"Servo Lock" Truth or Baloney?  
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All Forums >> Radios, Batteries, Clubhouse and more >> RC Radios, Transmitters, Receivers, Servos, gyros >> "Servo Lock" Truth or Baloney?
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"Servo Lock" Truth or Baloney? - 5/6/2005 1:53:26 AM   
BlueMax3


 

Posts: 269
Joined: 10/12/2002
From: Livermore, CA, USA
Status: offline 		I was at the field when an "experienced pilot" told me to never, ever turn my transmitter off before my receiver because it can cause the servos to "go into servo lock". He was not referring to the failsafe mode on a PCM system, because I have that and asked if that was what he was referring to. No, no, this is "servo lock". The guy was serious and I didn't want to get into it with him, so I think I just acknowledged what he said with an "okay, thanks" and left it at that so he would go away, far away. I did check to make sure that he doesn't use my frequency and luckily he doesn't. Anyone ever heard of this "servo lock". It sure sounds ominous. What say you, truth or baloney?

Travis
       Post #: 1

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 2:10:29 AM   
Eagle Al


 

Posts: 70
Joined: 3/28/2005
From: Bloomington, IN, USA
Status: offline 		I have no idea what servo lock is but both Air and Futaba instruct the following:

ON: TX then RX

OFF: RX then TX

I do it, and I don't know why. I guess I'm programmed to follow procedures.

I have heard about swamping the receiver. This happens when you leave the antenna down like in the house and the servos jiggle. You should always pin these guys down and naively ask him, "What is servo lock good sir?" He probably doesn't know either. Frankly I have never gotten any good information from the old geezer field crowd. Most of them don't know what they're talking about most of the time.

Ciao,

Eagle Al

_____________________________

He who ends up with the most toys doesn't win anything in this life. The winners are those who had a good journey!

(in reply to BlueMax3)
       Post #: 2

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 2:23:07 AM   
DMcQuinn



Posts: 1588
Joined: 1/9/2002
From: Chesterfield, MO, USA
Status: offline 		Servo lock is a real thing, although not necessarily a big deal. When you turn off your transmitter, the receiver may get some spurious signals and interpret them as a "full right" or "full left" signal, attempting to drive the servo to its extreme. modern servos have a mechanical stop so that they can only rotate so far. Then the servo motor stalls and it draws lots more energy from the battery. Left in this state for a long time, the servo motor could heat up. but there should be no permanent damage.

(in reply to Eagle Al)
       Post #: 3

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 2:48:02 AM   
BlueMax3


 

Posts: 269
Joined: 10/12/2002
From: Livermore, CA, USA
Status: offline 		McQuinn,

I wonder if this would ever happen with a PCM setup or only with a PPM setup? I've tried it a few times to test my fail safe and all it did was go into failsafe, which is what I expected. When I first turned my transmitter off with the receiver still on, the servos did nothing until it went into failsafe and then my throttle goes to idle, which is the default setting on my Futaba 9C. I wonder if the receiver can tell the difference between no signal and bad signal?

Travis

(in reply to DMcQuinn)
       Post #: 4

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 2:51:01 AM   
DMcQuinn



Posts: 1588
Joined: 1/9/2002
From: Chesterfield, MO, USA
Status: offline 		With a failsafe receiver, the servos are not at risk of "servo lock". the lack of signal is detected by the receiver and it tells the servos to go to the pre-defined position.

(in reply to BlueMax3)
       Post #: 5

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 2:54:54 AM   
JohnBuckner



Posts: 4000
Joined: 12/23/2001
From: Kingman, AZ, USA
Status: offline 		I would not be to quick to be disparaging of the "old geezer" as he gave some sound advice. With a Rx on without the Tx carrier signal stray RF noise can on occassion cause a servo to try to overdrive past its mechanical limits resulting in mechanical damage of the gears. As noted above its not real common but I,ve seen it happen and thats the reason 'All' manufacturers recommend the stated order of switch operation. Common sense would suggest heeding that advice where practical.

Buy the Geezer a cup of coffee.

John



_____________________________

"Keep your controllines tight"

(in reply to DMcQuinn)
       Post #: 6

RE: "Servo Lock" Truth or Baloney? - 5/6/2005 5:09:46 PM   
Rodney



Posts: 4887
Joined: 12/8/2001
From: FL
Status: offline 		Yep, John and the Old Geezer are correct. I've never seen it happen on PCM where fail safe has been set up correctly but will happen occasionally on any PPM or PWM system.

(in reply to JohnBuckner)
       Post #: 7

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 12:54:52 AM   
wisdom-seeker


 

Posts: 389
Joined: 5/29/2003
From: Danville, CA, USA
Status: offline 		Being one of those "old geezers" I can say that anyone who lets a receiver run without a signal, deserves what he may get. (So there! )

_____________________________

Wisdom-Seeker
Raven 30, OS32SXH,Eclipse 7, MP2, GY-401

(in reply to Rodney)
       Post #: 8

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 1:46:08 PM   
Steve Campbell


 

Posts: 4203
Joined: 12/8/2001
From: Zachary, LA, USA
Status: offline 		Well, Eagle Al claimed, in another thread, to be a 40-year veteran military/test pilot. By my reckoning, that would make him an "old geezer".

