Brown outs and Grey areas - the truth!

[Tim Mackey]

I have done some testing on a Spektrum AR6100E receiver to assess the brown out scenario. I made up a small capacity ( 600m/ahr ) 3 cell pack to replicate a low voltage scenario. An old S148 servo was arranged to be in an off load / semi stalled / stalled position and the battery was also fitted with a micro switch to enable quick shut off to assess the receivers Quick Connect firmware. Two DMMs monitor pack voltage and current consumed. A seperate Voltspy was also in circuit and shows that the pack was already at a critically low state (deliberately so) when first switched into circuit- as indicated by the last remaining red LED illumination. As can be seen, at first power up, and with quiescent current draw only, the receiver pulls around 50m/a which is as per Spektrums specifications. Battery voltage is a tad over 4 Volts.

Moving the servo proportionally increases current ( and, as expected depresses voltage )

Depending on servo load, current varies from 50+ m/a right up to off the scale of 200m/a and I set the final stages to be consuming approx 150 m/a in order not to fuse the MM.

You can see the brown out occur at just about 3.92V as the receiver LED blinks rapidly as power is rapidly fluctuating - setting the servo off load restores sufficient volts to re-power things, but obviously - as designed - the LED remains blinking to indicate a brown out has occurred. Allowing for possible inaccurate meter display, and slow reaction time ( I do not have access to an oscilloscope ) I would say brown out occurs at around 3.8V.

This is slightly higher than the specification states, ( 3.5V ) but certainly well below the 4.5v figure mentioned in other threads. As mentioned of course, it may well be that voltage did actually depress for a microsecond or two to 3.5V - I cannot prove /disprove that with my limited measuring equipment.

I didnt bother activating the micro switch as the test was conclusive enough.

Heres a picture first to explain the test rig

And heres the video

 

                                      HOW TO CHECK FOR QUICK CONNECT

                                 The first test I do with every RX purchased is for QC.

Heres the procedure

Ensure correct binding is done to the Tx first.

Then, switch on in normal correct sequence ( TX then RX ).

Disconnect power to the Rx by whatever means appropriate ( unplug battery, switch off etc etc ) and reconnect instantly.

Do not touch the TX during the testing at all.

If the Rx LED is now flashing then QC is enabled.

HOWEVER, if LED remains solid then it is not.  Even if it is flashing ensure that the receiver has actually reconnected correctly by observing how long it takes for it to regain control of the servos - this should be no more than a few milliseconds - if its like a couple of seconds or so, then it needs sending in for firmware upgrade.

The ONLY way to tell if you have suffered a brown out in a model with a properly configured QC Rx is by the fact that the LED will be flashing when you land.

IT is soooo fast when properly setup that you will NOT even notice in flight .

 

Edited By Timbo - Moderator on 05/07/2009 10:39:36

[Roger Wilco]

So do the ariels on non satalite receiver Spektrum receivers with DualLink such as the ASR6100, need to have their ariels set at 90deg in different planes?

this is copied from the Horizon site (glossary) I mentined in other thred:

DualLink™

Spektrum radios feature DualLink, a system that is specifically designed to resolve this problem. Every DualLink receiver is in actual fact two receivers, each with its own aerial, the two of which are oriented at ninety degrees to each other. When the transmitter if turned on it scans for and occupies two free channels and then starts to transmit the same data simultaneously on both. Because there are two paths (the term for the relationship of the position of the transmitting aerial relative to the receiving aerial) should one be lost due the other will continue to supply the signal.

 It would be nice to know, have any of the 'pegless' ones ever taken one apart, could someone from the magazine (with more clout than us) contact the manufacturer for a definative answer?

nice topic for an article? 

[Tim Mackey]

The AR6100 and so on, do not have the aerials at 90 degrees to one another - the AR6000 (DSM1 ) does.

The other "twin unit" receivers should be positioned at right angles to each other / vertical...horizontal either way is fine.

