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Analog vs. Digital

Old 01-07-2012, 10:25 AM
  #51  
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Default RE: Analog vs. Digital

I try not to get into posting resume's but I used to teach network cabling for Network+ and MCSE students at University of Phoenix including properly using all the latest Fluke test equipment. I also installed many miles of that Cat 5 and 6 (and Fiber optic cabling). So as I said, twisted pair cabling is great in preventing cross talk (interference between pairs of communication and data cables). I was also an avionics tech working on P-3's for a long time and somewhat of a recognized expert in my field in the Navy.

As for helis, I may be the heli forum moderator but I fly and review everything from small electrics to giant scale gliders. My current review project is the 130" H9 Pawnee.
http://s1232.photobucket.com/albums/...wnee%20Review/

So back to twisted servo wires, they do nothing to help in an RC installation.
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Old 01-07-2012, 11:10 AM
  #52  
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Default RE: Analog vs. Digital

Never met a Professor that was as smart as he thought he was.

What ever 'theory' may be taught, here is a real life experience.

"First hand experience - I had a 3.6 meter Ventus with flat wire to the elevator servo in the fin. 72 MHz radio. The elevator servo would oscillate once or twice around neutral after giving an input. Everyone said bad pot. New servo, same thing. Changed the extension to twisted wire and the problem disappeared."

Now this technique has been used in RC wiring for decades. To say is has no value is doing your modeling peers a disjustice IMO. It obviously DOES help in some circumstances, and certainly does no harm. Why not add it to your preventative measures.

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Old 01-07-2012, 11:13 AM
  #53  
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Default RE: Analog vs. Digital

Why is it that only Hitec recommend twisting the leads? None of the other major manufacturers need this treatment to make their servos work right.

Just a thought.

Bliksem
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Old 01-07-2012, 12:17 PM
  #54  
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Default RE: Analog vs. Digital

There is nothing wrong with Hitec servos... like was stated earlier, he tried several brands and they all jittered. This isn't a servo, battery, or Rx issue... this is a retract motor noise issue! Now let's get a solution going (hopefully from the MFR, sounds like he's working on it) and we can all get along again.

Once again, NOT a bad servo issue here!
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Old 01-07-2012, 12:28 PM
  #55  
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Default RE: Analog vs. Digital

ORIGINAL: Firepower R/C

There is nothing wrong with Hitec servos... like was stated earlier, he tried several brands and they all jittered. This isn't a servo, battery, or Rx issue... this is a retract motor noise issue! Now let's get a solution going (hopefully from the MFR, sounds like he's working on it) and we can all get along again.

Once again, NOT a bad servo issue here!
All motors make 'noise'. Shielding the system from it is the solution.

Many suggestions have been made, all of which have worked in the real world. No need to start over here.

At the top of the list is doing what the manufacturer recommends, using a separate battery, cutting the red wire, and isolating the RX in this way. That should be the first step. That is all I have ever had to do with these motors, using all kinds of servos.
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Old 01-07-2012, 12:43 PM
  #56  
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Default RE: Analog vs. Digital

What ever 'theory' may be taught, here is a real life experience.

"First hand experience - I had a 3.6 meter Ventus with flat wire to the elevator servo in the fin. 72 MHz radio. The elevator servo would oscillate once or twice around neutral after giving an input. Everyone said bad pot. New servo, same thing. Changed the extension to twisted wire and the problem disappeared."
I've had exactly the same problem!

Every time the problem was the same, high resistance on the extension lead connection.
Unplug & replug the connection a few times, problem solved. Lesson learnt - never put
servo extension lead connections in inaccesable places, solder the connection.

Nothing to do with twisted wires, if you had changed to another flat lead or just unplugged/
plugged a few times the result would have been the same. - John.
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Old 01-07-2012, 12:48 PM
  #57  
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Default RE: Analog vs. Digital

ram3500-RCU, my point was to indicate to those who think that this is a Hitec servo problem, that it is not. Nothing more, nothing less. No one is starting over here. And you have basically stated the same thing I implied about the MFR of the retracts...

Thanks, Rich
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Old 01-07-2012, 12:55 PM
  #58  
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Default RE: Analog vs. Digital

ORIGINAL: Firepower R/C

ram3500-RCU, my point was to indicate to those who think that this is a Hitec servo problem, that it is not. Nothing more, nothing less. No one is starting over here. And you have basically stated the same thing I implied about the MFR of the retracts...

Thanks, Rich
Roger that. Good point. Agreed and thanks.

Guess I just wanted to emphasize that, when the Down & Locked suggestions are followed, the best results will be had. They have done a lot of R&D on their components and know what works best.

Servos do were out, and can be damaged internally by crashes, and look otherwise in tact. Using these servos in any system can cause problems with glitching, not that that is the case here. I have also, on very rare occasions gotten new servos that seemed to be very 'noisy' as well. More so with Hitec. Again, in the hundreds of servos over the years, just a couple, but it can happen.
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Old 01-07-2012, 02:58 PM
  #59  
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Default RE: Analog vs. Digital

ORIGINAL: BarracudaHockey

Twisting wires is great for phone and network cables.

It does nothing for servo wires.
RIGHT!!! Thank you, BarracudaHockey. I was starting to feel like I was the only one in the RC hobby who understood this.

Twisting does not help with common mode noise. Twisting does not help with differential mode noise.

Twisting does help cancel out pickup from adjacent conductors in multiconductor cables such as found in phone and data lines. Twisting can help maintain a constant characteristic impedance, which is important in some RF applications, but not for us. Twisting helps keep separate wires in close proximity, which can help reduce differential mode pickup and radiation. But our servo wires are already held in close proximity by the plastic insulation. Twisting the flat cable does not help further.

