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Digital servos-long leads - 11/5/2012 11:56 PM   
Me410


 

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Status: offline 		My latest  and largest plane to date is a TF GS Corsair with a  86" WS.  I am starting to use digital servos more and more, and would like them in this plane. There are cautions about using long extension  leads with these servos.  I would use  Futaba HD extensions, but it is a  long way from the alerons to the reciever.

I would like to use Futaba hi torque BB std digital servos that they say could draw up to 2 amps each.

So how can you get around this long lead issue?
Not use digitals in the wing?

Thanks for any input

Tom

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RE: Digital servos-long leads - 11/6/2012 12:11 AM   
flyinwalenda


 

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Status: offline 		What servos are you using? Do they state not to use extensions longer than XX" ?
I use twisted 22 gauge wiring for longer leads instead of the flat cable  and never saw any jitter and power loss should not be an issue using heavier cabling. The less connectors you have in the line helps too so don't put two extensions together .


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RE: Digital servos-long leads - 11/6/2012 12:26 AM   
Me410


 

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Status: offline 		I plan on using Futaba digital S3152.  In the Tower Hobby ad,  see  "  -It is best to avoid long leads and Y-harnesses"  and of course the talk about high current draw.

After 25 years in the hobby, I only now trust HD brand name servo extensions. So I only want to use the HD Futaba stuff.

I did buy some 22 gauge twisted leads a  few years ago( I forgot who made them now )  But I had a failure with one , and I have had failures with other cheap extensions too.

I have a new 2400 mah 5 cell ni-cad from Hang Time Hobbys, so I know I have a good RX battery.

There must be tons of guys using long extensions on digitals,  right?

Tom

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RE: Digital servos-long leads - 11/6/2012 12:40 AM   
flyinwalenda


 

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Status: offline 		Well the connector pins can cause issues so it's always best to use as few as possible.  On long leads I use the twisted 22 gauge wire, solder directly onto the servo end and put my own connector on the RX end. I don't use Futaba digitals but I have seen that disclaimer on a lot of their servos.
In reality though, how long will the lead be ....36" ? 


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RE: Digital servos-long leads - 11/6/2012 1:39 AM   
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Status: offline 		For what it is worth, I use JR HD extensions in my 1:5.8 A-10.
While there is some loss at the connectors the servos have worked flawlessly with 48" and 36" length plugged together and the plugged into the servo.
No problems, all digital servos.
I wouldn't worry about it, just make sure they are secured. I use dental floss to tie the plastic plugs (together)towards one another, this is strong and places no load on the wires.
Dave

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RE: Digital servos-long leads - 11/6/2012 2:25 AM   
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Status: offline 		I would recommend www.taildraggerrc.com/servo-extensions-and-servo-accesories.html Great customer service and very reasonable.  His extensions are 20 AWG.  Best of quality.

Harry


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RE: Digital servos-long leads - 11/6/2012 3:43 AM   
Me410


 

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Status: offline 		Flyinwalenda:       The wire from the servo is 11"  the extension is 40"   then I need a  10" lead from my RX in that big Corsair body,  so a total of 51" of wire from servo to RX.
                                I used to solder extensions  to my servo wires, and yes, that's a safe and effective way to do things.  But I just don't want to do that any more, I am willing to 
                                spend for the best leads available.   Plus also, then the servos are more interchangable.

Ddennison:          I will be securing my connections with "Ernst" clips and may also tie them too, so they will not be coming apart.
                               Does JR caution thier customers about long leads and digital servos?

Flyallday:              Those " TaildraggerRC  " leads look good.   Have you used used them for years?  I ask because it can take few years to truly know if you have a quality item.




Maybe I could get some info from Futaba as to why thier warrning on extensions. Maybe it's just about the changes in the hobby. Not that long ago, most people were using analog servos with basic wires and batteries. Now most people are using digitals, needing bigger gauge wire and bigger batteries.  They may just be worried that people will not upgrade these items when they go digital.  But you would think they would state that thier HD extensions are up to the digital job.

