DCC Railways

Just started to get back into model railroading and OO gauge. As a newbie, needed to run a few simple questions past other model railway users. Running Hornby DCC select as my first step into DCC - plan to upgrade to a better DCC later finances allowing). Sorry if I listed the issues like bullet points, but felt it would make each issue easy to reply to.

a) My track layout is now built and using a dual circuit, I have all the points electro connected for DCC. Should I supply DCC connection to both tracks using a link wire, even though the points and track are all live? b) Running two locomotives (but with two others not selected) in sidings, runs fine on the DCC controller, but every so often, the engines both stop and the controller reboots (then both engines resume running). There are no shorts I can see, and at first I thought it was points related with the electro connected, but have elimated that. The power supply is 1amp as its the basic power unit that came with the Hornby Select. Do I need the larger 4amp supply? or is the 1amp sufficient? (Also thought a loco was shorting it at one point, but eliminated that as a cause as well). Finally: c) I have the point motors, enough for each point on my track (6 in total) and two point controllers each allowing 4 points/accessories. However wherever I put the DCC point controllers, I am going to be lucky if the wires from the point motors reached the controller for all

6, dont really want to buy a seperate DCC point controller for each, so I suppose I need to extend the wires from the points. Is there no quick easy way to do this without soldering or extending the wires? seems silly that the wires are so short!

Thanks all!

Also posted in rec.models.railroad

Reply to
Chris King
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Hi Chris

It is generally accepted that the DCC power bus should be connected to every part of the running rails.

It looks as though you are trying to draw more power than the 1 amp supply - you need to allow about half an amp per loco when moving plus a small amount for those sitting stationary plus the load from accessories such as point motors. You need a heavier power supply.

Hornby do not appear to list extension leads for their point controllers

- they don't even have the accessory controller on their own website! You can easily extend the leads using similar wire by using screw connector blocks to join the wire.

Regards.

In message , Chris King writes

Reply to
Bill Campbell

A good policy!

Depends what you mean by "electro connected". That's not a recognised term. See

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for more than you ever wante to know. I would also join MRF
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has a much more active DCC forum than the traffic here.

You should run the two wires from the controll as a "bus" aroound the layout and connect the the track at regular interval (known as "dropper wires"), preferably every piece of track, to avoid relying on electrical continuity of rail joiners (aka fishplates). Whan you move up to a bigger system you caould have 5 or even 10 amps flowing ina short circuit and it's important that all wiring is low impedance. It should also be mitigated by using "power districts" but that's a subject fro another post.

Assuming OO or smaller, and modern locos, then 1 Amp is more than adequate for this.

If the engines resume as they were then I would question the use of "reboot". If it has "rebooted" then I would expect everything to be in a quescent state. otherwise locos couls start running every time you turn the thing on.

It sounds like a momentary short. Again, review the wiring for DCC site and ensure you are not getting shorts on your points.

Twin-coil solenoid point motors? These take a very large current. The wiring needs to be as thick and short as possible for best results. Do the Hornby accessory decoders have a built in CDU? If not, I would not power them from the track bus.

MBQ

Reply to
manatbandq

Hi Bill

Think after consulation with a model railway shop and an assistant who has his own DCC layout, I have not used insulating fish plates on the inner rail. These are now on order and en-route.

Reply to
Chris King

Just ordered the Gaugemaster Advance. :) (not the express)

Sorry, couldnt think of the word, I meant using the Digital Electric point clips. what I omitted was the insulating plates on the inner rails on each point. This is being rectified.

OK ta, havent got space for a bigger system (yet!), but plan to DCC the inner track too, small house and no plans to move!

Yes, think this occured due to me forgetting the insulating plates on inner rail on points.

The controller does reboot or cut out / restart when this happens, as I watch the display, but again, seems I missed the insulating plates!.

Yup - I have :)

Sorry again my bad lingo, I have two point accessories each capable of driving 4 points from each one, I can power them from the track bus, my moan was the wires supplied on each point motor is pitiful, so need to extend them :( Why cant they supply them each with say 1-2 metres wire. I suppose its cost!

Reply to
Chris King

: Twin-coil solenoid point motors? These take a very : large current. The wiring needs to be as thick and : short as possible for best results.

