, set it to 8 volts, and plugged in a charged 3s (gens ace, 1300, 25c). It behaves exactly the same...although alot more glitchy while driving on flat ground/

I wonder if i got a bum servo? I'll send savox an email...i'm really bummed out, i was pumped to run this thing at my comp saturday.

[AR Fabrication]

What model number is the servo?

[korn_2956]

Originally Posted by losikid

at 2s (7.4 volts), i'm running direct lipo to my servo...al the bec may have done is boost it to higher voltage...but, after some searching and coming back to this thread, its not a buck/boost regulator

When i give it throttle, the servo dies completely. Strong as hell when not moving or moving on flat ground. minute i hit the wall and give my motor a load, it dies




25c, gens ace, ran my 7955 and 7954 just fine...when my motor was under heavy load they were weak, but they still had some juice...this brushless savox 2270 almost just dies, no control at all of the servo.





I just got done wiring a a bec, set it to 8 volts, and plugged in a charged 3s (gens ace, 1300, 25c). It behaves exactly the same...although alot more glitchy while driving on flat ground/

I wonder if i got a bum servo? I'll send savox an email...i'm really bummed out, i was pumped to run this thing at my comp saturday.

8v sounds like alot for a servo. Is that servo rated for that. Try 6v and see if it does the same. If that don't help your probably right about the servo.

[heyok]

What a strange problem.

Keep in mind that a charged Lipo is more like 8.4 volts.

Is there any way you can monitor the voltage at the servo when you are having this trouble?

[indiana mudcat]

Try wiring two of your packs in parallel to double the amperage. Sounds like voltage drop from the weak packs, 13.5 and a high power servo (plus I assume a dig servo) needs at least twice the amperage your able to feed it to run right.

Or power the ESC off one battery and the servo off the other. I think either way will stop the issue, but parallel batteries will help the motor also until you can get much better packs.

[rjsl59]

This is the Savox SB-2270SG Monster Torque Brushless Steel Gear Digital Servo.

Features:

•Combines leading edge technology with super high 12 bit (4096) resolution and unique steel gears.
•Super light-weight.
•Brushless motor provides high speed and torque, incredible efficiency, and amazingly low power consumption.
•Extremely strong unique steel gears ensure long-life and durability.
•The full aluminum case design not only looks good but also allows for cooler and smoother operating temps.
•Our servos are totally green – from materials to production, these servos are environmentally friendly.
•Ideal for rock crawlers, monster trucks, and every control surface for giant scale aircraft.
Dimensions(mm): 40.3x20.2x38.5
Weight(g): 69.0
Speed(@4.8V sec/60): .19
Torque(@4.8V oz-in): 291.6
Speed(@6.0V sec/60): .15
Torque(@6.0V oz-in): 347.2
Speed(@7.4V sec/60): .12
Torque(@7.4V oz-in): 444.0
Gear: Unique Steel
Bearing: 2BB
Case: Full Aluminum
25 Tooth Spline

sorry it's easier if ppl have the specs i find to figure out a problem, never heard of that problem before but dosen't sound like it's the servo if it works fine when sitting or a light load. maybe check the power and ground I've had a wire break on me and work fine on level ground but as soon as it starts flexing it looses either power or ground, worth a try.

[losikid]

Ok, so, tinkering a little more...here's everything i've tried

direct 2s, no luck
2s with a BEC, no luck
3S with a BEC set at 8 volts, no luck
3s BEC set at 6 volts, no luck
3S powering esc/motor, a seperate 2s lipo powering servo, no luck
3S powering ESC motor, a seperate 3s w/bec set at 8 volts, no luck

Wired my 7954 back in, with 3s and a bec, and she worked like a charm.

So i know power ain't an issue, my tx/rx is working properly, so i'm thinking its something todo with the RS. Only reason i say this, i've heard the RS likes to eat BEC's for breakfast, so maybe it back feeds signal or something and messes with other stuff.

I tried to call savox tonight, 5 minutes before they "closed", but they didn't answer. So i'll have to wait till monday.

I am stumped, i wish i had a few o scopes i could hook up to everything and monitor all the different signals and try and figure out whats causing the issues

[SMR 510RR]

It has to be the servo based on your testing...

It is strange that it is fine with no throttle input.

How are you wiring this up? Through the RX or direct to the servo? Im assuming that this "RS" you are speaking of is a Tekin RS?

It seems like a bad/loose connection maybe when the rig moves it messes up the connection. What exactly happens? Does it just go limp or does it center itself? If it goes limp I would say it is a power issue if it centers then you have some sort of signal issue.

