Retracts 'cycle' on switch-on

[Yorkman]

Hi all

I've fairly recently acquired an Art Tech/Horizon Hobbies Mosquito (as seen on ebay) and with some tweaking I'm pretty pleased with it.

One annoying thing, and I don't know if it's the model or the radio, is that when the flight battery is connected the u/c operates through one complete cycle. If they are retracted when connection is made then they extend and retract at normal speed. If they are extended then they 'slam' up and then extend slowly. The retract servos operate via a sequencer which opens/closes the gear doors, I don't know if this is a factor. The other servos 'kick', but I think that's normal. I'm using a Dx6i and AR 6200(?) rx. My only other model with retracts is the York, I remember that the retract servos also 'kick' on that, but they don't move through a complete cycle.

Anyone else suffer from this, or know why it does it, or how to cure it?

[Lee Smalley]

its bound that way, on initial turn on everything goes to failsafe position, try rebind with everything on the tx set as you want the failsafe ie gear down or up

[Tim Mackey]

Even after following Lees advice, it may still do it - normally caused by the retract servo(s) cycling if they are powered up without a valid Tx signal - most digital servos will not do this, but many analogue ones do.

[Allan Bennett]

Picking up on Tim Mackey's comment, you should always switch on your transmitter before you power up your model, and switch off the transmitter only after the model battery is disconnected.

If you're powering up your model without the transmitter switched on, servo and motor responses are unpredictable unless they all have fail-safe settings. But, even then, it's still not recommended because in theory the receiver could respond to a stray signal, or interference, from somewhere else if its own transmitter is not switched on.

If you're switching on your trannie first, and the retracts are still cycling, I don't have an answer

[Yorkman]

I'm pretty old-school in that way, in that I always power up Tx first, and always do a 'full and free' check before the off-once saw a guy launch his slope soarer without the Rx switched on....and then do it again the same afternoon!

I will try rebinding, seems like a plan!

Thanks.

[Martyn K]

Posted by Allan Bennett on 01/11/2012 08:47:41:

Picking up on Tim Mackey's comment, you should always switch on your transmitter before you power up your model, and switch off the transmitter only after the model battery is disconnected.

 

 

Getting off topic, but I am starting to wonder whether this is actually sound advice any more.

I can see the benefit of doing this on 35MHz to make sure that the servos set to a determined state (determined by the transmitter stick settings), but now, with 2.4GHz and (almost) universal fail-safes fitted as standard, turning the Rx on before the transmitter will ensure that a quick visual check can be made that the failsafe is actually working correctly, ie controls go to the failsafe setting and the throttle closes (or whatever you have programmed). You can also check that you are not being interfered with and there are no obvious glitching, noisy servos etc which would be overrun by a local transmitter which would swamp any much weaker interference.

So please, just why do we still advise switching the Tx on first? I don't do this anymore and so far, I haven't had one disaster as a result of that.

Your considered opinions are as usual most welcome.

 

Martyn

 

Edited By Martyn K on 01/11/2012 09:51:10

[Biggles' Elder Brother - Moderator]

An interesting question Martin. I must admit I stick to the Tx-on-first routine and its so ingrained that I can't see me changing easily. I suppose main points in support of that would be:

1. What if the failsafe isn't programmed, or is not programmed correctly - particularly wrt electric motors and their ESC's? Yes I agree the failsafe should always be set up - but we live in a real world and sometimes people get it wrong or forget. If you Tx-on-first then the failsafe can be tested - but if you Rx on first you are dependent on it.

2. Some ESC's won't initialise anyway without a "proper" Rx command.

3. You may well get retract U/C issues such as described here or smoke pumps turning on etc - with a large model that could be more than just embarrasing!

4. Do some Rx's "lock" into failsafe? I don't know but I could see a circumstance that turning the Tx on after the Rx has entered failsafe may not initiate Tx and Rx handshaking properly. Not sure about this, never tried it!