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RE: Digital servos-long leads - 11/6/2012 4:37 AM   
BuschBarber


 

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quote:

ORIGINAL: Me410

Flyinwalenda:       The wire from the servo is 11''  the extension is 40''   then I need a  10'' lead from my RX in that big Corsair body,  so a total of 51'' of wire from servo to RX.
                                I used to solder extensions  to my servo wires, and yes, that's a safe and effective way to do things.  But I just don't want to do that any more, I am willing to 
                                spend for the best leads available.   Plus also, then the servos are more interchangable.

Ddennison:          I will be securing my connections with ''Ernst'' clips and may also tie them too, so they will not be coming apart.
                               Does JR caution thier customers about long leads and digital servos?

Flyallday:              Those '' TaildraggerRC  '' leads look good.   Have you used used them for years?  I ask because it can take few years to truly know if you have a quality item.




Maybe I could get some info from Futaba as to why thier warrning on extensions. Maybe it's just about the changes in the hobby. Not that long ago, most people were using analog servos with basic wires and batteries. Now most people are using digitals, needing bigger gauge wire and bigger batteries.  They may just be worried that people will not upgrade these items when they go digital.  But you would think they would state that thier HD extensions are up to the digital job.

Warnings against using long servo leads were necessary back in the days of 72Mhz. With 2.4 this is not as big of an issue. I use 20ga servo leads whenever possible. I have used 36" leads without issue. Jets or Prop powered.

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RE: Digital servos-long leads - 11/6/2012 5:05 AM   
flyallday


 

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quote:

ORIGINAL: Me410

Flyallday:              Those " TaildraggerRC  " leads look good.   Have you used used them for years?  I ask because it can take few years to truly know if you have a quality item.



I have not used the TDRC extentions that long, I am going by excellent referals posted on another GIANT site.  I have spoken to the owner several times at length about his extentions and A123 batteries he carries.  Give him a call, his name is Chad.

Harry



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RE: Digital servos-long leads - 11/6/2012 7:28 AM   
A.T.


 

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Status: offline 		Use of servo extension leads and servo lead guage required.

Regardless of frequency, Servo lead guage matters more now than ever before, as explained MPX Newsletter July 2011

"Servo leads often have to be extended due to the installed position of the servos.
Where this becomes necessary in models with wingspans greater than 2.5 m the conductor cross-section plays a crucial role
in terms of the servos’ actual performance.

Typical calculation:
2 m cable with 0.25 mm² conductor cross-section, resistance approx. 400 mOhm (including connector), current drain of a High-Volt (HV) servo in normal use approx. 2A
-> U=R * I = 0.40Ohm * 2A = 0.8 V
This means that the voltage drop along the extension lead is 0.8 V per wire; positive and negative wires together produces a drop of 1.6 V.
In these circumstances a High-Volt (HV) servo used with a 2S LiPo battery is not operating on 7.4 V, but on only 5.8 V.

The servo can therefore never even approach its specified performance for 2S LiPo operation!

2 m cable with 0.5 mm² conductor cross-section, resistance approx. 100 mOhm (including connector), current drain
of a High-Volt (HV) servo in normal use approx. 2 A
-> U=R * I = 0.10Ohm * 2A = 0.2 V
In this case the voltage at the servo is still 7.0 V!

This simple calculation clearly shows what an immense influence the correct choice of extension lead can have on
the real-world performance of servos."

Much more information available under  "Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links
 
Alan T.


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RE: Digital servos-long leads - 11/6/2012 12:55 PM   
john josey


 

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quote:

ORIGINAL: flyallday


quote:

ORIGINAL: Me410

Flyallday:              Those " TaildraggerRC  " leads look good.   Have you used used them for years?  I ask because it can take few years to truly know if you have a quality item.



I have not used the TDRC extentions that long, I am going by excellent referals posted on another GIANT site.  I have spoken to the owner several times at length about his extentions and A123 batteries he carries.  Give him a call, his name is Chad.

