Brown outs and Grey areas - the truth!

[Rick Tee]

Timbo - forum moderator wrote (

see)Pretty much - except that often a standalone BEC ( UBEC ) will allso be deployed in a model that does not have electric flight batteries - EG: IC powered or gliders - in this case the unit is wired to a seperate battery ( usually a 2s LiPo ) and then this feeds the radio gear. This also makes for far greater efficiency as the watts in to the BEC will be far less than the watts out...thereby ensuring looooong flight times.

I literally cannot remeber the last time I charged my slopers which all deploy this system.

For greater understanding, and so as not to digress too much from the thread topic - see here.

Is this right? current in would be less than current out but the power would be the same or slightly less allowing for losses in the UBEC.

[Tim Mackey]

Yes Rick you are correct  - wrong terminolgy - my bad as they say these days  - I should say current drained from the supply battery will be less than the current flowing through the radio system. Here's an extract from the "article" the figures are only examples, and rounded off for easier understanding, but the principle should be clear.

Let’s say your radio and servos draw 4 amps @ 5 volts ---- that equals 20 watts of power ( 4 X 5 ).

This means that a 4-cell nickel pack ( at roughly 5V ) will have to drain at 4 amps. However, a 3-cell lithium pack at about 10V+ ( under load ) would only have to supply about 2 amps through the regulator at that higher voltage to deliver the same 20 watts power.

Thanks for keeping me on my toes Rick

[Brian Parker]

Timbo,

No problems, feel free to use as you wish, only remember the polar radiation/capture patterns were somewhat simplified, but are adaquate, if you use them.

Yes, Receiver location  pretty much as you stated, in all not so critical as the transmitter antenna. The 6200 with the slave correctly positioned with regard to the main receiver has got to be the preferred option over the 6100 at longer ranges, together with the care not to mask the reception paths.

Also your tests to date show quite substantial signal reflection (car/garage etc.) at close range. Out of phase reflections at longer ranges will be catered for by the 6200 and its satellite receiver but not, I would have thought, by the 6100.

All in all, when correctly set up this 2.4Ghz DSM modulation looks good, may even get one myself now I’ve had a closer look.

Regarding the problems with your rig, my posting yesterday was not perhaps clear (as is often the case), I meant for you to check across all connections/joints/etc with a meter to ascertain any voltage present across the joint/connection indicating resistance. Looks like you’ve already isolated it to insertion loss due to the meter.

Keep up the good work!

[Tim Mackey]

Hi Brian - thanks for clarifying that - yes I realise that there will be a lot of refected and somewhat stray signals floating around in the garage environment, but when I do the actual range / orientation testing I shall set it all out in the open - the internal testing was really more for the brown out / complete signal loss tests. I do not actually have any of the 6200 units, but several of the AR7000 - ( which are also twin units ) and these also have never let me down. I always ensure the aerials are positioned at right angles to each other as recommended by Spektrum.

This shows one of the AR7000s installed in my IC Spitfire - completely trouble free in all situations. I have several 7000s due mainly to them being the only ones availbale at the time I pourchased my Spektrum DX7 set..almost 2 years ago now.

[Tim Mackey]

Right. latest round of tests are now "published" showing the brown out situation regarding Spekky 6100 Rx.

3 short films demonstrate the remarkable ability of this little gem.

Tomorrow I hope to finish this batch of tests with some range test V battery voltage scenarios, aerial orientation differences - both Tx AND Rx positioning (Thanks Brian ) and - just for Jetsome - the effect of shielding the receiver with metallic foils and so on. No carbon fibre sheets I am afraid, but did think about surrounding the receiver with an Ice pack to simulate water enclosure.

Anyway...here's the 3 latest films. The voltspy colours didn't reproduce after U tube compressed the quality, but I assure you it is working, and the red LED at least is still visible when active.

As always, comments appreciated positive or otherwise

low voltage effect via PSU

Brown out with 3 cell NiMh

Brown out - effect on throttle

PS must figure out the right method of embedding the vids directly into the post - managed it once, but forget how!

