Very basic questions about using DCC.
- Thread starter Sarah Winfield
- Start date
Greg Elmassian
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with the LED suggestion I made, all you do is look for the green!
Sarah Winfield
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Thank you everyone and for the drawing JimmyB.
I hope tomorrow to have my loop set up if only temporarily.
SW
Neil Robinson
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Agreed but you don't necessarily have to worry about this when first connecting the wires. If it turns out that the switch is the "wrong" way you could simply turn the switch round
JimmyB
Now retired - trains and fishing
Sarah, don't thank me the drawing is Neil's, I just pointed you at it.
Sarah Winfield
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Thank you for pointing me at it Jimmy.
Thank you for posting the drawing, Neil
SW
Thank you for posting the drawing, Neil
SW
Sarah Winfield
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I'm persevering with my DPDT loop.
Off my main line I have 2 points into 2 parallel track. Before these meet the main line again I bring them into one track and then onto the mainline. Hope that makes sense.
Do I have to create a dead section on both parallel tracks and will I also need DPDT switches on both tracks please?
Thanks,
SW
Oh, I don't know what happened but I've gone all bold!
Off my main line I have 2 points into 2 parallel track. Before these meet the main line again I bring them into one track and then onto the mainline. Hope that makes sense.
Do I have to create a dead section on both parallel tracks and will I also need DPDT switches on both tracks please?
Thanks,
SW
Oh, I don't know what happened but I've gone all bold!
Neil Robinson
Registered
"Hello, I'm Julian and this is my friend Sandy."
Back to the point, Are you referring to this part of your proposed plan?
If so one switch would work for DCC provided you don't have simultaneous departures in opposite directions.
Personally I'd fit two and have center off versions of the switches if there's any chance of analogue working.
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Greg Elmassian
Guest
You don't need center off for analog, it just allows you to kill the power to the track.
In DCC, it is a negative, because if you can flip the switch quickly, you can do it with a train in motion.
In DCC, it is a negative, because if you can flip the switch quickly, you can do it with a train in motion.
Sarah Winfield
Registered
That's the area Neil.
No chance of analogue working. If I move away from DCC it'll be towards R/C.
Each dead section of my loops will be a station. I'll put the switch in the centre off position and align it parallel to the track so I know which direction to push the switch will be the direction I want to train to go.
Everything on my layout is at ground level although I've thoughts about changing points and switching switches from a standing position.
SW
No chance of analogue working. If I move away from DCC it'll be towards R/C.
Each dead section of my loops will be a station. I'll put the switch in the centre off position and align it parallel to the track so I know which direction to push the switch will be the direction I want to train to go.
Everything on my layout is at ground level although I've thoughts about changing points and switching switches from a standing position.
SW
PhilP
G Scale, 7/8th's, Electronics
Except the 'polarity' of a DCC track has no bearing on the direction of travel of the train..
You are supplying 'power' and 'control-signals' over the track.. The decoder in the loco uses the power to make things happen, and the control-signals to say what will happen.
On a DCC track, a chipped loco will travel in the direction you tell it to go.. Whichever way 'round' you put it on the track, forwards will be forwards..
You really need the LED's to tell you 'green is go' across your isolation gaps.
Quite righ as Phil says. This is why I suggested the Switch near a point and using the way the switch was pointing to indicate where the power was being supplied from.
Sarah Winfield
Registered
Still confused, I'm afraid.
My controller supplies the track with an AC voltage. Through the pick-ups this voltage is supplied to the locomotive's motor via the decoder?
My controller has "forward and reverse". Are they redundant if which ever way round I put my locomotive on the track it will always go forward? Now I know that can't be right since the unit does go in reverse as well as forward.
So obviously there is something which recognises which way is forward? Is that in the decoder or the controller please?
SW
My controller supplies the track with an AC voltage. Through the pick-ups this voltage is supplied to the locomotive's motor via the decoder?
My controller has "forward and reverse". Are they redundant if which ever way round I put my locomotive on the track it will always go forward? Now I know that can't be right since the unit does go in reverse as well as forward.
So obviously there is something which recognises which way is forward? Is that in the decoder or the controller please?
SW
PhilP
G Scale, 7/8th's, Electronics
The 'power' on the track is AC, and has nothing to do with the direction of the loco..
The decoder uses this 'raw' voltage to supply power to itself, and the rest of the loco electronics (sound, lights motor, smoke-unit).
This is done under control of the 'Controller' (known as a Central Station, 'CS' for short). The CS sends a command imposed on the AC track power. A decoder is looking for commands all the time, but will only act on a command if it has the same address as it is set to.
By turning the knob on your CS 'forwards', you send a 'go forwards' command over the track. The decoder recognises the command is addressed to it, and sends a DC voltage to the motor to make it go forwards. - The decoder generates this DC voltage from the 'raw' AC from the track.. That AC should never get to the motor directly.. The decoder can also be told to 'turn the lights on', and any other command it is programmed to obey.
