2.4 radio sets in mode 2

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19 March 2013 at 08:11 #39772
kenneth gault
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@kennethgault51984
Got a planet radio in2.4 to upgrade from 40 mega. On testing found if I switched off radio motors would run at high speed, 3 receivers all did the same thing. Bought radio link system and all ok if switched off
transmitter mtroniks speed controller(with built in failsafe) did just that, no motor rotation. After several months bought 3 additional receivers, unfortunately these behaved like the planet ones so I have not use them. I do not know if people are aware of this problem but if you are on 2.4 please run your model on the bench and then return sticks to neutral then with boat still live switch off tranitter and see what happens, you may get a nasty surprise. I presume this is the way some receivers are programmed. In aircraft left stick is elevator so loss of signal gives pitch down. What I do know is that I have 2 batches of radio link receivers which are marked and appear identical, but behave very differently.
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19 March 2013 at 08:11 #5217
kenneth gault
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@kennethgault51984
Throttle input if boat power is on and radio signal is lost
19 March 2013 at 10:18 #39774
Malcolm Frary
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@malcolmfrary95515
Probably a fail safe for its original intended use. A plane normally fails safe to "throttle off", which equates to pulling the stick fully back, or on a boat "full astern".

An ESC can be programmed to spot a lack of valid information coming from the receiver and act accordingly (i.e. no pulses = shut the motor off), but if the receiver on losing signal does its own thing, then that is cause to look at the instructions, if any are provided.

Not really a problem with the old type sets since they worked with live information in real time, but 2.4GHz sets work by transmitting instructions which the RX then interprets before converting to a suitable format before passing it on to the servos, ESCs etc.
19 March 2013 at 11:29 #39775
Dave Milbourn
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@davemilbourn48782
Interesting. I've just run a test on my Planet 5 to see what that failsafe actually does. In short – at least on my set – it does nothing.

Page 8 of the User Manual will tell you that on loss of a Tx signal the receiver will move all servos back to their centre position except the throttle, which will be moved to full motor stop for aircraft (or stick = all the way back).

In fact my set returns all four channels to a neutral signal value (1.5mS) for a couple of seconds and then turns the servo signals off (signal value = 0.00mS). This means that servos connected to any channel 1-4 will be returned to centre before the set switches off the receiver and the servos are set immobile at centre. This can be checked easily enough with your own set, using a servo in each of the outputs and watching what happens when you switch off the Tx.

If your set behaves like mine then all you need to do is set your ESC at motor stop = stick centred. If the signal is lost then the ESC will be reset to neutral (motor stopped) before it gets no signal at all, at which point its own failsafe circuit will kick in and keep the motor stopped.

If you radio does actually reset the ESC to full speed ahead or reverse then take the back off the transmitter and move the Mode switch to its other position. You then carry on using the SAME STICK as you were for the throttle (plugging the ESC onto the corresponding output pins, of course). If the Tx shuts down then the receiver will return the "new" throttle channel to full throw and move the ESC channel connected to the "old" throttle channel to centre. On my receiver the two channels involved are 2 and 3.

Read this again – it does make sense and it does work. There are no electronics involved, guys – it's just method and common sense (or forensics, if you like).

Dave M

Edited By Dave Milbourn on 19/03/2013 11:31:57

Edited By Dave Milbourn on 19/03/2013 11:32:54
19 March 2013 at 19:16 #39785
kenneth gault
Participant
@kennethgault51984
Thanks Dave M
I had set the radio dip switch to mode2 as I thought this correct for a boat ( throttle left). After your advice I opened the radio and set it to mode 1 . Then as you said moved the connections to the receiver so that throttle returned to left stick operation and rudder right, and yipee on switching off transmitter no motor rotation.
It still remains that the 2 batches of recievers behave differently the first batch do not give
motor rotation when transmitter switched off in mode1 or 2, the later batch of receivers only fail safe if the radio is in mode 1. I just need to move all the receiver connection on all my boats to reflect that my transmitter is in mode 1.
So the answer seems to be always set the radio to mode 1.
I still think there are plenty of people out there with boats and a radio set to mode 2 who are unaware that if they loose radio signal they may get engine rotation. I just hope they find out before they smash a boat or shred their fingers in a prop
19 March 2013 at 23:13 #39787
Dave Milbourn
Participant
@davemilbourn48782
Let's hope that they find their way here.
Dave M
27 March 2013 at 17:11 #39937
Soup
Participant
@soup
Kenneth I heartily agree things should fail safe. But the transmitter should never be switched off before the receiver anyway .

