Megapoints network problems

[young37215]

I have used Megapoints for several years having evolved to a network that totals about 25m in length controlling around 75 servos. So far all has been great, for an electrical novice Megapoints 'plug and play' has enabled me to build a control system I never dreamt was possible. All servo and network cables are cheap and cheerful servo cables purchased from Ebay.

 

I recently added a further servo controller to the existing 7 which required the network extending by about 3M to a total of around 30M. This has caused no end of aggravation, despite the addition of 2 Megapoints CAN to strengthen the network, I cannot activate the new controller through the Multipanel driven control panel. For extra fun I now get directional LED's flashing after a servo is activated on some, not all, of them which continues to ocur even when I disconnect the new SC from the network as the short video below shows! 

 

I have spent many hours reading through the Megapoints guides and think I have narrowed down the potential cause to network capacitance. The extended network is near the 100 feet constraint that Megapoints advertise in their guides as being the point where low capacitance cables are recommended for the network. If correct then I am told the solution is to rewire the network with low capacitance wire which will be a time consuming activity, therefore I want to be confident that this should resolve my problem. Mr Megapoints Dave Fenton has been helpful in attempting to find a solution to my problem but we have not got there yet. I am raising the issue on RMWeb in the hope that someone will have experienced similar issues or is sufficiently knowledgeable in electrical matters to provide guidance for me now and for others in the future.

 

 

 

 

 

Edited October 22, 2022 by young37215

[young37215]

I should have said that the servos actuated in the video all work as programmed, the change is just the flashing LED's. 

[Brian]

75 servos is a lot!  Is your power supply and power supply cabling up to the job?   I would be looking at something around a minimum of 5.0Amp and probably greater with 32/0.2mm cabling as a minimum.

[young37215]

Hi Brian

 

Thanks for the observations, I am grateful for your thoughts. My electrical comptence is minimal and my response below is not disagreeing with your view, rather I am explaining why I think this is not power supply related. 

 

I have 2 x 8 Amp regulated power supplies (Fusion PS101) supplied through 7 strand equipment wire that is 1.2mm diameter (7/02?). Each PS101 independently supplies a maximum of 5 Servo Controllers (SC's) through which I have run 75 servos for the last 2 years without issues. I have not increased the number of servos, just added an additional SC as a precursor to adding more servos.  I take the point that the power demand of the additional SC may be the cause of the problem and I will upgrade the power supply cable to 'future proof' it. However I still get problems when I revert to my old configuration which has worked for 2 years which suggests to me that this issue is not supply related. It is as if the additional servo controller has created a problem elsewhere in the network which remains even when I remove the new SC.

 

 

 

 

Edited October 22, 2022 by young37215

[njee20]

I found MegaPoints a bit temperamental when you start to get near the limit of available current; suddenly it would all fall over, and you’d have to unplug 10 or so servos for order to be restored, even though an additional one had tipped it over the edge. It would also go from working perfectly to complete servo anarchy with just one additional servo, so I also suspect upgrading the power supply cable may help, if not resolve it. 
 

That said, it’s odd that restoring your network isn't resolving the issue.  

[young37215]

2 hours ago, njee20 said:

I found MegaPoints a bit temperamental when you start to get near the limit of available current; suddenly it would all fall over, and you’d have to unplug 10 or so servos for order to be restored, even though an additional one had tipped it over the edge. It would also go from working perfectly to complete servo anarchy with just one additional servo, so I also suspect upgrading the power supply cable may help, if not resolve it. 
 

That said, it’s odd that restoring your network isn't resolving the issue.  

 

Interesting, thank you. There can only be upside to upgrading the power supply cable to 32/02 equipment wire so I'll do this and see what effect it has. At the end of the day it is only by ruling things out that I will find the cause of the problem. More time and expense but I am committed to Megapoints so it has to be done. 

 

I keep reading about the negative effects of 'electrically hostile environments' on servos. In the context of model railways can anyone suggest what an electrically hostile environment might comprise?

 

 

 

 

[young37215]

I have previously used Rapid Electronics wire but they seem out of stock for 32/02 equipment wire. Trying to find suitable cable that I can get my hands on quickly, I found this at Screwfix which is available for collection tomorrow.  

