FrSky conversion of JR XP7202

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Re: FrSky conversion of JR XP7202

Postby BobAZ » Fri Jul 16, 2010 7:54 pm

No, the button is recessed and needs a small "probe" to access it.

I have heard nothing about the model, so I presume that it is gone forever.

Since I don't have the receiver, I cannot determine whether the problem was with the RF or receiver.

I had previously converted the JR XP7202 transmitter to 2.4 GHz by using the Spektrum DM9 module. The 7202 does not accept modules, so I removed the RF from the DM9 and put it inside the TX – after removing the 72 MHz RF. I used the Spektrum AR7000 receivers and it worked great – never had a glitch. After reading your reviews about the DSM2 potential problem and the FrSky system, I decided that the FrSky would give me a "better" system than the DM9 hack. I purchased the DIY RF module and 8 channel receiver.

I am now wondering if I should have purchased the JR module instead of the DIY? What do you think? Is it the same - I thought so?

I wonder if I have a "bad" RF? Should I purchase another DIY module and receiver and try it again - with a much cheaper A/C?

Do you know if FrSky is coming out with a DIY telemetry RF? And if so, have you heard of a ETA?
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Re: FrSky conversion of JR XP7202

Postby RCModelReviews » Fri Jul 16, 2010 9:12 pm

I suspect you've been the victim of bad luck, just like those who ended up with zero GUID Futabas and expensive Spektrum receivers with faulty smart switches etc.

I'm about to do a FrSky DIY conversion on a 7200 series JR transmitter so you can compare yours with mine, when I document the process.

For the price of another receiver, I'd be temped to do some more testing.

You seem to suggest that your model flew away -- did you have the failsafes set to shut down the motor and/or put the model into a spin? Never leave the failsafe setting for the engine or motor on its default setting because that will simply cause your electric to sail off into the distance or your glow/gas engine to keep screaming if it was at full throttle when the problem occurred.

I've lost count of the number of times I've repeated the wisdom of *always* setting the failsafe. This is important for two reasons:

1. if you do have a loss of RF link (from interference or a failure of some kind) then you'll be able to see the model go into failsafe and it won't fly away.

2. if the failure is caused by something else (such as a faulty receiver battery, bad switch or whatever) you'll also be able to determine that because the failsafe will not activate.

A growing number of 2.4GHz systems (including the FrSky) now have good failsafe capabilities and it only takes 15 seconds or so to set them up. It should be an essential part of an installation.

So perhaps get a new receiver, put it in an old model, set the failsafes and then fly it high and far (upwind if you can) to see what happens. If failsafe kicks in then it's likely you have a dud transmitter DIY board. If it doesn't then either your last receiver was faulty or something else went wrong.
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Re: FrSky conversion of JR XP7202

Postby BobAZ » Fri Jul 16, 2010 10:53 pm

As I had mentioned previously, I had not set the fail-safe. I was anxious to see how it performed.

Should I purchase the HV receiver rather than the "standard" one? Is it the same except for being able to handle high voltage servos?
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Re: FrSky conversion of JR XP7202

Postby RCModelReviews » Sat Jul 17, 2010 1:13 am

I have some HV receivers here to test but haven't had time to put them on the bench yet. I expect that there should be no downsides to going with the HV receiver but will confirm that next week.
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Re: FrSky conversion of JR XP7202

Postby BobAZ » Sat Jul 17, 2010 6:28 am

The JR XP7202 is a seven channel TX. I bought the 8-channel receiver thinking that I could use channel 8 as a battery input. Hopefully, this was not the problem – using an 8-channel receiver with a 7-channel TX. Should I have bought the 7-channel receiver?
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Re: FrSky conversion of JR XP7202

Postby RCModelReviews » Sat Jul 17, 2010 10:52 am

No, the 8-channel is (IMHO) a better choice. The 7-channel receiver is fractionally lighter because it has top-pins and a very thin plastic wrap rather than a hard-case but functionally they're identical and who knows, one day you may upgrade to an 8-channel transmitter and want that extra channel in your receiver.
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Re: FrSky conversion of JR XP7202

Postby rafa » Tue Jul 20, 2010 6:08 pm

The only reason to use the slimer 7 chanel version is if you are to use it in models with little or no space like slim fuselage gliders , electrogliders , pylon racers or smaller models.
Otherwize its better to use the hardcased 8 chanels.
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Re: FrSky conversion of JR XP7202

Postby BobAZ » Tue Aug 17, 2010 11:44 pm

I recently sent a PM to Chase Wu at FrSky because I purchased another 8 channel receiver and got a couple of hits. This time I had set failsafe, which I had forgot to when my Trojan flew away. Below is the response I received from them.

Originally Posted by Chase Wu
Hello BobAZ,
Thank you for your PM, and I replied you via posted of #1165 (http://www.rcgroups.com/forums/showthread.php?t=1176328&highlight=frsky+2+4ghz+radio+system&page=78).

Please kindly find attached drawing on that post for your reference (sorry can not insert that in PM ). It is suggested to find the OC gate first; if failed, add one triode or 1K capactor.

PPM peak voltage would be 3.3V.

My response:
Was the lack of this circuitry the problem that I was having with the loss of signal?

Hello BobAZ,
1) S5850 or 2N5551 both can be used here as triode.
This is the reason that have caused your loss of signal.
2) HiModel will have JR modules in stock this afternoon.
3) I presume new V8HT with this new circuitry installed would be ready in about half a month.

Many thanks and best regards!
Eva

My response:
Thanks for the quick response.

You still have not responded to the following questions.

You did not indicate if I am interpreting the diagram correctly. Do I add the triode to the PPM wire from my JR TX? If so, then I understand the rest of the circuitry (resistor going to DIY PPM wire and another in parallel between there and the + wire). Am I correct?

I'm guessing that that means the JR Module and the DIY RF are different. Is that correct?

Does the following statement in your response mean that FrSky was the cause of me losing my model?

"Hello BobAZ,
1) S5850 or 2N5551 both can be used here as triode.
This is the reason that have caused your loss of signal."

It sounds like it was.

And now because I have brought this issue up you are correcting the problem.


I have not heard back from them – my last PM was yesterday, prior to that post they were very quick to respond.

I am now convinced that I have a problem with the DIY RF in my JR XP7202. Should I use the circuitry as Chase recommends in post #1165, the one recommended in post #1201, or something else? I don't have an oscilloscope, but if I can borrow one, what do I connect to get the PPM reading to see what the voltage is? Do I "tap" in by connecting to the PPM wire and ground from my TX? Do I need to disconnect the wires going to the DIY RF or is it OK to just connect to them without unsoldering?

It sounds like FrSky is making some changes to their modules and DIY RF because of problems. I don't want to try again until I know that this problem has been fixed.

Should I purchase a JR module and then remove the RF and put it inside my XP7202 (it has not module). I am not interested in the telemetry systems. I just want a system that works. I thought by going to the FrSky it was an improvement over my hack using the DM9 module which gave me DSM2. I had NO problem with it using an AR7000 receiver.
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Re: FrSky conversion of JR XP7202

Postby RCModelReviews » Wed Aug 18, 2010 2:46 am

I'm about to do a 7202 DIY conversion using an FrSky kit. I'll see what I find and document exactly what (if any) mods I make.

From memory, the Corona DIY kit also feeds the PPM input straight into the microcontroller without any level-shift considerations -- but I'll check that too.
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Re: FrSky conversion of JR XP7202

Postby funtana » Fri Aug 20, 2010 12:29 pm

Just to go back to the 8 channel high volt receiver, i now have several of these in use working from bec speed controllers, all working fine.
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