Dual receiver setup and sensors

[Nadim]

Hi there,

I am setting up a dual receiver and dual battery setup for a 94" gas airplane, as following:

1) BATT1 --> RX1 --> some servos; and
2) BATT2 --> RX2 --> rest of the servos, ignition, kill switch etc.

Both batteries are LiFe 6,6 V so I am not using any kind of BEC. Tx is the Taranis Plus, and both receivers are the (now quite old) D8R-II Plus, non-EU.

Now, what I wonder whether can be done or not is to get telemetry data separately from both receivers at the same time. Such data would only include RSSI and internal voltage (both receivers have the little black jumper plugged in the A1 sensor port, so to make it an internal voltage sensor).

It seems the Tx can't tell them apart though with respect to telemetry. If I try with the automatic sensor search, I only get one single voltage sensor on the A1 port (can't tell which Rx's), and one single RSSI signal output (which I again don't know which receiver is coming from). Is there a way to tell the Taranis to differentiate the two?

Thanks!

[Kilrah]

You can only have one receiver with telemetry enabled, the other needs to have it disabled at binding time.

[Nadim]

I didn't even know during all the past years that telemetry could be disabled during binding.

Forgive me to ask, how can I do that?

[jhsa]

Kilrah, he has two D8R-II Plus receivers. I don't think telemetry can be disabled??

João

[Kilrah]

I'm not sure either but no time to dig into it and check, hence why I limited myself to saying one needs telemetry disabled - might not be possible with his config indeed.

[Nadim]

I find no mention of it in the manual. I guess it is a feature available only on more recent receivers.

Do you guys think just using both D8R-II+ simultaneously, without worrying about telemetry, can cause some issue in the long run, like interferences or some "information load up" in the Rx or the Tx, that can cause system crashes?...

Or should I just invest money for a a new couple of receivers?...

Thanks as always

[bob195558]

If you use erSkyTx firmware on your Taranis, you can can use two transmitter modules at the same time, one for each receiver.
And choose which one you want for the telemetry (internal or external module).
This will give you 16 channels.
I find that the external module has a stronger signal then the internal module.

[Nadim]

Ha! Now That's an idea. Thanks. I actually do have an external DJT I am not using that I could try out.

I run OpenTX though, but I only need 8 channels, so no need to switch to erSkyTx.

Now concerning telemetry, I was reading here:
viewtopic.php?t=8401

and here:
viewtopic.php?t=10269

I made a plan that I would be thankful someone with more expertise than me could kindly confirm it would work as per my understanding.

1) I plug the external DJT in the back of the Taranis, and switch both modules on from OpenTX, both in D8 mode.
2) I bind Rx 1 to the XJT and Rx 2 to the DJT, both with telemetry ON (as there is no way to do otherwise).
3) Telemetry shown inside OpenTX will be the one, and only one, coming from the XJT and Rx 1.
4) Telemetry coming to the DJT from Rx 2 just stays inside the module I guess? My understanding is that it is not capable of traveling inside the radio and/or being processed by OpenTX. To see this data I would have to connect to the DJT one of those old FLD-02 telemetry screens from Frsky -- which also let you set the alarms limits. I happen to still have one!

Would the above work? I am a bit concerned about interferences and signal strength caused by the extreme proximity of the two modules. Is this a real concern?

Thanks guys!

[Kilrah]

You can of course also use the 2nd module in OpenTX with all channels.

Everything is fine as described, just make sure to orient the antennas 90° from each other or you might get telemtry losses occasionally.

[Nadim]

Thanks Kilrah, as always.

Yes the cool thing of this configuration is that I also get 8 extra channels "for free", which I didn't really need actually, as 8 were enough for the plane.

My original motive for going "dual Rx", indeed, was to reduce the Amps load on the Rx. I was fearing the D8R-II Plus' circuitry isn't capable of handling the current of 7 servos of a 93" plane. I still don't know how real this concern is, but to be safe, I decided to split them into two Rxs. In this way I'm going to keep things very simple: two LiFe 6,6 V each going straight into the Rxs, 4 servos each: no switches, no BECs, and no powerboards.

Now I'll see if I can make a wise use of those extra 8 channel to sort of improve safety even more...

[Nadim]

I thought I'd report back.

Unfortunately it turns out that the above configuration (two D8R-II Plus, one binded to the Taranis' internal XJT and the other one binded to an external DJT put in the moduel bay) doesn't work well: I get reduced range and telemetry is constantly lost and recovered once a second during flight.

My antennas inside of the plane are 90° each other, aren't close to the ignition or anything. Same for the transmitter: antennas angled 90° from each other. So I don't think I can do much to improve it...

So I removed the DJT from the bay, and binded both the D8R-II Plus and a V8R7-II, which has no telemetry capability, to the internal XJT -- of course both in D8 and both from 1° ch to 8°.

It's a pity, I wonder if every dual RF configurations have this kind of problems.

[Kilrah]

Is your DJT stock, or has it been modified to output telemetry to the Taranis?

[Nadim]

It is stock.