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[nsa66]

I'm pretty sure I know the reason for this problem. I suspect that the TX/RX are set up for helicopter use. With RC helis, the throttle channel is automatically set hard back on power up to prevent the rotor spinning up past takeoff speed. This is irrespective of the position of the stick. It is necessary for the flyer to actively move the stick to the fully down (idle) position to initialise the throttle before it will respond to changes.

Of course there is no reverse on a heli motor/engine, so mid-stick is actually half power. As you, presumably, have the stick set up as centre-off, then what is idle on a chopper is full astern to you (and your ESC)! 

[Peter]

I agree with nsa66, the system is set up for aircraft/heli use, with a failsafe at zero throttle on startup, as related to a forward only speed controller.

This obviously equates to full reverse with a forwrd/reverse type esc.

This is  borne out by the return to 'normal action' after the first operation of the throttle stick on the Tx, with the stick at centre travel now being zero motor speed, relative to the esc setup..

This should be able to be checked, by now switching the Tx off, with the model in a safe location obviously, whilst the Rx is still on.
The system should then go into failsafe, as per aircraft mode, for a zero throttle setting. However in the boat application, with a Fwd/Rev esc, this will be full reverse.

The only solution would be to find out how to reprogramme the throttle channel on the Tx, to give normal Fwd/Rev about midstick position, and remove the failsafe function.

[BlueWotsit]

Ive been following this thread with interest, particularly as on one of my boats, I too was getting the excessive throttle power at start up.

Reading the various issues, Im starting to wonder if a couple of other glitches I have had with different boats could also be connected to either the RX or the TX.


In each instance, the boat sails well for about 15 or 20 minutes, then loses forward power. Sometimes reverse works immediately, sometimes I have to wait a few seconds. Yet when I get to the shoreline and the boat is out of the water, forward motion works again. Back in the water and after about 20 yards it stalls again.

Of course first reaction is battery - but this I have ruled out as in each case its a 6v gell cell and the current drain is such that the boat should be able to run for several hours.

Second reaction is could the motor be faulty - have changed motors to a completely different type - same problem.

Third reaction is could the ESC be faulty - again changed to a totally different type - same problem.

I have also tried a second GC rx unit, with same results, all of which points to the transmitter glitching but where or what should I perhaps look into - it almosts seems to be an overheating issue perhaps ?

cheers
Andrew

[PMK]

BlueWotsit ~

"Of course first reaction is battery - but this I have ruled out as in each case its a 6v gell cell and the current drain is such that the boat should be able to run for several hours."
Is your ESC specified to work on 6 volts? Some ESCs have an internal voltage regulator which is there to supply a steady +5 volts to the rest of the circuitry. If this is the case, then your ESC is probably designed to operate at roughly 8 volts minimum. Since you're using just six volts, means it could very likely be the cause of all those nasties you described.

"Second reaction is could the motor be faulty......"
It could - but I'll bet it's not. The motor is probably pulling n amount of amps when it going flat-out. This can put quite a voltage drop on the battery, which means that your 6-volt gel-cell is no longer pumping out 6 volts.... causing your ESC to complain even more.

"Third reaction is could the ESC be faulty - again changed to a totally different type - same problem."
By now you might be getting the idea that the ESC is maybe perfectly okay, but that it's designed to operate on a higher voltage.

"I have also tried a second GC rx unit, with same results, all of which points to the transmitter glitching but where or what should I perhaps look into - it almosts seems to be an overheating issue perhaps?"
You're right - it could be any (or all) of those things, but I'd suggest that you check to see if your particular ESC is indeed suitable for 6-volt operation first.

Good luck.

[BlueWotsit]

BlueWotsit ~

"Of course first reaction is battery - but this I have ruled out as in each case its a 6v gell cell and the current drain is such that the boat should be able to run for several hours."
Is your ESC specified to work on 6 volts? Some ESCs have an internal voltage regulator which is there to supply a steady +5 volts to the rest of the circuitry. If this is the case, then your ESC is probably designed to operate at roughly 8 volts minimum. Since you're using just six volts, means it could very likely be the cause of all those nasties you described.

****Yes - its one of the Mtroniks range which have a wide variance in voltage capability


"Second reaction is could the motor be faulty......"
It could - but I'll bet it's not. The motor is probably pulling n amount of amps when it going flat-out. This can put quite a voltage drop on the battery, which means that your 6-volt gel-cell is no longer pumping out 6 volts.... causing your ESC to complain even more.

****The motor / battery combination had worked fine when used last summer with 27mhz - with small tug boats, and similar you dont have to be running at high speeds as that simply is not scale


"Third reaction is could the ESC be faulty - again changed to a totally different type - same problem."
By now you might be getting the idea that the ESC is maybe perfectly okay, but that it's designed to operate on a higher voltage.


***the change of speed controller to a different model Mtroniks again just a higher capacity one


"I have also tried a second GC rx unit, with same results, all of which points to the transmitter glitching but where or what should I perhaps look into - it almosts seems to be an overheating issue perhaps?"
You're right - it could be any (or all) of those things, but I'd suggest that you check to see if your particular ESC is indeed suitable for 6-volt operation first.

Good luck.


***thanks for the input - Im going to borrow a 27mhz setup over the next week having offloaded all of mine, as Im easy on the ESC situation seeing as how they had worked previously with the different TX / RX combo, also I had forgotten until I was looking this afternoon,  that in one of my boats the Model Slipway Sentinel which had also experienced the problem which is actually powered by a 7.2v NIMH

Sail boats are so much easier !!!!!!!!!!

