Jump to content

On the Busses


Recommended Posts

Power districts are DCC, nothing to Do with CBUS. DCC and CBUS are completely isolated except in a CBUS DCC command station such sad the MERG CANCMD.

  • Like 1
  • Agree 1
Link to post
Share on other sites

1 hour ago, Ian J. said:

OK, I'm going to break my vow of silence on the multilateration (I think that's the correct term instead of triangulation) subject to post this link to a youtube video. It's not model railways, it's clunky, but presuming it's genuine, it shows the usage of RF for location tracking (in this case for a VR headset tracker). It looks pretty accurate to me:

 

...

 

Impressive, might be a bit tight fitting the stuff into my H0e locos though :(, perhaps 00 has more space to support it :) 

 

I think I will stick with current sensing and Railcom for a while though, as that works extremely well for me.

Link to post
Share on other sites

For positioning independent of layout control,  there's the GamesOnTrack system, which uses ultrasonic speakers in stock, and fixed microphones, to compute a position for the stock on the layout.  Claims accuracy to 10mm.  Been around for a while now. 

 

The 0v common wire being discussed doesn't carry much current.  So, make it "adequate" without being silly.  

In the simplest form (but expensive on PSUs), each electronics device on the network could have its own power supply.  The current for each comes from its own power supply.   There is negligible current passing over the data lines or the 0v common wire.  
 

 

 

- Nigel

 

 

 

 

  • Informative/Useful 2
Link to post
Share on other sites

Posted (edited)
45 minutes ago, Crosland said:

Power districts are DCC, nothing to Do with CBUS. DCC and CBUS are completely isolated except in a CBUS DCC command station such sad the MERG CANCMD.

 

I understand, and agree. However, I'm going to be having power district 'junction' boxes for holding the SBOOSTs and their power supplies for each power district, so I'm planning on splitting the CBUS power supply in the same way, therefore that common 0V is needed between the junction boxes in the same way as it's needed for the SBOOSTs. Each of these systems, DCC; Boosters; CBUS; are entirely electrically separate from each other, but they occupy the same 'junction' boxes in their distribution around the layout.

 

Edit: of course, there is connection between DCC and SBOOST at the SPROG3, which in turn connected to the PC; and technically the CBUS is also connected at the PC, but I don't think of that as electrically connected.

Edited by Ian J.
Link to post
Share on other sites

3 hours ago, Ian J. said:

but presuming it's genuine, it shows the usage of RF for location tracking (in this case for a VR headset tracker).

I cannot see that it was working as claimed. That video of from 2013 and supposedly shows an FPGA device timing in picoseconds - a timing accuracy of one millionth of a microsecond or a count rate of 1THz, a thousand GHz.

 

From the info I can find, the fastest FPGA reached around 1GHz in 2019.

 

That guy posted a single "updated version" video in 2015 showing nothing but boxes with wires or connectors, and announcing a new company - whos web site does not exist now.

 

Radio distance measurement over small ranges such as indoors in just not practical, or at least with existing technology, the timing accuracy needed is phenomenal. 

 

A more practical system could be a single overhead camera & image detection setup - possible with even a Raspberry Pi or Jetson Nano - tracking unique appearance items by visual detail, or possibly use "invisible" symbols such as IR or UV visible ink and an appropriate camera.

 

Edited by RobjUK
typo
Link to post
Share on other sites

26 minutes ago, RobjUK said:

I cannot see that it was working as claimed. That video of from 2013 and supposedly shows an FPGA device timing in picoseconds - a timing accuracy of one millionth of a microsecond or a count rate of 1THz, a thousand GHz.

 

In the video I think he says nanoseconds, not picoseconds, so I think that one thousandth of a microsecond...? As I said and you quoted, I can only presume it's genuine, as I have no connection with the man at all. It was something I found while searching the subject of RF location tracking. I'm willing to believe it, though would want to see it in something other than the video for better proof.

Link to post
Share on other sites

3 hours ago, Nigelcliffe said:

 

The 0v common wire being discussed doesn't carry much current.  So, make it "adequate" without being silly.  

In the simplest form (but expensive on PSUs), each electronics device on the network could have its own power supply.  The current for each comes from its own power supply.   There is negligible current passing over the data lines or the 0v common wire. 

With a large layout it could get expensive providing a PSU for every module. If a 12V DC bus is used then the 0V is carrying the return current for all module attached to it.

 

If individual PSUs are used then a thinner common could be used.

 

The common connection between booster must never be skimped on as it is required to carry the full booster current.

