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[KitS]

Having sorted the shaft and bearing issues on my Nautix 'Hants & Dorset' ASR launch (thanks for all the good tips gentlemen) another problem has shown its head.


I'm running it with a twin-stick converted Planet T7 Tx and its associated Rx, with one 9.6V NiCad battery feeding two MTroniks 15A Viper ECUs, one for each throttle stick hopefully. It all seems to work OK until I give both sticks full forward throttle, when the starboard motor just stops as it passes 95% throttle.


I've tried it with the ECUs the other way round, and it works then too, and I get full throttle on both motors, but the port motor runs much faster than the starboard one with that that setup.


I have disconnected the red power lead from the starboard motor's ECU and I have done the recommended max forward and reverse throttle setups on both ECUs.


Any and all ideas would be welcomed.

[C-3PO]

I would guess this is due to the fact that the reciever output on the offending throttle channel goes outside of the range that the ESC tolerates

There may be an adjustment /setup on the ESC (see below) if not see if you can centre or adjust to say 25% or 75% (channel output may be reversed) the trim adjustment and then restart/power on. - However I can now see that the ESC does have a ESC Setup procedure so see detail below :)

From MTronikcs website - under hints and tips - https://www.mtroniks.net/prod/Boat-Speed-Controls/Viper-Marine-15.htm


Q, Throttle goes dead at the end of the stick travel after I set the controller to my transmitter?

A, This is due to the output range of the transmitter going  beyond the range that the Viper will recognise. The solution is  to set the E.P.A. (end point adjustment) to 70% on the throttle
channel and then reset the speed controller. This situation is  similar to a rudder which travels too far, you reduce the E.P.A. to 'tune' things to work over a suitable range. If your transmitter
does not have adjustable E.P.A. please contact Mtroniks

See the manual on the web link and follow the calibration sequence "ESC SETUP" https://www.mtroniks.net/download.asp?ResourceID=2194

Regards
C-3PO

[KitS]

Magic, thanks so much. 


That does sound like the problem, yes. I'll try and adjust the Tx and see how it goes.

[HMS Invisible]

KitS, this looks like a reconsideration since you don't use the autocal escs that exhibited the problem.

...However I can now see that the ESC does have a ESC Setup procedure so see detail below :)...

You have a looped negative connection which allows escs to interfere with the input signals of each other.
One of many diagnostics step for that particular problem is to break the negative wire loop created by one 9.6 battery for port and starboard.

 If two 9.6v batteries are wired together it is easy enough. If you have a single 9.6v pack the test is to unplug the port esc at the receiver. Since the port esc supplies 5v you need to find a way round that.

[KitS]

I have?


I wouldn't know a '...looped negative connection...' if it fell on my foot!


Please explain what that is and why I should avoid it, if I can. I'd rather not have to use two batteries, it's more weight and I'd have to find somewhere to put them both in a hull that's been built to hold only one.

[C-3PO]

To clarify - what are the ESC's?

MTroniks 15A Viper or MTroniks 15A Viper Marine?

Regards
C-3PO

[HMS Invisible]

I have?


I wouldn't know a '...looped negative connection...' if it fell on my foot!


Please explain what that is and why I should avoid it, if I can. I'd rather not have to use two batteries, it's more weight and I'd have to find somewhere to put them both in a hull that's been built to hold only one.

Yes you do have.
Motors and the red/white servo wires are omitted so you can see the loop in the stripped down diagram that shows the top esc throttled up & the dashed line and arrow shows the unwanted current that can interfere with the other esc.

I suggested a quick comparitive, diagnostic test to quickly see if it is causing the problem rather than keep swapping things about or consider unnecessary fixes.

[KitS]

MTroniks 15A Viper or MTroniks 15A Viper Marine?

They're the Marine version, with full throttle available for forward and reverse.


Sadly the EPA adjustment isn't available on the T7 Tx, it has no adjustments at all inside the case, just four switches to change from Mode 1 to Mode 2 for flyers.


Looks like I'll have to talk to MTroniks. 

[KitS]

I suggested a quick comparitive, diagnostic test to quickly see if it is causing the problem rather than keep swapping things about or consider unnecessary fixes.

I tried it with two battery packs and it seems to work OK, but that's not going to do what I wanted it to.


Chatting with another R/C modeller, he's done the same as I'm trying to and had no problems. 

[C-3PO]

Did you try the ESC setup? - Did it make no difference?



Regards
C-3PO

[KitS]

Yes, more than once, and it didn't. 

[Skrotiz]

I'm really curious about this "looped negative connection".
I have run dual and multi motor setups many times without any problems that only had the red servo wire disconnected from all ESC:s except one that feeds the receiver.


Is this really a common problem?
"Path of least resistance" should put almost zero motor current trough the negative servo wire.
But since the esc doesn't need that wire I would also suggest disconnecting it.