(Very simplified, before others jump-in, and correct the deliberate glossing over of many facts!)
Does that help a little, Sarah?
Sarah Winfield
Registered
Yes, definitely, thanks.
I understand (without knowing the technicalities) the addresses and how they have to be assigned to different locomotives.. So something in the CS knows which way to send a locomotive when it's forwards and reversed buttons are pressed and go faster control is turned?
I acknowledge that having diodes would help but I don't have them so I'm relying on me setting the DPDT switch correctly. If then I wire up in accordance with your drawing things should work.
The sequence should be, I have my DPDT switch (say S1) set to allow a train into the station, from the RHS, with the other end LHS cut off from any power by the isolated rail joiners. I stop the train, set the switch (S1) to the centre position and the isolating rail joiners cut all voltage to that section of track.
When the train is ready to depart I change switch (S1) to the other position allowing power into the LHS station track now unaffected by the isolating rail joiners at that end.
The only question now in my mind is do I need a DPDT switch at each end of my station track, please?
I'm sorry for all the trouble and probable frustration I am causing.
Sarah Winfield
I understand (without knowing the technicalities) the addresses and how they have to be assigned to different locomotives.. So something in the CS knows which way to send a locomotive when it's forwards and reversed buttons are pressed and go faster control is turned?
I acknowledge that having diodes would help but I don't have them so I'm relying on me setting the DPDT switch correctly. If then I wire up in accordance with your drawing things should work.
The sequence should be, I have my DPDT switch (say S1) set to allow a train into the station, from the RHS, with the other end LHS cut off from any power by the isolated rail joiners. I stop the train, set the switch (S1) to the centre position and the isolating rail joiners cut all voltage to that section of track.
When the train is ready to depart I change switch (S1) to the other position allowing power into the LHS station track now unaffected by the isolating rail joiners at that end.
The only question now in my mind is do I need a DPDT switch at each end of my station track, please?
I'm sorry for all the trouble and probable frustration I am causing.
Sarah Winfield
PhilP
G Scale, 7/8th's, Electronics
"I think she's got it!" - Said Dr Doolittle.. 
No, only ONE switch per isolated section. - Same 'outside' track you are connecting to.. TWO switches could mean you end up with a permanent short on the track..
So you need a switch for each of the two roads through the station.
With a centre-off switch: Any sounds etc. will cease once the power is turned 'off' with the switch.
No, only ONE switch per isolated section. - Same 'outside' track you are connecting to.. TWO switches could mean you end up with a permanent short on the track..
So you need a switch for each of the two roads through the station.
With a centre-off switch: Any sounds etc. will cease once the power is turned 'off' with the switch.
No you do not need TWO DPDT Switches only the ONE as I said. I propose a DPDT Centre Off so that there can be no flashover within the switch when you change polarity.
As for direction it does get some getting used to. As a test to help you understand set your loco in forwards with the Chimney Leading and the Controller Forwards. Now stop it. Take the loco off the track and put it back on as if you had turned it on a turntable. Now turn the controller Forwards again the Loco will still be going Chimney forst but the other direction because the system knows that the loco needs to go forwards.
If you did this in DC the loco would be running Bunker first as DC will still be the same polarity to each rail.
As we have said polarity is not an issue with DCC but connecting the Outer Rail to the inner via a reverce loop will cause a short which is why you need a DPDT and to feel confident of which line you are setting it to on the Reverce Section. Again please refer to the Diagram that I did for you and the other one that came later for your two loops.
PhilP
G Scale, 7/8th's, Electronics
Gotcha!
(Warning to Sarah! Severe thread drift..)
Analogue loco, pickup AND motor connected together, on each side...
If you turn analogue loco round, you reverse BOTH pickup and motor. - You only reverse one to alter direction of travel..
So the analogue loco will still go forwards..
What? I think you may have been away from DC for too long. Please read what I said again. Or are you refering to an Analog Locomon DCC? Which could well be a different scenario.Gotcha!
(Warning to Sarah! Severe thread drift..)
Analogue loco, pickup AND motor connected together, on each side...
If you turn analogue loco round, you reverse BOTH pickup and motor. - You only reverse one to alter direction of travel..
So the analogue loco will still go forwards..
Lift dc loco from the track (on a dc system) physically reverce it and it will run in the same direction if you do not change the controller.
The similarity of DCC is with DC 3 rail actually as the efferct of lifting a loco from the track and putting it back on again is that it will go the opposite direction but still orientated Chimney First if that is the way you ran it before lifting it off the track.
To test both of these DC and DCC options out put a loco on the track run forwards and do the lift off turn round as if on a turntable and put back on without changing the controller.