4 EDF Model Vulcan - motor/speed controller problems

[Frank Skilbeck]

Tony, the Rx puts out a pulse which varies in length to instruct the servo/ESC as to what position to adopt, this is generated by the chip in the Rx, although it's a voltage there is a very small residual current and if the chip can't provide it, the signal voltage will drop off and some ESCs can't see it and hence don't seem to arm.

 

I'm not sure how to slave the throttle channel on a Spektrum Dx7. (I don't think I can do this on my Dx6i). 

 

[Martin McIntosh]

Tony, your diagram does not show all four signal wires going into the Rx via the four way connector. Correctly wired, only one battery should be powering the Rx and servos. I have a TN Vulcan and wired it bat. 1, one inner and the other outer and vice versa for bat. 2 to keep the wiring similar. The Rx should easily operate four ESC`s, not always the case with some of the later HK MCR series retracts which need a 5V signal, not 3V which some ( Orange ) Rx`s do not do.

[TonyS]

14 minutes ago, Frank Skilbeck said:

Tony, the Rx puts out a pulse which varies in length to instruct the servo/ESC as to what position to adopt, this is generated by the chip in the Rx, although it's a voltage there is a very small residual current and if the chip can't provide it, the signal voltage will drop off and some ESCs can't see it and hence don't seem to arm.

 

I'm not sure how to slave the throttle channel on a Spektrum Dx7. (I don't think I can do this on my Dx6i). 

 

So to Andy Joyce's point it may be that I need to provide some additional power to the Rx?

[Philip Lewis 3]

Just to confirm (as it's not in the wiring diagram) the two negatives pf batt 1 and batt 2 are connected?

[Nik Harrison]

Tony,

I remember this problem when you posted before.  The advice at the time was to breakdown the problem into simpler parts.  That is use a servo tester to make sure each ESC/motor combination works individually and work up from there.

Motors in pairs then two motor pairs to get your four motors running.  Small steps will lead to the correct solution.

There is one point that you seem to miss in that you wanted redundancy but you are only powering the Rx from one ESC.  If that goes then so does the plane.  It does not matter what the other battery is doing.  I would feel happier with a UBEC.

You have supplied a drawing of your wiring, but can you be sure that is how it is actually wired?  If you build up your system in small steps than you can be sure what works and what doesn't.

Circuits that may help are on 4-Max website to assist in multi engine wiring.

Hope this helps, Nik

 

[TonyS]

14 minutes ago, Nik Harrison said:

Tony,

I remember this problem when you posted before.  The advice at the time was to breakdown the problem into simpler parts.  That is use a servo tester to make sure each ESC/motor combination works individually and work up from there.

Motors in pairs then two motor pairs to get your four motors running.  Small steps will lead to the correct solution.

There is one point that you seem to miss in that you wanted redundancy but you are only powering the Rx from one ESC.  If that goes then so does the plane.  It does not matter what the other battery is doing.  I would feel happier with a UBEC.

You have supplied a drawing of your wiring, but can you be sure that is how it is actually wired?  If you build up your system in small steps than you can be sure what works and what doesn't.

Circuits that may help are on 4-Max website to assist in multi engine wiring.

Hope this helps, Nik

 

Great memory Nik, I can barely remember what I did this morning let alone what someone posted many years ago. Good point re the Rx power. Pointless trying to get redundancy this way.

[Martin McIntosh]

Nik, surely that is the same as any single motor model running from one Lipo? Plenty of power left for the Rx and servos if the motor stops.

[TonyS]

Right everyone. I'm reliably informed that I need to 'stop messing about with my plane and get ready to go out' so, I'll sign off for now. Thank you everyone for the input. Lots to consider/try etc.

May I wish you all a Happy New Year and maybe, just maybe, 2023 will finally see this Vulcan take to the skies and I won't have to satisfy myself with a trip to Wellsbourne airfield to see a real one (mind you, mine could taxi on two EDF's just like that one does 🙂  )

T

[PeterF]

When I built a 4 EDF model I calibrated the throttle on the ESC to the RX one ESC ar a time so they were all the same. When coupled together they all worked. If you have separate batteries it is harder to do this. Also when you power up always start with the battery that powers the RX.

[Andy Gates]

Tony,

 

I think you need to involve someone else (maybe a club member familiar with multi electric motor setups) to double check that what you have done matches what you have written / drawn.

 

Then as others have said, go back to square one with one fan / ESC / battery combination and test that works, then slowly add fans / ESC's back into the system one by one to get back to all 4. At the point something goes wrong again, that is where your fault / incorrect assumption lies.

[Paul De Tourtoulon]

The signal strength hit a nail,,, I had the problem with a Spectrum receiver ( not my Futaba radio where they both worked )when two flap servos  (rubbish ones ) were on a Y lead on the same channel, they would not work,,,

[Mike Blandford]

I've just checked the only Spektrum receiver I have, an AR6210-X. The signal that drives the THRO output includes a 180 ohm series resistor. I looked because FrSky receivers also include a series resistor, the purpose of which is almost certainly to protect the processor driving the signal from external injected voltages. I would expect other receivers to have similar resistors in the outputs.