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Old 01-07-2012, 03:21 PM
  #60  
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Default RE: Analog vs. Digital


ORIGINAL: JPMacG

ORIGINAL: BarracudaHockey

Twisting wires is great for phone and network cables.

It does nothing for servo wires.
RIGHT!!! Thank you, BarracudaHockey. I was starting to feel like I was the only one in the RC hobby who understood this.

Twisting does not help with common mode noise. Twisting does not help with differential mode noise.

Twisting does help cancel out pickup from adjacent conductors in multiconductor cables such as found in phone and data lines. Twisting can help maintain a constant characteristic impedance, which is important in some RF applications, but not for us. Twisting helps keep separate wires in close proximity, which can help reduce differential mode pickup and radiation. But our servo wires are already held in close proximity by the plastic insulation. Twisting the flat cable does not help further.

Who said anything about twisting flat wires?
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Old 01-07-2012, 04:32 PM
  #61  
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Default RE: Analog vs. Digital

I'm not sure I completely agree with

Twisting does not help with common mode noise. Twisting does not help with differential mode noise.

Noise signals can appear on a cable for several reasons: capacitive coupling of nearby electric fields, inductive coupling of local magnetic fields, electromagnetic coupling. The coupled signal appears as an additional signal on the twisted pair. The twisted pair intercepts coupled signals equally, so the incident signals appear as common mode signals. These common mode signals are then eliminated by the differential receiver. So twisted pair wiring does aid in the elimination of noise.

I agree that in the RC world since the control pulse on the servo lead is transmitted single ended and not transmitted differentially then twisting servo leads really doesn't help.
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Old 01-07-2012, 04:49 PM
  #62  
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Default RE: Analog vs. Digital


[quote]ORIGINAL: Zeeb

ORIGINAL: panhndl


...Twisted wires are kind of pretty and it helps routing but as noted, that's really for phone wires and network pairs along with the ferrite ring deal; stretching for an answer and coming with ''it won't hurt anything'' types of solutions.

My FIRST action would be to change out the servo leads, then start verifying you have adequate current flow available.....
Change out the servo leads to what, since you say twisted wires are "stretching for an answer" ?
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Old 01-08-2012, 08:30 AM
  #63  
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Default RE: Analog vs. Digital

ORIGINAL: spaceworm


ORIGINAL: Zeeb



...Twisted wires are kind of pretty and it helps routing but as noted, that's really for phone wires and network pairs along with the ferrite ring deal; stretching for an answer and coming with ''it won't hurt anything'' types of solutions.

My FIRST action would be to change out the servo leads, then start verifying you have adequate current flow available.....
Change out the servo leads to what, since you say twisted wires are ''stretching for an answer'' ?
Just replace them with some new leads is a good start. You'd be surprised how many guys have chased issues especially with long servo leads only to find out they have an issue with either the lead itself or more commonly the connectors. Those tiny pins are susceptible to corrosion, wear and abuse and on a long run that extra resistance can cause issues. The other point is the power system where a lot of guys are underpowering their systems or failing to assure a good current path. That point was made by ram3500 when he indicated separate batteries should be used and repeated by Ron when he had the OP try the setup with separate batteries. Even ram3500's "evidence" that twisted leads will solve some issues is only anecdotal and like he said, it won't hurt anything.

I use twisted servo leads on my bigger models because I run 20g wire and that's how the vendor supplies those leads, not because I think it's an issue with external EMI getting into the system...
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Old 01-08-2012, 09:08 AM
  #64  
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Default RE: Analog vs. Digital

I have had jitter problems on ailerons from three different planes in the last year and a half, I have successfully repaired two planes and haven't made the effort on the third one yet. I do not have retracts on any of my planes because I am more into aerobatic airplanes, but so far the two planes I repaired were both defective hitec servos, one was a 645 the other a digital 5645. I was sold on hitec early on by fellow flyers recommendations, but my personal experience with futaba digital and anolog servos on two planes has sold me on them. They are "so smooth and QUIET"! I don't use futaba's radios but I will use their servos from now on!
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Old 01-08-2012, 06:04 PM
  #65  
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Default RE: Analog vs. Digital

ORIGINAL: kurt2022

I have had jitter problems on ailerons from three different planes in the last year and a half, I have successfully repaired two planes and haven't made the effort on the third one yet. I do not have retracts on any of my planes because I am more into aerobatic airplanes, but so far the two planes I repaired were both defective hitec servos, one was a 645 the other a digital 5645. I was sold on hitec early on by fellow flyers recommendations, but my personal experience with futaba digital and anolog servos on two planes has sold me on them. They are ''so smooth and QUIET''! I don't use futaba's radios but I will use their servos from now on!


The comments on this forum all have validity and everyone has experienced their own personal electrical problems in all R/C related systems not just a Down and Locked conversion, and ultimately found a cure, some found the culprit while others may have masked the problem which presented itself as the culprit. At Down and Locked we have been puzzled by this extremely rare issue that accounts for less than 1% of our customers. The fact that it is a lower than low percentage doesn't mean that we aren't concerned. Just the opposite is true we have field tested with every servo in question and have personally experienced no problems with the ones that we purchased directly we have had customers send us problem servos "indeed they have an issue with interference" the puzzling factor is we can test with two identical servos and have different results. At Down and locked we have state of the art test equipment and are currently testing methods to determine is it our problem or the servos problem. At this time we do not have an answer because we are not quick to make a judgment or conclusion until every possible scenario has been investigated. We have also spoken with the manufacturer of problem servos. We appreciate everyone's comments and we further respect their aircraft and the investment they have in them. It is with this respect that we will determine the cause and provide a cure, a time frame cannot be applied to this other than to say that it is a top priority at Down and Locked. If anyone has questions please feel free to contact us directly. Thanks again Mitch Stott
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