[roger]

I wish I had read this stuff two months ago. I helped my friend change two boats from 40MHz to 2.4GHz and we had the same problem … and it doesn’t half make you jump the first time it happens!

It looks like the same Tx - the Giantcod 2.4ghz 4-Channel Mode2 Transmitter – with the 7ch 2.4ghz Frsky receiver and Mtronics Marine 15 speed controller in both cases. We checked and changed round everything without solving the problem.

The only thing I could think is that the BEC supply means that both the ESC and Rx have to be powered up at the same time. I thought perhaps the ESC was wandering before the Rx had locked on to the Tx signal. (I guess I could have temporarily pulled the power pin from the BEC feed so I could use a separate Rx battery, but the workshop time ran out for the day and I never tried it.)

However, nsa66’s explanation seems much more likely (that the TX/RX are set up for helicopter use). davidsg1a said that Rob at Giant Cod suggested that the problem is fixable. Did he come back with any more details? Alternatively, has anyone else found out how to reprogramme the throttle channel on the Tx as Peter suggests?

[springersrus]

radio link 2.4 systems have a failsave on throttle  switch it on to another channel using the mode switch on the back of the tx pcboard this will swap to mode 1 and should be ok

[expat flyer]

Hi all,  I'm a bit late to read this interesting problem.

Does anyone know if it is common to any other systems ?

I have a Spektrum DX6i  with MR3000 receiver that does the same in my IOM yacht. Switch on tx, then rx, and the winch goes past the sail full out position before returning to a position corresponding to the throttle stick. I would not worry about this glitch but the sheet attachment smashed the tube that takes the winch line through the deck. It might be possible to adjust the sheet lengths and winch drum to move the attachment point, but I don't know how far the glitch would try to take it if it didn't reach the physical limit and stall.

The idea that it is a heli trick sounds plausible but my tx is converted to mode 2 and is programmed for aircraft not heli.

None of my other tx's do this (DX6 and DX7), nor my other systems (Hitec and Futaba) - they all go straight from the parked position to wherever the stick is.

When I have time I'll see if a servo in the throttle channel does a similar movement.


Jerry

[Martin (Admin)]

I know this is an old topic but Ii found this on Griant Cod... and I just went through this pain at the weekend. 

I like the 'swap pot / channel' idea!


Re: Setting the failsafe on RadioLink 2.4ghz

Postby Phil_G on Wed Mar 24, 2010 9:08 pm

To explain, please for a minute imagine the Radiolink is installed in an electric plane, with a conventional ESC.
In common with Futaba radios, the Radiolink transmitter has a 'reversed' throttle channel with respect to the ESC input, and to operate an ESC conventionally, the 'reverse' switch must be set for the throttle channel. It does not have a failsafe. In the absence of a signal, the channel pulses from the receiver to the servos will cease. In a conventional ESC, this will cut the motor, so although its not specifically a 'failsafe', the result is a safe situation with the motor stopped.

The Radiolink transmitter expects to be controlling a unidirectional motor or engine, where motor speed is proportional to the amount of 'forward stick', and with low throttle (or throttle cut in the case of electrics) with the stick towards you. In a conventional setup therefore, the 'safe' position is with the throttle stick pulled fully back.
With this in mind, Radiolink added to their transmitter firmware a further safety feature, a 'throttle-lock'.
What this means is that if the tx is powered up with the throttle advanced (ie anywhere but fully back) then the throttle channel will transmit 'low throttle' until it is unlocked. To unlock, the throttle stick is pushed forward, then returned to the 'low' position.
Throughout the unlock process, the channel continues to send 'low throttle' pulses to the ESC. For high-powered electric planes this is a real boon for safety.

Now, with a bi-directional ESC, our safe 'low throttle' position is actually full reverse, and the neutral 'motor off' position is seen by the throttle-lock feature as a dangerous setting, which it over-rides with what it assumes to be 'low throttle' until you unlock it. This is why your motor is spinning up in reverse.

Two things you can do, one easy, one a bit more involved, but better.
The easy wasy is to switch on the tx first, pull the throttle right back, forward, then back again. It is now unlocked. Set it to mid-way and switch on the rx.

A better way would be to swap the wiring to the throttle pot with the wires from the elevator pot. This will put the throttle-lock feature on the elevator, which I assume is unused in your application. You will of course need to move the ESC to channel 2.

There is a third way which may work, I don't know as I've not tried it and my own Radiolink gear is long gone. Inside, in the centre of the board, is a switch labelled 'mode 1 or 2'. This switch might move the throttle-lock to channel 2. At least it is very easy to try. You may or may not need to switch the ESC from channel 3 to channel 2 again.

Hope this explains what's happening, and gives you an idea or two as to how to overcome it. If not just shout again.
Cheers
Phil.

http://www.giantshark.co.uk/forum/viewtopic.php?f=9&t=3734&st=0&sk=t&sd=a&hilit=radiolink+pot

[dodgy geezer]

Two things you can do, one easy, one a bit more involved, but better.
The easy wasy is to switch on the tx first, pull the throttle right back, forward, then back again. It is now unlocked. Set it to mid-way and switch on the rx.

A better way would be to swap the wiring to the throttle pot with the wires from the elevator pot. This will put the throttle-lock feature on the elevator, which I assume is unused in your application. You will of course need to move the ESC to channel 2.



http://www.giantshark.co.uk/forum/viewtopic.php?f=9&t=3734&st=0&sk=t&sd=a&hilit=radiolink+pot

I have used the first approach for a long time now, and think that is better. The point about it is that it 'forces' you to positively turn on your Tx and operate it first, before turning on your Rx, which is a good habit to get into.....