Link to post
Share on other sites

Posted (edited)

My intent is to provide a PSU for each power bus within each district:

 

DCC for track (an SBOOST)

DCC for accessories (another SBOOST, running in parallel to the one for track)

CBUS for accessories

Direct 12V DC for intermittent accessories (point motors, etc) that don't get their power from DCC

Direct 12V DC continuous accessories (LED lighting, etc) that don't get their power from DCC

 

So, in each power district junction box, 5 individual PSUs suitable to their required usage. For smaller configurations fo the layout, I may very well only use the one power district and hence just the one junction box, but the principle of being able to add districts and the consequent junction boxes for them remains necessary, so the common connection for Boosters and CBUS needs to be present. My remaining outstanding concern is the amperage capability of those two common connections, bearing in mind there is no specific number of districts and therefore junction boxes with PSUs for them. What should the wire and plugs/sockets for those common connections be capable of in terms of amps?

 

On a side note, if I'm willing, as per James Petts earlier reply, to live with only CBUS accessories I can do away with the DCC for Accessories bus, and its PSU. In v3 of the bus arrangement I've already sacrificed the 16V AC bus and the additional layout lighting bus, however I remain open to bringing them back. I might be able to do something similar for the DCC for accessories bus. However, I am loathe to lose the flexibility of being able to mix and match DCC accessories from different sources.

 

Edit: thinking about it, if I were to only use CBUS accessories, I could lose the direct 12V DC bus for intermittent accessories as well.

 

Edited by Ian J.
Link to post
Share on other sites

6 hours ago, Ian J. said:

OK, I'm going to break my vow of silence on the multilateration (I think that's the correct term instead of triangulation) subject to post this link to a youtube video. It's not model railways, it's clunky, but presuming it's genuine, it shows the usage of RF for location tracking (in this case for a VR headset tracker). It looks pretty accurate to me:

That seems to be a home-made job where size wasn't as important as it is to us. 

I suppose it may be possible in time to produced a micro-miniaturised version with a DCC decoder built in, at least for larger scales.

Obviously it's the receiver in the loco that has to be minimised, size of the locating beacons is less of an issue.  But it would also need to be capable of locating multiple devices simultaneously, which doesn't seem to be of particular interest to this chap. 

Link to post
Share on other sites

55 minutes ago, Michael Hodgson said:

That seems to be a home-made job where size wasn't as important as it is to us. 

I suppose it may be possible in time to produced a micro-miniaturised version with a DCC decoder built in, at least for larger scales.

Obviously it's the receiver in the loco that has to be minimised, size of the locating beacons is less of an issue.  But it would also need to be capable of locating multiple devices simultaneously, which doesn't seem to be of particular interest to this chap. 

 

He's got it working like GPS - the transmitters send out a signal which the object uses to locate itself. In the case of his object, it happens to be a single VR headset, but there's no reason why there couldn't be multiple headsets each locating themselves, just like there are millions (perhaps billions) of sat-nav devices in the world, and each locates itself. Thus for model railway purposes, that self-locating would need to be built into a receiver in the decoder. Unlikely with his tech as it's way too clunky, and not likely in the near future for model railways. However, remember that for a decoder it doesn't need quite as much tech as a VR headset, no need for the elements relating to pitch and yaw, etc.

Link to post
Share on other sites

4 hours ago, Ian J. said:

In the video I think he says nanoseconds, not picoseconds, so I think that one thousandth of a microsecond...?

Yes, he says nanoseconds, but supposedly measured and displayed to three decimal places, so down to 1/1000 nanoseconds. Smoke and mirrors, to be polite.

 

 

Back on topic -

Can you use a single 12V supply for both the CBUS module power and LED lighting? That may simplify things a bit.

 

Link to post
Share on other sites

2 hours ago, RobjUK said:

Yes, he says nanoseconds, but supposedly measured and displayed to three decimal places, so down to 1/1000 nanoseconds. Smoke and mirrors, to be polite.

 

 

Back on topic -

Can you use a single 12V supply for both the CBUS module power and LED lighting? That may simplify things a bit.

 

 

I'm wondering if the measurement shown is left of decimal, microseconds, right of decimal down to three places, therefore one thousandth, therefore nanoseconds? Anyhoo, yes, off topic now.

 

I'm still getting feedback here and in the MERG forum for answers to some of my queries. One new question would be can the the CBUS power also power other things, perhaps non-CBUS accessories. I want to keep the lighting separate if at all possible.

Link to post
Share on other sites

@Crosland Having reached a position with the CBUS 0V reference wire side of things with help from the MERG forum users, I now come back to a similar issue with the SBOOSTs reference wire.