[SA Allan]

Intresting stuff , but after loosing a TN Moskito on its 5th flight (first time it was 100% completed) I've gone and bought 6200's for all my models . After many a hour in the workshop it was quite a moment.

Incidently it was a V1.6 6100 with a 3 amp UBECdriven off the flight battery that still had 60% after the crash .

[Frank Skilbeck]

Excellent, very interesting. From the vids it looks like loss of signal is more critical than a brown out as it takes longer to reboot.

However would this be the case though if it was just the signal being temorarily shielded, as when the Tx is switched off and on it has to scan for two free freqencies. Maybe a future test but not sure how you would shield the signal?

The other thing to note was the increased load of one unloaded servo when it move the current wetn from around 40mah to over 300mah, imagine if you had several servos and a few of them were loaded.

[Frank Skilbeck]

Timbo - just thinking about it, reading through the earlier threads there seems to be some concern that a low Rx power supply reduces the range of the Rx, would it be possible to repeat the test with the range test button activated to see if brown out occurs at a higher Rx supply voltage when the Tx signal is weaker.

This would put that one to bed.

PS the only plane I've lost to radio problems recently was on 35 Mhz, but as the Rx battery fell out during aerobatics (don't ask) I don't think I can blame the radio.

[Brian Parker]

Excellent! Highlights the clarity gained from a series of good short practical demonstrations over hundreds of written words.

The time factor between a short loss of power and recovery as opposed to a signal loss and recovery was conclusive.

 

Much appreciate your efforts and look forward to the next in the series.

The effects of a lowering voltage on receiver range/antenna orientation should prove informative.

[Jack Bagley]

Hi Chaps,

                  Just back and have been reading this thread with some considerable interest. I have put a couple of thoughts and comments out about the Spektrum radio on other threads as I have experienced it over the months, but in all honesty, I have not come across the problems that some of you seem to have. Through the grapevine though, I was warned of the possibility of "brownouts" occuring in certain conditions such as every one in the thread has described, so applying due dilligence, I have since used a separate lipo for the servo supply, and so far I haven't had a problem with either "brown out" or any range loss. There were a few glitchy spots around on 35Mhz, but since "upgrading to 2.4Ghz, no problems. This has just been my experience with the gear for what it's worth. Other chaps using Futaba 2.4Ghz don't appear to have had any of the described problems either. I must confess to not having flown with electric motors at all, so maybe, I still have a lot to learn about this new "black art".   I do wish you all well with this problem, meanwhile, best wishes to you all, Jack

[Tim Mackey]

SA Allan wrote (see)

Intresting stuff , but after loosing a TN Moskito on its 5th flight (first time it was 100% completed) I've gone and bought 6200's for all my models . After many a hour in the workshop it was quite a moment.

Incidently it was a V1.6 6100 with a 3 amp UBECdriven off the flight battery that still had 60% after the crash .

I think you will find some people are NOT pleased with the 6200s at all....aparantley range is not good ( ask Scott not me, I dont have any )

[Tim Mackey]

Frank Skilbeck wrote (see)

Timbo - just thinking about it, reading through the earlier threads there seems to be some concern that a low Rx power supply reduces the range of the Rx, would it be possible to repeat the test with the range test button activated to see if brown out occurs at a higher Rx supply voltage when the Tx signal is weaker.

This would put that one to bed.

I already stated in the posting that this was being included within the next round of testing

PS the only plane I've lost to radio problems recently was on 35 Mhz, but as the Rx battery fell out during aerobatics (don't ask) I don't think I can blame the radio.

[Tim Mackey]

Frank Skilbeck wrote (see)

Excellent, very interesting. From the vids it looks like loss of signal is more critical than a brown out as it takes longer to reboot.

Errr, dont get me started on the difference between brown out and signal loss Frank LOL

However would this be the case though if it was just the signal being temorarily shielded, as when the Tx is switched off and on it has to scan for two free freqencies. Maybe a future test but not sure how you would shield the signal?

