Sebart Miss Wind resilient power and RF install

[MattyB]

Posted by Bob Cotsford on 15/06/2016 15:44:15:

Matty, the S-Bus lead provides one source for current supply (FrSky rate their SBus decoder and hence the SBus feed at 6A), then I use a second power only lead to the X10+ board's power connection pads. Ok it's an extra connection when fitting the wings but it does give reassurance that the 4 digital servos and 2 electronic retract units are well fed.

Note to self - learn to read more carefully... Apologies!

Posted by Bob Cotsford on 15/06/2016 15:44:15:

So 2 batteries, one direct to the receiver in the fuselage, another direct to the wing mounted gubbins. Probably overkill for a 1.20 size model but it helps me sleep at night

No, I don't think so - given this stuff is so relatively cheap and light now why not build in some resiliency? I have a feeling all my larger models will be getting setups like this in future when they can be squeezed in...

[Chris Bott - Moderator]

One way to use 2x X4R would be to use a DJT or XJT module in the transmitter bound to one Rx. That way you would also have two completely independent RF paths, thus adding to your redundancy.

[MattyB]

Sounds good in theory, but Jim Drew from XPS has stated that it won't necessarily work due to the high latency between the inbuilt RF and the module...

"The X10+ is designed to be used with two receivers that are receiving the same signal from the same transmitter module. The Taranis outputs sends data to the internal and external transmitter electronics sequentially. So, there is a pretty long delay (in computer terms) between when the internal and external modules are actually transmitting. We know that with a single transmitter module the receivers will be receiving the data at the exact same time, but there can be a slight difference in how quickly data is processed and sent serially using the Futaba SBUS protocol. So, knowing that, there is a window of 1ms. The worst case I saw during development (using dual X8R receivers) was about 65us. So, 1000us (1ms) is a very wide window. However, with the internal and external module, there is about a 5ms difference. That's two wide to be latency efficient."

[Chris Bott - Moderator]

OK thanks Matty, that's important to know. What a shame.

[MattyB]

Just to be clear, I'm not sure anyone has categorically proved whether dual path redundancy using a Taranis and external module would work with the X10+ - the above is only Jim Drew's opinion based on his initial testing some years ago. Personally I would be surprised if it did not work if an XJT in D16 mode was used in the module slot; after all the internal RF is effectively just an XJT minus it's case, so I can't see any reason why there would be any additional latency (in that mode I don't believe the XJT is doing the PPM conversion step which adds latency, though I could be wrong). I'd happily test it, but I only have a DJT not an XJT, and the DJT doesn't work with the X series of SBUS enabled RXs.

Edited By MattyB on 16/06/2016 09:40:54

[Steve Balaam]

Whilst researching this project I discovered FRSKY have their own redundancy bus product albeit more expensive than the X10. Has anybody formed an opinion yet on the FRSKY product.

[MattyB]

Yes - I looked at it, but early adopters have had issues, one of which caused the loss of a large, expensive scale glider (read from the bottom of this page for more info). FrSky now seem to be troubleshooting the issue with the help of a couple of people in the community and new firmware was tested and released this week, but I would steer clear of it for now until the issues are resolved. It's also a lot bigger, heavier and more expensive than the X10+, though it does have some additional telemetry features plus overload protection built in.

Edited By MattyB on 16/06/2016 10:24:24

[MattyB]

OK, so as of last night everything is installed - I just need to setup the TX (I have a basic setup done on the PC in OpenTX Companion, just need to transfer it over and setup the rates, expos, telemetry alarms etc) and finally CG it. Install came out quite nicely, though obviously there is a small weight penalty to this resiliency of ~100g - a price worth paying I think.

Will post some photos tonight; hopefully the weather will hold fair for a maiden at the w/e.

Edited By MattyB on 22/06/2016 11:33:46

[MattyB]

So she’s flown… and just about survived!

Rushing to complete this by the weekend I installed the Turnigy HV SBEC I had successfully tested on the bench with a 3S pack. Plugged in a 6S… nothing. Well, not quite nothing; within a few seconds the SBEC was red hot and trying to burn its way out of the model! I quickly unplugged, let it cool then tried again outside the model with the same result. Left to cool again it worked fine on 3S, but clearly it’s a faulty unit or the standard 3S one wrapped up in the wrong packaging. Too cheap to bother returning, it will now be retired for bench testing only.

Thinking laterally I decided to go with the inbuilt 3A static/5A burst SBEC built into the ESC for the maiden flights; though not my preferred option loads of people have stated online this is fine for the Miss Wind, and I had my Optiguard installed should there be an issue. With the red wire duly replaced in the throttle plug everything was tested and all looked good, so off to the field on Sunday we went.

Following another at the field and the reconfiguration of a few telemetry alarms off I went, and initially all seemed well. Having spent a couple of mins getting the plane roughly trimmed out the TX started chirping – I was operating on the backup power from the Optiguard, with voltage at the RX only 4.6V! This put a bit more pressure on my first landing than normal as I didn’t have the rates configured as wanted, but I managed to get it down unscathed without any damage. Phew - I was not really hoping to test my resiliency on flight 1..!

On testing on the ground there seemed to be no output from the ESC BEC, but it was not hot and cycling the power brought it straight back up; very strange. I left it on for 30 mins to test and it stayed up with no issues, but after a conflab in the pits and no root cause identified everyone agreed it would be foolhardy to fly with this setup again. The red wire was duly removed (I’m getting good at that…!) and the rest of the days flights were with a spare LiFe pack. By the end of the day I had it nicely trimmed and it felt fairly under my thumbs – it’s just so accurate compared to everything else I own. Still a long way to go before I can really wring it out though!