1 )TX ON 2) RX ON 3)RX OFF 4)TX OFF

Most(?) 2.4 radios have a fail safe anyway that will close throttle if signal is lost (Think of model cars if signal is lost they go to neutral throttle (if not brake) and steering centered ) .

If the radio does not have a fail safe [1] itself one can be bought.

Conjecture :-

Maybe it doesn't fail safe as it is converted from 40MHz to 2.4 GHz it is not a native 2.4 .

[1] Most 2.4s do, some won't and most other radios won't[2] . It is down you to decide if the on-board fail safe is sufficient and works well enough or if you'd prefer an external unit.

[2] Even a cheapo Planet set has a fail safe
27 March 2013 at 18:23 #39939
Dave Milbourn
Participant
@davemilbourn48782
Even a cheapo Planet set has a fail safe

Yes, it does – but that failsafe does not necessarily (or consistently?) do what it's supposed to do according to the manual i.e. return the throttle to zero (for aircraft). Please see my first posting above.
I totally agree that under all normal circumstances the Tx should be switched on first and off last, but switching it off with the RX still powered up is the only way of reproducing a situation where the failsafe shoud kick in. It's wise to test these things IMHO rather than trusting them to behave and then finding out in an emergency that they don't.
Failsafe is like BEC – if it's built-in then it will cause misunderstanding until and unless you thoroughly test what's going on in there.

Dave M
27 March 2013 at 20:55 #39945
Soup
Participant
@soup
@Dave see Point [1] Just after the [2] above.

Basically what I meant was buy an external fail safe if the one on the radio doesn't work as well as you'd like.

Aside :- Full size aircraft have the throttle set up the opposite way to cars(full size) etc so that if the throttle cable snaps, the engine goes to full throttle. Mind you with a full size it SHOULD only be the throttle that's bust wheras on a model ALL control will be lost.
28 March 2013 at 07:14 #39949
Paul T
Participant
@pault84577
Soup

I am a little confused by your comment relating to throttle fail safes on full size aircraft..which aircraft are you referring to.

Paul
28 March 2013 at 08:35 #39950
Soup
Participant
@soup
@Paul. I think all aviation carburettors.

In this case a Rotax engine as fitted to a Europa.

**LINK** From about 04:00

ASIDE:- He is (I think) trying to be humorous but I just find him annoying/childish.

Basically the springs etc on the carburettor are set up in such a direction that if the throttle cable breaks the throttle should go to full open (after all you can land with full throttle[1] but you can't (usually) maintain height at idle).

[1] Engine off but full throttle.

Some WWI aircraft didn't really have a throttle at all. Power was reduced by switching the engine on an off such as Monosoupape engines as fitted to Sopwith pups , Sopwith camels etc. A switch on the control column "blipped" the magnetos on and off, prolonged use of this "Blip" switch caused unburnt fuel to collect in cowlings etc leading to a much increased fire risk. Just something else for WWI pilots to worry about . The RFC didn't issue parachutes in those days.

