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Author Topic: Strange radio/electronics issue  (Read 845 times)

ChrisH1981

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Strange radio/electronics issue
« on: October 29, 2019, 09:35:58 PM »

Evening guys, im having a strange issue regarding my motors cutting out at full throttle.
Its a bit of a long explanation...but bare with me!


I am using a Planet T7 transmitter and 4xR6m receivers to control 4 of my models. The transmitter is set up in mode 2 (throttle on the left stick). Two of my models show symptoms of loss of signal at full throttle/high speed.
I have recently done a complete re installation of electronics hardware in one of the models thinking that it would cure the problem, but after eliminating all the obvious things like receiver brown out due to a BEC or faulty RX power pack or the main battery not supplying enough power to the ESC I have narrowed down the problem to the TRANSMITTER.


If i push the throttle stick (left side) all the way up on its travel the motors stop, restarting again as I return to centre, but if i remove the ESC lead from the throttle channel and plug it into the elevator channel (right up/down stick in mode two) I get the full range of throttle without the motors stopping.


This is repeated in my other model(s)


Sorry if the post doesn't make much sense, Ive been working on this for a good 5 hours now and my brain is frazzled!
Look forward to your replies.


Chris H
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Ralph

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Re: Strange radio/electronics issue
« Reply #1 on: October 29, 2019, 09:48:22 PM »

Sounds like the pot (variable resistor) on your transmitter stick is the problem.  I'd try spraying it with an electrical contact cleaner in the hope that it's just dirty rather than faulty. If you're not up on electronics it's the bit with 3 wires attached to it which will be mounted on one side of the back of the stick.  Hopefully that'll do the job otherwise you might need to replace the pot if you can find a matching replacement.
Good luck
Ralph
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #2 on: October 29, 2019, 09:52:50 PM »

Thanks Ralph I shall give it a try :-))
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C-3PO

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Re: Strange radio/electronics issue
« Reply #3 on: October 29, 2019, 09:58:01 PM »

Chris,

What happens with the throttle channel mid stick, does the motor turn? - What happens with the motor if you move the stick to the lowest position? Do you have reverse on the ESC? What model is the ESC?

It could be a combination of several things. Have you checked the channel reverse switch under the little panel bottom right of the Planet transmitter?

C-3PO
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #4 on: October 29, 2019, 10:03:48 PM »

Hi C-3PO! Yes mid stick the motors turn and I get a nice increase in power right up until maximum travel on the throttle stick, then sudden death!


In full reverse, the motors will achieve maximum RPM with without cutting out. I have an action electronics p94 unit powering two MFA 540/1 motors.


I have a feeling you might have hit the nail on the head with the reverse switch. It is in the normal position now, what would reversing the switch do?

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C-3PO

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Re: Strange radio/electronics issue
« Reply #5 on: October 29, 2019, 10:08:32 PM »

Hi Chris,

This may sound odd - if you turn the radio upside down the throttle stick would work as expected? Sounds like you don't have reverse motor control..

From your description the receiver signal going into the ESC is simply reversed resulting in max revs stick down, half revs midstick and no revs stick up..

Simply flick the channel reverse switch and you will reverse the above

If I have got this wrong then Ralph's diagnosos may well be correct - perhaps moving the throttle adjustment tab might help - the ESC may be seeing a signal outside it's range of input

C-3PO
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #6 on: October 29, 2019, 10:12:25 PM »

No C-3PO, Im getting directional control forwards and backwards.


You are on the right line by saying flicking the reverse switch will help and im going to do this tomorow, I will let you know how i get on!!
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C-3PO

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Re: Strange radio/electronics issue
« Reply #7 on: October 29, 2019, 10:14:53 PM »

My misunderstanding of your situation - sorry.

I would put a servo on the throttle channel receiver pins and watch what happens to the movement as you move the stick.

That may well determine what is going on...