 

Can you let me know what you believe a suitable wire size / capability would be for that? I'm planning on using the same size of wire for power connections (approx 5A or 6A) around the layout as much as possible, but I'm concerned about my need for flexibility on how many power districts there could be. While it might only be two to start with, it could become three quite quickly, and end up as many as needed (five, perhaps even ten, or more, depending).

 

Also, Judi in the MERG forum mentioned not wiring the CBUS PSUs to mains ground as a result of the laptop probably having cross-connection with the 0V and mains ground (earth?). Would the same be true for the SBOOST power supplies?

Link to post
Share on other sites

6 hours ago, Ian J. said:

 

Also, Judi in the MERG forum mentioned not wiring the CBUS PSUs to mains ground as a result of the laptop probably having cross-connection with the 0V and mains ground (earth?). Would the same be true for the SBOOST power supplies?

 

Terminology alert....    Do NOT install your own wiring from layout low voltage 0v to mains earth. Not ever. Regardless of what might be mis-stated on various websites, maker's forums, misheard comments etc.. 

 

I think Judi's comment was about power supplies.  Some of those with 3-pin mains leads into them will be wired internally with the 0v reference connected to mains earth.   That's fine for a single PSU, but as soon as two are cross-connected at the low-voltage 0v, there's a potential problem of paths via mains earth (=bad).  So, to avoid this issue, just use PSUs on a layout which have a 2-pin mains lead into them.   I think all the MERG kitlocker items are 2-pin (and generally very good value for money). 

 

 

 

 

- Nigel 

 

Link to post
Share on other sites

Posted (edited)
5 hours ago, Nigelcliffe said:

 

Terminology alert....    Do NOT install your own wiring from layout low voltage 0v to mains earth. Not ever. Regardless of what might be mis-stated on various websites, maker's forums, misheard comments etc.. 

 

I think Judi's comment was about power supplies.  Some of those with 3-pin mains leads into them will be wired internally with the 0v reference connected to mains earth.   That's fine for a single PSU, but as soon as two are cross-connected at the low-voltage 0v, there's a potential problem of paths via mains earth (=bad).  So, to avoid this issue, just use PSUs on a layout which have a 2-pin mains lead into them.   I think all the MERG kitlocker items are 2-pin (and generally very good value for money). 

 

 

 

 

- Nigel 

 

 

Yes, Judi's concern was the mains to PSUs element, not the layout side of the PSUs. My thought is that the SBOOST PSUs (and in fact all layout PSUs, maybe?) should also only have two wires from the mains and no mains ground.

Edited by Ian J.
Clairty
Link to post
Share on other sites

@Crosland When connecting a SPROG to an SBOOST, does the SPROG Tr A / Tr B to SBOOST In A / In B actually carry any power, or is it then just a signal path? The SBOOSTs obviously supply power to the track so I can't see a need for the SPROG to also output track level amperage. I ask because I'm wondering what wire size to use for those connections, and following on from that what kind of plug/socket can be used. I'd like to make use of 8 pin dins I already have for that bus, if it's only signal and not power.

Link to post
Share on other sites

46 minutes ago, Ian J. said:

@Crosland When connecting a SPROG to an SBOOST, does the SPROG Tr A / Tr B to SBOOST In A / In B actually carry any power, or is it then just a signal path? 

 

It's just a signal path, and is opto-isolated in the SBOOST. That means you do not nbeed to worry about a 0V reference between the SPROG and the SBOOST (I hope I didn't confuse thing more with that statement!).

 

Whether or not PSUs have an earth pin depends on the power rating and the intended application. Above a certain power (65W comes to mind but I could be wrong) it's diffciult/expensive to implement the input filtering and meet EMC regulations so an earth connection is included. You can easily test this connect through to the 0V of the output with a continuity tester or multi-meter. Obviously do this when it's not plugged into the mains :o 

 

Our usual 12V PSUs are not earthed, our usual 15V supplies are earthed. At the moment (on-going post-covid supply disruptions) we are having to buy what PSUs we can get hold of. We are still buying from reputable, UK-based distributors, but I cannot promise whether they will be earthed or not.

 

Link to post
Share on other sites

1 hour ago, Crosland said:

 

It's just a signal path, and is opto-isolated in the SBOOST. That means you do not nbeed to worry about a 0V reference between the SPROG and the SBOOST (I hope I didn't confuse thing more with that statement!).

 

Whether or not PSUs have an earth pin depends on the power rating and the intended application. Above a certain power (65W comes to mind but I could be wrong) it's diffciult/expensive to implement the input filtering and meet EMC regulations so an earth connection is included. You can easily test this connect through to the 0V of the output with a continuity tester or multi-meter. Obviously do this when it's not plugged into the mains :o 

 

Our usual 12V PSUs are not earthed, our usual 15V supplies are earthed. At the moment (on-going post-covid supply disruptions) we are having to buy what PSUs we can get hold of. We are still buying from reputable, UK-based distributors, but I cannot promise whether they will be earthed or not.

