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Aug 16, 2018, 05:24 AM
Thermals, Tom
RyanNX211's Avatar
No.
Take the same problematic arrangement and swap in either a Futaba FHSS or Fasst and there are no issues.

The XPS Nano works almost as well. Fire up the engine and the control surfaces are unaffected. Do a range check with the engine running. Good!. Now try shutting the engine off (either the throttle stick or a 2 position switch if youíve set it up that way). Nothing! Red ignition armed light is illuminated and wonít go out. Plane runs out
Of fuel and flight controls and ignition switch are working properly again. With ignition turned off, check that there is not spark. Confirmed
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Aug 16, 2018, 05:37 AM
Thermals, Tom
RyanNX211's Avatar
Quote:
Originally Posted by JimDrew
I *think* you guys are having problems with servos moving on their own? Andy's explanation is 100% correct in that this is a SERVO issue, not an RF issue. Andy mentions that Spektrum receivers use high impedance servo outputs. So do all XPS receivers. The reason for doing this is that if you have a short circuit on the servo bus it won't kill the CPU, and thus crash the model. A lower impedance output would certainly help drive the servo to the proper position by having a signal level higher than the noise threshold, but you run the risk of killing the receiver completely should a servo short out (like signal to ground). I could make a receiver with low impedance outputs that would probably resolve this, but I am not thrilled with the idea of releasing something that could knowingly kill itself. The notion that one brand is better over the other because of this particular point is a bit silly. If you changed the output resistors on a Spektrum, XPS, Lemon, etc. to a low impedance value, they would all work just fine because they are all 2.4GHz devices and are immune to this type of noise from an RF stand point.

I am guessing that various receivers have different output resistors to set the impedance and those are typically parts with 5% tolerance in their spec, so I could see that maybe some of the exact same receivers might behave differently all depending on how much RFI/EMI is occurring.
.

Andy sent down some higher end receivers and some suppressors. The latter did nothing for the receivers that had issues.
Two of the receivers he sent down did not show any issues. Is Spektrum using LOW Impedance servo outputs on their higher priced servos? I ask because they worked on the same test platform... same batteries, same servos, same distance, same engine, same spark plug....

All this has elicited from him is some ad hominem attacks noted by his supervisor. You'd think they'd appreciate us finding an achilles heel. FrSky had the issue pointed out to them and they came out with a resilient receiver. I have no idea what they did.
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Aug 16, 2018, 02:20 PM
Quote:
Originally Posted by RyanNX211
No.
Take the same problematic arrangement and swap in either a Futaba FHSS or Fasst and there are no issues.
You are confused about what high impedance vs. low impedance means. If you changed the output resistors in a XPS Nano receiver that would probably "fix" the "issue" (although the issue is not with the receiver - see below). The Futaba receivers I have here use output resistors that are have 10 times lower impedance than our receivers. With the Futaba receivers there is a chance that shorting an output signal to ground (like an internal short in the servo) could exceed what the voltage regulator can supply for current and thus make the receiver no longer functional, OR the CPU itself could be damaged if the short is to the + battery side instead of ground. Using the proper output resistors to prevent these possibilities just makes good sense. It's something that I refuse to change, because it is right.


Quote:
Originally Posted by RyanNX211
The XPS Nano works almost as well. Fire up the engine and the control surfaces are unaffected. Do a range check with the engine running. Good!. Now try shutting the engine off (either the throttle stick or a 2 position switch if you’ve set it up that way). Nothing! Red ignition armed light is illuminated and won’t go out. Plane runs out
Of fuel and flight controls and ignition switch are working properly again. With ignition turned off, check that there is not spark. Confirmed
Ok, so you have FINALLY stated what problem you are having!

The issue you describe is due to device (Mark II/III) controlling the ignition on/off - period! Like any device that uses a PWM pulse from a receiver, it needs a signal level that is above a certain threshold and that device most likely has inadequate filtering for it's own power supply (which is used as the reference for the input signal). If the input voltage is fluctuating (which happens ever time the coil is fired) the voltage reference that is compared to the input signal from the receiver changes. I can tell you that properly filtered devices that control an ignition system, like the Tech-Aero BEC, have no issues with any radio systems - including 72MHz based. I would get a different ignition system or fix that one by adding some filtering. Put a scope on ground and the positive inputs into the ignition device. That will tell you everything.

I absolutely agree with Andy's assessment. This is not a RF problem or it would affect all brands the same. This is not a receiver design issue either. This is a design issue with the Mark II/III products. Have you tried using a simple servo signal booster connected between the receiver output and ignition? That might "fix" this "issue" by supplying a higher output voltage signal to the Mark II/III. Servo City sells one, and their website does a good job at explaining what they do:

https://www.servocity.com/12-boosted-extension

Filtering requirements for ignition systems is no joke! You need a LOT of filtering in order to get rid of the current spikes and EMI/RFI. The X24 has this type of filtering built-in for it's ignition driver. Tech-Aero's iBEC does as well. You can see a description of the filtering that is absolutely needed when working with ignition systems on their website:

http://www.tech-aero.net/ultra-ibec

By comparison, the Mark III board (based on the pictures of it) has only a few capacitors on the board, which is not enough for filtering the power input into the CPU, let alone filtering out ignition noise.
Last edited by JimDrew; Aug 16, 2018 at 03:38 PM.
Aug 16, 2018, 03:59 PM
Thermals, Tom
RyanNX211's Avatar
Still haven’t explained why two of the receivers he sent worked
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Aug 16, 2018, 04:09 PM
Thermals, Tom
RyanNX211's Avatar
Spektrum 2.4 receivers and ignition noise (0 min 30 sec)
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Aug 16, 2018, 04:12 PM
Thermals, Tom
RyanNX211's Avatar
I only brought up the Mk3 because it was the only unit that had any issues with the Nano.
The Nano works fine (testing limited) with other systems such a as Davidson, Condensor, Schmitt Trigger. You can not say this about other systems except with Futaba which seems to work with everything.

