Brown outs and Grey areas - the truth!

[Doug Ireland]

I agree with Timbos last post. Its not the first time I've seen the untimely demise of a beautifully built model due to a slap-dash radio installation.

[Tim Mackey]

Spektrum market these rather over priced devices but state clearly in some of their marketing blurb that they are of no benefit in airborne systems and should not be used.

The theory is that the small charge retained by the capacitor ( because indeed that is all it is - an electrolytic capacitor ) would help buffer against voltage drop out. Car racers traditionally used fairly low voltage main batteries and BECs, whereas airborne models are supposed to have better supply. They also remind us all ( very correctly ) that NOTHING is a satisfactory substitute for a properly specified, large capacity, supply battery.

[Nick Brotherton]

Interesting, I had been advised recently to install 5 cell 6v batteries for the receiver if flying spektrum, after being told that they recommend these. However they have 4.8 batteries for sale on their own website. The voltage for these receiver is up to 9.6 so cant see a problem using 6v.

I'm now thinking it may be best to use the highest pack you afford or see a lot of hours of work go to waste?

Nick

[Tim Mackey]

Well providing the model can handle the extra weight of the 5 cell pack then generally speaking I would say yes - use 6V ( a few servos are limited to 4 cell incidentally...but not many these days. Some servos I spotted the other day on a website were spec'd right up to 7.2V ( ideal for use with 2 x A123 cells and no regualtor required ! )

Most receivers are happy on 6v or even more....the Spektrums are rated at up to 9V.

I must just stress again that a 6V supply can in most cases actually cause a slightly higher current drain through the system, and this can catch some folk out - they think that using a 5 cell instead of a 4 cell will give longer flight times - it wont!

Whatever battery configuration you end up using, you MUST ensure that the cells in the battery are capable of delivering the required current and also that they do not "collapse" and give very low voltage when put under a little pressure. Some AAA and even some AA cells are NOT GOOD in this respect, and for larger installations you are wise to use something like a subC type size cell battery - or of course... a LiPo and suitable regulator.

[Always broke]

I have been using 2x A123 cells direct with no regulator but 2 High quality switches in parallel  on 2 of my 50cc models with no probs at all most of this year, using Spectrum Rx and a mix of Hitec and JR digitals. I never ever use 4 cell packs on my Spectrum gear only 5 cell or 2x A123, perhaps one reason I have never had a single Glitch or fault with it since it came out. Also on models  using High torque servos I always use 2 switches and Sub C or 2/3 rd Sub C  packs that hold there voltage under load not like a lot of AA packs which drop there voltage under load. Not a fan of regulators just something else to go wrong.Just my views and works Perfectly for ME.

[Tim Mackey]

Thats good to hear AWB. Although I agree with your system, as I mentioned above, and just to be absolutely clear to those thinking of trying this - PLEASE make sure that your servos especially are suitable to be run on this slightly higher voltage ( 2s x A123s fresh off the cooker  = 7.2V ) I accept no responsibility for servos letting out the magic smoke due to them being powerd on this high voltage.

[Vasantraj Pande]

The discussion in this thread is fascinating and I certainly admire the wealth of knowledge people have - thanks for sharing. However I’m still puzzled about whether to use 4.8v or 6v and the talk about the different characteristics between NiCd and NiMH and the added effect of the battery capacity and all the other variables still has me confused. In my case, prompted by the onset of winter (strong winds, low temps et al) I’m in the process of resurrecting an ic plane of a few years ago.  I was flying it previously on 35mHz and using a 4.8v NiCd Rx battery of 1100mAh capacity.  The Rx was a JR NER649S and the four servos were all JR NES 517. I now want to use my DX7 so propose to install a new AR7000 receiver and a new 4.8v battery the capacity of which is 2200mAh. Then I was advised by a club friend that most use a 6v supply with Spektrum!!!!!!!! Though I’ve understood and enjoyed the technical content of this thread, I confess to not being totally aux fait with matters electrical so, if anyone can please advise me on which I should use, I’d be grateful. Thanks for your time.

[Tim Mackey]

6v would be better....and at 2200mahr capacity the slight extra current used would be un-noticed as far as duration is concerned. However, your servos are pretty old by todays modern standards, and are actually a model that JR do not authorize for use on 6V systems. I would guess they will be OK, but must point this out to you for safety reasons. Good 6V compatible servos are very inexpensive these days, and if I were you, I would probably replace them, and use the older 517s in 4 cell applications, or maybe non critical applications like perhaps rudder? 