C-3PO
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grendel

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Re: Strange radio/electronics issue
« Reply #8 on: October 29, 2019, 10:26:15 PM »

I have a different radio, different speed controller and a similar problem, when going full speed the motor cuts in and out, its a 1A motor on a 30A viper speed control, if I back off the stick, no problem, if the battery gets low - no problem, just a problem at full speed., I have recently redone a loose motor connection (after the last episode) so that may have fixed it (not had a chance to test yet) and it only ever happens when its out on the water, never during testing.
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Taranis

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Re: Strange radio/electronics issue
« Reply #9 on: October 29, 2019, 10:30:03 PM »

Some ESC's cut out if the output signal is too high. I know my Mtroniks ESC cuts out if my output from Spektrum is set to 150 max so I have it set to 145.
Equivalent to limiting servo travel
Plant T7 seems to have no means of adjusting this only the stick trim toggle
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C-3PO

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Re: Strange radio/electronics issue
« Reply #10 on: October 29, 2019, 10:40:19 PM »

If I have got this wrong then Ralph's diagnosos may well be correct - perhaps moving the throttle adjustment tab might help - the ESC may be seeing a signal outside it's range of input

C-3PO

A receiver pulse of 1.5 ms width will typically set the servo (ESC) to its "neutral" position (typically half of the specified full range), a pulse of 1.0 ms  will set it to 0 (ESC FULL reverse) , and a pulse of 2.0 ms to 90 (ESC Full Forward)

Some radios are able to use and extended range and output 0.80 - 2.2 ms rather than 1.00 - 2.00 ms - I have a sneeky suspicion that Planet use the extended range, I am sure I have bumped into this before - I will put one on a scope tommorrow and measure the range

C-3PO
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Capt Podge

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Re: Strange radio/electronics issue
« Reply #11 on: October 29, 2019, 10:50:19 PM »

I had a similar problem when running a club 500 in that it was ok to about three quarters throttle but any higher and the motor cut out.
I replaced the esc (mtronics marine viper 15 amp) with their 20amp version. Problem solved.
Went on to win a number of trophies after that :-))


Regards,
Ray.
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C-3PO

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Re: Strange radio/electronics issue
« Reply #12 on: October 29, 2019, 11:07:01 PM »

So the Planet T5 set I have outputs at the receiver 1.0 - 2.0 ms which is standard - unless you have the stick trim tab (normally a black slider) next to the stick axis in the full up position in which case the receiver outputs 2.16ms which may be enough to upset some ESC's which may well be limited / configured to only accept 1.0 - 2.0ms and any signal outside this range is rejected.

Try putting the trim tab to the right of the throttle channel stick to the lowest position - move it towards the bottom edge of the transmitter (strangely this did not reduce the lowest pwm signal below 1.0ms) and I think you problem may well disappear

C-3PO
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jaymac

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Re: Strange radio/electronics issue
« Reply #13 on: October 30, 2019, 08:50:45 AM »

is the left stick spring loaded if not then you dont know when it is centred. I had problems with that action controller till I refitted the centering spring. Maybe why yours is ok on the right stick
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Netleyned

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Re: Strange radio/electronics issue
« Reply #14 on: October 30, 2019, 09:22:59 AM »

I have had the same problem with an old
Radiolink Tx with an Mtroniks 20Amp esc.
Just tried moving the trim fully down and
Hey presto! It now works fine :-))
Thanks C-3PO  O0
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #15 on: October 30, 2019, 09:54:51 AM »

Thanks for all your useful comments guys, I am frustratingly stuck at work at the moment so cant implement any of your ideas yet, but I will let you all know if the issue is resolved later!
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DaveM

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Re: Strange radio/electronics issue
« Reply #16 on: October 30, 2019, 09:56:13 AM »

P94 is programmed to 'autoset' the neutral i.e. it will seek and 'fix' the throttle signal to neutral at whatever position the stick is centred when you switch it on each time. It will also reject any signal pulse outside the band 0.8 - 2.2ms; the motors will cut out beyond these limits. Only very early versions have a fixed neutral (not autoset).
DaveM
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #17 on: October 30, 2019, 10:02:33 AM »

Ok Dave so is there a way to work around this?
If I increase the trim tab upwards, would this move the neutral point thus giving a shorter forward throttle range (not very well described but I hope it makes sense)
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Netleyned

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Re: Strange radio/electronics issue
« Reply #18 on: October 30, 2019, 10:05:31 AM »