I plan to completely sheild the receiver with a some tinfoil that can be quickly moved in /out of position after I have established the almost critical range required to operate / fail

The other thing to note was the increased load of one unloaded servo when it move the current wetn from around 40mah to over 300mah, imagine if you had several servos and a few of them were loaded.

I have done another thread of tests ages ago showing exactly that sort of thing - cant find it now - but its around. One thing I did find during testing was that some of the smaller servos and not  always digis  -  were much thirstier than their grown up cousins.

[Tim Mackey]

Brian Parker wrote (see)

Excellent! Highlights the clarity gained from a series of good short practical demonstrations over hundreds of written words.

Thanks Brian.

The time factor between a short loss of power and recovery as opposed to a signal loss and recovery was conclusive.

As I said to Frank - dont get me going on that subject - I think YOU know why LOL

Much appreciate your efforts and look forward to the next in the series.

The effects of a lowering voltage on receiver range/antenna orientation should prove informative.

yep...might be while now before the next round - I forgot I was away in London from Friday morning until Sunday night late

[Tim Mackey]

Jack Bagley wrote (see)

Hi Chaps,

Just back and have been reading this thread with some considerable interest. I have put a couple of thoughts and comments out about the Spektrum radio on other threads as I have experienced it over the months, but in all honesty, I have not come across the problems that some of you seem to have. Through the grapevine though, I was warned of the possibility of "brownouts" occuring in certain conditions such as every one in the thread has described, so applying due dilligence, I have since used a separate lipo for the servo supply, and so far I haven't had a problem with either "brown out" or any range loss. There were a few glitchy spots around on 35Mhz, but since "upgrading to 2.4Ghz, no problems. This has just been my experience with the gear for what it's worth. Other chaps using Futaba 2.4Ghz don't appear to have had any of the described problems either. I must confess to not having flown with electric motors at all, so maybe, I still have a lot to learn about this new "black art".

I do wish you all well with this problem, meanwhile, best wishes to you all, Jack

what problem LOL

Hi Jack ( that always make me smile in an infantile sort of way ) This particular thread was not started as result of problems - in fact exactly the opposite! Others do seem to have experienced problems with brown outs being to blame, but, like yourself, I have NEVER suffered a single problem with all my Spekky gear, and I have been using it for almost 2 years exclusively, in all my many models, and in many different conditions - sloping, small busy urban sites, large public parks, farmers fields with pylons across the middle, large "proper flying fields" and coastal high altitudes.

I just thought it was time someone did some practical tests to establish certain things...namely

1) At exactly what voltage does brown out occur.

2) What is the real effect of brown outs with QC enabled receivers

3) The different effects on the model between brown outs and radio signal loss

4) The effect of range / voltage / aerial orientation etc

[Rick Tee]

Great job on the videos Timbo, looks like the problems some have experienced are signal loss rather than brown out. Which explains the throttle cut and why it was all working again when inspecting the wreckage. 12 sec + delay eek! just tested my 35mg Hz gear, control is restored instantly when the signal is restored. So either range or installation seem to be the cause.

Does range increase/decrease with receiver voltage?

[Myron Beaumont]

Cant imagine it increasing

[Tim Mackey]

Well as i say Rick...this particular test is scheduled next - but am pushed for time at the moment so next week is likely.

[Frank Skilbeck]

Rick, re the 12 second delay this was after the Tx was switched off and on, not recovery from say interference. When the Tx is switched on it has to scan for 2 free frequencies before it starts to transmit. The Rx is scanning all frequencies all the time until it see's it's transmitter. So I would guess that recovdery from loss of signal, rather than Tx rebooting, would be much quicker. But Timbo's tests will show this.

Aparently on the 7000 series Rx's you can interogate the Rx after the flight and it will tell you how many times the signal has faded, people doing this have not reported any loss in control when the Rx has reported that it has had momentary loss of signal (note we are talking milliseconds here), so I suspect that recovery from loss of signal will be pretty instantaneous.