What this means is if an ESC draws a small current from the signal when it is high, the voltage at the output of the receiver will be lower than expected. As you add more ESCs to the signal, it will get lower still, and may therefore no longer be high enough for an ESC to detect properly.

 

If it is possible on your Tx, can you make a second channel output a copy of the THRO channel, then use the THRO output for 2 ESCs and the copy channel output for the other 2 ESCs.

 

Mike

[Simon Chaddock]

Tony S

I have 3 four engine home built models, all scale, 2 EDFs, 1 prop.

I can only endorse the suggestion to ditch the radio for testing and use a servo tester to control the motors. First each motor singly and then using two servo testers to control the inboard and out board pairs individually. When you have done that then you know they work. If the fault returns with the radio you now know where to look.

On all my 4 engine all the motor signals come directly from the receiver no problem.

 

Personally I am wary of using two batteries simply because of the potential earth issues.

I work on the principle that with conservative power management, at least initially, the most likely electrical failure will be a motor or ESC rather than the battery. If such a failure occurs its power off and glide! Until I have confidence in the set up I keep high and within gliding range. Just to be sure I practise glide approaches on each plane too.     

 

Edited January 1, 2023 by Simon Chaddock

[Allan Bennett]

In the opening post it was mentioned that all four ESCs/EDFs have worked at different times, but only one pair at a time.  As others have pointed out, the wiring diagram looks okay, except it could be improved by giving the two power sources a common ground, and by giving the receiver a dedicated BEC.  Assuming the model is wired in accordance with the diagram, then to me the only possibility is the inability of a single receiver channel to drive 4 ESCs.  I have read of this being an issue before.  If the OP has 4 spare servos available, this could be checked by connecting them to the 4-way connector in place of the ESCs.

[Nik Harrison]

Martin,

The point I was making about an ESC failure is that when they fail they tend to go up in smoke.  The result is no 5v to the Rx - result is crash.  An ESC is more likely to go up in smoke than a UBEC as the currents in evolved are so much higher in an ESC.  Potential solution is to use the 5V supplies from all four ESCs, via Schottky diodes (minimum voltage drop) to ensure isolation between ESCs.

[john davidson 1]

You all seem to be  missing the point that there are TWO batteries and Four ESCs. As in my previous post slaving two Motors of four to the throttle channel channel will work, I have done this with my twin battery F82 Mustang. Read your manual on how to slave channels , not difficult. One battery to the slaved channel , one to the master.

[TonyS]

41 minutes ago, john davidson 1 said:

You all seem to be  missing the point that there are TWO batteries and Four ESCs. As in my previous post slaving two Motors of four to the throttle channel channel will work, I have done this with my twin battery F82 Mustang. Read your manual on how to slave channels , not difficult. One battery to the slaved channel , one to the master.

I've been at this thing again today. The manual makes no sense to me re slaving channels. The example given seems to suggest having the throttle channel as the master and the throttle channel as the slave which to me makes no sense at all. Appreciating this is just the example I've slaved Aux 2 to the Throttle and it still doesn't work!

Anyone want to buy a partly completed Vulcan!!!!

Seriously. I've swapped the Rx for a slightly larger one and one that offered another channel. I've provided the Rx with a separate power supply. I've tried to slave the Aux 2 to the throttle as best I can given the instructions don't make a lot of sense to me.

Still I only get 2 motors running.

I've also used my cheap and cheerful (and only) servo tester to see if I get anything from the speed controllers which I do, even if the signal is very broken up, on all four.

 

The first diagram re the wiring is the correct one - for some reason I can't delete the original which showed the batteries connected to the wrong speed controllers.

 

 

 

 

Edited January 1, 2023 by TonyS

[TonyS]

OK. 

So, on advice, I thought I'd build this up motor by motor. I connected one of the outboard motors power leads to a single battery and ensured that this had the red positive connected in the the ESC cable. I then tested this set up and, as we'd expect, the motor primed and functioned correctly.

I then connected the motor next to it, one of the inboard fans, connecting the power leads from this and the first fan to the single battery, ensured the red positive was disconnected from this second ESC and guess what, only the inboard fan worked. Clearly the power from the first ESC (outboard fan) was making it to the Rx but no signal was getting back?

[john davidson 1]

slave channel 5 ( or 6) to the throttle channel,  then throttle goes to to two ESCs      channel 5 (or 6) goes to the other two ESCs ,   each of the two batteries are on separate channels. treat each channel as a completely separate twin in other words. a single red wire from any one ESC is enough 

 

I assure you I had the same problem  , one motor would work some times not, sometimes the other way

Edited January 1, 2023 by john davidson 1
thoughts

[Nik Harrison]

Tony,

From your last post with two motors connected but only second motor running.  This would indicate to me that the signal from the Rx could be too low in volts to drive both ESCs.  It works on the first ESC but when connected to the second ESC at same time only the second ESC responds.  Could you try substituting the Rx with the servo tester.  This will, hopefully, give a better voltage signal to enable both ESCs to be driven at the same time.  I have had to use a signal booster on my Spektrum Rx to enable 4 ESCs to be driven successfully.  First 4 ESC model I made was no problem, but the second one I made with different ESCs using same Rx would only drive two at a time.  All ESCs are not created equal.