I can see a possibility for fryed wires if the main negative wire to one of the ESC:s would get disconnected for some reason.

[HMS Invisible]

I'm really curious about this "looped negative connection".
I have run dual and multi motor setups many times without any problems that only had the red servo wire disconnected from all ESC:s except one that feeds the receiver.


Is this really a common problem?

Common enough for Electronize to print their WIRING paragraph and Mtronics to come up with a pricey opto-isolator.
And here are two examples:- Example 1 Example 2   
Save yourself some time reading ineffective over suppression suggestions  by skipping the first 32 replies in Example number 1 (and dioding which would not work in theory and in practice) Neither would pulling out the negative on one of the servo plugs.

...
"Path of least resistance" should put almost zero motor current trough the negative servo wire.

Well I did an arithmetic calculation using a typical length of 16 awg & 22 for the servo cable to get 5% in the 12 year old picture given in the first example. That doesn't even account for cable inductance.
What figure do you get?

But since the esc doesn't need that wire I would also suggest disconnecting it.

It won't work.
I have given about half a dozen workable remedies in old forum posts.

I can see a possibility for fryed wires if the main negative wire to one of the ESC:s would get disconnected for some reason.

No kidding?
I put a bold warning in instructions over 20 years ago to make a solder joint if you really insist on sharing the ballery with a Y-connection.
Then there is corrosion or over tightening a screw terminal termination on a single sided pcb of a third party dist. board.

[Skrotiz]

Thank you soo much for these answers.


I haven't done the calculations on current through receiver and was more "going with the guts" but thinking about it one more time tells me you're calculations are probably correct.a



I definitely have to check up on this.
I'm not exactly sure were talking about the same thing here. Having one ESC only connected to batt +&- and signal wire to receiver while having the other ESC connected to the same battery and all three wires to receiver should work(I haven't tried).


But again, thank you so much HMS Invisible for your input.

[Umi_Ryuzuki]

There is a difference between the Marine Viper, and the Mirror Viper ESC.Two of us here,
on this 'other' side of the pond were trying to run dual Mirror ESC, and eventually gave up.
Either we would get a cut out, or every time the model was powered up, one of the Mirror ESC would be in reverse.
Both of us were using a single SLA battery.
.
It didn't matter whether we flipped the servo reverse switch on the transmitter, or if we
flipped the wires at the motors. The Mirror ESC in dual throttle configuration was erratic.
 I changed out the ESC to two Viper ESC, and the other fellow switched to Robbe Marine ESC.
.

The negative loop issue isn't something I had heard of, but I had the same issue with the old Blue Box ESCs.
Single battery, dual ESC configuration.

[HMS Invisible]

Thank you soo much for these answers.


I haven't done the calculations on current through receiver and was more "going with the guts" but thinking about it one more time tells me you're calculations are probably correct.a

I am glad of an opportunity to explain the potential hazard due to risky wiring practice, which it is without ferrite toroid or opto-isolation remedy.
The finite cable resistance is what people forget in this situation.
15cm of 16awg from esc to the Y-junction would give 0.002Ω and 30cm of 22 awg of each servo cable would be 0.016Ω making the desired route of 0.002Ω in parallel with ((0.016+0.016+0.002)= 0.034Ω) or leading to the 5% backdoor current. One of the forum examples had many parallel connections which makes the hazard even worse.

I definitely have to check up on this.
I'm not exactly sure were talking about the same thing here. Having one ESC only connected to batt +&- and signal wire to receiver while having the other ESC connected to the same battery and all three wires to receiver should work(I haven't tried).


But again, thank you so much HMS Invisible for your input.

The esc signal noise diagram is what you can get on the esc inputs from a high drain motor and long supply wires.
I understood you to mean unhook the negative in the non-bec esc's servo plug to break the loop to leave only white. It may break the loop but it makes the noise signal even more horrendous. The mid way situation is a 10kΩ so try a resistor first. 
At least you understand that wire resistance gives rise to a problem with a threshold level and that is where my try 555 motors comes from. Also consider that unless an esc is switching above 10kHz it is switching the motor stall current on/off at part of the throttle range.

Other things worthy of note is rc receivers don't all send pulses of the same amplitude and some inexperienced esc, and other rc, product designers would use crude pulse counting (and don't even think of using edge triggered timers with induced signal line noise!) where others have an artificial intelligence routine to effectively sift out a signal from background chatter. This is what I did on migrating to microcontrollers. While both esc makers could claim to have software glitch filtering the former would ineffective at filtering out signal line noise from sharing a battery. So even a change in rc set and esc brand as well as wire lengths can make all the difference to whether it works or not.

