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Discussion Starter · #1 ·
Hello all..

No updates recently regarding Breitfurt as I have been busy elsewhere. As this is not layout specific I thought it would be better to star a new topic.

Does anyone have any experience of of the use of route switching using diodes and a capacitor discharge unit? I am a bit confused as how it all works.

When using a CDU in a normal 'one switch per turnout' can one replace the normal passing switches with normal SPST switches. I imagine that this is OK if one has one CDU per turnout but that is not financially viable. But what about with 43 turnouts?

On a related matter, forgetting traction power, where one has switches controlling signals and turnouts, is there any preference as to whether the switch should be on the live or earth side of the unit being operated? The reson I ask is that I want to apply some partial automation using simple logic, probably with relays. In my electronics days the switches (usually semiconductors) always grounded the control lines. However, I am not sure if this is such a good idea when using model rail AC. The is getting quite critical now as I have started wiring the signals.

I hope all that makes sense!

All the best,
Chris.
 

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Chris,
With a CDU you still need a brief contact - if you use an SPDT switch the low resistance of the point motor coil will hold down the voltage across the capacitor and it will not recharge for the next operation. I personally use press-switches to operate my solenoid motors from a CDU. Or you could use one centre-biased SPDT switch instead of two push-buttons.

Re diode matrix - I use these for my small (four-road) fiddle-yard - one button at the entrance/exit of each road switches the appropriate points to allow trains in or out from the selected road. On the assumption that you connect the +ve side of the CDU to the press-switches, all you need do is to connect diode(s) from the switch output to feed the appropriate point-motor coils. Use 1N4001s or similar. The band on the diode indicates the end that should go to the point motor coil.

See "Wiring the Layout" by Jeff Geary, KRB Publishing 2002, ISBN 0 9542035 5 0. This has a clear description of the diode matrix and also a very good explanation of how to wire up a double-slip and some other useful circuits. There is also a free CD which runs a program which helps you wire up a layout for analogue control.

Regards,
John Webb
 

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Chris, there are many sites on the Web if Googled but this one is possibly one of the best
http://brian-lambert.co.uk/Electrical-2.htm#Diode%20Matrix

Now in this hobby, unless you are using common return, switches can be in either leg but it is better to maintain uniformity & have all of them in the same polarity espec ially if using diodes to create blocking paths like a diode matrix.
The CDU has been answered well by John but this is also helpful http://brian-lambert.co.uk/Electrical.htm#...0Motor%20Wiring.
 

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Thank you John; very helpful in many respects. Quite simply. the reason I was hoping to be able to use the spdt was so that the switch would indicate the position of the turnout on the panel thereby doing away with some other method. However, I guess that it is not too important as one would normally set up a rote every time one wanted to run a train. My concern was with setting up one route and running a train into it as I set up another conflicting route. I shall have to go away and think about that one. I was also wondering about using the route setting to set up self latching relays that would also connect traction current to the rails. However, with some 55 separate track circuits that is a helluva lot of relays! I can feel a compromise coming on. I've already got over 200 wires runs under the layout and this will end up at about 350 once the layout is finished! And that does not include any lighting wiring that I add later.

I'll have a look for that book; it could well help, if not for my current project maybe a future one.

Once again, many thanks.

Chris.
 

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Discussion Starter · #5 ·
Thanks Ron.

Yes, I'm sorry, I have been a bit lazy looking things up. I'm suffering from info overload at the moment and have developed Googlitis - a rare disease which causes lassitude and mild depression and a tendency to scream 'I give up' or worse at regular intervals. I guess I have too many irons in the fire at the moment. If I hear that I am not exhibiting in April, I will heave sigh of relief and do something else for a while.

All the best,
Chris.
 

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My fiddle-yard is worked by second-hand Hamment and Morgan solenoids - these have a built-in switch which I use to send back information on the point position to the control panel. (Can also be done with PECO and Seep motors which have switches fitted.) I have a +/- 12 volt pair of cables running round the layout for various uses including point indication. The point switches between the two voltages and a single wire runs back to the control panel where two LEDs are wired 'Back to back' with one common resistance. When +ve one LED lights, when -ve, the other does. Halves the number of wires and connections needed for point indication.

Regards,
John Webb
 

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Discussion Starter · #7 ·
Hi John,
That would be great with my static N scale layout when I start on it. But Z scale points don't have that option as the motors are built in to the track and have no switches.

If there were a team working on the layout it would be a lot easier but this is very much a one-man show. When I exhibited back in November I used a temporary control panel with some 60-70 wires passing to the layout (see picture). Now I have purchased a sheet of Aluminium twice the length for the new panel. In addition to the power feeds, it will have to manage signals (with red/green feedback) as well as the pointwork (again with tell-backs) and uncouplers. The indicators don't have to be driven by the item they represent (this is not a real railway) but can be some form of SR bistable at the switch.

For a first layout, this is a very complex p[roject but I feel that I can hack it with a bit of on-line help.

Lunch time so must go!

With best wishes,
Chris.
 

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