Have you tried it in a different rig to see if there is some sort of interference that is happening with your current ESC/Motor setup?

[losikid]

Originally Posted by SMR 510RR

It has to be the servo based on your testing...

It is strange that it is fine with no throttle input.

How are you wiring this up? Through the RX or direct to the servo? Im assuming that this "RS" you are speaking of is a Tekin RS?

It seems like a bad/loose connection maybe when the rig moves it messes up the connection. What exactly happens? Does it just go limp or does it center itself? If it goes limp I would say it is a power issue if it centers then you have some sort of signal issue.

Have you tried it in a different rig to see if there is some sort of interference that is happening with your current ESC/Motor setup?

It acts dead, no holding power, kinda glitches, buzzes funny,..

I soldered the power leads onto my male deans plug, and i'm not a complete newb when it comes to soldering either.

I don't think its a power issue, i plugged that suker directly into a separate battery, with a common ground to the other battery so it works.

One last thing i'm going to test, is make two individual circuits, bind my gt3b to two rx's, and run my TEKIN RS off one and the servo off the other. Its gotta be innerferance since its only when my motor starts to bind up (just a little load,

My tests are, drive from my work bench, across the carpet, and hit the closed door at about 45 degree's. As soon as my drivetrain binds up abit, i loose complete control of the servo, and it just moves where ever my car pushes my front tires.

I'll get some vid here in the next few days, its just crazy weird. Why does it work fine until i start moving. My Hitec works just fine

[BELADOG]

Originally Posted by losikid

Ok, so, tinkering a little more...here's everything i've tried

direct 2s, no luck
2s with a BEC, no luck
3S with a BEC set at 8 volts, no luck
3s BEC set at 6 volts, no luck
3S powering esc/motor, a seperate 2s lipo powering servo, no luck
3S powering ESC motor, a seperate 3s w/bec set at 8 volts, no luck

Wired my 7954 back in, with 3s and a bec, and she worked like a charm.

Not voltage issue. Its an Amp issue.
Its an extremely amp hungry servo. I had it for a day, experienced the same.

Ran it through the little Castle Bec and no change.
3s with the ProBEC and worked fantastic.
Hitec draws about 5-6A under load. That Savox about twice that.

When your motor loads the battery there is not enough left for the servo and it struggles.
This is why its fine till you load the motor.
The pro bec is 20A max and with a large enough capacity battery you will be fine.

At least try it with a larger batt and see.
2200 @ 20c is only 40A!
a 13.5 and a 10A servo is bound to struggle with that.
even a true 40c 2.2 pack is gonna be pushing it right?

[666]

I bought the same servo the other day. If I fart the dawm thing looses power. Not impressed at all.

I'm running a BRXL, 3 cell, the BEC on it is powering the receiver, and have a CC BEC set at 7 volts. Put my Hitec back in, it throws the truck around, no hesitation.

The old saying, you get what you pay for.

[BELADOG]

Originally Posted by 666

...same servo.... If I fart the dawm thing looses power. Not impressed at all.
...The old saying, you get what you pay for.

agreed.
I'm back to the Hitec as well.

Sent the Savox on a one way flight accross the shop and into the bin


ps.
Whats the Amp draw on your farts?

[losikid]

Originally Posted by BELADOG

Not voltage issue. Its an Amp issue.
Its an extremely amp hungry servo. I had it for a day, experienced the same.

Ran it through the little Castle Bec and no change.
3s with the ProBEC and worked fantastic.
Hitec draws about 5-6A under load. That Savox about twice that.

When your motor loads the battery there is not enough left for the servo and it struggles.
This is why its fine till you load the motor.
The pro bec is 20A max and with a large enough capacity battery you will be fine.

At least try it with a larger batt and see.
2200 @ 20c is only 40A!
a 13.5 and a 10A servo is bound to struggle with that.
even a true 40c 2.2 pack is gonna be pushing it right?

I gave the damn thing an entire battery separate from my motor to work off of. Only connection between the two batteries was a ground. so i could run the same rx. So, for some reason i'm doubting an amp issue, it might be but i gave it an entire battery.

[losikid]

Originally Posted by 666

The old saying, you get what you pay for.

its a $150 servo, not really a "cheap" servo...

[666]

Originally Posted by losikid

its a $150 servo, not really a "cheap" servo...

Yup and it sure does not work well does it?

[losikid]

Originally Posted by 666

Yup and it sure does not work well does it?

Hell no, i think i'd be better off throwing rocks at my tires to turn them