 

https://www.screwfix.com/p/time-6491x-blue-1-core-2-5mm-conduit-cable-100m-drum/32256

 

It looks like 32/02 equivalent but I am not certain. Please can anyone clarify, can I use this?

 

 

[Brian]

Radiated interference from sparking motors or wheels on rails etc. induced into Servo control lines and possibly the bus pair too.

 

Upgrading the two power feed wires from each supply can only be a good thing.  You can "Tap off" these heavier wires near to each module and use a smaller wire size to power a module if that helps. 

BTW does Megapoints require that the 0 volts (negative) of the 12v supplies (in your case two of them) are connected together? Making a common to all modules O volt connection, as this is the case with the similar MERG modules!

[Brian]

It is a solid conductor of 2.5mm2 in size. Ok to use on a fixed never to be moved layout, but it is not suitable for portable layouts, as it can fracture eventually with flexing movement. 

[Trofimow]

Do your issues manifest during normal operation, or only at startup?

 

I am currently running 203 Megapoints servos on my still expanding network, all powered from a single 10A supply via a panel mounted ammeter.

 

In normal operation the current draw is negligible and is only significant at system startup. This has been addressed by dividing decoder network into 5 power zones, started sequentially at 10 second intervals.

 

I did have random control issues once the network length became significant, but this was resolved by installing a CAN bus.

Edited October 22, 2022 by Trofimow

[Brian]

Bitsbox have a twin and slightly larger 42/0.2mm wire in stock Link to Bitbox  IMO an excellent price, but note its copper clad Aluminium conductors. Though Ive never had issue with this sort of wire!

Brimal have 32/0.2 wire in stock Brimal link

CPC have 32/0.2mm reals in stock  CPC 32/0.2mm

 

Can't say its next day delivery though!

Edited October 22, 2022 by Brian
Extra text added.

[young37215]

47 minutes ago, Brian said:

BTW does Megapoints require that the 0 volts (negative) of the 12v supplies (in your case two of them) are connected together? Making a common to all modules O volt connection, as this is the case with the similar MERG modules!

 

Megapoints do'nt have any need for power polarity as I understand it. The network daisy chain does and I have checked this several times to make sure it is correct. On the basis that everything had been fine for some time prior to installing the new servo controller, I do'nt think I have polarity issues.  

 

38 minutes ago, Brian said:

CPC have 32/0.2mm reals in stock  CPC 32/0.2mm

 

I bought a reel of this, thank you.  I am away for a few days so the 3 day delivery time is not so much of an issue. My impatience is I want to find the solution so that I can stop thinking about the problem! 

 

41 minutes ago, Trofimow said:

Do your issues manifest during normal operation, or only at startup?

 

The flickering LEDs were constant during the 5 or so minutes I had the network powered up to take the video. They were still flickering this morning when I turned the power on. At no stage have I been able to issue any commands to the new servo controller using my control panel and Multipanel. 

 

 

41 minutes ago, Trofimow said:

I did have random control issues once the network length became significant, but this was resolved by installing a CAN bus.

 

I have just purchased 2 x CAN network adaptors in the hope that they would resolve my problem. So far they have not but if I have power supply issues then I need to sort them before passing judgement on the CAN's effectiveness. What was the approximate size of your ' significant length'? I am interested to compare this against my 30M.

 

 

41 minutes ago, Trofimow said:

In normal operation the current draw is negligible and is only significant at system startup. This has been addressed by dividing decoder network into 5 power zones, started sequentially at 10 second intervals.

 

I have 2 independent 8 Amp supplies, when all was working correctly one supplied 3 servo controllers and the other 4. The new servo controller was connected to the 3 where at 2 Amps per servo controller on start up and 8 controllers in total I am clearly tight to the maximum output.  The network is not divided into power zones, I am not sure what the effect would be of overloading the power supply.  

 

 

Edited October 22, 2022 by young37215

[Trofimow]

34 minutes ago, young37215 said:

What was the approximate size of your ' significant length'? I am interested to compare this against my 30M.

I have not measured it, but I guess I'm running around 60M now, and the problems started at about half that, which would be similar to where you are now.

I put in the CAN bus on Dave Fenton's advice and all came good.

