Failsafes and the Spektrum DX5e

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25 April 2014 at 20:09 #48411
Kimosubby Shipyards
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@kimosubbyshipyards
The Spektrum DX5e failsafe declares itself as adjustable. The default is as the Radiolink, full back on the THR stick. I've yet to get the unit to change this failsafe position even though the manual explains how to change it, stating it is adjustable.

Another problem with the Spektrum is the time lag between switching on the receiver and it locking onto the transmitter signal. Up to 5 seconds sometimes. This means that the receiver is on, no signal so the failsafe engages, the THR goes to full back, then signal found, so THR goes to the stick setting on the transmitter. The failsafe setting also ignores the trim adjustment settings, it overrides them.
The Spektrum DX5e has no Mode change available, it comes in Mode 2, so the left hand stick is the THR. For myself, this stick controls the sail winch. We yachters adjust this so that with the stick full back it equates to sails pulled tight in. (Set this way we cannot over sheet and cause damage.) Forward stick movement lets the sails out, and we can control that by eye even at distance.
Sail winches are powerful and travel quite quick, so if a receiver lock-on takes 4-5 seconds, the winch travel due to the failsafe can over travel the winch end point and cause havoc even breaking sheets etc before the signal connection is established and the winch travels back to the transmitter stick position. Luckily the first time this happened for me I had the winch at a mid range position and also have a spring in the system to keep tension on the drum. The spring hit the deck pulley and the spring was pulled to double length before the signal was established.
As I said, even if the trim adjustment is fully one way, the failsafe ignores it and travels to the full range of the trim in the opposite direction. This overrides the “in-use” end point for full in.

Since writing this I have found that my "used" set had a slightly misaligned THR potentiometer causing a slight overrun. I've now adjusted that, but there are occasions when the failsafe still overruns.

My solution, as did the previous owner, was to swap the wire form the THR stick over to the other stick (re-soldering 2 wires) and then using the ELE channel on the receiver for the sail winch. This channel is not affected by the failsafe, so signal loss, and switch on "lag" do not result in the winch wildly running up and down as signal lock-on is established.

NOW the disheartening bit, you can only do this if using the AR500 receivers, which have (7?) channels. The marine MR200 only has 2 channels so you cannot "loose" the failsafe else where! Be warned, I strongly advise by my own experience not to use the MR200 receiver unless you actually want a failsafe on the THR stick.

You can insert a switch into the system between the receiver and winch which interrupts the signal (white) lead only, but this will only permit you to isolate the winch at switch on, not provide cover for signal loss whilst afloat. We use this system for the very expensive RG winches, the earlier models, as the switch on dwell and signal pulse (DM probably knows more of the technical bits) caused the winches to go to "learn mode." The latest RG winches are made 2.4GHz compatible.

So lets hear your tales of Spektrum please, I know you have some, I've only had mine out the box for three days.

Aye Kim

Edited By Kimosubby Shipyards on 25/04/2014 20:12:58
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25 April 2014 at 20:09 #5301
Kimosubby Shipyards
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@kimosubbyshipyards
My experiences, and yours are?
25 April 2014 at 21:09 #48415
Gareth Jones
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@garethjones79649
We have used a couple of Spektrum DX5e transmitters for about 5 years. Until last year these were used with a number of AR500 5 channel receivers with no problems at all in yachts and powered models. In fact I did not even realise there was a failsafe fitted.

Last year I bought a couple of MR200 marine receivers and fitted the first in a 36R yacht with a Hitec lever arm sailwinch. I had exactly the same problems as described by Kim, in that a few seconds after powering up the receiver, the sailwinch would move abruptly to an extreme position, beyond the 'minimum throttle' setting. The first time this happened the servo arm jammed against one of the frames and tore the servo from its mount. I could not get the combination to work reliably so I eventually swapped the receiver for an AR500 in a Springer hull. The MR200 sometimes has the same problem on start up in the Springer but the only consequence is a quick blast of full reverse on the motor. I have been out to try it tonight and out of three switch ons, two were OK but the third gave a short spell of reverse.

The second MR200 is now in a tea clipper and we have had the same problems with that, although not to the same extent and at the moment it seems to be behaving itself. I have just had a few minutes experimenting and found that if you switch off the transmitter with the receiver powered, the sailwinch moves to an extreme position. I then rebound the receiver to the transmitter with the stick in the central position and, now when I switch off the transmitter, the sail servo moves to the mid position. So, it seems that the failsafe position is adjustable as advertised. However whether that means the big glitch on start up is also completely cured remains to be seen.

Regards

Gareth
27 April 2014 at 11:53 #48468
Malcolm Frary
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@malcolmfrary95515
A friend got a second hand Seawind last year. Its only real problem was a busted sail arm. I am now wondering if the previous owner had this same problem. My friend is a Futaba user, he might not be affected.

The failsafe is probably burned deeply into the control logic of the receiver, and thus inaccessible. No amount of programming of the transmitter will change it. On perceived signal loss, it must revert to using a locally generated "safe" signal to the throttle channel, no matter that what is a turn off signal to a plane or car is a full reverse signal to a boat. That it might be re-programable under setup conditions is good for normal running, but under brown out conditions which is not really a signal loss and where there are so many variables, it might reawaken in a "new from the box" condition, and behave accordingly. The underlying failsafe will still be there.
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