5. I suppose the main "discomforting" feature I feel about always turning the Rx on first would be that you are deliberately, and routinely, creating a situtaion in which the model is live but has no control signal - and that sort of "goes against the grain" if you know what I mean! We have to turn one or the other on first - it seems intuitively sensible to turn the source of control on first and so ensure as far as possible that the model "wakes up" into a controlled world as it were.

I do agree that it is well worth reveiwing "rules" like this from time to time - just to see if developments in technology have made something redundant. And you may well be right that with modern equipment it is by no means as critical as it was - but I think I'll be sticking with the old way - it just seems safer to me.

BEB

[Martyn K]

Hi BEB

A very good point about the 'live' scenario, especially with leccie models, something I hadn't really considered too much as I have only recently started playing in this arena.

However, I have tried the "Rx on first" on 2 different ESCs and neither have done anything untoward, ie the default failsafe for an ESC is engine off which is surely a good thing and in itself a worthwhile test. The thought of a glitch and the ESC going full throttle is actually quite frightening.

I think the point I am making is that when you "Rx on first", the model should be secure and you should be prepared and positioned for 'any' eventuality, not just blindly following a startup sequence. If all goes to plan then you will have confidence that your model will behave properly if your Tx dies or whatever is likely to go wrong with the ground station.

However setting off a smoke cannister would be a really good visual indication that you have lost Tx control - although probably not what the pilot would have really wanted..

Martyn

[Frank Skilbeck]

Getting back on topic, I have a Dx6i/AR6200 and this is a trait of this setup, when the Rx is first powered up sometimes the servos glitch over to full travel and back. I think what happens is that when the Rx is first powered up there is a delay in sending the position signal to the Rx and some servos on seeing no signal move to one end of their travel, once they get the signal they go to the predetermined position.

Fortunately the ESCs on seeing no signal don't transmit power to the motor.

[Allan Bennett]

Going off-topic again, I'm no electronic engineer, and I believe that nothing man-made is infallible. So, one scenario I can envisage is a (faulty?) receiver responding to signals from another transmitter -- be it interference, or another flyer's trannie -- in the absence of the "proper" signal from the transmitter that it's supposed to be bound to.

The point about checking the fail-safe settings is a good one, but I would rather do that by switching the transmitter off momentarily after having powered up in the normal sequence (and checked that everything's responding correctly), for that more accurately represents the scenario the fail-safe is meant to work in. If you power up the receiver with no transmitter signal present, that's not exactly what's going to happen in the air, so is not a true test of the fail-safe.

[Chris Bott - Moderator]

Posted by Frank Skilbeck on 01/11/2012 14:15:17:

Getting back on topic, I have a Dx6i/AR6200 and this is a trait of this setup, when the Rx is first powered up sometimes the servos glitch over to full travel and back. I think what happens is that when the Rx is first powered up there is a delay in sending the position signal to the Rx and some servos on seeing no signal move to one end of their travel, once they get the signal they go to the predetermined position.

Fortunately the ESCs on seeing no signal don't transmit power to the motor.

The start up action of some Spektrum receivers (and only Spektrum I think) is different to the failsafe.
During the period when the Tx and Rx are making a connection, the surfaces move to the position that the transmitter was telling them to be in when the bind was done.

Of course the bind is done at the start of the setup sequence when all sub trims etc are usually at zero. If subtrims are then moved significantly to centre surfaces then every time the Tx/Rx are switched on, the surfaces will go to the zero subtrim positions until connection is established and the Rx knows what the Tx is telling it.

This is why Spectrum say that once averything is set up, another bind should be done. After doing this, surfaces wont kick to extremes while powering up.

(Throttle is an exception here where spektrum Rx's give no output at all until connection is established and of course things are actually more complicated as not all models of spectrum receiver act the same)

Yorkman it's definately worth trying binding the receiver again, with the retract switch already in the position you would normally store the model in, and always switch the Tx/Rx on with the switch in that position. Not sure this will work with your particular servo, but it's wortha a try.