 

Your 16A total available power is quite a bit greater than my 10A. My 5 power zones are each fused at 5A slow blow, and with the sequenced start up I have not had any power related issues. The zoned power architecture also helps to prevent any wiring size issues.

[BoD]

I don’t know the Megapoints system but Is it possible that the new servo controller is faulty and causing the issue?  Can you easily revert to the configuration you had and know works then swap an existing controller with the new one. You would at least then establish that it is the increase  in length/power consumption that is the issue.

[young37215]

33 minutes ago, BoD said:

I don’t know the Megapoints system but Is it possible that the new servo controller is faulty and causing the issue?  Can you easily revert to the configuration you had and know works then swap an existing controller with the new one. You would at least then establish that it is the increase  in length/power consumption that is the issue.

 

Nice idea Warren and I might try it if the current plan does'nt deliver. However I do'nt think the new servo controller is defective because I was able to programme it the usual manner on a standalone basis which suggests the problem is network related rather than the new controller. I have restored the layout to its pre-existing condition but I am still getting the intermittent flashing LEDs which again suggests a network problem. My suspicion based upon Dave Fenton's counsel and the experiences other Users have described above, is that I was already at or around the limits of the network and the additional controller pushed me over. Hopefully the combination of higher capacity power supply and the newly installed CAN adaptor will resolve the problem. 

 

I will update the thread with the outcome once I have put this into practice. In the meantime I am crossing fingers, toes etc.

 

Edited October 22, 2022 by young37215

[AndyID]

23 hours ago, young37215 said:

I have used Megapoints for several years having evolved to a network that totals about 25m in length controlling around 75 servos. So far all has been great, for an electrical novice Megapoints 'plug and play' has enabled me to build a control system I never dreamt was possible. All servo and network cables are cheap and cheerful servo cables purchased from Ebay.

 

I recently added a further servo controller to the existing 7 which required the network extending by about 3M to a total of around 30M. This has caused no end of aggravation, despite the addition of 2 Megapoints CAN to strengthen the network, I cannot activate the new controller through the Multipanel driven control panel. For extra fun I now get directional LED's flashing after a servo is activated on some, not all, of them which continues to ocur even when I disconnect the new SC from the network as the short video below shows! 

 

I have spent many hours reading through the Megapoints guides and think I have narrowed down the potential cause to network capacitance. The extended network is near the 100 feet constraint that Megapoints advertise in their guides as being the point where low capacitance cables are recommended for the network. If correct then I am told the solution is to rewire the network with low capacitance wire which will be a time consuming activity, therefore I want to be confident that this should resolve my problem. Mr Megapoints Dave Fenton has been helpful in attempting to find a solution to my problem but we have not got there yet. I am raising the issue on RMWeb in the hope that someone will have experienced similar issues or is sufficiently knowledgeable in electrical matters to provide guidance for me now and for others in the future.

 

 

 

 

 

 

I can't view the video.

[young37215]

7 minutes ago, AndyID said:

I can't view the video.

 

 

That is because I had changed it back to Private in Youtube. On refection this devalues the threads usefulness for future reference so I have changed it back to Public.  The video should now be visible once again

 

[AndyID]

Could you post a sketch of all the Megapoints bits, their interconnections and power sources indicating the cable types and lengths? Also the number of connected servos.

 

If I understand correctly the problem still exists even when you revert to the previous configuration. Do I have that right?

[roythebus1]

I sometimes wonder why articles such as this are put in the non-DCC section when it involves modules and the like. I'm a bit of a dinosaur when it comes to electrics, switches and relays are my thing and much easier to understand. These DCC things are beyond my interest.

[Nigelcliffe]

1 hour ago, roythebus1 said:

I sometimes wonder why articles such as this are put in the non-DCC section when it involves modules and the like. I'm a bit of a dinosaur when it comes to electrics, switches and relays are my thing and much easier to understand. These DCC things are beyond my interest.

 

Megapoints and the problems described has nothing to do with DCC.   

 

 

-  Nigel

[young37215]

12 hours ago, AndyID said:

Could you post a sketch of all the Megapoints bits, their interconnections and power sources indicating the cable types and lengths? Also the number of connected servos.

