Tony Nijhuis 50" Vulcan EDF version

[William Macleod]

Hi Tony,

I am trying to setup two motors and esc's to one battery on a foamy Canberra

I am finding similar issues as you are. I had no problem with a foam vulcan with two pushers wired as suggested in the responses although one motor would not always start ( randomly I may add) till the other was at about 1/3rd throttle.

On my Dynam C47 the wiring seems to be both esc's with red wires intact connected through a "y" ,lead to the Receiver. no problems ???? How does that work?

Mind you many years ago I had two small edf's that ran off one Esc without any problems.

I am also running out of ideas so will just disconnect both red wires on the "Y" lead and solder in a Ubec through the battery lead. Any other ideas gratefully welcomed.

Bill

 

Edited By William Macleod on 19/09/2020 11:24:23

Edited By William Macleod on 19/09/2020 11:53:37

[PeterF]

Posted by Nik Harrison on 19/09/2020 10:55:47:

Tony,

I've had a similar problem powering 4 ESC but from a Spektrum Rx. It turned out that the Rx could only power any 2 ESC at a time. The current drive from the Rx was insufficient. I used an op-amp to make a unity gain amp and the extra drive capability made it all work OK. Since found that there was no need to make one as I've now found a commercial product that does the same.

Try this

Cheers,

Nik

Nik,

Glad I was not imagining coming across this problem before. The op.amp. solution is I think the same little device that E-Flite have in their 3 way lead for some of their retract sets, to make sure that the signal is powerful enough to run 3 retracts.

It also avoids the need to set up a second throttle channel on a mixer, especially useful if the Tx or Rx channels are fully spoken for.

[William Macleod]

Peter.,

 thanks for the link I have ordered one. So does the signal booster just plug in between the Receiver and the esc "Y" lead? Bill

Edited By William Macleod on 19/09/2020 13:48:05

Edited By William Macleod on 19/09/2020 13:48:21

[Craig Carr]

That’s very interesting Nick, thanks for posting.

Peter, whilst I’ve never had a problem on my vulcan with the 4 motors, very occasional one of the 3 retracts might stop working (on a 3 way splitter lead). I’ve swapped the units for replacements and it still occasionally happens. But switch everything off and and on again and hey presto they often start working again  ....  would you recommend one of those on the retract circuit ?

keep persevering Tony. I had mine out on Tuesday. Wheels down flight thanks to the aforementioned intermittent issue

 

Edited By Craig Carr on 19/09/2020 14:47:49

[Nik Harrison]

Tony,

There maybe a bit a confusion setting in. The (poor) signal I'm referring to is the control signal (white core) from Rx to servos/ESC etc. The main power to the Rx/Servos is supplied by one of the ESC units and this is not normally a problem unless you have too many servos in the system. Typically it may supply between 3A and 5A depending on the ESC type. I have tended to use a UBEC instead of the ESC supply.

The Rx I used was only capable of supplying around 2mA of drive on the white servo signal. I had used the same Rx driving 4 ESC successfully but with a different ESC setup it could only work with 2 ESC. The opamp was used to boost the white signal so that it could now supply upto 50mA current drive. This cured the problem.

So a single opamp was used to boost the throttle signal which then successfully fed the 4 ESC units via a 4way connection. You do not need 4 boosters.

I have also used this "boost" technique when having problems driving 2 servos from same Rx signal, i.e. rudder and nose wheel steering. Either servos worked OK on its own, but connecting both with a "Y" lead had them go crazy. Solved by using a "boost" for each servo which ensured that the servos could not interfere with each other. Again problem solved.

Hope this all helps to sort out your problem. The examples I've mentioned all happened on the same model and I was scratching my head for some time before I settled on a solution. Don't give up I'm sure you'll get there.

Cheer,

Nik

[Martin McIntosh]

Any chance of a sketch of the op amp cct please? I shall be quite capable of building it and it could solve one or two problems of my own.

[Nik Harrison]

Martin,

No problem. The only reason I did not include the drawings before is that not many seem to be used to using a soldering iron these days. Have fun.

Craig,

I'm sure this would solve your gear problem.

Cheers,

Nik

[Martin McIntosh]

Thanks Nik, simple enough.