Harry




Hi Tom, I've recently transfered a radio installation from one airframe to another (both F-16's) and out of curiosity i measured the total lenths of all the extentions and to my suprise it was just under 7 metres !! The model had flown great for six years on that set -up. (JR 8411's and JR HD extentions all round)

what A.T. says is correct, but for your set-up you describe, i wouldnd think you would have any problems.

Cheers
        john



< Message edited by john josey -- 11/6/2012 7:49 PM >

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RE: Digital servos-long leads - 11/6/2012 1:23 PM   
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Status: offline 		FWIW while twisted wires are great for phone and network cables, they do nothing for servo extensions other than make the actual wire run longer. Oh, and they look pretty

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RE: Digital servos-long leads - 11/6/2012 2:41 PM   
dirtybird


 

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quote:

ORIGINAL: BarracudaHockey

FWIW while twisted wires are great for phone and network cables, they do nothing for servo extensions other than make the actual wire run longer. Oh, and they look pretty


+1

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RE: Digital servos-long leads - 11/8/2012 5:28 PM   
Me410


 

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Status: offline 		Thanks for the input guys.
I am going to go with digitals in the wing and Futaba HD extensions. 
I know you don't need digitals in a warbird, But I swear it feels more responsive.  Or maybe thats all in my head : )

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RE: Digital servos-long leads - 11/8/2012 6:14 PM   
rmh



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Status: offline 		Present digitals are the most responsive - I buy all digital stuf now - mostly the Spektrum Savox ones .
But do you NEED em?
are you a precision aerobatics or heli flier ?
If not - opt for the better grades of non digital but do NOT skimp on servo ratings for torque.
speed ratings don't bother - if the servo is good quality the speed differences noted don't mean much
-as compared against good torque ratings
The point is - get a servo which moves the surfaces easily throughout required travelunder load. And be certain no servo ever bumps into end of travel - or into end of surface deflection.

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RE: Digital servos-long leads - 11/21/2012 11:00 AM   
MAXIAN


 

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Status: offline 		interesting topic, question, but an extension with more resistance, also implies a higher consumption of current and battery?
thank you

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RE: Digital servos-long leads - 11/21/2012 12:00 PM   
BarracudaHockey



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Status: offline 		No not really, and unless you had a problem, certainly in not in any practical way that you'd notice.

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RE: Digital servos-long leads - 11/21/2012 12:50 PM   
dirtybird


 

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quote:

ORIGINAL: MAXIAN

interesting topic, question, but an extension with more resistance, also implies a higher consumption of current and battery?
thank you


A higher resistance means less consumption of current. Check out Ohms law.
But your servo will produce less torque. It gets less voltage.


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RE: Digital servos-long leads - 11/21/2012 12:53 PM   
dirtybird


 

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Present digitals are the most responsive - I buy all digital stuf now - mostly the Spektrum Savox ones .
But do you NEED em?
are you a precision aerobatics or heli flier ?
If not - opt for the better grades of non digital but do NOT skimp on servo ratings for torque.
speed ratings don't bother - if the servo is good quality the speed differences noted don't mean much
-as compared against good torque ratings
The point is - get a servo which moves the surfaces easily throughout required travelunder load. And be certain no servo ever bumps into end of travel - or into end of surface deflection.


Especially since servo torque is wildly over stated by most manufacturers.

