Point Motors and Signals with R8247

[am549]

Hi All

I'm about to start wiring up my layout (it's taken a while to find the time to build it and now I'm more or less settled can hopefully push on) and have a couple of questions about the possibility of linking signals (such as the R406) to change as the point motors fire via the R8247

I have seen a couple of posts mention this and the need for a "latching relay" but it seems the accompanying diagrams aren't present.

How easy is the above to achieve and will I need to go out and purchase a soldering iron to do so or are there any kits available which can achieve the above? Are there any resources available which could help me better understand this?

Thanks

[96RAF]

Page 17 of the R8247 v2.0 user manual.

There is another way in that you have a pair of R8247s with the same addresses, one set up for points on pulse and the matching unit set up for always on for signals. Then when you throw the point the signal will also change.

If your R8247 is v2.0 then you could use the cascade feature and have the solenoid on one port and the matching signal on another port. Set the cascade so that when the solenoid port fires it triggers the signal port.

The v2.0 manual can be downloaded from the support section but it does make heavy reading to get your head round the special mode options.

[am549]

Thanks I had seen that diagram but it threw up a few more questions, mainly around a recommended latching relay (ideally one which I can just wire straight into with no soldering) and whether I could use the existing DCC bus for power?

[96RAF]

Generally single relays require soldered connections, but you can get single and multiple relay boards with screw terminals.

BCL Components for instance and other similar suppliers. Here are a few examples for you. BCL has some handy wiring diagrams as well.

https://www.bclstore.co.uk/product-page/bc218-relay-board-8-way-twin-coil-latching-relays-with-3-amp-spco-contacts

https://www.bclstore.co.uk/search-results?q=Latching+relays

https://www.esr.co.uk/shop/contents/en-uk/search.php?searchphrase=latching%20relay&start_page=1&searchFormSortBy=R-A&searchFormRootUse=A

You can take your power from the track bus but best advice is to run a separate accessory bus fed from a circuit breaker. Be aware that the accessory load deducts from total power leaving less for locos, so if you have very many points think about using a power district booster set up. Such schemes have been covered on the forum before.

[am549]

Thanks the BCL site is really useful with the diagrams. I'll have to knock my own diagram up to check I've got it correct. I'm hoping with it being DCC some of it will be a bit simpler for the inputs as there's no switch to contend with.

There's not loads of point motors on the layout, at this moment it's only the ones I can't reach which will have motors on (5 so far) but once I've got more time I suspect the front will also get some motors as well so 10 in total for the bottom fed from 2 R8247's.

I'll look at putting in an accessory bus for the lighting as I suspect they'll be quite a few signals going in. Looking at the diagrams it looks like I'd be able to have 2 signals per board which will be really useful with station and main line signalling (red for the line, green for the station and vice versa when switched).

Thanks for the help so far!

[96RAF]

The relays are change-over, hence each relay will support one two-aspect signal (green one way and red the other way). As they are latching you only need a pulse into the coils with the signals being lit from an external power supply via the relay main contacts.

This article I wrote may interest you as it looks at using multi-relay panels via an R8247 but with the added benefits of an external CDU. Apologies for the poor legibility of some of the diagram texts. I can post originals if required.

http://www.halton96th.org.uk/relay-module.html

[am549]

Yes I had come across your post during my searching last night which did highlight it all quite well!

The 5th picture here https://www.bclstore.co.uk/product-page/mr204-latching-switch lead me to believe that I could hook 2 signals up to a single relay (effectively replacing the CP indicator with another signal) which if the led's are wired correctly (if my logic follows) when one signal is green the other is red and when the relay triggered it reverses.

Hopefully I've understood that correctly...

I've ordered some of those switches and a power distribution module for a lighting bus. Just waiting for those to arrive with some ballast underlay mat and a couple of extra track pieces and can get it bolted down soon and finish the wiring.

[96RAF]

Yes you can use back to back leds or bi-colour leds as a red-green or green-red indicator. If using 3-legged leds they need to be common anode to work with direct DCC drive (e.g. R8247).

I built some to use as point position indicators driven by PL-13 switches from the point solenoids - see here for build info. These were common cathode leds.

http://www.halton96th.org.uk/article5.html

Yours could be driven by the change-over relay(s).

[am549]

I'm hoping the above is right.

I'm slightly confused as the point motor will come direct from the PAD (most diagrams have switches in which won't be needed here).

[RB51]

Correct am549, all images are held for moderation which doesn’t usually take very long. R-

[96RAF]

That is not going to work as drawn. You must keep the PAD output and the main contacts sides away from each other. Ignore the common 0v connections that Brimal has drawn.

The Pad terminals are oddly marked as + C - but C is positive common to all ports whereas + and - are not polarities as marked but floating negatives until command switched one way or tother when they become true negative.

Working from the MR204 manual you need to connect the C to 0v and + to C1 and - to C2. 0v here is being used as coils common per the Hornby diagram earlier.

