Powser supply, circuit and surge protection

[smithdom]

I'm planning my first DCC layout (OO), very rough schematic below, roughly accurate. I plan to use a SPROG 3 with JMRI, but am pondering power districts and circuit protection. Points outside the sidings will be motorised, probably using the Cobalt motors. I'll have some powered semaphore signals, building lighting etc. I want to explore sensors and possibly block detection. I'm thinking a power bus for each of the main lines, and perhaps another for point motors etc, not yet watched anough YouTube channels to be sure. I don't expect to be running more than three locos at a time, but they will be sound fitted. I have a regulated 15V 3A power supply. Will that be enough? Should I circuit protect each power bus? If so do I just split the power after the sprog and insert a circuit breaker before connecting to each bus? Any recommended circuit breakers? Should I include a surge protector for power on? If so, where should that go? I read that a snubber at the ends of each bus is advised. Any advice from those that have been here and done it much appreciated.

[melmerby]

11 minutes ago, smithdom said:

I read that a snubber at the ends of each bus is advised

That's debatable.

I've got a decent length of track from the DCC system to the farthest feeds (about 40 feet) yet trying a snubber /bus terminator or whatever people choose to call it  made absolutely no difference to the DCC waveform. (using an oscilloscope to view)

Edited February 28, 2023 by melmerby

[Nigelcliffe]

If using Cobalt Digital motors, and wanting to split the accessories and track bus, then don't use the single "frog" output on the motors for the turnout frog.  Instead use the full change-over switch contacts.   If using the single frog output, a short will connect the accessory and track bus, which was precisely what you were trying to separate !

 

Other than the caution over Cobalt wiring, just connect stuff up and don't worry about it.  Snubbers, surge protectors, etc.. are all optional and probably not needed.

If wanting to split the accessories from track, then the PSX and Tam Valley cutouts seem quite decent for commercial units (or the MERG ones for DIY builders).    You only really need them for the track, the accessories are split off before the cutout device. 

 

 

- Nigel

[Phil Bullock]

The Tam Valley circuit breakers seem to be essentially modified frog juicers. If frog juicers are used on the layout I wonder how the circuit breaker does not trip at the same time the frog juicers switch? 

[smithdom]

27 minutes ago, Nigelcliffe said:

If using Cobalt Digital motors, and wanting to split the accessories and track bus, then don't use the single "frog" output on the motors for the turnout frog.  Instead use the full change-over switch contacts.

I was planning to use servos, inspired by Rob at Little Wicket, but when I watched videos of Cobalt installation I thought it would simplify powering the frog correctly. From what you are saying this is not necesarily the case. I confess I don't know what you mean by "full change-over switch contacts". I'm using PECO electrofrog turnouts.

[smithdom]

37 minutes ago, Nigelcliffe said:

or the MERG ones for DIY builders

Thanks for the pointer to MERG. More reading coming up...

[Nigelcliffe]

26 minutes ago, smithdom said:

I was planning to use servos, inspired by Rob at Little Wicket, but when I watched videos of Cobalt installation I thought it would simplify powering the frog correctly. From what you are saying this is not necesarily the case. I confess I don't know what you mean by "full change-over switch contacts". I'm using PECO electrofrog turnouts.

 

The other switch on the Cobalt - takes two wires in from the track feed, one wire out to the frog.

 

And if that's puzzling you, then DIY MERG district cutouts are probably not for you. Just buy one or two Tam Valley ones.

 

- Nigel

 

[jamesed]

16 hours ago, smithdom said:

I was planning to use servos, inspired by Rob at Little Wicket, but when I watched videos of Cobalt installation I thought it would simplify powering the frog correctly. From what you are saying this is not necesarily the case. I confess I don't know what you mean by "full change-over switch contacts". I'm using PECO electrofrog turnouts.

 

Using Cobalt IP Digitals will simplify things. What Nigel was pointing out is that if you intend to power you motors from an accessory bus then you need to connect your frog dropper to terminal S2C (6th terminal down in the photo) and not to S1-FROG (3rd terminal down) so that your frog isn't powered from the accessory bus.  Having connected the frog to S2C you then need to wire S2-L and S-2R to your track bus.   The S2 terminals are a completely isolated single pole changeover switch.  The down side of this is that you don't then have the S2 switch available to control signals or mimic panel LEDs etc.   