I have about 10 of these AR6100s ( I think ) in all sorts of models, including large 50" slopers. I ALWAYS simply fit the receiver so the aerial is "acrosss" the fuselage, almost always buried completely in foam, or within the wooden structure. As for range..... I often fly my slope soarers WAY out and over the sea, and again....not a single issue - the range is just stunning for what are supposedly "park fly" receivers.

UPDATE. Loss of signal experienced in a small flying wing at fairly close range.

Edited By Timbo - Moderator on 04/07/2009 15:31:54

[Tim Mackey]

JETSOME wrote (see)

Your experiment looks fine but you are working at very close range. When I did my test the transmitter was about 20 -30 yards away from the RX with the range button pressed. It would be nice if you could repeat the test with simulated distance as in my experiment with the Canberra. Also note that my rx was a 6700 of the early type with no QC. So far though Timbo so good!  

The range will have absolutely no effect on the measurement and experiment here. This was purely concerned with brown outs, and the actual voltage levels at which this occurs. Losing signal, or weakening signals will not activate the flashing LEDs - these are purely here to indicate a power drop which was sufficient to actually cause the receiver to stop working.

I can see no point in conducting the same test with the Tx further away... happy to do so...but you need to explain why I should  IYSWIM

[Tim Mackey]

No problem John... I will gladly replicate the test using the tx at a distance and under range test conditions.... I would have thought that providing the receiver shows a steady LED this indicates sufficient power to operate irrespective of the range involved - the sensitivity of reception would not - I think - be affected by power supply levels - it is either working "on"..... or dead "off" !

I may be wrong and perhaps a more technically savvy person than I will confirm it one way or 'tother.

The one thing it has pretty much convnced me of, is that 3.5V ( the official figure specified ) is the absolute minimum level...and I feel that 4V is probably a safer guide. In other words, if anyone wants to do a simple test of their intended installation ( or indeed existing installations ) stick a simple DVM across the power supply used ( could be done easily enough with a spare channel on the rcvr wired to a remote socket for example ) and waggle the sticks - if the meter holds AT LEAST 4v in this scenario you should be fine. If you have an LED indicator as well ( such as the "voltspy" devices ) you could confirm at what point the combined illuminated LEDS match a 4V level....when they flash in future you know you are getting critically close to disaster.

These figures are of course what I consider MINIMUMS - and a good 6V high capacity supply is the best option.

I wonder how far away the 8V servo is.... would make life a whole lot safer and more straightforward as we could then start using a nice 2s Lipo without regulator to power our radio - most receivers already have no problem with the higher voltage ( indeed Spekkies are good up to 9V ) but its a bit useless whilst servos are either 4.8V or 6V max. Of course,  the manufacturer must continue making the receivers operational down to the current 3.5V level also....and that way we have a meaningful ball park to play in !

I have toyed with the idea of fitting a diode or two in series with my 6V servos +ve feed and giving it a go. 

[Myron Beaumont]

I wondered where my two Maplins meters had gone .Its that chap with a large reel of illegitimate solder he quickly moved out of view at the beginning oif the best movie I've seen this week .Nice one Timbo !

[Lee Burke]

Very interesting, Timbo, and great to see the test on video too.  Presumably with several servos working at the same time the voltage drop would be more severe, and even worse with digital servos?

[Ultymate]

I have a friend from the Manchester area who flies large scale aerobatics and has been using 2s lipos direct to his R/X and servos with no reg in circuit. He uses a mix of servos from all three major suppliers and to date after a couple of years he reports no problems whatsoever.

[Tim Mackey]

Now very strange that you should mention that Lee - I have been a busy boy today doing lots more filming of tests of exactly that.,, the results are quite alarming and a MUST SEE.

I also did one to show the results of signal loss as opposed to brown outs, as well as ( just for Jetsome ) the same test as the first, but with the tx at distance in range test mode. I have literally just finished filming, and now have to coallate all the info, edit the film, stick it on U tube, and then post here.

Will hopefully be on later tonight.... more likely tomorrow. Dont miss it if you value your models

Hi Myron... the solder reel was merely holding down the battery microswitch - and anyway its not illegal for home use -YET! 

