Operating solenoid points via DC & DCC

[Chrissaf]

Yes, BUT.

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To do so, you must separate the three wire point (port) outputs from your DC Analogue wiring using relays or switches. You cannot allow the DC Analogue supply that is currently being used to operate your points to come into electrical contact with the output of the R8247. Therefore you must not just make direct parallel wire connections

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Relay Option.

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The + C - output of the R8247 is used to operate relays with a SPST (Single Pole Single Throw) contact. TWO RELAYS will be required per port on the R8247. The relays should ideally be operated via 12 volt DC coils. Using half of a SPDT contact arrangement can alternatively be used to substitute a SPST set of contacts.

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The SPST relay contacts then get directly wired in parallel with your existing DC Analogue change-over switch. Something like this:

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I edited existing schematics I had available to me in preparation of this reply, Hence why PECO motor products and standard electrical momentary action centre off toggle switches are shown, but the principle is the same

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The relay option can be expensive if there are a number of points to support given that there are two relays required per port (point).

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Switch Option.

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A cheaper option could be deployed using three pole rotary switches, but this option is more onerous to deploy because it would require more in depth rewiring to incorporate the DC to DCC circuit separation. The middle pole marked N/C (Not Connected) shown on the rotary switch ensures 100% that during the switching of the rotary switch from DC to DCC and back again, that it is impossible for any electrical momentary connection between the DC and DCC supply circuits.

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Something like this (CDU is optional):

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2. Can I have the R8247 controller wired up to the track (and solenoids), ready for DCC control but still use analogue DC voltage to the track to control the trains in analogue mode, without damaging the R8247 controller?

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The R8247 port side is isolated from the DC operation as long as you follow the guidance given above regarding relays vs rotary switch wiring modification. However on the track side (DCC power input) of the R8247, the DCC input to the R8247 must not be connected to the DC supply connected to the track during DC Analogue operation.

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The R8247 comes with a DCC track power clip to connect to the track to pick up the DCC track power from the DCC controller. This clip (if used) must be removed from the track when operating the layout in DC Analogue mode. This also includes the DCC controller you are using. The track output of the controller and the track input to the decoder must not be allowed to come into contact with your DC analogue track supply.

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I would advise that these DCC and DC track feeds are fed through a DPDT change-over (break before make) switch. This would ensure that no DCC controller equipment (controller OR accessory decoder) can be inadvertently left connected to the track when operated in DC Analogue mode.

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Note how the R8247s are NOT wired directly to the track using the Hornby supplied power clips. They are 'hard wired' directly to the DCC controller 'TRACK A& B' output to simplify the change-over switching arrangement.

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The R8247s do however need to be temporarily connected directly (one at a time) to the DCC controller 'PROG A & B' output when being configured with their DCC addresses.

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One other important thing to note. If using DC Analogue R602 / R8206 Hornby track power clips / power tracks. These are NOT compatible with DCC data signals and will cause no end of issues if you leave them in circuit when using DCC. They must either be replaced with the R8241 / R8242 DCC versions. Or modified to make them DCC friendly. Once modified for DCC working, the power connections are perfectly OK to use on DC Analogue. The DCC modification involves opening up the track connectors and removing the internal suppression capacitor....see photo below. This mod must also be done on your DCC programming track piece as well.

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TIP: As this is your very first post, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

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Particularly as my reply includes an image. If you use the blue button, any reply you write, may be held back for image approval. Even though it is already a previously published image.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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[Chrissaf]

I currently have an analogue railway system that I intend to convert to digital using the Hornby Elite. All my engines are now fitted with DCC decoders, ready for DCC conversion of the layout, but are still able to run from the analogue 16v DC controller. I have Gaugemaster solenoid driven points on the layout controlled by (passing) switches from a 19v DC supply (I currently use a Fleischmann mimic layout with built in switches for the point control). I intend to use the Hornby R8247 accessory controller for the points but also want to retain the mimic DC switch control as my 6 year old grandson finds that easy, quick and simple to use. 2, questions:

1. Can I still switch the points with the analogue DC switches when the R8247 accessory controller is also wired to the solenoids and powered up (but not being used at the same time !) without damaging the R8247 controller ?