One of my problems is that certain HK retracts no longer work with their own Rx`s because they require a 5V pulse whereas the Rx`s only output 3V. Earlier units work fine and of course I may as well bang my head on a wall than get them to sort it out. This cct may also help to sort out multiple fans not running up to full speed at the same time.

Edited By Martin McIntosh on 20/09/2020 16:21:52

[Nik Harrison]

Martin,

Having looked at the drawings as shown it is difficult to see the opamp name. It is a TS358, only because I had these in my spares box. Any 5v operating opamp will do. The package I used was a DIL 8pin device.

Cheers,

Nik

[Martin McIntosh]

Cheers, I still have a few various types kicking around from my electronics days.

[William Macleod]

Sorted it out. What you do is;

1. buy the lead as discussed above

2. before it arrives complete the wiring using one battery.

3. be amazed that by connecting both esc's via "y" lead it works!

4 try it with removing just one red wire from one Esc ...still works !

so clearly all the problems disappear once you order and pay for the solution.

Test flight tomorrow. Bill

still confused!!

Edited By William Macleod on 20/09/2020 17:13:32

Edited By William Macleod on 20/09/2020 17:34:54

[Nik Harrison]

Martin,

The opamp setup I used is a unity gain arrangement. It acts as a current amplifier not voltage. 3V in will give 3V out but the current drive is increased. If you want to increase the voltage then a couple of resistors are required. See diagram. If you decide to use it as a voltage amp then you also get the benefit of the current drive increase, so win/win.

Cheers,

Nik

[Martin McIntosh]

Thanks again Nik, just what I need for the retracts.

[TonyS]

Well, not great progress here I’m afraid.

I’ve purchased the opamps and used 4 in total, three between the Rx and the three ESC’ S not supplying power to the Rx and one to the retract that’s now ceased to work. That done I’m still only getting 2 motors working and still have one main leg retract not functioning. Pretty much no effect therefore.

The last thing to try is putting two motors on a different channel then mixing that channel with the throttle channel.

if this doesn’t work look out for a part-completed Vulcan in the classifieds!

Tony

[Nik Harrison]

TonyS,

Sorry to hear it has not worked out. My suggestion would be to simplify the problem by working through each one in turn.

1. Remove the throttle channel, which is your power supply at present, and use an alternative power source. Spare AA battery pack for example.

2. Remove all servo leads except the undercart channel. Find out why the undercart set up is not working. Check each leg individually - using a servo tester?

3. Build up to driving all three legs and see what happens.

4. Once the legs are sorted start adding more channels and check channels work as you go along.

5. Finally add your motors one at a time while still using the external power supply. Make written notes as you go along so you can remember what worked and what didn't. It's too easy to forget what you have/have not tried.

I find that when you feel like binning the whole thing it is time to start as simple as possible. Fix one problem at a time and you may find that things start to fit into place and other stuff starts to work. Don't give up.

Nik

PS  Forgot to add that if using both external supply and trying to run motors from your Lipos then you must remember to have a common 0V connection between them.

Edited By Nik Harrison on 24/09/2020 19:15:07

[Martin McIntosh]

Good advice there but remember what I said above about the HK MCR series retracts no longer working with certain Rx`s. They should work OK on a servo tester though, so this may mislead.

[Nik Harrison]

TonyS,

I was looking over previous posts on this problem. Namely your post of 31/08/20 in which you showed the circuit you were using.

The problem is the 0V connection. You do not have any 0V connection between the two LiPo batteries therefore each pair of ECSs are using a different reference. This means the second battery supplied ESCs do not understand the signals given to them, so do not respond.

Install an 0v connection between the LiPo leads and I'm sure things will improve. This does not have to be a high current cable as high current should not be going down it.

Martin,

Having followed your Concorde build I'm still waiting to see air underneath it! Don't disappoint me. Lol.

Cheers,

Nik

[Martin McIntosh]

So am I Nik. I am booked in tomorrow and Tue. but it depends on the wind and even if the grass has been cut the cuttings would stop me again.

[TonyS]

Hi Nik,

This all sounds very positive. It would be really helpful if I had the slightest clue what an 0v connection was or how to make it. Answers on a postcard (or via this thread) would be very welcome indeed...

Thanks\

T

[Nik Harrison]

TonyS,

I'll get a drawing together tomorrow and post it. How is the problem with the undercarriage going?