[KitS]

I've just tried the boat with two batteries, with as near the same voltage as I can manage, and I meticulously setup the max-min throttle settings as described in the MTroniks 'manual'.


I get EXACTLY the same effect as I did before, the starboard motor stops when the Tx throttle reaches about 85%, whereas the port motor behaves perfectly.

[HMS Invisible]

I've just tried the boat with two batteries, with as near the same voltage as I can manage, and I meticulously setup the max-min throttle settings as described in the MTroniks 'manual'.


I get EXACTLY the same effect as I did before, the starboard motor stops when the Tx throttle reaches about 85%, whereas the port motor behaves perfectly.

At 2.49 your finding was:-

I tried it with two battery packs and it seems to work OK, but that's not going to do what I wanted it to.


Chatting with another R/C modeller, he's done the same as I'm trying to and had no problems. 

If you have no connection between the two packs other than at the receiver (as recommended in the WIRING statement) you have eliminated the possibility of wiring noise in the negative wires.
I suggest you proceed with fault finding with separate batteries or in isolation.
I don't know what you have in the way of test equipment or rc gear for substitution or if you are describing one particular esc is misbehaving.
Is it the bec esc that cuts out?

[KitS]

I only have one Tx with dual sticks, the one I'm trying to use, and otherwise I only have a multi-meter.


And it's the non-bec ECU that's cutting out.

[HMS Invisible]

A useful diagnostic at this end is, instead of a motor, can you get the esc to supply a much lighter load, like a small 12-24v bulb or resistor, and trace the voltage to confirm the esc can reach 100% duty cycle. I don't mean estimate from motor rpm.

It isn't crystal clear at this end whether the problem always occured with one particular esc, whether you have tried it supplying bec or what exactly you swapped over in the first post.

[KitS]

It's always been with the same ECU, and only on one motor.


I swapped the ECUs from one motor to the other and it worked OK, but one was much faster than the other at the same throttle setting. That's obviously no good for steering when both throttles are linked as would be the case under normal running conditions.

[HMS Invisible]

It's always been with the same ECU, and only on one motor.


I swapped the ECUs from one motor to the other and it worked OK, but one was much faster than the other at the same throttle setting. That's obviously no good for steering when both throttles are linked as would be the case under normal running conditions.

I think the esc was actually reaching 100% throttle and rpm dropping off due was to a higher load on the motor, perhaps friction was dependant on rotation direction.
A bulb or resistor in place of a motor can prove an esc was at 100% throttle but the test could be skipped if you can measure high motor current at a lower rpm.

[malcolmfrary]

It's always been with the same ECU, and only on one motor.


I swapped the ECUs from one motor to the other and it worked OK, but one was much faster than the other at the same throttle setting. That's obviously no good for steering when both throttles are linked as would be the case under normal running conditions.

Having read the earlier posts (this one grew really quickly), it looks like the "usual suspects" of Mtroniks' software going into panic mode at seeing an out of range pulse and dud connections re-routing the negative feed have been eliminated, but the motor speed of one of the motors is not as expected.  I would now suspect that motor of being the main, or remaining, culprit.  A slow running motor, if it supposed to be identical to its partner, is either not pulling its weight, or might be putting a heavier load on its bit of the system.
With problems like this, there is nothing in the rule book to say that for any one problem, there is only one cause at any one time.
Substitution tells a lot - a problem should go with the item moved, but if there is more than one problem.......

[Netleyned]

For what it's worth,
I have a springer with a 20 amp Mtronics Marine
With and old Radio Link Tx/Rx. No epa, or suchlike.
The motor used to stop on full throw of
the stick. I found by moving the trim to it's lowest
setting, the motor spins up to full revs on full stick.
Ned.
With a Spektrum Tx/Rx, without setting end points I don't experience the drop off at full throttle.

[John W E]

Hi there KitS


Before all the wizardry and technology goes whizzing over our heads; I have a sneaky feeling this may be a transmitter problem.


I have a Planet T5 which gave me similar problems.   Not only with MTroniks speed controllers but also ACtion speed controllers.   If I am reading it correctly, you are using 2 channels.   Presumably Channel 3 and Channel (I think it will be Channel 1).    If this is your set up; you are encountering the same problem that I had - where you don't seem to have the same 'signal throw' on the channels.


Have you access to a different transmitter and receiver?    Preferably, not Futaba as the same problems exist with that.   So you can try the set up with a different transmitter and receiver to see if the same thing happens.   If it does, have you tried swapping the speed controllers over on the RX? and does the same thing happen?     If this all happens and the same fault exists I am afraid you may have to be stuck with it - or - the other option is to go for a mixer.    If you aren't bothered about mixing the prop speeds you could if you wish fit a 'Y' lead between the receiver and the speed controllers.   This should, in theory, give you both speed controllers operating at the same speeds.


John