Transmitter advice needed please

[Oli Dainton]

Hi all,

I am just starting electronics work and assumed one of my old transmitter /receiver combos from flying days would do the job.

I have a Futaba T7C and Spektrum DX6i.

Seems like the Futaba failsafe is locked to left stick throttle channel and the spektrum only has a two position switch, whereas instructions for audio module suggests three position is required.

Also despite trim and subtrim being zeroed on elevator channel of dx6i, the motor runs unless elevator stick almost all the way back.

So I wondered if these transmitters could ever actually work for my PZIII safely or do I have to bite the bullet and get a new dx6 or dx8?

Since Armortek themselves use dx6 for testing I guess it has three position switch and ability to put failsafe on any desired channel?

Thanks in advance

[Peter Silcock]

Hi all,

I am just starting electronics work and assumed one of my old transmitter /receiver combos from flying days would do the job.

I have a Futaba T7C and Spektrum DX6i.

Seems like the Futaba failsafe is locked to left stick throttle channel and the spektrum only has a two position switch, whereas instructions for audio module suggests three position is required.

Also despite trim and subtrim being zeroed on elevator channel of dx6i, the motor runs unless elevator stick almost all the way back.

So I wondered if these transmitters could ever actually work for my PZIII safely or do I have to bite the bullet and get a new dx6 or dx8?

Since Armortek themselves use dx6 for testing I guess it has three position switch and ability to put failsafe on any desired channel?

Thanks in advance

Oli, I use Futaba T7C's on all my models. I wouldn't worry about the failsafe too much , I've never needed one on any model. To me the T7C is the easiest one to use, unless you want a massive number of functions. Others will have a different opinion no doubt.

[Oli Dainton]

Thanks for the reassurance Peter, I would rather not have to spend another £300+, if possible!

It would be good to know if fail safe is a widely used feature in this community, or just as a ‘nice to have’

[Adrian Harris]

> It would be good to know if fail safe is a widely used feature in this community, or just as a ‘nice to have’

You don't need it until the time that you turn the transmitter off before the tank, then you really, really need it

The problem only exists if you leave the Futaba fail safe unconfigured. In this state the tank will start reversing at full speed on one track if the transmitter is switched off, or goes out of range. Spektrum fail safe seems to work out of the box.

Adrian.

[Ralph Gerharz]

I have fail safe and use it.
My young boys drive our tanks about with often other people attending and the dangers of one of them out of control is just not acceptable!
We use 6 channel FS-GT5 Transmitters.
The transmitter is the one hand type most often used with RC vehicles. Both drive motors are controlled with the single steering wheel using a 5 Dollar US. V-tail mixer. I have found this very practical and enjoy the realism for use on the MK IV.
If moving both Tanks from the shop to the car I can drive both at the same time, one in each hand.
Ralph

[johnny johnson]

I have only just started this tank hobby so my experience is limited but I have been playing with R/C cars, planes, boats and subs, since the 1980s, I run failsafes on all my gasoline cars because loss of signal means a 30lb car running 30 to 40 MPH out of control, I have never had any electric anything take off after loss of control but we are talking about a whole lot more money with a tank so I will run a failsafe just because of that.

[Oli Dainton]

> It would be good to know if fail safe is a widely used feature in this community, or just as a ‘nice to have’

You don't need it until the time that you turn the transmitter off before the tank, then you really, really need it

The problem only exists if you leave the Futaba fail safe unconfigured. In this state the tank will start reversing at full speed on one track if the transmitter is switched off, or goes out of range. Spektrum fail safe seems to work out of the box.

Adrian.

My next question would be if I was planning on using single stick control, in which case the fixed fail safe to throttle channel on the T7C would result in, at worst, bouncing off barrel elevation. Since I cannot configure neutral throttle failsafe on the right stick, I am not sure if losing transmitter signal would behave like centred right stick or if it becomes unpredictable how those channels behave in such a circumstance.

[Adrian Harris]

I'm not 100% sure what a receiver actually does in the case of a lost signal as I've never switched the transmitter off when one of my tanks was in motion. The receiver will either continue to send out the last good signal it had, or it will return all channels to their neutral position.

The throttle fail safe is dangerous because it goes to -100%, rather than centred stick (0%), though this can be turned off in the menu. I guess you'll have to raise the tank up off the tracks and experiment.

I've run my Sherman BARV up to 120 metres away and not had any problems with signal quality or response. I was only able to do this as we had an empty rugby pitch on which to drive around, so I knew there were no obstructions or hazards it could hit.

Adrian.

[Gerhard Michel]

I think the behaviour of a receiver missing its transmitter signal is depending on the manufacturer of the RC equipment, but most of the modern GHz receivers have a free programmable fail safe for each channel, and a modern ESC stops the motors immediately when missing a convenient input signal.

Modern RC equipment has a large operating distance. HoTT receivers will work up to 4,000 m away from transmitter (free on air). Our tanks may be 150 m or more apart in our sandpit, and we never had transmitting problems. Nevertheless a working fail safe is a good thing, because these ultra short waves may be jammed even by simple obstacles like a tank turret between receiver antenna and transmitter.