Just my £0.02 worth

[Vasantraj Pande]

Thanks for your prompt help and advice Timbo.

Previously I was having 10 minute flights on my 4.8v 1100mAh pack on 35 mHz, unfortunately I can't remember exactly how many flights I used to have but it was probably five or six before a recharge was necessary.  The 6v pack I can get is of 1700mAh capacity, so presumably if I kept to the same flight duration I'd expect my onboard voltmeter lights to show orange after fewer flights?  Seems logical.  Oh yes, I remember now being told the 6v pack in question consists of NiCd cells but not sure if that makes a difference to this situation. 

It occurs to me from what I understand you to say, it would seem there is an alternative to the one you suggest and that is if I stick with the existing servos I should use the 4.8v pack?  It would seem to be 'second best' but nevertheless, presumably, viable?  Unless, of course, that in turn, raises the confusing (to me anyway) combination of other variables eg, type of plane, style of flying etc and the resulting load on the battery and the subsequent possibility of dipping below the threshold of the Rx lower voltage supply limit?  Hmmm, seems to my simple mind that using 6v would do away with all that uncertainty!!!!!!!

[Tim Mackey]

Well, this topic has always been a hot potato. I have done extensive testing of the Spektrum AR6100 rcvr, and shown that it is perfectly capable of operating right down to the 3.5V lower voltage threshold and indeed even lower! This info is within the early stages of this thread.

Providing your receiver has the latest firmware it is "quick connect" enabled, and therefore a brief brown out would cause no visible problem anyway!

I have operated several models on simple 4 cell packs, or low capacity cheap BECs and have suffered no problems at all - but the usual disclaimers apply! One problem is that I /we cannot say for sure that all is guaranteed fine - after all, many factors are involved in the setup , including installation quality, are pushrods or control surfaces binding /high friction, weight of control surfaces, model size and weight, flying style, weather conditions etc etc.

My original advice remains the same. Buy 4 new 6V servos ( digitals NOT required ) and use 6V supply

My preferred ( but slightly more expensive and complex ) system would be

6V+ capable servos.

AR7000 / 9000 dual receiver properly installed and orientated.

2 X A123 cells powering the radio/servos directly via quality heavy duty switch.

Next best ( for me ) would be as above, but using a good quality digiswitch regulator combo unit such as this, together with a 2000m/a+ 2s lipo battery instead of the A123s. These switches are digital not mechanical, and cannot be accidentally knocked off, or otherwise fail due to dirty contacts etc, and also incorporate a regulator to feed your system with smooth constant power from a high voltage supply such as 2 x Lipos. They are excellent units and IMO very reasonable price considering todays exchange rates. I used several in my larger models, including a 90 size IC powered Spitfire which has 5 high power digital servos, and it has been completely faultless - it even has a built in LED warning system to indicate the state of charge of the battery supply. Top piece of kit! ( Available also in the UK from Als hobbies if buying direct scares you. )

I "feed it" from a cheap 3000 m/a 2 s Lipo ( around a tenner or less these days )

next best....as above but a large capacity 6V NIxx battery of at least subC size instead of lipo and digiswitch.

Of course, A123s or Lithium Polymer cells require a dedicated charging system, and you may not wish to do this. Again....all just my personal opinion.

[Vasantraj Pande]

Timbo, thank you for that extensive and exhaustive reply.

My financial situation dictates that I go for the cheapest option and will therefore pursue the 6v route of your original suggestion - I'm not sure whether my new and still boxed AR7000 has the latest firmware or not but I would expect so ... certainly hope so, I'll see if the Horizon web site can tell me.

Just had a call from a club buddy who suggested that I consider remaining on 35mHz to avoid all the hassle!!!!!!!!

Arggghhhh.

Thanks again.

[Tim Mackey]

Nah...go for the 2.4Ghz route. An easy way to tell if your rcvr is "quick connect" is as follows.