 

The changeover on a Cobalt takes place at the mid point of travel of the switch rail so this means that you don't have to make any wiring modifications to the Electrofrog points. Just solder a dropper to the group of wires directly beneath the frog and leave all the link wires in tact. Just make sure you've got the dcc polarity correct on each motor as you go along - if it's wrong you'll get a short but is quickly rectified by swapping over the track bus wires in the DCC IN tetminals. 

 

I run my Cobalts from the track bus and don't find that to be a problem.  Their current draw is extremely low. This enables me to use the S1-Frog terminal and I then run coloured light signals from the S2 terminals feeding 12v dc into S2-C

 

 

 

 

Edited March 1, 2023 by jamesed

[D5158]

This may help if the image loads.

[RFS]

51 minutes ago, jamesed said:

Having connected the frog to S2-C you then need to wire S2-L and S2-R to your accessory bus. 

 

You mean track bus here not accessory bus. 

 

55 minutes ago, jamesed said:

The changeover on a Cobalt takes place at the mid point of travel of the switch rail so this means that you don't have to make any wiring modifications to the Electrofrog points. Just solder a dropper to the group of wires directly beneath the frog and leave all the link wires intact. Just make sure you've got the dcc polarity correct on each motor as you go along - if it's wrong you'll get a short but is quickly rectified by swapping over the track bus wires in the DCC IN terminals. 

 

The reason for using a frog power switch is it allows you to improve the reliability of the electrical connections. If you don't remove the link wires and bond the stock rail to the blade rail, as is widely documented, the stock rail and open blade rail are opposite polarities and hence the back of a metal wheel has the potential to cause a transient DCC short if it touches it on passing through.  It's only a couple of minutes to fix this before laying the point. I solder a dropper wire on to the stock rails which is simply soldered across to the blade rail. 

[jamesed]

19 minutes ago, RFS said:

 

You mean track bus here not accessory bus. 

 

 

The reason for using a frog power switch is it allows you to improve the reliability of the electrical connections. If you don't remove the link wires and bond the stock rail to the blade rail, as is widely documented, the stock rail and open blade rail are opposite polarities and hence the back of a metal wheel has the potential to cause a transient DCC short if it touches it on passing through.  It's only a couple of minutes to fix this before laying the point. I solder a dropper wire on to the stock rails which is simply soldered across to the blade rail. 

Yes I mean  track bus, thanks. I'll correct that.

 

I repeat there is no need to modify the Electrofrog points when using Cobalts. You can still power the frog, the frog rails and the switch blades but, unlike with other types of frog switchers, the Cobalts don't switch over until the mid point of travel so at that point the switch blades aren't in physical  contact with the stock rails.  The Peco points are well enough designed for this to work fine but you do need to remove the springs.

 

 

 

 

 

 

Edited March 1, 2023 by jamesed

[Phil Bullock]

24 minutes ago, jamesed said:

Yes I mean  track bus, thanks. I'll correct that.

 

I repeat there is no need to modify the Electrofrog points when using Cobalts. You can still power the frog, the frog rails and the switch blades but, unlike with other types of frog switchers, the Cobalts don't switch over until the mid point of travel so at that point the switch blades aren't in physical  contact with the stock rails.  The Peco points are well enough designed for this to work fine but you do need to remove the springs.

 

 

 

 

 

 

Speaking from my own experience that makes motor alignment critical to avoid a short. There is much more tolerance in motor alignment if the advice to break the frog link wires and fit a link between the stock and blade rails is followed.

Edited March 1, 2023 by Phil Bullock

[jamesed]

1 hour ago, Phil Bullock said:

Speaking from my own experience that makes motor alignment critical to avoid a short. There is much more tolerance in motor alignment if the advice to break the frog link wires and fit a link between the stock and blade rails is followed.

Well, the motor needs to be reasonably well alligned anyway but it doesn't need to be spot on.  As long as the blade has moved far enough away from the stock rail to break contact before the motor reaches its half way run point it will be fine.  If it hasn't done that then it probably won't throw all the way anyway.    I've fitted 22 of these in the last few months exactly on that basis and they all work a treat.  However,  it is important to remove the spring in the point first. It's also important to check the polarity as you go along, after you've turned off self-centering. 

[DCCconcepts]

34 minutes ago, jamesed said:

Well, the motor needs to be reasonably well alligned anyway but it doesn't need to be spot on.  As long as the blade has moved far enough away from the stock rail to break contact before the motor reaches its half way run point it will be fine.  If it hasn't done that then it probably won't throw all the way anyway.    I've fitted 22 of these in the last few months exactly on that basis and they all work a treat.  However,  it is important to remove the spring in the point first. It's also important to check the polarity as you go along, after you've turned off self-centering. 