 

If I understand correctly the problem still exists even when you revert to the previous configuration. Do I have that right?

 

A rough sketch attached below showing outline network and power cable runs. The measurements are approximate because there are in excess of 30 cables all located under baseboards which are difficult to access. The network cables shown in blue are various servo cables of up to 2M in length daisy chained together with the least number of joins practical to fit the task. Power is from 2 Fusion PS101 each outputting 8 Amps of regulated 12V DC to power 4 servo controllers (SC)  and 1 CAN network adaptor with the supply to the left of the page additionally powering the Multipanel. Wire shown in black is currently 07/02 which has proved adequate for the last 2 years, I will upgrade this to 32/02 over the next few days.   

 

At present the flickering LED problem continues when I remove the new Fort William SC from power and the network. This is not the exact previous configuration; if I explain what I am working on it should be clearer why. There have been 5 servos at Fort William for the past 2 years, historically 3 were controlled from the Ardlui SC and 2 from the Mallaig Junction Yard SC. I wanted 3 more servos at Fort William hence the decision to add the extra SC.  Initially I added it and connected to power but not the network. I connected the existing 5 servos and added the 3 new ones which were all programmed as usual and appeared fine. Only then did I add the network cabling and attempt to operate the Fort William SC using the control panel switches. It would not work and after checking and double checking my cabling, I spoke to Dave Fenton who recommended adding the 2 x CAN. These were added but to no apparent effect, this was the point in time I raised this thread. 

 

I could attempt to revert back to the exact previous configuration but it would be an effort to re-attach the servo cabling exactly as it was and for which I see minimal return. At no stage has the Fort William SC responded to the commands from the control panel, this is the problem that I want to resolve and my hope is that a combination of the new wire and addition of the CAN will deliver. I'll do this in 2 parts, the power cable upgrade first just to see if it solves the problem on its own.   

• Each SC shows the number allocated to the network and has a figure for the number of servos attached
• The network has 3 CAN segments, each has pull up jumpers attached to 2 x SC
• There are 2 power district cable runs for the network effectively dividing the layout in half 

 

 

[Trofimow]

Given that you are running 60% more power than I am and only one third the number of servos, I would be surprised if your troubles are power related, which points towards network issues.

 

Power aside, our network configurations are quite similar, but I would make the following observations.

 

I have tried to place the CAN decoders to minimise the length of daisy chain between the servo decoders. The CAN bus itself is laid with screened CAT5 network cable.

 

The cabling between the CAN decoders and the servo boards, and the daisy chain between the boards has been done with ebay servo cables as you have done, except that if a run exceeds one metre I have used a twisted triplet of wires instead to try to improve noise rejection.  No such run exceeds 3 metres.

 

I would be very wary of using long runs of plain servo cable, for fear of generating noise on the network.

Edited October 23, 2022 by Trofimow
edited for clarification

[AndyID]

A bit off topic but there was a lot of discussion about servo twitch etc at this topic

https://www.rmweb.co.uk/topic/121357-no-twitch-servos/

Unfortunately the images are no longer visible but I can probably still find them if anyone is interested.

[beejack]

On 22/10/2022 at 15:51, Brian said:

It is a solid conductor of 2.5mm2 in size. Ok to use on a fixed never to be moved layout, but it is not suitable for portable layouts, as it can fracture eventually with flexing movement. 

No it's a single core cable with 7 strands.  All conduit cable is multi strand cable otherwise it wouldn't be able to be pulled through a long mulitbended piece of conduit.

The single core refers to the fact that it's a single cable rather than the number of strands.   The picture doesn't help with the confusion either showing a solid core cable.

[AndyID]

I wonder if I have this right?

 

All the switches are on your control panel and they are all connected to the MultiPanel or to expansion boards.

 

The LEDs on your control panel are only fed from the MultiPanel or from expansion boards.

 

You are not using any feedback from servo positions.

 

The servos are all working properly.

 

The problem is the LEDs are flickering.

 

If all the statements above are true it looks as if the MultiPanel might be misinterpreting network traffic as positional feedback information due to weak signal and/or interference. But that''s a guess.

 

It's unlikely the MultiPanel is misinterpreting control panel switch information. If it was the servos would be going bonkers too.