Turntable,points and signals

[Spireitedave]

Hi I have recently moved and left my old analogue layout behind,I am in the process of building a new layout 17'x 4'.Initially this will be analogue as I have a few bits that I salvaged from my old layout.However I am fitting dropper Wires for a subsequent DCC conversion.....I have picked up the basics on here.

I would like to have a maximum of 3 locos running at any time .However then I would like a Hornby Turntable, 10 sets of motorised (surface motor) points and 8 colour light signals but operated on the Hornby yellow,black and green lever frames.......from a separate power source.

1) Could I operate the lever frames with one common return ( the wire that plugs into the end of the block of levers)

2) What is a CDU I keep seeing mentioned and would I need one ?

 

For clarification I envisage using a Hornby Elite for the DCC side and an old analogue controller non controlled output for the accessories.

[2e0dtoeric]

A CDU - Capacitor Discharge Unit - is a simple way of giving solenoid-type point motors a good kick, to make sure they go full-travel, but at the same time, cannot cause them to overheat and burn out, as can happen with a simple switch. You only need one CDU, no matter how many point motors you have.

Do NOT use the Hornby point switch with them, (I don't recall the R number) there are known problems with it failing. You can use the other methods, pointer and stud, or sprung-centre-off toggles to operate them.

You can use the permanently-on swtches with the light signals, but check whether they are bulb lights, or led. Bulbs use a lot more power than led's, will work when wired either way around, and can get very hot - but led's will not, they only work with the wiring one way, stay cool,  and there should also be a resistor in the wiring for the led's, to keep the current flow reduced.

As you now have separate power supplies for points and signals, you cannot use one common return wire for all.

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You MUST keep dc and DCC circuitry totally isolated from each other and you must not try to run dc loco's using a DCC controller, even though the instructions with the controller say you can. You will very quickly destroy the motors. With the DCC FITTED loco's, they can run on a dc track, unless you have disabled dc running on one of the CV's.This gets mentioned every day or so, in different threads!

DCC READY loco's are dc loco's fitted with a socket ready to accept a decoder. They do not have the decoder in them!

Do not try to have dc and DCC controllers both connected to the track at the same time. You will probably get smoke and a big repair bill!

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Turntable - again there are loads of answers to this query. You can operate it via a decoder and your DCC controller, or you can keep the turning function controlled by your dc one. That bit is easy. Where the difficulty lies is in the track-bed on the t/table, and if not modified slightly, this can lead to all kinds of error messages!

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Before you go any further with anything, read Chrissaf's guide with the misleading title about track extension packs, in the very top of the General thread. You will find answers to most of your queries in that.

[Spireitedave]

Thank you on further reading it seems that the RO70 turntable is best fitted with a loco decoder and operated via the Elite controller.

I intend starting afresh with DCC fitted locos my remaining analogue locos are in the main older and will simply become cabinet exhibition pieces.

 

[Chrissaf]

is best fitted with a loco decoder and operated via the Elite controller.

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That's not strictly accurate. See these two previous posts which are the combined thoughts of the forum members on the conversion and operation of the R070 TT.

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Physical modification of TT for DCC

http://www.hornby.com/uk-en/forum/r070-hornby-turn-table-to-dcc-including-images/?p=1

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Configuration of RailMaster / eLink & RailMaster / Elite to operate R070

http://www.hornby.com/uk-en/forum/r070-turntable-configuration-in-railmaster/?p=1

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[Spireitedave]

Thank you for your guidance again.I have printed off Chrissaf's guide and this certainly helps.

My old layout was built 25 years ago and I had numerous points controlled by Black Hornby lever frames, obviously these were "old" style point motors on older track.If I understand you correctly the new Hornby motors need "sprung centre off toggles" which are readily available and the circuit should include a CDU.

My old layout had some Hornby Colour light signals and I imagine these are classed as lamps rather than LED.Now I think back they were on a separate power source o the points.Would I be correct in assuming commercially available LED signals would include a resistor ?

[Chrissaf]

 Would I be correct in assuming commercially available LED signals would include a resistor ?

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Yes...all LEDs should have a resistor in series with them to limit the current to protect the LED from damage. The one exception to this is when you build a 'constant current' driver circuit to control the current to a LED. This is how many commercial LED driver power supplies work. Constant current driver circuits can be built easily by an experienced electronics constructor, but a simple resistor solution is easy and cheap to implement and needs very little skill in electronics design. Commercial LED products for railways such as LED signals and street lighting etc usually always include a suitable resistor with the product. Either built in and integrated into the product, or supplied separately in the packaging for the user to install.

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My old layout had some Hornby Colour light signals and I imagine these are classed as lamps rather than LED

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The original Hornby R406 dual aspect signals indeed did have incandescent bulbs in them with all the issues that bulbs have (power consumption, heat and shortened life expectancy). The current batch of these Hornby brand signals still have the same R406 stock code number but have been updated by Hornby to replace the bulbs with 5mm LEDs. The style of these signals are in my view oversized in scale and 'Toy Like' in appearance. There are quite a few online model railway lighting specialists making and selling very realistic LED based signal products. I use products by "CRSignals" and "Layout4U".