 

 

Ta, useful to know.

 

I'll need to make sure I use non-earthed PSUs once I actually get around to acquiring them.

 

Back to my earlier question, what would your recommendation be for a wire size for the SBOOST reference? You mentioned on the MERG replies that it doesn't have to be capable of the combined power of the SBOOSTs, but as I won't have a fixed number of them due to there being potentially n number of power districts, is it possible to have one wire size that could work for all possibilities, excepting making it humungously thick to handle very high amps...? Would 6A 32/0.2 be OK regardless of number of SBOOSTs?

Link to post
Share on other sites

20 hours ago, Ian J. said:

I've got something of a wiring diagram done:

 

1700174576_SPWiringDiagramv1.png.45c3304d9a78c11ee2fa59e41de7acbe.png

 

Needs work, but it's a start.

Ian J,

 

Nice bit of drawing work there. I'll bet your eyes 'hurt' a bit after all that drawing.

 

One bit I don't understand (although it might have been explained earlier) is the logic behind splitting the 3 cables from the CANUSB4 into PD1 and the 3-sided connector, and then splitting the 4 cables from the SPROG4 in a similar way. Why not put the 3 cables from the CANUSB4 through PD1 and all the 4 cables from the SPROG4 through the 3 sided connector? I'd have thought it would be easier to troubleshoot.

 

Ian

  • Thanks 1
Link to post
Share on other sites

12 minutes ago, ISW said:

Ian J,

 

Nice bit of drawing work there. I'll bet your eyes 'hurt' a bit after all that drawing.

 

One bit I don't understand (although it might have been explained earlier) is the logic behind splitting the 3 cables from the CANUSB4 into PD1 and the 3-sided connector, and then splitting the 4 cables from the SPROG4 in a similar way. Why not put the 3 cables from the CANUSB4 through PD1 and all the 4 cables from the SPROG4 through the 3 sided connector? I'd have thought it would be easier to troubleshoot.

 

Ian

 

It doesn't help that I haven't yet put in a wire colour key to help with what each wire is doing.

 

The brown wire out of the CANUSB4 is a 6A for the 0V reference link that is routed via the layout to each power district (PD1, PD2, PD3) through a 6A capable plug/socket (PX0551/2).

 

The light grey (stand in for white) and green wires out of the CANUSB4 are the signal only wires (low power) routed through a lower power capable (1A?) 8 pin din.

 

The orange and grey wires out of the SPROG3 are also signal only in the same 8 pin din.

 

Those get sent to the PDs via the junction boxes which, as they have only got 8 pin din plugs/sockets, can't handle 6A power lines.

 

The red and yellow wires are 6A power inputs to the SPROG3 from PD1's SBOOST.

 

The purple wire is a 0V reference link for the SBOOSTs and also goes via the layout for distribution, though it never needs to get back to the SPROG3.

Link to post
Share on other sites

It could be argued any DCC layout could be two wires to the track only. However, anyone using that has to accept its limitations, things like short circuits cutting all power to everything; reliability of the track as an electrical 'bus'; limitations on size (only one power district); etc.

 

What becomes apparent in a more capable DCC system is, it's the simplification by usage of buses that makes things easier to wire up with no need for massive multiple wire cables to individual boards.

 

My system has some more complexity in order to create a modular power district system that can expand or contract with however the S&P's modular boards are configured. I'm not even sure such modularity would be achieveable in a pure DC system, or at least it would probably be more complex.

Link to post
Share on other sites

6 minutes ago, Ian J. said:

It could be argued any DCC layout could be two wires to the track only. However, anyone using that has to accept its limitations, things like short circuits cutting all power to everything; reliability of the track as an electrical 'bus'; limitations on size (only one power district); etc.

 

What becomes apparent in a more capable DCC system is, it's the simplification by usage of buses that makes things easier to wire up with no need for massive multiple wire cables to individual boards.

 

My system has some more complexity in order to create a modular power district system that can expand or contract with however the S&P's modular boards are configured. I'm not even sure such modularity would be achieveable in a pure DC system, or at least it would probably be more complex.


 

im definitely in the Dcc camp. Is a modular power district needed?. If I need to add something to a particular buss I just splice in new cables, but I am talking from from the system which I use which is Digitrax and the power requirements you need are different possibly. Although very clever the diagram you designed is it over complex for the end result. Fault finding looks a nightmare :huh:. Wire sizes to accessory boards don’t have to be particularly large only that they should be capable of dealing with what’s required of them.

  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...