2. Can I have the R8247 controller wired up to the track (and solenoids - see above), ready for DCC control but still use analogue DC voltage to the track to control the trains in analogue mode, without damaging the R8247 controller ? (as I would like to wire them up now ready for DCC control in the near future and my 4 year old grandson will find it much easier using the old DC control of one train at a time, even when the DCC controller is fitted, until he is old enough to use the DCC system)

[96RAF]

While Chris is preparing his diagram, here is one way of doing it.

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[Jacov]

Very many thanks. Fortunately I am a control and systems engineer and have done extensive work on the full size railway signal and control systems, so this layout is a relatively minor exercise (at least it was when I started !!!).

 

I will go with the relay option. I already use some very small relay switches designed for model railway layouts (Gaugemaster GM500D double pole, self latching, DCC friendly) in parallel with the point solenoids (i.e. they are operated by the same signal that controls the points) in order to switch a 12v supply to the various signal lights on the layout that show the position of the points. They cost £6 each and I have 11 points to manage (i.e. I will need 3 R8247 units) so it will not be too expensive and gives the best option as wiring and wiring changes are minimised.

 

I was already intending to put a double pole isolation switch (mounted on the front face of the railway layout for easy access and use) in the 2 supply lines between each of the accessory controllers and the track connector so that I can separately switch off and isolate each/all controllers in order to have just one connected at a time when I am programming them (I assume that they can be programmed from the main track connection TRACK A/B and I don't have to specifically connect each one to the program connector PROG A/B). The 3 switches will now also serve the purpose of isolating and protecting the accessory controllers when I use the analogue DC track control.

 

I have built-in sockets on the track layout board to plug the cables in from either of the controllers (DCC or analogue - the train control socket is the same one for both controllers so that only one controller can be used at a time, so I don't need a changeover switch between controllers) and for the signal lights and point solenoids power supplies, so changing over between the controllers (depending on which grandson wants to use the railway) is fairly easy. The points are not internally electrically connected, so that when switched in analogue mode one railway line or the other is isolated, so that the only train that will respond is the one for which the points are set (we have 5 trains, which are Thomas the Tank and Friends and each lives in its own siding). However, all the siding and branch lines are are wired up via a multi contact isolating switch to the main loop so that all the rail lines can be connected together when in DCC mode, so that the DCC controller can power and talk to the whole layout.

[96RAF]

I use simple 12v car headlight flasher SPST relays at around £3 each. Quite bulky but not had a single failure of the 32 in use for the past 15 years. Same thing goes for the qty three 2-pole x 6-way rotary switches, although I had my doubts about their reliability for the task when I bought them - again totally unfounded though.

 

A point of note the acc decoder only needs to be set on pulse as this is long enough for the relay coil to pull in and deliver the CDU charge through the main contacts. The relay then drops out to standby allowing the CDU to recharge. My set up will easily set a route of 6 points rapid firing in turn - its quite satisfying to hear the music as they all go over in sequence.

 

I have been thinking of going over to solid state relays to bring the bulk of the relay panel down, but their failure mode seems to be to ON so maybe have to wait for the old panel to die.

[Chrissaf]

The GM500D relays are not going to be suitable to use as relays shown in my previously documented 'relay option'.

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The GM relays are 'Latching Relays'. You need a relay where the operating make contacts are 'Momentary Action'. Thus you need 2 wire coiled relays and not the 3 wire coiled relays that GM use. Using 2 wire coiled relays means that two relays per port are needed as shown in my drawing.

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These are my 'home made DIY relay boards' that I am using on my layout for a similar task. I eventually found 12 volt relays whose pins pitch were the same as standard Vero copper strip board (not all relays have this pin pitch and relays compatible with Vero strip board pin spacing are difficult to find). These RZ03 relays were £1.30 each from Rapid online, but are now discontinued on the Rapid online catalogue. To fit standard copper strip board, you need to find relays that have a pin spacing that is a multiple of 2.5mm. Sometimes referred to in the relay spec sheet as 5mm pitch...this is an unusual pitch for PCB mounted relays...they are more typically 3.5mm.