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RE: Digital servos-long leads - 11/21/2012 1:07 PM   
rmh



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Status: offline 		No onementions the servo/extension connectors
This is where the real issue lies .
Don't believe it?
Take an extension- any extension any length you use
plug in a 6 v battery to one end and stick a load of aprox 4 amps on the other ( a couple of 1157 taillight bulbs in parallel will do) - now when the bulbs are lit - -wait a while- about 10-20 mins- feel along the wire and the connectors
Where is it hot?
the wire ?
the connectors?
OR grab your old vacuum cleaner and do the carpet - feel the cord - is it warm -if so feel the plug - which is warmest .
years back a local bunch of clowns decided aluminum wiring in new homes and even the feed to the homes could be done for lower costs -in aluminum!
The wire wasn't the problem but the connections -in outlet boxes /terminals etc., prooved to be a disaster .
wasn't hard to find where the resistance problem really was . just follow the smoke -

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RE: Digital servos-long leads - 11/22/2012 5:08 AM   
417mack


 

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quote:

ORIGINAL: dirtybird


quote:

ORIGINAL: MAXIAN

interesting topic, question, but an extension with more resistance, also implies a higher consumption of current and battery?
thank you


A higher resistance means less consumption of current. Check out Ohms law.
But your servo will produce less torque. It gets less voltage.


If it takes a given wattage to operate the servo at a given load  and resistance is increased something else must increace voltage or current.  With a battery voltage can  only decrease as load or resistance increase,  this may explane some 2.4 lockouts. This is my understanding of Ohms law but I may be wrong.

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RE: Digital servos-long leads - 11/22/2012 1:11 PM   
rmh



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Status: offline 		You are on the right track-
The guys who experience "problems" really shouldd look at the entire packag - batt/wires servos - all while working -not individually
The do it yourself extension connectors are frankly, NWAS.
If you are doing a 2 lb model which draws meager current - then they are likely ofk BUT if you do the old heat test - (apply a load ) you will find these setups -unlees perfectly c rimped and perfectly assembled - are poor conductors.
It is really too bad that the old Dean's 3 wire fittings were never adopted as a standard .

Take a handful of the "industry standard" fittings -by various mfgrs or even simply different ones as sold at different times by your favorite mfgr.
The connection tension /fits vary all over the place .
it is always easier to blame any problem on the receiver .
That way no one knows how the rest of the system was done
By you-

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RE: Digital servos-long leads - 11/23/2012 8:06 PM   
Four Stroker


 

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Status: offline 		I actually measured the resistance of a Futaba HD pin pair - 3 mOhms. The old time Deans 3 pin servo connectors (still available) single pin pair is only 1 mOhm. The Deans are good if you are making your own cables. The 4 pin has a nice ridge to pull on. A real crimper is about $500~$700. ALL OF THE AFTERMARKET cable guys have a bunch of illegal orphans in a sweat shop using $10 crimpers. It really does not matter how nice of a guy they are.

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RE: Digital servos-long leads - 11/24/2012 2:01 PM   
Rotten40851



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Status: offline 		in my Aeroworks Edge 540's (DA50 & DLE 55) I have used the Flat HD servo wire from HiTec , cut the male end off the servo and soldered the exact length wire needed ( up to 36 inches ) with Hi tech 7955's and Spektra 6030's with no issues whatsoever.  I use (2) 2600 NiMh 6 Volt NoBS  packs  with (2) HD switches both plugged into the Rx for redundancy. It's a little extra work, but well worth it in my opinion. If I were you ( the OP) I would go back to soldering my connections instead of using the extensions.  My 2 cents  

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RE: Digital servos-long leads - 11/24/2012 3:29 PM   
rmh



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quote:

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in my Aeroworks Edge 540's (DA50 & DLE 55) I have used the Flat HD servo wire from HiTec , cut the male end off the servo and soldered the exact length wire needed ( up to 36 inches ) with Hi tech 7955's and Spektra 6030's with no issues whatsoever.  I use (2) 2600 NiMh 6 Volt NoBS  packs  with (2) HD switches both plugged into the Rx for redundancy. It's a little extra work, but well worth it in my opinion. If I were you ( the OP) I would go back to soldering my connections instead of using the extensions.  My 2 cents  

This std procedure for any large IMAC/ Scale stuff we build for ourself and others
Using the least number of connections possible is the goal -always
NoBS has some GOOD NiMh packs - and recommends the high energy types . good stuff
I am stuck on genuine A123

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