Just cured the same problem on my Dickie Tug conversion. DX6i and Mtroniks 15 Amp p&p
Backed off Throttle travel from 110 to 100% and
it's cured. Taking the trim back had no effect.
Probably the difference between basic and
programmable TX's.
Thanks Andy for the tip :-))
Ned
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ChrisH1981

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Re: Strange radio/electronics issue
« Reply #19 on: October 30, 2019, 10:10:27 AM »



Ned you are absolutely right. Im due a transmitter upgrade I think :-))
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DaveM

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Re: Strange radio/electronics issue
« Reply #20 on: October 30, 2019, 10:18:55 AM »

Chris
Radios differ from one marque to another. I'm not sure that the trim will alter the signal pulses at each extreme, but you can check by putting a servo into the throttle connection and noting the position of the disc at full stick with the trim set first at one end and then the other. If you were to use a computer radio then you'd be able to set the end-points.
I had a lot of problems with a Spektrum Dx5e in this respect - I grew to hate that set - but the Planet T5 I had never prompted P94 to cut out the motors. I've never handled a T7. I now use Hitec radios exclusively (Optic 6 and Aurora 9) and there are no issues like this.
DM
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C-3PO

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Re: Strange radio/electronics issue
« Reply #21 on: October 30, 2019, 10:42:23 AM »

I'm not sure that the trim will alter the signal pulses at each extreme
DM

Hi Dave - I tested the Planet T5 last night

Trim full up - stick full up 2.16ms /  stick full down 1.161ms

Trim full down - stick full up 1.850ms / stick full down .960ms

Clearly "computer" radios often have both the trim range (cannot override computer min/max settings - only adjust within software set range) and a software range often set as a percentage e.g. 110% (2.0ms x 110% = 2.2ms)

C-3PO
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malcolmfrary

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Re: Strange radio/electronics issue
« Reply #22 on: October 30, 2019, 11:09:28 AM »

Pulse widths.
The norm that has been general for a lot of years is that neutral happens at 1.5mS, full forward at about 1.8mS and full reverse at about 1.2, with a requirement that avalid pulse must be more than about 0.7mS long.  Some ESCs accept a longer pulse, longer than what they regard as "full forward". 
Some go into a panic mode when presented with an overly long pulse and play safe by switching off.
The result there is that full forward is reached at about 3/4 stick throw, once the ESC is giving full power there is no way to turn it up to eleven, so it just gives full power until the signal gets regarded as invalid. 
With a mechanical trim, the entire window is moved, so hitting the over length pulse scene is more likely.  The slider just moves the body of the pot, causing the wiper to use different bits of the track.  Using software control to trim is possibly the finest way of increasing confusion, especially if the ESC self programs.
The T5 mentioned sounds like it is capable of going out of the useful range.  OK for servos to get more travel, less so for ESCs. Anything above 2mS is generally over length for a pulse to fit into the 50ppS window and still have room for the quiet period that is needed for the receiver to know that one pulse has finished and another is due.  Might be different with digital systems, but the stuff that plugs into them still needs to work with the old "real time" gear.
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grendel

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Re: Strange radio/electronics issue
« Reply #23 on: October 30, 2019, 12:32:05 PM »

thanks for the explanations, that gives me something to try out next time it happens and makes perfect sense out of what the motor was doing at full throttle. I do believe I had pushed the trim forward as I am running a sound module and used the trim to get the idle correct (thus had pushed it forward.)
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Re: Strange radio/electronics issue
« Reply #24 on: October 30, 2019, 02:13:58 PM »

Threeps

Interesting. I'd been inclined towards Malcolm's point that only mechanical trims would push the pulses that wide but it seems not. Your data says that Planet 5 is  just within the tolerance of P94 whereas T7 might not be. Without a scope it's difficult to tell, and one T5 or T7 might be a whole heap different to the next one off the line.

I hold to the theory that ROC manufacturers are happy to use wide-tolerance components (they're cheaper...) and that QC in the fine-tuning department is a luxury they feel is also unnecessary. As MF says, with a servo you can just screw the disc on a little further around to adjust for such variations, whereas with a speed controller and a non-computer radio you're stuck.

We live and learn...  8)

DM
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