[Peter Silcock]

Oli, if you are worried about a failsafe, why not have a look at the plug in failsafes you can buy for less than £10. As I say I have never needed one, but fitting these might put your mind at rest.

[Stephen White]

There are two good reasons for setting the failsafe, loss of signal and low Tx or Rx battery. Although modern frequency hopping technology is robust and resistant to EMC threats (interference), our Rx antennae are within a metal box which can degrade signals in certain aspects. Unless you're running telemetry, your Rx battery power supply may be affected by the current draw on the main power batteries. Our models can draw significant power peaks which could degrade the Rx power supply to the extent that signal is lost.

If you're operating anywhere near the public, an out of control model is unacceptable and if one were to cause injury, it would be very damaging to the reputation of our hobby. Moreover, if the failsafe isn't properly set, it may cause an insurance claim to be invalidated.

Failsafes work by detecting a loss of signal (not a momentary loss but are triggered after about ten seconds of continuous loss of effective signal). Once the loss of signal is recognised, all channels are driven to their failsafe positions set during binding. They need not freeze the outputs in the conditions applied when the signal failed if they are set up properly. When binding the Rx and Tx, the sticks can be set to produce no motor output and the tank will come to a halt when the signal is lost. Note that it can take up to ten seconds to kill the motion but it's better than having a runaway model.

For Spektrum, there are three Failsafe modes. You only need to be concerned with the Preset Failsafe. Instructions for setting it up are in the Knowledge Base. It's really very simple to set up.

For Futaba, the situation is very unsatisfactory. On the 7C, the failsafe can only be set to Channel 3, which does not therefore cover the two channels used to drive the motors of the tank. The Failsafe should be disabled to avoid it operating on one channel only which could make a situation worse.

I've no experience of using the external failsafes, such as the Futaba FSU2 failsafe (link below) but I can't see why you wouldn't be able to buy two and apply them to the two motor output channels. Perhaps someone has experience of doing that?

https://www.eurorc.com/product/17993?cu ... zIEALw_wcB

Of course, once you get beyond the basic Futaba and Spektrum radios and enter the world of software defined radios, which are the future, the failsafe modes can be tailored to our exact needs. In addition, radios such as the FrSky Taranis have RSSI (Radio Signal Strength Indication) which gives you real time data on signal quality and alerts can be setup to warn you if the signal is degraded, in time to take action.

[Gerhard Michel]

The risk of having a runaway model is present even when using modern GHz RC equipment. In Hausen I saw until now 2 near-accidents:

1. The first model started uncontrolled out of its stop position at a public street with full speed, jumped over the kerb, missed some visitors and dashed against a tree. After this it stopped, and from this moment it could be controlled normally again! The fault could never be resolved.

2. The second model, a heavy quarter scale Kingtiger, climbed at a bold hill when it reversed and dashed downhill. A youngster tried to stop it manually and of course failed, but got no injury. The model stopped at the hill base just in front of some visitors. The owner had installed both a fail safe and an ESC, which stopps and shortcuts the motors when leaving a correct signal. Moreover the owner had installed a main circuit braker for the whole tank. The engines took much current to climb the hill, and the main circuit braker blowed. Receiver AND ESC were out of electric supply, and all safety precautions were ineffective! The motors were smooth-running spur gear units, which couldn't stop a 330 kg monster.

The curiosity: WITHOUT an automatic circuit braker the model wouldn't have had any problems to climb the hill. Even a stop by transmitter or failsafe would have caused the tank to roll down slowly due to the EMK brake of the ESC. Therefore the additional circuit braker in this case was the worst solution!

[Mark Heaps]

Good point Gerhard,
In the absence of all electrical power, gravity takes over and some of our beasts are quite heavy. Fail-safe relays short-circuiting the motors are unlikely to stop it but would slow it down till it rolls to a stop on level ground.
Mark

[Stephen White]

Gerhard, it's better that we keep discussion to Armortek models to help Oli. In the absence of adequate power supply the Armortek tanks will come to a rapid halt unless they're on a significant slope, in which case they can usually be stopped with an obstacle placed in front of the track. The case for a failsafe is compelling and it's a pity Futaba are wanting in that respect.

[Peter Silcock]

Gerhard, it's better that we keep discussion to Armortek models to help Oli. In the absence of adequate power supply the Armortek tanks will come to a rapid halt unless they're on a significant slope, in which case they can usually be stopped with an obstacle placed in front of the track. The case for a failsafe is compelling and it's a pity Futaba are wanting in that respect.

I think Gerhard was helping Oli by explaining what can happen with models. I don't agree that Futaba are wanting. In over 45 years of using Futaba radio gear on planes, 1/4 scale ic race cars and 1/3 scale ic dragsters as well as Armortek and other makes of tanks, I've never had a single failure nor have I ever had a model go out of control. The existence of a failsafe in a model cannot take the place of careful battery monitoring, careful wiring and continuous maintenance and checking. JMO obviously.