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Old 04-18-2013, 05:10 PM   #1
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Default Servo's direct on 2S lipo - am I doing it wrong ?

I had a big brand (meaning: very expensive) High Voltage servo and decided to not power it from my Hobbywing SCT Pro anymore but hook it up directly to my 2S lipo's. So I pulled the power wire from the servo plug, and connected it to the positive wire of my lipo. Worked fine, but after 2 days the servo stopped working. Sent it back for RMA.

Waiting for that one to return, I bought a different Big Brand (even more expensive) HV servo. Emailed the company even to ask if it would be ok to connect it straight to 2S lipo, they said it would be fine. Installed it default powered by the Esc, worked. Hooked it up straight to the 2S lipo tonight, and suddenly it's in a coma - doesn't work. Reverting to the normal setup doesn't help, nomatter what I do the servo is dead.

Am I doing it wrong or is this a bad coindicence ?
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Last edited by Pygmy; 04-18-2013 at 05:29 PM.
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Old 04-19-2013, 09:03 AM   #2
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Did you follow a wiring diagram? That doesn't sound right.
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Old 04-19-2013, 10:44 AM   #3
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You probably should connect the positive and negative wire of the servo to your battery. Having the ground still going through the BEC in your ESC might be causing problems. I have my servo connected directly to my battery and only the signal wire from the receiver and I haven't had any problems.
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Old 04-19-2013, 12:10 PM   #4
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It sounds to me like it's a grounding problem caused by the the lack of complete isolation. Does your receiver support hv?
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Old 04-19-2013, 07:53 PM   #5
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Ground loop, probably.

+/- should be wired directly to the battery, with your signal wire being the only thing hooked up to the RX.
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Old 04-21-2013, 02:33 PM   #6
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Quote:
Originally Posted by nitrousdave View Post
You probably should connect the positive and negative wire of the servo to your battery. Having the ground still going through the BEC in your ESC might be causing problems. I have my servo connected directly to my battery and only the signal wire from the receiver and I haven't had any problems.
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Ground loop, probably.

+/- should be wired directly to the battery, with your signal wire being the only thing hooked up to the RX.

Okay, so not connecting the ground to the battery as well would be my problem.
Apparently this destroys the servo, can anybody explain why ?

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It sounds to me like it's a grounding problem caused by the the lack of complete isolation. Does your receiver support hv?
No, my receiver supports up to 6v.
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Old 04-21-2013, 03:06 PM   #7
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I was looking at this Ko Propo setup and I noticed they also just connect the positive wire to the battery:

http://www.redrc.net/2012/01/ko-prop...d-servo-wires/

This looks the same as what I did - signal and ground from the receiver, power from the battery. How would their setup not destroy the servo if mine would ?
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Old 04-21-2013, 09:29 PM   #8
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Weird. Certainly good practice to avoid a ground loop, but if I'm following correctly it doesn't appear you have a loop. If you attached the ground from both the battery and from the receiver (which is grounded back to the battery via the ESC I believe) then I believe you would create the ground loop.

Are you positive that there was not a mechanical problem, making sure the steering wasn't binding at any point in the full suspension travel? (I wonder, not sure, is a HV servo more resistant to abuse because of the greater power, or less because there is more power to cause burnout?)
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Old 04-22-2013, 04:51 PM   #9
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So before I blow a third servo, I'd like to have final confirmation, once and for all :

The correct way to wire my system with high voltage servo is thus :

- Esc powers receiver via Throttle channel
- Servo yellow/white signal line connected to receiver
- Servo power (red) & ground (black) connected to red & black Lipo wires

.....right ???
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Old 04-22-2013, 05:04 PM   #10
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Quote:
Originally Posted by Pygmy View Post
So before I blow a third servo, I'd like to have final confirmation, once and for all :

The correct way to wire my system with high voltage servo is thus :

- Esc powers receiver via Throttle channel
- Servo yellow/white signal line connected to receiver
- Servo power (red) & ground (black) connected to red & black Lipo wires

.....right ???
That's the way that I would do it if it were my system. Even though the adapter you listed shows otherwise. This is the only way to completely isolate each power supply from each other.
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Old 04-23-2013, 07:46 AM   #11
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Quote:
Originally Posted by Pygmy View Post
So before I blow a third servo, I'd like to have final confirmation, once and for all :

The correct way to wire my system with high voltage servo is thus :

- Esc powers receiver via Throttle channel
- Servo yellow/white signal line connected to receiver
- Servo power (red) & ground (black) connected to red & black Lipo wires

.....right ???
I don't think that's how the picture you posted shows it wired up. Servo + to lipo +, servo - to receiver -, servo signal to receiver signal is how the pic shows it.
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Old 04-23-2013, 08:29 AM   #12
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Here is how I wire up my HV servos using the following harness which connects directly to the balance port for direct power to the servo. If you don't feel comfortable wiring up your own, I'll be happy to sell them for $5 shipped within the lower 48:

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Old 04-23-2013, 08:38 AM   #13
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Quote:
Originally Posted by billdelong View Post
Here is how I wire up my HV servos using the following harness which connects directly to the balance port for direct power to the servo. If you don't feel comfortable wiring up your own, I'll be happy to sell them for $5 shipped within the lower 48:

That is exactly how I've done it too. Male balance plug goes to the batteries balance plug and the servo plug goes into the receiver. I've run non-HV servos like this without problems (ones that are rated for 6.0V at their top).
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Old 04-23-2013, 01:38 PM   #14
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Quote:
Originally Posted by neospud View Post
I don't think that's how the picture you posted shows it wired up. Servo + to lipo +, servo - to receiver -, servo signal to receiver signal is how the pic shows it.
Yes, and the setup like in that pic is how I killed my last 2 servos. That is why I was surprised to see that pic and wrote :
"This looks the same as what I did - signal and ground from the receiver, power from the battery. How would their setup not destroy the servo if mine would ?"
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Old 04-23-2013, 01:50 PM   #15
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I have seen some LiPo's have their wires colored in reverse to where the single Red wire coming from the balance port is true negative and the remaining black wires are looped positive in series, you should double check polarity with a voltmeter before assuming any color.

More info here:
http://scriptasylum.com/rc_speed/lipo.html

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