You really don't understand the relation between voltage drop, distance and conductor size do you MBQ?! What you wrote above makes no sense what so ever, are you /really/ saying that you would use say 4.0mm wire if the distance between the power source and load was 300mm apart, because that is what you have implied. OTOH you may well need to use a 10²mm solid busbar if your load is 1000+ ft away!... :~)

: Do the Hornby accessory decoders have a built in CDU?

For the benefit of the 'newbies', CDU = Capacitor Discharge Unit.

Not sure if a CDU would actually make any difference, just alter when any problem might exist, whilst a CDU no doubt allows less power to be drawn /during/ the solenoid operation the same -if not greater- power is still consumed due to the CDU needing to recharge *after operation/discharge*.

Reply to
Jerry

Yep, point controllers do have inbuilt CDU. If you still have the Select then its useful to use it solely for the points - avoids any power drain on main controller whilst points recharging. Have you decided if you want computer control, Hornby Trackmaster looks rather good, but only works for the Elite.

Length of wire - well thats typical of most devices nowadays, probably manufacturers say most people happy with that length and would be a waste to supply more - wouldnt comment on if they are correct cos dont know.

Cheers, Simon

Reply to
simon

Yes I do, thank you, nice of you to ask.

I would use wire appropriate to the situation. The point is that a solenoid point motor can take quite a few amps. Some people claim to get away with using cat5 wiring to connect them. I would use something rather thicker.

In simple terms, thicker is better than thinner, shorter is better than longer.

If the OP doesn't understand my point then hopefully he will come back for clarification.

You need to understand the difference between power and energy. A CDU can deliver the neccessary high current pulse, over a short period of time, to fire a solenoid motor. It delivers a certain amount of energy into the load.

A CDU is generally designed to recharge over a much longer period, drawing a much lower current. The energy is the same (plus any losses in the circuit). The much lower recharge current means that said CDU

*might* be suitable to be powered from the DCC track bus without upsetting the system too much. With a 1 Amp power supply in the OPs I would say it's still marginal.

A further possibilty with a CDU is to build a voltage doubler into the recharge circuit. The energy stored in a capacitor, and available to deliver to the solenoid, is proportional to the voltage. Personally, I would look at increasing the capacitance first since energy stored is proportional to the square of the capacitance.

MBQ

Reply to
manatbandq

.

Good point. Also means points can still be operated if the main system shuts down after a short due to running against the points.

If running trains into the buffers in lieu of proper control of stopping is good... At least that's what I heard about the early versions. If you want to pay for software then go for RR&Co, otherwise look at JMRI or Rocrail.

MBQ

Reply to
manatbandq

Good point. Also means points can still be operated if the main system shuts down after a short due to running against the points.

If running trains into the buffers in lieu of proper control of stopping is good... At least that's what I heard about the early versions. If you want to pay for software then go for RR&Co, otherwise look at JMRI or Rocrail.

MBQ =========================================

Don't need computer control to run train into buffers :-) Will take with pinch of salt, am still amazed at what some people do. When get own copy then can say what can happen - can even trace commands if required.

Cheers, Simon

Reply to
simon

Snipped

Be careful not to confuse Hornby's Railmaster with their Track-master.

Both products exist but the latter is for layout design using Hornby sectional track. The computer control system for use with the Elite, is RAILmaster

Regards,

Riddles

Reply to
Riddles

Well, yes, but it depends on the size of the layout. It's all about impedance and volt drop. On my old layout I used 4.0mm^2 for the power bus, the new layout is much bigger but split with a power booster so the furthest from the controller of any part of the track is about

20ft, this is OK in 2.5 but I run four radials, two in each direction, and split off to 1.5 then 1.0 before soldering to drops which are 0.5 or less, soldered to the joiners, but kept very short.

I have no power drop issues anywhere, even when running the track cleaner pushed by the deltic, which is one motor running flat out with another on the same length of track right behind it.

I'm using a Lenz LZV100 and LV100 booster, four handsets, something like 500ft of track and up to six engines moving concurrently. Points are on a separate circuit though. Guy

Reply to
Just zis Guy, you know?

Good point, thanks.

Cheers, Simon

Reply to
simon

: Some people claim to get away with using cat5 wiring : to connect them. I would use something rather thicker. : : In simple terms, thicker is better than thinner, shorter : is better than longer.

Indeed, in VERY simple terms, but as soon as one grasps relation between voltage (drop), current draw, distance and conductor size plus -in the case of latching solenoids- switching time...