[Tim Mackey]

Ultymate wrote (see)

I have a friend from the Manchester area who flies large scale aerobatics and has been using 2s lipos direct to his R/X and servos with no reg in circuit. He uses a mix of servos from all three major suppliers and to date after a couple of years he reports no problems whatsoever.

Interesting.... would like to know the servos concerned Brian. I wonder what would happen in the event of an incident and post crash investigation ? Would Insurance be arguing about using equipment outside the spec etc ??

[Tim Mackey]

Sorry guys, deleted a few of these, ( including one of my own ! )  as this thread is still very much alive and on topic  it is also quite a serious matter and needs to remain so........ for a while yet anyway

[Ultymate]

I really don't know Tim as I say he's been flying that way for a couple of years now and no adverse affects. I suppose you could ask the same question about a 3S lipo in a trannie I know you do it and I do too

[Tim Mackey]

Ah but a tx has a voltage regulator to step down the output to the required level - servos do not !

[Tim Mackey]

Heres test number 2 video - more to come later today.

PS this has sound to explain what I am doing - Geez I hate my own voice

[Former Member]

[This posting has been removed]

[Tim Mackey]

I have just done another 2 tests which seems to suggest that this is not so with the AR6100. There is sound again on the vids to explain proceedings...but simply put the rig was as follows...

Very low voltage pack ( sub 4v ) connected up to AR6100 and single full size servo on throttle channel.

Throttle set to full open ( in order to monitor for failsafe due to signal loss ) tr aerial vertical ( as in normal use)

Tx then taken well away in range test mode ( IE bind button pressed ) with aerial as normal

Tx aerial then lowered so aerial pointed "into the doughnut of death" position

Monitored to establish if failsafe occurred .....which it eventually did at great distance and certainly not line of sight

Superb results ...even with battery near critical brown out situation - but brown out did still not occur.

Videos 3 and 4 of the above will be posted up in a few minutes

[Tim Mackey]

Video 3 now up.

[winchweight]

Very interesting stuff.

[Tim Mackey]

I have several other sequences "still in the can" awaiting editing and hosting.... but meanwhile here's number 4 which is basically a second attempt at invoking failsafe - this time we did it by pointing the aerial at the receiver but from an even greater distance !

Several more tests will be posted ...maybe tomorrow now

[winchweight]

In your tests the helper is the other side of the car. Could the car be refracting the signal and scattering it enough to negate the doughnut effect?

[Lee Burke]

Does anyone know how wide that that doughnut might be?  And is it a collumn or an inverted cone? Getting a bit off topic with that, though.

[Tim Mackey]

The car is outside on the drive, slightly uphill. The garage door is obviously open, and my wife stood approx 25 paces further up the hill which is our drive onto the main road. It is impossible to actually even see the rig from where she stood, and this in itself somewhat dispels the tales that 2.4Ghz works only with "line of sight"

I would guesstimate that if anythig.... the position of the car elative to the doorway / rig / tx would reflect the signals  completely away from the door aperture....but as can be seen...it still worked right up until the time she pointed the arial pretty much straight at the car and beyond to the rig.

[winchweight]

Fairy nuff, just wondered.

[Tim Mackey]

Yes it is very impressive - I have also found that control is maintained even if the TX is taken around the side of the house completely out of line of sight, and behind a solid brick wall. I have dismantled the rig now, in order to get on with some proper modelling !

The remaining videos which I shall post up soon show the considerable difference that different servo types can have on creating a brown out - watch this space!

[Tim Mackey]

Well typically for me I have decided to set it all up again !

I want to film the scenario that Shaun had over in his " my sea fury is dead thread " which of course involved an all electric system with an ESC and UBEC rather than a seperate battery and throttle servo. As you will doubtless see on that thread, there is still discussion about the possibility that this was caused by brown out, and the receiver going into failsafe. Despite already proving that the only way a receiver will enter failsafe is through radio interference or radio signal loss, there are of course subtle differences between ESC throttles and servo throttles!

I have actually done these tests already but did not film them.

Whilst I have it all rigged again, I will try and remember to do the tests you sugggested involving screening the rcvr in metallised paint fuselages or equivalent.