 

By default, the motor is delivered in the central position, self-centring is not enabled.

So it's a case of giving it an address with the SET/RUN switch and away you go.

The default accessory address is 1.

 

Best Regards,

The DCCconcepts Team

[RFS]

3 hours ago, jamesed said:

Yes I mean  track bus, thanks. I'll correct that.

 

I repeat there is no need to modify the Electrofrog points when using Cobalts. You can still power the frog, the frog rails and the switch blades but, unlike with other types of frog switchers, the Cobalts don't switch over until the mid point of travel so at that point the switch blades aren't in physical  contact with the stock rails.  The Peco points are well enough designed for this to work fine but you do need to remove the springs.

 

The modification to Electrofrog points is to prevent potential shorts as the open blade is live and opposite polarity to the stock rail. Nothing to do with Cobalts, other point motors or no motor at all. If you're happy that all your stock has correct back-to-back wheels measurement, and you don't have the risk of shorts, then that's fine.  Bear in mind that Peco code 75 is more susceptible to this issue than code 100 because the blade is closer to the stock rail. 

 

Also I believe no longer an issue with the finescale bullhead points with Unifrog.

Edited March 1, 2023 by RFS

[Phil Bullock]

11 minutes ago, RFS said:

 

The modification to Electrofrog points is to prevent potential shorts as the open blade is live and opposite polarity to the stock rail. Nothing to do with Cobalts, other point motors or no motor at all. If you're happy that all your stock has correct back-to-back wheels measurement, and you don't have the risk of shorts, then that's fine.  Bear in mind that Peco code 75 is more susceptible to this issue than code 100 because the blade is closer to the stock rail. 

 

Also I believe no longer an issue with the finescale bullhead points with Unifrog.

Importantly also provides a reliable feed to the closure rail and blades that is not dependent on contact between the switch blades and the stock rail ….

Edited March 1, 2023 by Phil Bullock

[RobinofLoxley]

@smithdomHave you got your own building, or just straightened the plan out for ease of understanding? Its 20 metres long!

[RedgateModels]

On 28/02/2023 at 18:12, smithdom said:

Thanks for the pointer to MERG. More reading coming up...

 

The MERG DCO has been very well designed to cope with most controllers/boosters, would recommend it to anyone.

 

Just as an aside, my article in the Spring 2023 BRM might be useful to the OP

[smithdom]

On 02/03/2023 at 09:37, RobinofLoxley said:

Have you got your own building, or just straightened the plan out for ease of understanding? Its 20 metres long!

Just straightened out. My room is about 7m x 5m and the two main tracks runs around the perimeter with a lift up bridge for access.

[smithdom]

On 01/03/2023 at 11:46, Phil Bullock said:

Also I believe no longer an issue with the finescale bullhead points with Unifrog.

I earlier incorrectly stated I'm using all electrofrog turnouts. In fact all turnouts that I intend to motorise are Peco bullhead code 75 unifrog. I volunteer on the Gloucestershire Warwickshire Railway in the Permanent Way department and I'm setting out to model Winchcombe Station, Greet Tunnel (entrances) and eventually Stanway Viaduct. At the moment it feels like ambition exceeds capability by a factor of 10, but that's the joy of the journey.

[Phil Bullock]

1 hour ago, smithdom said:

I earlier incorrectly stated I'm using all electrofrog turnouts. In fact all turnouts that I intend to motorise are Peco bullhead code 75 unifrog. I volunteer on the Gloucestershire Warwickshire Railway in the Permanent Way department and I'm setting out to model Winchcombe Station, Greet Tunnel (entrances) and eventually Stanway Viaduct. At the moment it feels like ambition exceeds capability by a factor of 10, but that's the joy of the journey.

 

Will you be at the diesel gala in July? See you there if so… we are in the goods shed at Winchcombe with our layout

[ISW]

On 02/03/2023 at 09:50, RedgateModels said:

The MERG DCO has been very well designed to cope with most controllers/boosters, would recommend it to anyone.

I can second that. They're quite easy to build and no problem to wire up and install. Here's 6 of mine installed on underside of the Upper Level of my layout:

 

It may 'look' complicated, but it's just 6 Bus Wires with each one protect by a MERG kit#57 (DCO).

 

Ian