So how about it, Al? Which are you?

(in reply to wisdom-seeker)
       Post #: 9

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 4:59:13 PM   
Eagle Al


 

Posts: 70
Joined: 3/28/2005
From: Bloomington, IN, USA
Status: offline 		I am certainly an old geezer, but I have never offered advice without getting into some details. Also I try not to be dogmatic.

Ciao,

Eagle Al, always young at heart!

_____________________________

He who ends up with the most toys doesn't win anything in this life. The winners are those who had a good journey!

(in reply to Steve Campbell)
       Post #: 10

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 5:02:06 PM   
John Redman


 

Posts: 1073
Joined: 1/1/2002
From: Mahomet, IL, USA
Status: offline 		This servo lock as stated is something that can occur when you turn off the transmitter and leave the reciever on. It can only happen with a PPM system. with PCK the servo will go into a hold position which is the last known position. If the user has prgrammed a failsafe position then the servos will move to a predetermined position set by the user. Being PCM and leaving the reciever on will not hurt a thing except drain your batteries over time. Being a PPM system what can happen is the servos can drive from one extreme to another, which normally ends up being past the limits the aircraft is setup to and can break control linkages, servo gears and such. The other problem is if using digital servos and the servos drive hard one way and sit you can blow the amps in the servo by the excessive current drain.

The more prefered method is to switch the reciever off first.


_____________________________

John
BVM Rep

(in reply to Steve Campbell)
       Post #: 11

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 9:39:34 PM   
Eagle Al


 

Posts: 70
Joined: 3/28/2005
From: Bloomington, IN, USA
Status: offline
quote:

ORIGINAL: BlueMax3

I was at the field when an "experienced pilot" told me to never, ever turn my transmitter off before my receiver because it can cause the servos to "go into servo lock". He was not referring to the failsafe mode on a PCM system, because I have that and asked if that was what he was referring to. No, no, this is "servo lock". The guy was serious and I didn't want to get into it with him, so I think I just acknowledged what he said with an "okay, thanks" and left it at that so he would go away, far away. I did check to make sure that he doesn't use my frequency and luckily he doesn't. Anyone ever heard of this "servo lock". It sure sounds ominous. What say you, truth or baloney?

Travis


You made sure that he didn't use your frequency (implying he might be angry enough to bring you down)? Were you two about to draw guns or something? I think I'd stay away from him and maybe his field (or his lecture day).

Ciao,

Eagle Al


_____________________________

He who ends up with the most toys doesn't win anything in this life. The winners are those who had a good journey!

(in reply to BlueMax3)
       Post #: 12

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 9:55:55 PM   
BlueMax3


 

Posts: 269
Joined: 10/12/2002
From: Livermore, CA, USA
Status: offline 		Just to set the record straight, I never called the guy an "old geezer". I think those were someone else's words. I myself would never refer to someone like that. I think it's disrespectful and I will be old someday (hopefully).

I may not have chosen the best words in my original post. I was trying to be funny, but may have ended up offending someone. If I did, then I apologize. I really did want to know about what he referred to as "servo lock" because I had never read anything about this in my Futaba manual or on the Website and had never heard of it. Furthermore, to me it seemed inconsistent with a PCM system with a failsafe mode enabled. I always use the normal on and off sequence described herein, but he made it sound so serious I wanted to learn more about it.

Also for the record, I have a tremendous appreciation for how knowledgable some people are in this hobby. I am eternally grateful that they are willing to share their knowledge with others, including me. I know practically nothing compared to some of these people, but learn a little more every day. This is one more thing I have learned.

Thanks,

Travis

(in reply to Eagle Al)
       Post #: 13

RE: "Servo Lock" Truth or Baloney? - 5/7/2005 10:13:04 PM   
iflyj3



Posts: 1015
Joined: 5/18/2002
From: Paris, KY, USA
Status: offline 		Travis,

You said nothing wrong in your post. I thought it was respectful and I am an old Geezer.
In 50 years, I have not heard the term Servo Lock either and I have designed and built servos. Sometimes people describe things in their terms or terms they are repeating. A few years ago I heard a fellow use the term, in reference to NiCad batteries, surface charge. I thought, what the heck is surface charge? It turns out, it was his description of the peak that disipates when the batteries are first used.

You are correct in asking what terms mean. Sometimes the person using them doesn't know either. Others here have described their definition of servo lock and I won't expand on that as they have covered very well.

_____________________________

Dan Thompson (Long live the ACE MicroPro 8000)
Visit www.groups.yahoo.com/group/mp8k for support

(in reply to BlueMax3)
       Post #: 14

RE: "Servo Lock" Truth or Baloney? - 5/8/2005 3:42:06 PM