: You need to understand the difference between power and energy.

I do thanks, unlike you, your description of a CDU,which is laughable.

: A further possibilty with a CDU is to build a voltage doubler : into the recharge circuit. The energy stored in a capacitor, : and available to deliver to the solenoid, is proportional to : the voltage

Next you'll be suggesting perpetual motion...

Reply to
Jerry

In article , " snipped-for-privacy@hotmail.com" writes

No it isn't; E = 0.5CV^2. That is, proportional to voltage squared but only proportional to C.

David

Reply to
David Littlewood

Lets hear yours, if you think you can do better.

Here's a good walk-through

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you will see that any sensible CDU design includes the current limit on the recharge side. This limits the *power* but allows the capacitor to charge to almost the full voltage (hence the same

*energy* stored).

Why would I need to do that?

Let me know which bit you are struggling with and I'll explain it in simple terms.

There are plenty of resources on the 'net that will explain the formula for energy stored in a capacitor.

If you know someone who is a member of MERG then get them to show you the schematic for the CAN_ACC4, a voltage doubling CDU.

MBQ

Reply to
manatbandq

Ooops! Trouble is everything is done in a spreadsheet these days. It's nearly 30 years since I had to derive formulae like these.

Thank you for the correction, unlike a certain other poster who described my description as "laughable" but didn't seem able to correct the mistake.

MBQ

Reply to
manatbandq

Yes, but that amount of charge can be built up over a period of time so that the peak current at any time can be low (depending on how quickly you wish to re-activate the point motor).

Jeff

Reply to
Jeff

Does it, looks to me that it limits current draw on the recharge side *when the CDU is discharging*, thus protecting the recharging side from possible overload.

: limits the *power* but allows the capacitor to charge : to almost the full voltage (hence the same *energy* : stored).

A CDU has to recharge in seconds, that is because the next operation could (and probably will) be in seconds, the larger the CDU is (thus the more work it can do, either bigger or a greater number of solenoids) the MORE current it will draw during this recharging phase -from the power bus in this case- and as the OP's problem appears to be a lack of available amps...

All a CDU is designed to do, to use a figure of speech, is to give a "good kick up the arse" to the solenoid - it is not designed to limit power draw during recharging because that is not the point of the unit, or shouldn't be...

: > Next you'll be suggesting perpetual motion... : : Why would I need to do that?

Because that is what you are suggesting, clue there is no such thing as a free lunch, if you double the voltage, you need to double the current as there is little point in having mega volts but no amps [1], think about it... One of the reasons why the national grid distributes at a HIGH volts/watts and then converts down to *lower* volts/watts (ultimately to 240v, typically, for UK domestic use), have it your way -with your magical "voltage doubler"- and the national grid would distribute the street level supply @ ~ 110v and then up-convert to 240v at the intake of the end user.

It could be done but it would actually be more dangerous, one of the reasons why the USA use duel phases @ 110v (with a centre tap return) to allow the provision of a SP 220v high power supply for cookers. water heaters etc.

[1] clue, it's the amps that do the work, not the volts...

: If you know someone who is a member of MERG then get : them to show you the schematic for the CAN_ACC4, a : voltage doubling CDU.

You're missing the point MBQ, but no surprise there, yes these units exist but they actually draw more current *for the same work*, OR, draw the same current but do less work.

Anyway, I've never liked CDU's, better to simply use a high current (amps) common power supply and suitable switching, either directly or -better still- via relays [2] with smaller low current control switches on the control board

[2] that then also allows interlocking to be deployed if one wishes).
Reply to
Jerry

Doesn't that amount to the same thing!!!!!!

This type of CDU is only of any use at all if there is significant voltage drop in the wiring to the point motor when it operates, or the power supply is not up to supplying the full current required by the motor. Otherwise after initial switch on the capacitor does nothing useful.

No, the amount of current drawn will be dependant entirely on the series resistance of the motor. As long as there is sufficient energy in the capacitor to throw the point a larger capacitor will be no better, other than being able to throw another motor without re-charging.

Yes, it must otherwise you will overload the psu.

You miss the point doubling the voltage will double the current through the motor (Ohm's Law), that will kick it harder. Because of the short pulse the motor is not overheated by the higher voltage.

Regards Jeff

Reply to
Jeff

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