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EDIT:

Farnells currently have these RZ03 5mm pitch relays with 12 VDC coils in stock at about £2 each (price varies with quantity ordered).

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I assume that they can be programmed from the main track connection TRACK A/B and I don't have to specifically connect each one to the program connector PROG A/B).

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This assumption is incorrect. The Hornby R8247 Accessory Decoders are old technology and do not support programming on the main. They can only be programmed on the 'PROG A&B' output using 'Direct Mode' programming. Something I did highlight in my previous reply....see extract replicated below:

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You are of course at total liberty to use a non Hornby brand Accessory Decoder, Nearly all the other brands are 'self learning' decoders and can be programmed when connected to the main track output.

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Then there is the Arduino option. There are well documented projects on the net with all the necessary software freely downloadable that can turn an Arduino board into a DCC Accessory Decoder and interface with a commercially available Arduino relay shield board. Search for "rudysmodelrailway" for details. I built Rudy's Arduino based DCC Sniffer with no prior Arduino programming experience and it worked first time.

 

[96RAF]

Can I just point out that in analogue  mode you must arrange for the R8247s to be disconnected from the main.  The easiest way to do this is to connect them directly with the Elite rather than via the track. 

 

I might also add that your day job skills probably won't help that much with model railways. 

[Jacov]

Many thanks to everyone for the additional help. I realised after I had posted my last reply that the Gaugemaster relay was not suitable due to its latching on, which would permanently power the point solenoid and probably burn it out. Thanks to RAF96 and Chrissaf for the help on suitable relays.

 

I have a short programming track on the layout, connected to the PROG A/B and will arrange switching so that I can connect each R8247 accessory controllers to it, one at a time (probably using a 2-pole 3-position toggle switch on the track connection side of each controller that can

A - connect the controller to the main track

B - connect the controller to the programming track

C - isolate the controller (when in analogue DC use)

[96RAF]

I use the same DPDT isolation switching method to connect my rolling road to either the Prog or Track outputs of my controller. The centre OFF ensures there is a dead spot between the two ONs.

[96RAF]

In contrast to Chris’s more compact relay panel, this is mine. One R8247 missing - off board for testing purposes.

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The other side mounts the CDU and terminal boards.

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[Jacov]

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This is my version of the relay unit to buffer the Accessory Controller. The relay is a 6A SPST-NO (single pole, single throw, normally open) Non-Latching Relay 12V DC Coil AgSnO2 V23092-A1012-A302 (shown with standard 5mm pitch Vero board) and is available for about £2 each on Ebay. The 3-hole plugs on the left connect to the 3 sockets on each of the 4 accessory control outputs of the R8247 and the 2-hole plug (numbered 1 and 2) on the right connects to the left and right coils of the point motor drive unit with a centre common for all 4 point motors connected to the centre of the 3-plug unit on the right (marked C).

 

[Jacov]

The 2-lead input to my 3 R8247 accessory controllers are connected to switches that separately connect each controller either to the main track (for digital running), the programming track (to set up and program each controller) or OFF (to isolate and protect the controller when running in analogue (DC) mode). The pictures show the 3 switches as they will be mounted on the layout board with the protective cover to ensure that the switch toggle is not accidently moved, especially when running in DC mode - to protect the accessory unit from damage.

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[Chrissaf]

Nice eBay find. Based upon the size, shape and encapsulation, I would expect that internally they are based on a 'reed' switch, but this is just an assumption.

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Should somebody else want to source these relays, then here are an eBay selection. The selection I found however, do not seem to match the price point Jacov stated.

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Jacov, if you still have the link to the exact ones you sourced cheaper then there is no issue posting it back here.

[96RAF]

6A at 240vAC.

I leave the big sums guys to work out if they will be OK for CDU surge current at 12-15v DC

[Chrissaf]

The only thing I added to my relay board that Jacov has not..... just to be 'belt n braces' was the inclusion of 0.1uF spark quench capacitors wired directly across the relay 'make' contacts. After 6 years I have not had to replace any relays because contacts have welded together.....the caps help with preventing that.