Bind as normal to the tx. Connect a servo to any port and confirm that all works as normal. Now whilst the rig is sitting there idle and all powered up, simply switch off / otherwise disconnect the power supply to the rx, and then reconnect - this can be as brief or as long as you like. Do NOT switch off the Tx. Upon reconnecting the rx power, the LEDs on the rxs should be flashing. If they are not flashing but solid, then you have an old receiver. HH will upgrade this free upon you returning it to the service centre. All Spekky rcvrs distributed to the trade since around early spring of this year are quick connect enabled...but some unscrupulous retailers are STILL selling on their old stock - ask me how I know!

If the rx has a firmware version of 1.6 or higher printed on the case...... then it will be QC. 

[Vasantraj Pande]

I shall be going for the 2.4gHz route ...... eventually, that's for sure.

I can see no mention of the firmware version on the rx casing so thanks for the tip regarding the check, I might use my acromaster, certainly I need to send the existing receiver in that plane back for the update.

All this just goes to show what a minefield the transition is from 35mHz to 2.4gHz, to me anyway; I didn't realise there were so many ins and outs and pitfalls to catch the unwary.  I suppose someone just starting out and choosing the 2.4gHz route would get compatible kit from the onset.  Hope so anyway.

Thanks for your time and advice.

[Peter Jenkins]

Timbo

 

Was flying my E-Flite Sea Fury and found that on the first flight I get a solid LED on connecting the battery (Spectrum 6100 Rx).  On the second and subsequent flights, I get a flashing LED when connecting the new battery - Tx on first as always.  I did a range check and found it gave me control at 20 mtrs with the reduced power switch selected.  No problems when I flew the model.  From your note above, it would appear that the blinking LED indicates that QC is enabled.  My question is how long between switching off power and switching on power before you just get a normal steady LED indicatior?

 

Regards

 

Peter

[Tim Mackey]

That sympton is not indicitive of brown out / QC action.

There are two "types" of flashing LED.

The rapid pulsing occurs when the Rx is not correctly bound to the Tx.

Slower flashing indicates a brown out. 

The important thing to remember is that "brown out flashing" can only be seen whilst all power is still connected and the TX remains on.

If you switch off either the TX or RX (irrespective of switch off sequence ) the flashing will stop.

[Peter Jenkins]

Timbo

 

Many thanks, but.... I'm still confused as to why sometimes the LED is steady and when I connect another battery to fly again I get a blinking LED.  Surely once bound the Rx stays bound?  Also, it is almost always the second flight of the day when the flashing starts.

 

A confused Peter!

[Tim Mackey]

Yes indeed - once correctly bound the Rx will not lose bind unless told to do so.

Another forum user  had a similar scenario recently, and had been actually "binding" incorrectly, by not using the battery port of the Rx for the bind plug. Also, ensure after successful binding that the bind plug is removed and then the RX switched off, then the Tx.

I think you are only partially bound as it were - I suggest you read the manual very carefully again and re-bind your model then see how it goes.

If it still seems wrong, please post back here and we will sort you out.

PS it is not uncommon for people to have left the bind plug in all the time - you havent have you....

PPS confession they say, is good for the soul

Edited By Timbo - Moderator on 26/04/2009 09:45:35

[Peter Jenkins]

Thanks Timbo.  I think my problem may lie with the sequence of switching things off.  I know that I used the battery port for the bind plug and that I removed it afterwards (the big orange flag is a useful reminder and I have to put the one of the servo plugs back in as well!

Thanks again, Peter.

[iawnski]

ok guys well i have a spektrum  ar 500 rx /my tx is on then  i connect the rx i get a few notes from the esc and the rx light stays on  no blinking ,is this the right way for it to be, or do ineed to send the rx off to hh?

[Tim Mackey]

That is the right way, but has nothing to do with "quick connect" Kev.

Leave everything as above, switched on, and with a servo or two plugged in. Then remove power to the RX only, LEAVE THE TX ALONE. If you are using a BEC from the ESC to power your Rx, then simply unplug the main flight battery, and then plug it back in again as quickly as you can. Is the LED on the Rx now blinking?

If so, then you have QC enabled. #

However, with many of the AR500s, it doesnt work as fast as it should - control of the servos should be instant after plugging back in - but sometimes it can take several seconds for control to be resumed...even though the LED blinks.  If this is the case, then you have an early version of QC firmware in the Rx, and it should be sent to HH for free update. Proper QC enabled Rxs will regain control of the servos in milliseconds...so fast in fact that you will never even know you had a "brown out" - thats exactly why the LED blinks - to let you know you did!  In flight you will never know.

