Planet transmitter conundrum

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10 May 2011 at 19:14 #30576
Kimosubby Shipyards
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@kimosubbyshipyards
A colleague has recently received his
Planet T5 tranmitter and purchased a hard case receiver. Together we
“bound” the two then tested with a servo for operation and all
appeared ok. So off he went happy that the system sent and received
signal.

Yup, you guessed, I got a call to say
that he set up as we had during the test but he could not get the
motor to run at all. The rudder worked fine. He was not sure about
using other sockets so got in touch.

The receiver has the channel sockets in
a close vertical row down the left hand side, and the outer pin is
the -ve and the inner pin the signal. Each socket is labelled with an
abbreviation for flying use, so for simplicity I refer to the sockets
by number, 1 at the top down to 8 at the bottom. Socket 1 is labelled “B” for
battery – if a separate battery is being used.

He wished to use the system for a boat,
wanting to use a “Tornado 50A ESC with integral BEC lead, and this
was plugged into socket 2 (THR) and the rudder servo plugged into
socket 3 (RUD).

I checked the ESC instructions, and the
web, and there are no set-up procedures to “train” the ESC to
stick movement.

All was connected as should be, so we
switched on, watched the amber LED on the receiver and waited for a
steady continuous glow (about 5 seconds.) The RH stick when moved
left or right operated the rudder servo left and right! The LH stick
when moved up or down resulted in nothing.

I looked through the instructions for
the T5, and in MODE 2 setting, the RH stick is rudder and LH stick
throttle. We tried the ESC BEC plug in all the other sockets 4, 5, 6,
7 and 8 and still nothing when the LH stick moved up or down. The
rudder worked from socket 3 with each different connection of the ESC
BEC.

[Checking the ESC instructions again I
noted that the unit has three electrical safeties being 1) BEC
supplies 4.8 V only regardless of input; 2) if the supply power falls
to 4.8V power will only be supplied to the receiver (the ESC will
shut down) 3) there is an over voltage protection to protect the ESC
(maximum rated voltage is 12V or 10 cells). Ureka, I thought, he was
using a 12V lead acid battery and (yes DM) the voltage from it was
12.9V, hence exceeding the 12V maximum.]

So we reset all the connections back to
those at the start, plugged into a 6V lead acid (giving 6.7V) and
tried again. Yup, the rudder worked but not the motor, in any socket.

The only combination not used was the
rudder into socket 2 (THR) and the ESC into socket 3 (RUD) – THEY
BOTH WORKED! We went back to 12V and they both WORKED again. Only now
we had rudder on LH stick up and down and ESC on RH stick moving left
and right. Still at least we had motor response.

So we tried differing combinations of
sockets till we got LH stick left/right working the rudder and RH
stick up/down running the motor – I think these were sockets 4 and
5 possibly (AIL and ELE).

Then looking at the T5 instructions
again, in MODE 1 the throttle is RH stick, so we changed the mode
setting switch inside, pushed it up. Yup, you guessed it, we now have
motor control on the LH stick up/down and rudder on the RH stick
left/right (though this had to be reversed.) Exactly what we wanted.

There is still no response off socket 2
to the Tornado ESC, though any other servo attached to it has normal
function. As I say a conundrum indeed, but one we have solved such that the operating functions are as required. Please lets
hope he only wants to stick with two channels!!

Anyone know what we did wrong – or
can explain what occurred, we can’t? But it now works as he wants it to do and is happy with that.

Kimosubby
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10 May 2011 at 19:14 #5121
Kimosubby Shipyards
Participant
@kimosubbyshipyards
a solution was found BUT?
15 May 2011 at 14:38 #30629
Dave Milbourn
Participant
@davemilbourn48782
Kim

For some inscrutable reason the Chinese manufacturers of these budget 2.4GHz sets do strange things to the nominated throttle channel. I have handled several sets now and found that the signal pulse width at neutral, while being almost always spot-on the standard 1.50mS on every other channel, was way different on the throttle. For example, a Spektrum DX5 was 1.38mS and a Planet 1.44ms. This means that any device that wants to “see” a specific signal value at neutral – such as a reversing ESC – will not do so and thus will sit dumbly forever waiting for one. These channels also produce signals at their extremes which are considerably less than those of the channels i.e. a servo will travel only about 75% each way. Servos, being stupid creatures electronically, will happily accept any old signal vaue as neutral – they just move the geartrain and the pot until the feedback signal corresponds with that received!

My solution has been minor surgery of the stick unit i.e. moving the trim pot with reference to the stick until I get exactly the signal I need, and all is well. This procedure does, of course, invalidate any warranty – but I’d question the practical worth of any warranty for sets which come direct to the end-user from China. I must add here, to be fair, that both of the sets mentioned above have recognised UK import and service agents.

Futaba sets? No such problem!

Dave M
15 May 2011 at 17:52 #30636
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Dave,

thanks for what sounds like the reason for the conundrum. We have tried other makes of ESC and got identical zero response on the designated THR socket and again all working fine when moved to other locations.

As I said the owner and user is quite satisfied with the operation as we have set it – (that’s till he desires more channels!)

I suppose the trim pot/stick adjustment requires a scope to monitor what is being changed, but we will leave that in the hands of you electronics guys.

Thanks, Kim.
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