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[Jacov]

The relays are here

12v relay on Ebay

https://www.ebay.co.uk/itm/6A-SPST-NO-Non-Latching-Relay-12V-dc-Coil-AgSnO2-V23092-A1012-A302-Multi-Qty/302843936077?ssPageName=STRK%3AMEBIDX%3AIT&var=601746716555&_trksid=p2057872.m2749.l2649

£10.99 pack of 5

The following pictures show the actual layout - n gauge Thomas the Tank and Friends (except the BR Diesel which is used to pull the track cleaning car round the system and therefore needs a more powerful motor than the Thomas trains). Its shown in its current analogue/DC mode, with  Fleischman active mimic to control the points (which I will be keeping when converting to DCC as my young grandsons find it easier and quicker to use than working through the digital options). The baseboard has foldable legs underneath so that it can be easily stored. All the buildings are just placed on the board when in use, they are not fixed, so the board profile is small for storage. The DCC controller will go where the current DC controller is sitting and will plug into the same sockets

. Near the centre (above the station) is the short programming track, which also plugs into the Hornby DCC unit

You can also see all the ground level signal lights that change their aspect (i.e. colour) as the various points switch over. Some of the track sections are isolated and fed via the point control relays to stop a train approaching points that are set against it, to prevent the train being derailed !!

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[Jacov]

Chrissaf - Am I correct in assuming that would mean 8 capacitors, each one wired across the relay output (i.e. the side connecting the power to the point motor coils) of the 8 relays on each of my boards.

What is the technical spec of the capacitors and where did you get yours from please?

[Chrissaf]

Am I correct in assuming that would mean 8 capacitors, ..................

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Yes....connected across the output 'make contacts' of the 8 relays.

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What is the technical spec ............?

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Any general purpose 0.1uF Ceramic capacitor with 50 volt rating or above. As examples, this could be Ceramic Disc or Ceramic Resin Bead. I prefer the 'Resin Bead' myself.

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These are the actual ones that you can see in my relay board photo and where I got them from.

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[Jacov]

Many thanks Chrissaf - same capacitors ordered from your source and will be soldered underneath on the boards across the relay outputs (there is a small space that they will fit in between the pins ! )

[Flashbang]

Just to mention... There are accessory decoders available that  ..  A) Do not necessarily take power from the DCC system, leaving that to run the trains. and ..   B) Can have DCC operation and Push Button/Momentary toggle switch operation too, which is IMO the same as using DC (via switches) and DCC (via the DCC console or PC).  One make in particular has a CDU for each output which ensures it is always ready for any route setting etc or rapid sequential operation and unlike the R8247 you don't have to wait for the single CDU shared by all four outputs to recharge. That make is now available in 2, 4 and 8 way output ports.   No need for relays or a separate CDU etc then!

 

So IMO it is always worth looking at what you want the accessory decoder to do operation wise and then look around at what is available.  😀

[Chrissaf]

I suspect that you are very similar to me in that you get more enjoyment from designing and building the control aspects of a layout than actually playing trains.

[Jacov]

Relay board modified to include the spark quench capacitors across the relay outputs

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(Chrissaf - you hit the nail squarely on the head !!)

[Jacov]

I am currently designing a new 00 gauge Thomas and Friends layout for my grandsons, which will be all digital, but I still want to use the Fleischman mimic panel with its (analogue/DC) point control switches. I have just discovered that the Train-Tech PC2 quad point decoder can do this. The decoder is similar to the Hornby accessory controller and is compatible with the Hornby DCC, except it can only be used for point control or other momentary signal devices as its output is only pulsed and it cannot give a permanent output (e.g. to power signal lights). Its main advantage is that each of the 4 channels have an additional 3-pin connection on the decoder box that can be connected to a passing connection switch (i.e. the analogue/DC switch used to control points on the old analogue layout - such as the switches in the Fleischman mimic setup) which overrides the DCC setting but still moves the points via the controller, hence eliminating the need for a separate DC power source and the relay interface discussed above..This allows me to use both DCC and analogue control of the points, making it easier for my grandsons to control the many points on the new layout.