What is different about the Spektrum receivers above besides price ?
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Aug 16, 2018, 11:11 PM
Quote:
Originally Posted by RyanNX211
Still havenít explained why two of the receivers he sent worked

They could have lower impedance servo outputs.
Aug 16, 2018, 11:15 PM
Quote:
Originally Posted by RyanNX211
I only brought up the Mk3 because it was the only unit that had any issues with the Nano.
The Nano works fine (testing limited) with other systems such a as Davidson, Condensor, Schmitt Trigger.
That should tell you right there that the problem is the Mark III unit.


Quote:
Originally Posted by RyanNX211
What is different about the Spektrum receivers above besides price ?
Ugh! Andy (and I) have already stated the reason. It most likely the servo output impedance. It's not a "problem" with the receiver(s). It is a "problem" with the Mark III's really poor design for clamping EMI/RFI. I would bet that if you put 10 ohm resistors on the Spektrum receiver's servo driver outputs, that it would magically work. Nobody in their right mind would do that because you then open up yourself to liability for building a system with no bus protection.
Aug 17, 2018, 12:12 PM
Thermals, Tom
RyanNX211's Avatar
Quote:
Originally Posted by JimDrew
That should tell you right there that the problem is the Mark III unit.




Ugh! Andy (and I) have already stated the reason. It most likely the servo output impedance. It's not a "problem" with the receiver(s). It is a "problem" with the Mark III's really poor design for clamping EMI/RFI. I would bet that if you put 10 ohm resistors on the Spektrum receiver's servo driver outputs, that it would magically work. Nobody in their right mind would do that because you then open up yourself to liability for building a system with no bus protection.
Didnít work with Spektrum but that hasnít been tried with the Nano.
Donít get so hung up on the Mark3. That isnít even used with Spektrum because youíre much better off not using a 4cell batt with their system (yes I know they used to provide one with the DX7)
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Aug 17, 2018, 12:34 PM
Thermals, Tom
RyanNX211's Avatar
This is all reminiscent of me grounding the jet today because of the stench of jet fuel coming from the toilet. You can’t get jet fuel in the toilet the systems are unrelated

I had to offer to lock the mechanic in the lav to see how long it would take to become asphyxiated before I got them to acknowledge: Hey! The $hi##€R smell like JetA!. I suspect they’ll have an explanation faster.
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Aug 17, 2018, 05:33 PM
Quote:
Originally Posted by RyanNX211
Didnít work with Spektrum but that hasnít been tried with the Nano.
Donít get so hung up on the Mark3. That isnít even used with Spektrum because youíre much better off not using a 4cell batt with their system (yes I know they used to provide one with the DX7)

I am not hung up on the Mark 3... you have basically proved through your explanations and videos that it has a problem.
Aug 18, 2018, 07:51 AM
Thermals, Tom
RyanNX211's Avatar
Quote:
Originally Posted by JimDrew
I am not hung up on the Mark 3... you have basically proved through your explanations and videos that it has a problem.
Whatever preconceptions you may have about the MS MkIII, can you please put them out of your mind and focus for a moment. Iím looking for the cause of these issues. The solution is secondary because we found out a while ago that swapping in any Futaba receiver makes the problem go away no matter what kind of switch is being used. It was a mistake on my part to introduce the Mk3 into the discussion at this point because itís created such a diversion. I merely wanted to acknowledge that the Nano (despite its similarities to the Spektrum products) performed flawlessly until that servo eliminating system was introduced. AND it only had issues with activating the off switch and this was only with one engine.

In every one of those videos, whether in a plane or on the bench, the Mk3 system WAS NOT USED.

Please commit the green text to memory prior to any further diagnosis or recommendations.

Now, we may be on the cusp of disclosing a fix for the AR400 Spektrum which is , by far, the cheapest and most unusable offering available for this application. The fix does not involve any of the recommendations offered heretofore. It will then be tested with the DSMX clones, old FrSkys, and finally with the Nano at which point we will add that darn MS Mk3 to the test.

Please stand by. . . .
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Aug 18, 2018, 09:24 AM
Thermals, Tom
RyanNX211's Avatar
For what it’s worth, the MS Mk3 is not necessary for breaking in engines on the bench.
It’s only required to turn off the engine when you can’t hear it.
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Aug 18, 2018, 09:29 AM
Thermals, Tom
RyanNX211's Avatar
That is to say, turn off the ignition when you can’t tell if the engine has quit (high or quiet)
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Aug 18, 2018, 02:20 PM
Quote:
Originally Posted by RyanNX211
I merely wanted to acknowledge that the Nano (despite its similarities to the Spektrum products) performed flawlessly until that servo eliminating system was introduced. AND it only had issues with activating the off switch and this was only with one engine.
And WHAT switch was this? The Mark III, correct?

I don't care about ANY other brands of receivers that you have tried and tested. This is the XPS vendor area. I only care about any issues with our products. So, if you have a problem with one of our products I am happy to help, otherwise please don't ask about any other products.


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