So what next? I am not 100% sure tbh. I could fit the CC SBEC for ~£20, but on 6S it is only rated at 5A and though very lightweight it worries me that it does not have a substantial heat sink. There are a couple of alternative units from HK that might fit the bill, or I could try another one of the ones that failed (hmmmm, probably not…!). The final option is to go with a dedicated unregulated LiFe pack and live with the extra weight (not a big issue as I will only be sport flying) and the faff of remembering to charge it (potentially a bigger issue, though mitigated by my Optiguard). Time for some careful thought…

Edited By MattyB on 28/06/2016 14:30:20

[Colin Carpenter]

Matt. Glad you and the Sebbie survived . Can't offer any explanations but the separate pack seems bombproof and most of us remember charging batteries every evening before flying ! I expect it felt superb under the thumbs. My 30,s do . Any pics ? Colin

[..]

Matt, please don't take this the wrong way but after these scares wouldn't you be better off just running a bog standard simple set up to start off ?

You say it's your first bigger model and it would be such a shame to destroy it , You clearly know your way around an electric plane more than me but on my IC stuff I keep it simple to start and add any bells & whistles gradually as I go along.

It's a nice plane but moving up to this size and power things can happen a lot faster than with the smaller planes.

Cheers J ..

[MattyB]

Posted by Justin K. on 28/06/2016 17:38:35:

Matt, please don't take this the wrong way but after these scares wouldn't you be better off just running a bog standard simple set up to start off ?

You say it's your first bigger model and it would be such a shame to destroy it , You clearly know your way around an electric plane more than me but on my IC stuff I keep it simple to start and add any bells & whistles gradually as I go along.

Well, the "bog standard simple set up" for electric planes of this size is to use the ESC BEC with no redundancy - that is what Sebart themselves use and recommend. Had I done so in this instance the Miss Wind would be matchwood, so I am very happy I installed power system resiliency! The problem here was in the primary power source (the SBEC which failed on the bench and the ESC BEC which may have failed in the air), not the resilient power and RF systems which are well tested by others (these are not new products in the market) and are working fine. It's that primary power source I am now mulling over; if I do simplify and go for a separate RX LiFe I could dispense with the Optiguard, but if I then ever forgot to charge the RX pack there would be an issue again. For the sake of 40g I think I will keep it.

Posted by Justin K. on 28/06/2016 17:38:35:

It's a nice plane but moving up to this size and power things can happen a lot faster than with the smaller planes.

Actually one thing I did notice was that this plane is not the fastest - I've got plenty of quicker models. Yes it's more powerful than my 25 sized and parkflyer machines, but unless you open it up to full throttle it doesn't really go that fast, I guess because you want a pattern plane to fly fairly slowly to give more time to be precise during complex manoeuvres. The vertical performance though is pretty fantastic compared to my other models, but then that's what ~140W/lb does for you!

Edited By MattyB on 28/06/2016 18:35:59

[MattyB]

Posted by Colin Carpenter on 28/06/2016 16:09:16:

Matt. Glad you and the Sebbie survived . Can't offer any explanations but the separate pack seems bombproof and most of us remember charging batteries every evening before flying ! I expect it felt superb under the thumbs. My 30,s do . Any pics ? Colin

Yep, it really is a lovely model to fly, precise and elegant. No pics, but my Dad has some video from one of the latter flights - I will try and get it posted up to Youtube if I can talk him through how to do that.

[..]

Posted by MattyB on 28/06/2016 18:28:59:

Posted by Justin K. on 28/06/2016 17:38:35

>>Well, the "bog standard simple set up" for electric planes of this size is to use the ESC BEC with no redundancy - that is what Sebart themselves use and recommend. Had I done so in this instance the Miss Wind would be matchwood,<<

Lol , and who are they to be recommending stuff .

[Allan Bennett]

Matt, for what it's worth, I use CC 10A BECs on 6S in many of my models -- 500 and 550 helis, as well as my Xtra Wot and similar-size Sukhoi. There's always the CC 20A BEC Pro if 5A at 6S isn't enough for you.

[MattyB]

Posted by Allan Bennett on 28/06/2016 20:27:57:

Matt, for what it's worth, I use CC 10A BECs on 6S in many of my models -- 500 and 550 helis, as well as my Xtra Wot and similar-size Sukhoi. There's always the CC 20A BEC Pro if 5A at 6S isn't enough for you.

Thanks Allan, much appreciated. Given that unit is also capable of 10A bursts and you have had good experience with it I will probably go with that option.

Once installed MW will be ready for her Letchworth Rugby club debut!

Edited By MattyB on 29/06/2016 09:45:50

[MattyB]

Have ordered the CC BEC from RCPitstop - handily they will set the output to the voltage of your choice before sending it out, saving you the cost of buying the ~£20 Castle USB lead! Great service, and they have despatched it within 4hrs too - recommended.

[MattyB]

A quick update... I put three packs through the Miss Wind in relatively windy conditions yesterday, and the new setup with the CC BEC worked perfectly - no scary telemetry alarms this time. This airframe is just magnificent - it made mincemeat of the wind which was gusting to 20+, and never felt less than rock solid. I would never attempt a rolling circle with my smaller models in such conditions, but I did two in succession with the MW, and later I even managed a right handed one which I always usually get muddled on! Highly recommended.