FrSky Taranis - user chat

[john stones 1 - Moderator]

All my models now done, 2 were models I have flown a bit and when moved over on to Taranis 100% movement gave me more servo travel than I had on the 9x for the same %. I am not mistaken because the servos where stalling so it was noticeable. Anyone else had the same ?

John

[Phil Green]

Going back to the Frsky SBUS to PWM decoder, to recap - the SBUS output from the receiver is at a fixed frame rate of 9ms. The SBUS-PWM decoder repeats its PWM (servo) outputs at the frame-rate it receives, so all the servo channels are at 9ms repetition which is a big problem for conventional servos.

I did some individual PWM frame-rate dividers which work fine, but its a bit untidy having four of them between the decoder and the servos, so the intention was always to make one inline unit that would sit between the rx and the decoder to lower the actual SBUS framerate to give an analogue-friendly value on all four channels.

I just finished it tonight, it works great on the bench using Bobs receiver and decoder which he kindly loaned for the project (thanks Bob)

Here are four scope traces, not very exciting but you can see how the 9ms incoming frame-rate is dropped to 18ms.

First this is what the SBUS signal looks like, note the 9ms repetition rate:

Next is a typical servo output from the decoder, again note the 9ms framerate. Bad for conventional servos!

Heres the same servo signal with the new SBUS-frame-rate divider between the rx and the decoder, note the 18ms framerate which is the object of the exercise (all 4 servos are at this rate):

And heres a dual trace showing the SBUS input from the receiver, and the new SBUS output to the decoder:

Cheers
Phil

Edited By Phil Green on 05/09/2014 01:10:28

[John Privett]

Yes, I'm fairly sure I have more servo movement than I had with the Futaba T7C.

Looks like your 2,000th post coming up next John!

[Chris Bott - Moderator]

Brilliant stuff Phil, that looks like it will be really useful. I ought to put one on my Sea Fury, even though it seems to be working fine with the analogue servos I have fitted.

John I've not noticed and difference in servo movement when transferring models from Spektrum gear.

[Bob Cotsford]

First, about 80% volume in the mix tab will give a similar range of movement to other brands 100%, I guess the greater range of monement helps to give a high resolution.

Second, that's looking very good Phil, just the job for warbirds with a flap, aileron and retract in each wing half. Instead of the 6 connections on my Macchi or Ki61 this would cut it down to one connector per wing.  I take it all 16 channels are still available to the decoder?

Edited By Bob Cotsford on 05/09/2014 09:54:39

[Former Member]

[This posting has been removed]

[Chris Bott - Moderator]

From another forum it seems that to convert from Futaba to Taranis, you should set throws to 86% of your Futaba settings, and from Spektrum to Taranis you should use 80%.

How true this is I don't know, but it may be worth a try.

It seems that I'm just enjoying larger throws

[Plummet]

I bought a Taranis a few weeks ago but I have not had the chance to play with it until now.

Looking at the web documentation I had found led me to believe that I needed to devote a bit of time to get to know it.

So - I am on holiday staying with friends on the Channel Islands - and I have my TXs and a couple of models with me. Now is the time.

I have often found that the best way of learning about something is to write myself some documentation - so that is what I spent yesterday afternoon starting to do. I have to say that I am very well impressed by the facilities it offers.

My plans for today are to configure it for my Phoenix sim, and to then put a RX in a model and to configure that.

My documentation is in the form of a 'Mind Map'. If you haven't encountered one of these, then I would recommend them to you if you have to organise and or present information. It allows you to create notes in a branching tree structure.

You start by giving a name to your info - and this forms the 'root' of your map. You then think of the major topics that need to be covered by the map, and create branches for each of them. Just repeat the process on each topic creating more and more branches until you have all the info on there that you wish to include, and probably more that is superfluous. Do a bit of trimming or hiding and reorganisation, and job done.

Some time ago I needed to create a looping 'Powerpoint'* type presentation. I did a brain-dump of the sort of info I wanted to present using the mind-map software, and then found that it was a trivial task to convert it directly into a presentation.

Were I to do this with the incomplete mind-map I have already got from the Taranis I would have a VERY long and EXTREMELY boring presentation. A cure for insomnia anyone?