However, WITHOUT the proper QC enabled, you will almost certainly know you have a brown out, 'cos the 'plane will likely crash out of control. You have been warned.

 

[iawnski]

hi timbo thanks for that mate will do another check tommorow and let you no whats going on iawnsk

[Klippy]

Hi Timbo, so, as I understand it, the cheaper 2.4gig sets tend to use a single frequency of the 70 plus that are theoretically available, sometimes without even first checking to see if it's available. Sounds like a 'shoot down' waiting to happen! Even if there's a unique code embedded in the signal, consider the following scenario:- you and 2 or 3 club members are flying, late-ish afternoon, and it hasn't rained for a day or so. The 35meg, 2.4gig, argument/discussion has been resolved, you're all flying 2.4! 2 of your members are even flying the same cheepo as you. As in 'here guys I've got this Tx/Rx combo, it's fantastic, flying for a month now, and no problems', sound familiar?

Now, you're flying right hand circuits, (club rule) and the other guys are to your right, you call finals (or landing, depends on the club. I personally prefer a system where you call downwind, base and final, but that's another discussion)

As you come over the fence you lose control, and, if you've set your failsafe properly you regain control within 20m and land (probably with nothing worse that needing to change underware)

As I see it, what can potentially happen is the following:- 

1/ late in the day so low receiver voltage

2/ the guys to your right are closer to your model than you are

3/ transmission doughnut slightly better set that yours (antenna)

4/ more than one Tx using the same algorythm, not code, there's a difference.

5/ your Rx gets swamped (temporarily) by the stronger signal

6/ even worse, because of the quantities these cheepies are sold in, 2 of you are on the same frequency!

I'm just setting out what may be a worst case scenario, some one please correct me if I'm wrong.

Question, will the failsafe even kick in? You haven't actually lost signal, just intelligence.

[Tim Mackey]

Not sure how this discussion got in here really Tony.... all the thread was discussing really was the brown out scenario of Spektrum Receivers - more particularly the 6100E. Discussing cheapo new kid 2.4Ghz stuff was not part of the thread. The only part of this lot that I can see which is perhaps directly relevant is the question of failsafe and brownout.

failsafe does not apply in the case of brown out, as this is a signal related feature, not power related. If a brown out occurs, then you effectively lose all power to the system including the servos, so they phsically cannot be driven to failsafe, or any other position for that matter.

As for the cheapy stuff, even that has to have GUID to comply with the regulations so the situation where one Tx controls anothers Rx should technically never arise.

Edited By Timbo - Moderator on 27/04/2009 12:00:29

[iawnski]

nice one tim done the tests and its qc cheers boyo,anyone down sunday weather pemiting

[Vecchio Austriaco]

Even many have posted their experiences I would like to add mine. May be it is of some help for somebody. 

Purchased a DX 7 last April as our old airfield suffered from a lot of interferences at the 35Mhz band. Also my son has a DX6i and is happy with that. 

First crash happened in some 150m distance- no signal - servos in failsave mode - Katana down. No sign of blinking lights on the receivers (AR 6200). Second crash one month later - in the landing curve loss of signal - Sukhoi down. May be the curve has been been part of the problem, I normally have the antenna in a 90° position to the left, so if I turn only my head and not my body the antenna points to the plane. 3rd crash - even closer, about 80 m, again lost control in a low curve,  control came back some 2 m before ground - unfortunately I don't have that quick reactions - Edge 540 down. 

In all cases I was sure that it was not a brown out - if you are in a landing curve you normally don't have the trottle open too wide....I use 3A Becs or on one of the models even a switched Bec and only 3-cell Lipos which I never empty completely. Except from one slow flyer I use only AR6200 or AR7000 receivers. 

After discussions with my local model shop and some other Spektrum users I sent the radio to Horizon. Their comment was "Output power too low - we have reprogrammed and adjusted your transmitter" 

So may be some of the DX7 users suffer from the same problem. 

Also look out for carbon tubes and other pieces of this famous material. Try to move your receiver away from those and make a range test with different positions of the model. 

Simple moving of the receiver 4 cm away from the wing tube on a foamy made the difference between no range and normal range. 

In the meantime I changed club & airfield - now there are no 35MHz problems - and in case of the slightest problem on the repaired DX7 I will move back to my old Futaba 35MHz system. 

Have a nice flight.