Then run your signals through the relay main contacts (T1&T2). Depending upon if common anode or cathode - Run the leds common direct via a suitable resistor from either the pos or neg of your power supply (as applicable) and connect the colours to the latched change-over contacts (2&3). The common of the main contacts (1) goes back to your external power supply.

The solenoid if fired by the same port is simply connected in parallel with the relay coils. The solenoid pulse will activate the associated relay direction.

I have to go out this morning but will try to knock up a noddy diagram for you when I get back. Please confirm which signals you are using (R406 or bi-colour - common cathode or common anode).

[am549]

I've purchased these signals from Amazon and can confirm they have a common anode

https://smile.amazon.co.uk/dp/B07JNFDRDL/ref=cm_sw_r_cp_api_i_Q3K9GC8TEZRVPVH7KDZF?_encoding=UTF8&psc=1

[96RAF]

Just looking at the MR204 manual again and there appear to be diodes across the latching coils which means it is not directly suitable for use with a PAD as they will not ‘fire’ using a positive on the 0v terminal and a negative on the C1 or C2 terminals. Try it with a 9v battery briefly touching it to the relay connections. It may be as simple as reversing the diodes. I will ask Brimal.

Edit - this back from Brimal (BCL Store)...

We do a MR204p which has the diodes reversed for a common positive situation. These can be purchased on our web site.

https://www.bclstore.co.uk/product-page/mr204p-latching-switch-positive-common

The alternative is as you say to reverse all 3 Diodes.

The diodes used are 1N4004, which you can purchase on the web site part No:DD102

https://www.bclstore.co.uk/product-page/a-selection-of-diodes-rectifiers

[am549]

You are correct, it doesn't fire with positive on the 0v and negative on the relay connections.

Looks like I should have ordered this version

https://www.bclstore.co.uk/product-page/mr204p-latching-switch-positive-common

[96RAF]

See my edited post above. If you can solder reverse the diodes or request a return and reorder from Andrew - direct email andrew@brimal.co.uk He is as you can see aware of the situation.

[am549]

Unfortunately I don't own a soldering iron so a swap will be needed.

I've updated my diagram so hopefully this is now correct

[am549]

I've also got a spare hornby power supply kicking around (the one that came with the out of box controller, 19v @500ma I believe).

Would this be suitable for running the accessory bus off? I suspect it'll just be for signals for the immediate/medium term.

[96RAF]

The signals are common anode so you need to swap your red and black wires over at the Aux Power supply. The relay will then be switching the negatives and returning them back to the Aux neg.

Note also that Hornby point motors have black as common positive with red and green as the direction negatives, so you need to swap your red and black here as well.

Your power supply will be OK if the output is DC - see the label. DC is a dotted line with a solid line. AC is a wavy line. I would also use another 1K resistor in series as they may be a tad bright on 19v with a single resistor.

[am549]

Hopefully this is right now. Confused me slightly as the anode cable on the signals is black and not red.

[96RAF]

Hi

I have just realised (from your earlier link to the product) that your signals as provided are wired with black as the common positive and red-green are the lights negative, not blue, brown and red as drawn.

To accord with your signal lamps the red wires from lamps go to the relay number 2 terminals, the green wires go to the relay number 3 terminals and the black wires go to your red choc block. This may seem all backwards but that is the way these folk wire things contra conventional wiring circuit colours.

The lamps circuit then is Aux power positive (red) to chock block, via each 1K resistor to lamps black. Lamps red to relay 2 terminals, with lamps green to relay 3 terminals. Relay 1 terminals back to the Aux negative.

Sorry I should have said swap black and green colours at the point motor not the wires (not black and red as stated) so your drawing should be motor common (black) to R8247 C connection and relay coil 0v. Motor directional (red and green) to R8247 + and - connections and relay coil C1 and C2 respectively.

If either the lamps and/or the point motor fire the wrong way then simply swap red and green wires for the odd man out.

We are nearly there.

[am549]

Amazing Rob

Thanks so much for all your help with this. I just need to get the MR204p instead of the MR204 and we should be in business

[96RAF]

I am sure Andrew will credit you against supply of the ‘p’ version. I have always found him a great guy to deal with.

I am sorry it took so long to get to the end game by iteration and that my diagrams are not a patch on those Chris would have provided, but it should work.

[am549]

They're legible which is the main thing and more than helpful given the time you've already spent in explaining it all. How do I sent you a beer?

Probably worth investing in a soldering iron longer term I suspect so can make these things up (and relearn to solder!). Time to hunt for an occasional soldering iron...

[96RAF]

Soldering - there you go - https://uk.hornby.com/community/forum/faq-how-to-solder-for-model-railways

[am549]

MR204P's arrived today, working perfectly in an isolated test (just the aux power and a 9v battery to switch the contacts). Also found a 12v 1.5amp power supply which I suspect will be much better than the 19v hornby one.

Got a few bits to sort on the board (mainly sticking some ballast underlay down) before getting the signals in and wired up with the point motors. Plan for the evenings this week (hopefully!)