Edited By Soup on 28/03/2013 08:57:39
28 March 2013 at 10:28 #39953
kenneth gault
Participant
@kennethgault51984
My point with the failsafe on the throttle was that it did not go to zero it goes to full reverse! And though I would normally switch the radio off last while building I always switch the radio off to simulate radio failure, by doing this I found the problem on the bench not on the water. Now operating in mode 1 but still using left stick for throttle, my right stick fore and aft operates the deck gun, so now if I loose the radio signal all that happens is the gun goes full left, the fail safe is still there, it’s just on a stick where it does not matter.
As for real aircraft the tornado throttles are an electrical signal to the engines if the aircraft suffers a total electrical failure the engine controls are lost and they go to max fuel they then accelerate to destruction within 2 seconds. They don’t fly too good after both engines blow up. Logic would say they would have designed it so that zero volts is say 3/4 power and control is + or – volts either side of that. But RR didn’t make them like that. All modern airliners have engines that are electrically controlled /via pilots input to computer. I do not know what happens on an airliner if the engine control suffers a complete electrical failure, but as I passenger I am not sure I want to know.
28 March 2013 at 14:41 #39958
Soup
Participant
@soup
Rather defeats the point Kenneth if you lose signal the gun will traverse to one side and no interferance will move it meanwhile the throttle is free to go all over the place. Of course I could be reading you all wrong (not unlikely), but I don't think so.

Would swapping modes so the radio failsfe is on a non-important (word?) channel [disabling the failsafe would also work but Murpys law dictates that it would be left on when it really hattered.] and an additional (seperately purchased) failsafe not be the best method?

Edited By Soup on 28/03/2013 14:44:32
28 March 2013 at 14:57 #39959
kenneth gault
Participant
@kennethgault51984
No,
When signal is lost there are no output signals on all the other channels from the receiver. This means my Mtroniks speed controller ( with built in fail safe) activates and ensures the motors can not run. The problem with the built in fail safe on the receiver is that when signal is lost it gives a reverse command on output 3 of the receiver, if the speed controller is connected to this then you get reverse, the fail safe on the speed controller is thus not going to prevent this, it has not got a signal loss it is being told to go in full reverse. I can not disable this failsafe it is in the programming of the receiver, so it is now moved to a stick that is not going to do any damage. The fact that if I loose the radio signal my deck gun goes full left is not going to do any damage, the point is the boat will stop
28 March 2013 at 18:00 #39963
Paul T
Participant
@pault84577
Soup

I never encounted a throttle fail safe in full size piston engine aircraft

Paul

Edited By Paul T on 28/03/2013 18:25:43
28 March 2013 at 20:10 #39966
Soup
Participant
@soup
I think calling it a fail safe is a tad "over egging the pudding" it is merely the springs on the carb are set up such that the throttle cable breaking means the carb (s) go to full power rather than the other way around.
28 March 2013 at 23:08 #39969
Dave Milbourn
Participant
@davemilbourn48782
Posted by Soup on 28/03/2013 14:41:23:Would swapping modes so the radio failsfe is on a non-important (word?) channel

Haven't we already arrived at that conclusion? Do keep up at the back there!
DM
29 March 2013 at 07:32 #39971
Paul T
Participant
@pault84577
Hello Soup

The programme showing the building of an aircraft is a little misleading, the throttle springing open in the event of cable failure is peculiar to Rotax units and perhaps has something to do with this particular manufacturers engines being fitted to smaller light aircraft such as hang gliders or the fact that they run on petrol rather than avgas.

The larger Rotax units that have been fitted to aircraft such as shown in the programme have caused some discussion within the home made light aircraft world as to whether or not this system is a good or bad idea.

I have never come across the system in Cessna or Piper aircraft as they tend to be fitted with Lycoming engines hence my confusion with your statement.

Paul

Edited By Paul T on 29/03/2013 07:34:02
2 April 2013 at 20:29 #40079
Soup
Participant
@soup
WARNING:- NO MODEL BOAT CONTENT IN THE POST THAT FOLLOWS .

So it's only the small(er)Rotax units, ah well live and learn eh.

I would have to be on the side of those in the disscusion who went for the full power with snapped throttle cable . It seems an eminiently sensible way to me but then again I have no knowledge of the opposing stance.
7 April 2013 at 14:58 #40141
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Hello all,

just noticed you are discussing the failsafe positions here as well. I've just posted on

Failsafe throttle setting for r/c boat

about the Radiolink T4EU sets and my findings.

Kim.
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