Plummet

*Of course, as I avoid windows I did not actually use Powerpoint, but the LibreOffice equivalent.

[Bob Cotsford]

there's also an 'extended limits' setting in Model Settings that gives you even more movement - 125% iirc.

Plummet, have you checked out Open TX University?

[Plummet]

Posted by Bob Cotsford on 05/09/2014 11:06:11:

Plummet, have you checked out Open TX University?

Not yet - but thanks for the hint.

From my reading yesterday I am wondering if the "extra" servo movement is related to the trim. I think that I read that on the Taranis (by default but changeable) the trim adjusts the centre point of the servo without moving the end points.

It implied that on other TXs the trim also moved the endpoints. So for them 100% + 25% trim gives a servo range of -75% to +125% , and 100% - 25% trim gives -100% to + 75%.

On the Taranis the centre point may move to + or - 25%, but the endpoints are always 100%.

(I haven't read this whole thread yet, so sorry if I am teaching egg consumption to grannys.)

Plummet

[Bob Cotsford]

There are options to control how trims act on the limits but I've not played with them, I just use whatever is default.

[Chris Bott - Moderator]

I believe that the trims do also move the endpoints. However there are also hard limits, which we can set where we like, and a servo will not go beyond those whatever we do.

[Dave Bran]

Reprise:- I use Futaba, Spektrum, and FRSky Taranis. Seven 2.4GHz Tx's. (and some 35's)

Before Taranis appeared I was often desperately trying to get Spektrum to give enough throw and decent resolution in combination, and though Futaba was def much better, even that sometimes was restricting.

(I do like my models very responsive!)

With Taranis (either FRSky internal or via a FASST module on it) I'm def getting more throw. On FASST Rx planes I have moved across, the increase from 140% Futaba to Taranis default 100% has been quite marked.

[PatMc]

If Extended Limits is activated in the Model Setup page the servo limits can be set between +/- 150% & the subtrim set between +/- 100% in the Servos page. Most servos won't be capable of using the full movement but it does allow flexibility when a badly positioned servo arm that can't easily be accessed causes a problem.
Also if aileron differential is set in the Servos page by moving the subtrims both servos full movement can be used instead of it being reduced at one side. However if the ratio needs to be changed retrospectively the servo arm would have to be removed & re-positioned to the new centre.

[john stones 1 - Moderator]

I used mine for the first time today, to be honest I can't tell the difference between it and my 9x apart from it's lighter.

Range check is very good, I get a long time out of the 800mah battery. £140 with an 8 channel receiver, my J.R days may be over. I need to change the trim to a coarser setting though.

John

[Biggles' Elder Brother - Moderator]

John I agree - fine trim is great when what you have is basically set up model and you just need to tune to slightly altered day-to-day conditions. But when maidening a model you can run out of trim very quickly!

One thing I would think carefully about before trying is "expo-trim". I put this on my Sbach when I first set it up, it was a mistake! To me the expo is the wrong way round with the steps getting bigger as you move away from zero! So when you get to right trim setting its doing great big steps either side of where you want to be! Knowing Taranis it wouldn't surprise me if you can reverse this - ie have the big steps at the centre getting progressively smaller!

BEB

Edited By Biggles' Elder Brother - Moderator on 07/09/2014 22:37:57

[andyh]

Posted by Biggles' Elder Brother - Moderator on 07/09/2014 22:36:58:

To me the expo is the wrong way round with the steps getting bigger as you move away from zero! So when you get to right trim setting its doing great big steps either side of where you want to be!

really? do you know anyone who flies with reverse/"falling-rate" expo?

[john stones 1 - Moderator]

The trim is very fine compared to what I am used to BEB I put about 10 clicks of elevator in, yet when I landed could not notice the difference, I never use expo I can't get on with it, I prefer to set rates up. If they ever bring a smarter (blingy) box out I reckon they would grab a fair few customers.

John

[Phil Green]

Posted by andyh on 07/09/2014 22:50:17:

really? do you know anyone who flies with reverse/"falling-rate" expo?

Yes, Paul Luby flies his helis that way so its not unheard of.

