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DCC Auto train stop


thesteambuff
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Can anybody help, I have a DCC layout with hidden sidings I would like to stop the train automatically just before the ( electrofrog) point when it is set point is against it.

I have tried running the power down through the points as in the DC fashion and a break in the track   and running current back up to it from the other end of the track, that does keep the train moving up to the brake in the track, This stops the train but shorts when the loco is bridging the brake due to the polarity changing when the point direction is changed. 

Very frustrating

post-13191-0-12014500-1500764584_thumb.jpg

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Ah, the classic mistake of wiring a DCC layout as if it where a DC one. While the principles are the same, DCC is much less forgiving in sloppy wiring, as well as blatant design flaws, then DC is.

What you need are separately switched stop sections with no connection to the polarity of the frog. Because I suspect you've wired these stop sections parallel to the frog. For that, you need an extra switch on the point motor, but that only needs 2 wires (whereas the switch for changing the polarity of the frog has 3). I'll make you a diagram if you need one, tell us if you do (as there's a fair few more folk here perfectly capable of making that diagram for you!)

 

HTH!

HI Dutch master

 

Thankyou for your reply,yes i would be grateful for your kind offer of a wiring diagram as i am so confused by it after changing the wiring so many times, 

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Ah, the classic mistake of wiring a DCC layout as if it where a DC one. While the principles are the same, DCC is much less forgiving in sloppy wiring, as well as blatant design flaws, then DC is.

What you need are separately switched stop sections with no connection to the polarity of the frog. Because I suspect you've wired these stop sections parallel to the frog. For that, you need an extra switch on the point motor, but that only needs 2 wires (whereas the switch for changing the polarity of the frog has 3). I'll make you a diagram if you need one, tell us if you do (as there's a fair few more folk here perfectly capable of making that diagram for you!)

 

HTH!

Hello again

 

Not sure how i an add another switch as on the opposite side of point there is no room,any ideas.

 

thanks

David

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Look here, specifically the bit about asymmetric DCC down the page:-

 

http://www.wiringfordcc.com/switches.htm

 

You can fit a double pole switch to your points in a number of ways. If you have decoders that support asymmetric DCC use the BM1 modules and the trains will slow gently to a stop, if not just leave them out and the trains will stop dead unless they have a stay-alive.

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I assume you switch the points remotely, right? If so, you can use a relay to switch both the polarity of the frog and the stop section of the track. Relays come in all kinds of different shapes, sizes and functionality, the one you need is a bi-stable DPDT relay, like this one: link. <- Note, this particular lot contains 5 relays! (no affiliation with the seller, at all!)

 

To avoid making diagrams that are of little or no use to you, I need to know a few things:

 

1) how do you control the points

2) if you control your points remotely, do you use a CDU to power them

3) are you prepared to use relays as those above (or similar, if you can source them locally)

4) any other info you think I'd need to know

Thank you for your reply.

1)They are controlled from momentary on off on switches.

2) yes a CDU

3) yes if that is the simplest way.

4)The micro switches are wired to LED's on the the panel to denote which track is routed,the other end of the sidings are isolated by a lift up section as per attached photo.

Would like to avoid any more wiring to panel as already congested (see photo).

 

Cheers

David

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post-13191-0-39900100-1500829326_thumb.jpg

post-13191-0-03739500-1500829864_thumb.jpg

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Look here, specifically the bit about asymmetric DCC down the page:-

 

http://www.wiringfordcc.com/switches.htm

 

You can fit a double pole switch to your points in a number of ways. If you have decoders that support asymmetric DCC use the BM1 modules and the trains will slow gently to a stop, if not just leave them out and the trains will stop dead unless they have a stay-alive.

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When you get down to the bit talking to Lenz BM1 modules all they are are 5 diodes with the rail connection across 4 vs 1 to provide the voltage drop on one side of the DCC signal to form the asymmetric . I can provide strip-board build plan for you if required.The ref out to the Lenz site provides more background to the system logic.

Rob

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David,

 

Seeing you've been given several options to explore, I'm withholding my diagram(s) as not to confuse you. If the other options fail to work, let us know and we'll make you the required diagrams (me or anyone else, that doesn't matter of course).

 

Best of luck!

Hello

 

I think i prefer your option as i feel it would be easier ,i have ordered the relays.

if you could send me a diagram i would be most grateful.

 

many thanks

David

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I don't think that one extra wire makes it more complicated, and there are four points in the above diagram that require it.

 

Here is the full version as shown on Wiring for DCC

 

attachicon.gifdutch stop section 1.jpg

 

And here is an alternative version if you want the stopping sections both in the left rail.

 

attachicon.gifdutch stop section 2.jpg

 

I don't think that one extra wire makes it more complicated, and there are four points in the above diagram that require it.

Hi Suzie

 

Just a thought as i am powering from a CDU will this be to much power and damage the relay.

 

David

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Hi Suzie

 

Just a thought as i am powering from a CDU will this be to much power and damage the relay.

 

David

 

It is down to the voltage you are getting out of your CDU. If it is above 24V you really need 24V relays, but below that you should be OK with 12V relays.

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It's worth noting that these 12V relays have a coil resistance of about 1k, while Peco point motors are generally around 80-100 ohms.

Peco PL-10 point motors are about 4 ohms per coil. The similar Hornby point motors are about 5 ohms per coil.

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A standard 12v or 24v relay can not be operated via a solenoid point motors feed circuit. The pulse to the motor coil is only applied for a fraction of a second so a standard relay will probably never operate or at best operate then immediately drop away.

You have to use a twin coil latching relay.  Then the latch coil connects to one solenoid feed wire while the other unlatch coil connects to the other solenoid feed wire. The relay once energised remains mechanically latched indefinitely until the unlatch coil is powered momentarily and it then releases the mechanical latch and drops away the relay to its de-energised state. 

 

You can make your own with a twin coil latching relay and some 1N4001 or 1N4002 diodes. Or Gaugemaster sell ready made units under their part number GM500 for conventionally operated solenoid motors or GM500D for solenoid motors operated via a DCC accessory decoder.

 

Basic idea is shown here... http://www.brian-lambert.co.uk/Electrical%20page%202.html#Unable

 

Don't forget on DCC layouts that any lights will be turned off and any sounds stop operating if a loco enters a dead track section. Sound systems may have to go through their start up sequence too when rail power is reapplied to the stop section.

 

Edited to add URL link

Edited by Brian
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