[Martin Harris - Moderator]

Posted by Martyn K on 01/11/2012 09:50:24:

Posted by Allan Bennett on 01/11/2012 08:47:41:

Picking up on Tim Mackey's comment, you should always switch on your transmitter before you power up your model, and switch off the transmitter only after the model battery is disconnected.

 

 

Getting off topic, but I am starting to wonder whether this is actually sound advice any more.

~

So please, just why do we still advise switching the Tx on first? I don't do this anymore and so far, I haven't had one disaster as a result of that.

Your considered opinions are as usual most welcome.

 

Martyn

 

Edited By Martyn K on 01/11/2012 09:51:10

Although they don't, unfortunately, go into any explanation, Jeti go to the lengths of making specific mention in their Duplex 2.4 manuals:

Operation of the DUPLEX system is very similar to a FM system. We recommend switching on the transmitter first and thereafter the receiver. The transmitter confirms the on state of the receiver by a short beep. When switching off the system we recommend to switch off the receiver first and after that the transmitter.

Until there's any good info to the contrary, I'm happy sticking to the "old" procedure.

Edited By Martin Harris on 02/11/2012 13:28:19

[Bob Cotsford]

I think the recommendation to switch on the Tx first is good base line advice as it will most often result in a safe situation regardless of how the rx initialisation and failsafe function.

You know the old 'rules are for the obedience of fools (or noobs) and the guidance of wise men' saw.

[Frank Skilbeck]

Posted by Chris Bott - Moderator on 02/11/2012 09:06:33:

Posted by Frank Skilbeck on 01/11/2012 14:15:17:

Getting back on topic, I have a Dx6i/AR6200 and this is a trait of this setup, when the Rx is first powered up sometimes the servos glitch over to full travel and back. I think what happens is that when the Rx is first powered up there is a delay in sending the position signal to the Rx and some servos on seeing no signal move to one end of their travel, once they get the signal they go to the predetermined position.

Fortunately the ESCs on seeing no signal don't transmit power to the motor.

The start up action of some Spektrum receivers (and only Spektrum I think) is different to the failsafe.
During the period when the Tx and Rx are making a connection, the surfaces move to the position that the transmitter was telling them to be in when the bind was done.

Of course the bind is done at the start of the setup sequence when all sub trims etc are usually at zero. If subtrims are then moved significantly to centre surfaces then every time the Tx/Rx are switched on, the surfaces will go to the zero subtrim positions until connection is established and the Rx knows what the Tx is telling it.

This is why Spectrum say that once averything is set up, another bind should be done. After doing this, surfaces wont kick to extremes while powering up.

Yep did all that and fail safe is all surfaces at mid position and throotle to off, but the servos all kick to a full deflect position and then back to the neutral position. I also think on some Spekky Rxs the failsafe is only on the throttle channel, my M Link and FrSky set ups don't exhibit this behaviour. I broke the tail wheel link on my parkzone P 47 because if this (AR600 RX I think), due to holding the tail dpwn which plugging in the battery, Tx already on, the servo kicked and broke the link to thr tail wheel as it couldn't move.

[Chris Bott - Moderator]

The only failsafe on a AR6200 receiver is on the Throttle channel as you say, all other channels "hold last position". So failsafe is not mid position on all surfaces.

What the channels do at switch on is a completely differnt thing, they do not assume failsafe positions. (There is no failsafe except Throttle.). They go to the position that was being commanded at bind.

Unless, maybe it's a thing that your particular servos do independantly of what the Rx outputs are doing.

[Yorkman]

Didn't expect to start such a lively conversation when I broached this subject! I'm now thinking that after initial 'bind' I may have had to reverse the 'gear' channel-haven't had chance to fiddle yet, will report back.

On the subject of Tx or Rx first-I only fly electric, so it's Tx on, double check throttle fully closed and u/c selector 'as required'. I know it shouldn't happen with 2.4, but in the 'old' 35mHz days, nearby frequencies certainly had an effect if one's own Tx wasn't on, servos chattering and moving-could be entertaining with a lekky model standing on its own wheels....