Cheers,

Nik

[TonyS]

Thanks again Nik,

this could be the only route to keeping the project rolling.

sadly my father in law was taken ill (in the QE in Birmingham with pneumonia 😬) so we’ve been too preoccupied to allow for model fixing/building. Hoping he’s on the right path now so maybe I’ll get an hour tomorrow.

T

Edited By TonyS on 27/09/2020 20:06:49

[PeterF]

Posted by Nik Harrison on 27/09/2020 16:40:14:

TonyS,

I was looking over previous posts on this problem. Namely your post of 31/08/20 in which you showed the circuit you were using.

The problem is the 0V connection. You do not have any 0V connection between the two LiPo batteries therefore each pair of ECSs are using a different reference. This means the second battery supplied ESCs do not understand the signals given to them, so do not respond.

Install an 0v connection between the LiPo leads and I'm sure things will improve. This does not have to be a high current cable as high current should not be going down it.

Martin,

Having followed your Concorde build I'm still waiting to see air underneath it! Don't disappoint me. Lol.

Cheers,

Nik

Nik,

As the ESCs are BEC type I would expect them to have common negatives from battery side to signal cable side so they would have a common negative reference so on a simplistic basis they should be OK as the 4 in 1 cable ties them all together. Am I missing something, is there some issue of small current flows through the one ESC to power the model causing voltage differences on the negative cable.

I have a twin with wiring like Tony's and separate batteries, it works OK, but in thinking about this, I have battery pack telemetry on both flight batteries and this provides a common negative link between the two batteries. Perhaps I have just answered my own question.

It is certainly worth a try.

Peter.

[Nik Harrison]

TonyS,

Sorry to hear about your father-in-law and hope it all works out OK.

I have done a few experiments with my own set ups to check I'm making sense. PeterF is correct that the signal 0v is connected to the LiPo 0v internally on each ESC. I double checked on some of my own ESCs. My fault sorry.

Back to trying to work out what is wrong.

To double check that the 0v connections are as they should be could you check a few points with a Digital Multi Meter (DMM). If you haven't got one they are not expensive and extremely useful.

1. Check continuity between A and B, then between A and C.

2. Check the signal connection (white) between A and each ESC.

3. If it is still not working try changing which ESC supplies the power. i.e. from 3 to 4. This should prove whether ESC 1 & 4 work. Maybe with ESC 2 & 3 disconnected. I tried an experiment where I powered up an Rx then powered up the ESC to emulate your original ESC setup which powered 1 & 4 last. It powered up and worked OK.

Hope this at least gives you some ideas where to look.

Cheers,

Nik

[Martin McIntosh]

Tony S,

0V is the battery negative (-ve, the black or brown wires). My Vulcan and Lancaster each use two batteries and the Rx only requires a supply from one ESC; it is a bad idea to let them all supply it so on my four way `Y` leads three of the red wires are disconnected. Each battery supplies a pair of motors/fans. The drawing above looks to be correct to me. I link my ESCs together with a four way socket as supplied with some quads to synchronise the motors when setting up. HK sells them for pennies.

No chance to try the Concorde today because the grass was a little long and damp.

[TonyS]

Nik, Martin,

Thank you both for the help here.

I think that we're on the right track.

Firstly, on a test with a single motor and set up as normal the main leg retract fails to operate. if I swap it out on the three way lead with a basic servo the servo works so it seems to me that for some bizarre reason the retract has packed up! Considering it did work and hasn't been anywhere but the bench I can't work out why it's suddenly broken. I've checked the wires and they don't seem broken so I'll check with a DMM later. If it's bust I'll need to work out where I can get a replacement.

As for the motors. I've hopefully worked out how to mix channels and put two motors onto the throttle channel on a Y lead and two onto the Aux channel on a Y lead. What happens now is that I can get the two motors that are on the Y lead (with the one delivering power to the Rx) working. The other two simply bleep as if they haven't managed to 'handshake' with the Rx.

The concern I have is that

1. I may not have set up the throttle/aux mix properly - the instructions in the Spektrum manual don't quite match up with the RX channels available
2. By putting two ESC's on a different channel they may never be able to initialise properly when the Rx is powered up

I am beginning to think that the build is fine but the electrickery here is getting well beyond the limits of my knowledge.

T

 

 

Edited By TonyS on 28/09/2020 19:25:16

Edited By TonyS on 28/09/2020 19:26:37