Just a quick comment on the SBUS data-frame rate-divider, we've established that the SBUS to PWM converter follows the frame rate of the incoming SBUS data from the receiver - but in playing with the divider I found that the frame rate is only checked on power up - once the system is running you can change the repetition rate of the SBUS data and the servo PWM from the decoder stays locked at whatever it was on power up!

Cheers
Phil

Edited By Phil Green on 08/09/2014 00:35:03

[Biggles' Elder Brother - Moderator]

Posted by andyh on 07/09/2014 22:50:17:

Posted by Biggles' Elder Brother - Moderator on 07/09/2014 22:36:58:

To me the expo is the wrong way round with the steps getting bigger as you move away from zero! So when you get to right trim setting its doing great big steps either side of where you want to be!

really? do you know anyone who flies with reverse/"falling-rate" expo?

Sorry Andy - I meant the expo trim - not the expo itself. Taranis offers the ability to have your trim steps change exponentially. And that works like conventional expo - ie steps get bigger as you move from the centre. But for a trim adjustment that is not really want you want - you want the steps to get smaller as you move towards the "in trim" setting.

BEB

Edited By Biggles' Elder Brother - Moderator on 08/09/2014 11:21:28

[andyh]

Posted by Biggles' Elder Brother - Moderator on 08/09/2014 11:17:43:

Posted by andyh on 07/09/2014 22:50:17:

Posted by Biggles' Elder Brother - Moderator on 07/09/2014 22:36:58:

To me the expo is the wrong way round with the steps getting bigger as you move away from zero! So when you get to right trim setting its doing great big steps either side of where you want to be!

really? do you know anyone who flies with reverse/"falling-rate" expo?

Sorry Andy - I meant the expo trim - not the expo itself. Taranis offers the ability to have your trim steps change exponentially. And that works like conventional expo - ie steps get bigger as you move from the centre. But for a trim adjustment that is not really want you want - you want the steps to get smaller as you move towards the "in trim" setting.

BEB

just had a look & you can set trim to Expo or Extra Fine/Fine/Medium/Coarse - which I assume are linear - if you want, Expo is just the default setting

I would have thought that you'd want the finest trim setting round the centre of trim. that way, so long as you have a fairly in-trim model to start with, you can make sensitive adjustments. if I have a model that's so far out of trim that I need to use the extremes of trim, I adjust the clevises or whatever to get it roughly in trim & then make final fine adjustments on the Tx

horses for courses I suppose, but Expo trim makes sense to me. reverse-Expo trim would mean that you couldn't make fine adjustments to a mostly-in-trim model. or I'm possibly misunderstanding what you;re trying to achieve ...

[Biggles' Elder Brother - Moderator]

Andy - I'm not "trying to achieve" anything in particular! And I know what the trim options are on Taranis having had one as my only Tx since Feb!

The simple fact is that some time ago I tried expo-trim on one model, just to see what it was like - I didn't like it as I don't feel it works very well - just my opinion. I was merely passing that experience on to John. That's all.

BEB

[Chris Bott - Moderator]

It must be a very personal thing. I really like the expo trim. If a model is close to trimmed, then small increments let you fine tune nicely. But if it's a long way out, big steps get you there nice and quickly. If you want to fine tune after that, then go to the bottom of the (I think) servos page and reset trims. This puts trim centre, wherever you last left the trims. Next, go up again and fine tune your model.

[Bob Cotsford]

BEB, have you tried the 'instant trim' special function? Just in case you or anyone else has missed it, it sets the subtrims so that the instantaneous stick positions represent neutral. So take off, hold the sticks so that the model flies straight and level (or thereabouts if it's way off) then flick the switch that you have assigned as instant trim and it sets the subtrims for you. Centre the sticks and you should have a model that flies close to straight and level ready for fine trimming. Once you have the model back on the ground you can adjust the pushrods to get rid of the applied subtrim and then disable the instant trim, you really do not want it enabled except for a trimming flight.

[Chris Bott - Moderator]

I've used it Bob, well, I have on a disposable model, and it worked perfectly. What I'd suggest though, is that it's best to ask someone else to hit the switch. That way, you can concentrate on holding the model straight and level.

Having proved it to myself, I haven't dared use it during a maiden. Not sure why.