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
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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.

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Bill Campbell

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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.
On 2012-01-09 08:55:18 +0000, Bill Campbell said:

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Chris King
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wrote:

A good policy!

Depends what you mean by "electro connected". That's not a recognised term. See http://www.wiringfordcc.com/ for more than you ever wante to know. I would also join MRF http://www.modelrailforum.com/forums/index.php ? which 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
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On 2012-01-09 14:32:38 +0000, snipped-for-privacy@hotmail.com said:

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!
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<snipped for brevity> : 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 10mm 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*.
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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
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.
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
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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
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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
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Good point, thanks.
Cheers, Simon
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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
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<snipped> : 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...
<snip> : You need to understand the difference between power and energy.
I do thanks, unlike you, your description of a CDU,which is laughable.
<garbage snipped> : 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...
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Lets hear yours, if you think you can do better.
Here's a good walk-through http://home.cogeco.ca/~rpaisley4/CDPSU.html where 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
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wrote in message

<snip> : > I do thanks, unlike you, your description of a CDU, : > which is laughable. : : Lets hear yours, if you think you can do better. : : Here's a good walk-through http://home.cogeco.ca/~rpaisley4/CDPSU.html : where you will see that any sensible CDU design : includes the current limit on the recharge side. This
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...
<snip> : > 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...
<snip> : 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).
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Regards, Jerry.



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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
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: : > <snip> : > :> I do thanks, unlike you, your description of a CDU, : > :> which is laughable. : > : : > : Lets hear yours, if you think you can do better. : > : : > : Here's a good walk-through : > http://home.cogeco.ca/~rpaisley4/CDPSU.html : > : where you will see that any sensible CDU design : > : includes the current limit on the recharge side. This : > : > 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. : : Doesn't that amount to the same thing!!!!!!
No, and you seem to have a sticky key on your keyboard.
: : 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. :
Thus it would be bloody useless on a layout were one might be operating multiple numbers of solenoids, sometimes simultaneously (via a route setting matrix for example) and at other times sequentially - the latter being the more usual.
: : : > : 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... : : 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.
Exactly, so unless the capasitor is overly large the unit must charge quickly, or the next operation might not happen, these units are not about limitting current draw during charging but current avalible during discharge.
: : > : > 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... : : Yes, it must otherwise you will overload the psu.
Which, unless one designs the unit not to (as mentioned below, in which case the solenoid will fail to operate and the unit will be prevented from recharging) that is exactly what will happen if the power supply or the unit is not of sufficient capacity, A CDU is no substitute for an inadequate PSU!
: : : > <snip> : > :> 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. : : 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. :
No, I get the whys and wherefores thanks, what I'm saying is that in doing so (stepping-up) you need to increase the input current used, always far more efficient (power use wise) to step-down.
It would actually make more sense for these point solenoids to be made to work at a (continuous rating) of ~ 6 to 8 volts and then power them for short periods at 12 to 16 volts, without any need for a CDU.
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The capacitor is discharged through the solenoid, *very* quickly, regardless of its size. The recharge will still be quick, even if it is an order of magnitude or more slower than the discharge time.

If you have no current limit circuitry then all you have is a power supply connected to a capacitor connected through a switch to a solenoid. What do you think happens when you close the switch?

Bingo! That's *exactly* what a CDU is for.
Think of a how a toilet flush works. The cistern fills relatively slowly. Flush, and it empties very quickly to wash the turds away. Wait for it to refill, repeat...
The flush lever is the point operating switch. The cistern is the capacitor. The turds are the point blades. The sudden deluge of water is the current pulse through the solenoid. The inlet is your "inadequate" PSU. Oh, hang on, so long as you don't need a s**t more often than the cistern can fill then it's perfectly adequate.
MBQ
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wrote:
<snip> : > [Exactly, so unless the capasitor is overly large : > the unit must charge quickly, or the next : > operation might not happen, these] : > units are not about limitting current draw during : > charging but current avalible during discharge. : : If you have no current limit circuitry then all you have : is a power supply connected to a capacitor connected : through a switch to a solenoid. What do you think : happens when you close the switch?
If you had a PSU of sufficient power you wouldn't need to have a capacitor in the circuit, well not connected as in a CDU, so your point (pun not intended) is what, exactly.
: > A CDU is no substitute for an inadequate PSU! : : Bingo! That's *exactly* what a CDU is for.
Oh right, so you are now claiming a solenoid can't work without a CDU?! Duh, you really are a dimshit MBQ, perhaps if you took your nose away from Google and actually did some modelling for a change...
I have been at this game for the last 40+ odd years kiddo, never have I used a CDU when powering such solenoids, although I have also never used the same PSU as the traction current is obtained from, especially the sort of model railway PSU common way back when CDUs started to be used...
--
Regards, Jerry.



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The point is that we would not be discussing CDUs if the power supply were so over specced (compared to what could be used with a CDU) to the extent that it could power a solenoid once a second, say.

Don't try putting words in my mouth. I'm claiming that a CDU allows the use of a power supply that would otherwise be inadequate to switch a solenoid motor. It's quite a simple concept
MBQ
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