It's more akin to a 35 mhz pcm (of multiplex IPD) system than a regular ppm system, and doesn't allow bad data to be sent to the servo's and will failsafe if no good data is recieved within a specific timescale.

[Jack Bagley]

Hi Timbo,

                 Many thanks for your reply, I'm suddenly pleased that I haven't been living and flying in a sort of fools paradise. I might even go as far as to say in my case, "ignorance is bliss"! The only minor irritation that I have experienced with the Spektrum radio is positioning the satellite Rx and antenna in some of my more compact models. Usually though, a glass or two of Claret oils the grey matter enough to overcome this! The chaps using Futaba radio would not encounter this problem. Would be interesting to see if this aerial space diversity system is really needed, any comments from either Spektrum or Futaba on this? It does however pay to angle the Tx antenna to relative vertical whilst holding the Tx in your most comfortable flying attitude. I use a cradle case as I find the Tx most uncomfotable to hold when using the standard strap and hook. I do hope that every one else enjoys their flying trouble free as do Timbo and I! 

                          Very best wishes to you all, Jack 

[Yorkman]

Got my third spektrum-controlled flight in yesterday, and very happy to report a completely problem free experience.

Range checked to 40 paces, no glitches, hiccups, unexpected control movements...

It's early days, but looking good.

[Tim Mackey]

Have finished the tests now, and really need to get on building stuff which is way overdue. This last lot is showing the effect of shielding the receiver with aluminium painted fuselages, and proper metallic aluminium kitchen foil. I did some tests up at the Orme, but unfortunately we cocked up the filming somewhat, but rest assured the results were pretty much the same as those obtained this morning back here at home. The Orme range testing was done at almost 80 feet ( 30 large paces ) all with the range test button pressed throughout. The tests back home, have all the info you need recorded on the soundtrack. I link to the garage based tests first, as this explains the rig in more detail., but do take time to bother to watch the field tests too ( at the great orme ) which are more realistic due to the distance between Tx and Rx.
The tests also incorporate the effect on range / sensitivity / reliability of operation when the receiver is supplied with a critically low supply voltage of 3.5V and even lower !!

I also did some current consumption testing at 4 cell and 5 cell voltages, and was surprised to find that no significant difference was recorded. Summary of those is here

1) Throttle idle.  2) Servo arm horizontal with heavy weights attached for loading.

3) WOT             4) Peak current recorded and total m/a consumed during 2 minutes of stick waggling !

First off @ 4.8V

1)  40ma      2) 140ma     3) 110ma.      4) 280 m/a and .006AH

Then @ 6 V

1) 40ma       2) 120ma     3) 90ma         4) 300m/a and .007AH

Here’s a link to the videos of the other testing - Surprising results !

Garage based ( view first )

Orme field testing

[Lee Burke]

Really great tests, Timbo.  Thanks very much for all the time and effort you have put into this.  Your results show that the 2.4Ghz system is almost bomb-proof.  Apart from when the voltage is dropped beneath a reasonable amount, there was just that one event of signal loss when you directed the antenna at the Tx, but that, curiosly it seemed did not occur again when you retried it.  On the whole very reassuring results. 

In a much simpler, and less effective way I have tried to get my Futaba 2,4Ghz receiver to lose the Tx signal by placing it in a tin box and by placing large vans between the two - all to no effect.  great tests and nice results.  Good stuff.

[Tim Mackey]

cheers Lee.

I am definately done with testing ...for now

[Brian Parker]

Timbo,

Many thanks for all the work you have put into these tests.

The voltage tests virtually confirmed the earlier test results.

The antenna orientation test confirmed the need to present the receiver with a ‘broadside’ transmitter antenna and not to point it at the model.

Perhaps hair splitting….An observation regarding the ‘Screens’ in the screening tests. Whilst demonstrating that the transmitted signal could penetrate metallic paint and foil or be reflected up the open end, they were probably too large to have any de-tuning effect (if indeed this could happen) on the receiver input circuitry.

In all, this has been an interesting, informative and reassuring thread, again many thanks for all your time and effort.