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Black Hornby lever frames, obviously these were "old" style point motors on older track.If I understand you correctly the new Hornby motors need "sprung centre off toggles" which are readily available and the circuit should include a CDU.

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In my view implementing a CDU either externally when manually controlled by a switch or when integrated into an Accessory Decoder under DCC control should be mandatory, or at the very least desirable. The Hornby Black R044 lever switches have not been updated in internal operation design for decades and have operational issues when used with a CDU, hence the recommendation to use an alternative  switch type with a CDU. Yes you can use a standard electrical toggle switch that has a centre off and is a non locking changeover, but if you prefer the lever style of switch that looks similar to a Hornby black lever switch then you can use the more up to date Peco PL-26 range of switches that are totally compatible with a CDU.

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Just to reiterate. When solenoid points are operated by an Accessory Decoder via DCC control. The Accessory Decoders usually include a CDU circuit inside them to provide the high current kick required by the point solenoid. This almost becomes a mandatory manufacturer design inclusion requirement because the point operating voltage created from the DCC line voltage is borderline (a bit too low) in terms of operating a solenoid point motor robustly. Accessory Decoders that do not have an integrated CDU in them usually compensate for this by having an alternative external power supply input capability where a higher than DCC voltage can be provided from a separate external power supply. Such a decoder with the dual power option is the ESU Switch Pilot  Accessory Decoder and does not include a CDU within it.

 

[Spireitedave]

Thank you very much.I think I am up to speed now.No doubt I shall have more queries as I progress.

[Chrissaf]

 EDIT - Should have been "Layouts4U" not "Layout4U" in my last reply.

[Spireitedave]

I intend using Hornby surface mounted point motors and I understand the choice of Peco or equivalent switches and a CDU.I have noticed that Gaugemaster make a PCU1 point controller unit but that it is nominally rated at 24 volts  - is this too high ? Has anyone used one ?

 

Secondly probably answered my own question but when changing my layout over to DCC and using a bus wire to all lines then I assume the Hornby point clips are not required.Assume they are only required if no bus wire fitted.

[Chrissaf]

Re: PCU1, the installation guide also says 24V at 1 amp max. Solenoid point motors require a lot of current. For current read power. So 1 amp at 24 volts is 24 watts but so is 2 amp at 12V equal to 24 watts. Watts = current x voltage. The voltage output of the PCU1 is a high voltage to compensate for its lower than ideal current output. As the PCU1 has an internal power supply, a power supply at a lower current rating is a far cheaper component for Gaugemaster to use in its construction than a higher current power supply. 24V is at the upper end of Solenoid coil ratings. The tech spec for the PCU1 also states that it has an internal CDU, so unless the PCU1 goes faulty, the Solenoid point motors should be adequately protected by the PCU1 from being over-heated. That is one of the benefits of using a CDU (Capacitor Discharge Unit). At the end of the day, Gaugemaster have designed the PCU1 to operate Solenoid point motors, so one must assume they know what they are doing with the technical specifications.

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Re: clips, you are correct in that if you have implemented a Bus to all parts of the layout. The Bus circumnavigates the need for the clips. However, it can be useful to leave the clips in situ. The reason being, is that the clips connect the fixed rail track power to the moving switch rails. Without the clips, the power would be totally reliant upon the side contact pressure of CLEAN fixed (stock) and moving (switch) rails.

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PS - I run my Solenoid points at 22V without issue. I built my own DIY equivalent of the PCU1 from individual components.

[Spireitedave]

Once again Chrisaff thank you so much for your help.I will use the 16 v AC output from my old controller for connecting the CDU and point motors using Peco switches.

 

 

I know I am very much "old school" but as my layout is in the garage I am most careful to ensure after use the mains power input is not only switched off but also unplugged.I am sure you agree this is sensible practice experience especially as I graduate to DCC with its higher power usage .

My latest query given the above is that the CDU "stores" a considerable electrical charge is this stored after mains disconnection in a similar fashion to a battery or does it degrade .

[96RAF]

Yes a CDU stores energy but once you have powered down, just flip a point or two to discharge it.

Rob

[Chrissaf]

It depends upon the design of the CDU circuit, many CDU's will include a discharge path for the capacitors once the input power is removed. But even if they don't, the charge on the capacitors will degrade over time due to internal capacitor leakages.

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It is easy to test to see if the CDU design is self discharging. Power it up, power it down, wait 30 seconds, then try to throw a point. If nothing happens, then the CDU has an inbuilt discharge path for the caps.

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The reason for the 30 second wait, is that the power supply that is providing the power to the CDU may have some smoothing capacitance (if DC) that is also holding a charge, so not only is the CDU discharge circuit, discharging the internal CDU capacitor, it has to discharge the power supply capacitors as well.