Hornby points

[bill s]

I'm new to rail modelling. I've started on a dcc layout and like what I've done to date. I've purchased two sets of Hornby point motors with the corresponding lever switches to operate them. I tried connecting them into the ac output of my dcc Prodigy Express controller but they don't seem to operate with this set up. 

Do the points operate on ac or dc? Secondly, do I need a separate power unit for them?  These basic questions will probably have been asked before but despite searching the forum I can't find any answers to the above problem. I've come across the acronym CDU quite a bit.......does this refer to a control unit for the point motors? I live many miles from any retailer so find asking folk direct a problem.  Many thanks for any info to help me.............regards.

[Dungrange]

CDU stands for Capacitor Discharge Unit, which is a device that stores electrical charge in a number of Capacitors.  When the points are switched, the units discharge and provide additional power to throw a number of point motors.  If you are just throwing a single point, then you probably don't need a CDU, but if you were to set a route and throw several points at the same time, then a CDU would probably be recommended.

 

Unfortunately, as I have neither a Prodigy Express controller or Hornby point motors, I can't definitely answer your other queries.   However, if the Hornby point motors are these http://www.Hornby.com/uk-en/surface-mounted-point-motor.html (ie R8243) the specification states that these are DC.  As such, it is probably not surprising that they don't work when connected to an AC output.  You will therefore either need a separate controller with a DC output or fit a bridge rectifier (four diodes) between the AC output and the point motors to convert AC to DC.  However, this would be pulsed DC and it may also be necessary to fit capacitors to the circuit to smooth the voltage.

[bill s]

CDU stands for Capacitor Discharge Unit, which is a device that stores electrical charge in a number of Capacitors.  When the points are switched, the units discharge and provide additional power to throw a number of point motors.  If you are just throwing a single point, then you probably don't need a CDU, but if you were to set a route and throw several points at the same time, then a CDU would probably be recommended.

 

Unfortunately, as I have neither a Prodigy Express controller or Hornby point motors, I can't definitely answer your other queries.   However, if the Hornby point motors are these http://www.Hornby.com/uk-en/surface-mounted-point-motor.html (ie R8243) the specification states that these are DC.  As such, it is probably not surprising that they don't work when connected to an AC output.  You will therefore either need a separate controller with a DC output or fit a bridge rectifier (four diodes) between the AC output and the point motors to convert AC to DC.  However, this would be pulsed DC and it may also be necessary to fit capacitors to the circuit to smooth the voltage.

Thanks for your reply Dungrange (David?). It says in the blurb it can be used with digital connector r8216/accessory decoder or dc. I'll try a dc controller which I assume will supply the necessary voltage. Thanks for informing me what CDU stands for. I'll try & get at least one point working B4 obtaining a CDU but will get one once I'm up & running. Thanks again. Any other comments welcome! Sorry to be so basic but reading other topics on the forum everyone is very helpful to new comers! It's a big learning curve for me..............

 

[Dungrange]

The R8216 Accessory decoder is to allow the point motors to be controlled by your DCC controller (ie you can give each point an address, just like the locomotives) and then use your Prodigy Express controller in place of switches.  I think that this unit just takes its power from the track, but I've no idea how it compares to other accessory decoders on the market.  However, if you want an analogue set up with switches, then you'll need a DC power supply with the switches wired in series with the point motors.

 

Good luck and I think you will find plenty of helpful people on RMWeb - I've had dozens of questions answered by others.  Every day is a day for learning.

[bill s]

Hi David  -  thanks again for your reply.  I see from the Hornby web site that the R8216 has been replaced with the R8247. According to the blurb this unit allows up to four point motors to be operated on DCC layouts.  Doesn't say how one connects it into an existing layout controller (like my Prodigy Express). 

[Grovenor]

The accessory decoder just connects to the track and gets its commands the same way the locos do. No need to do anything to the Prodigy.

Personally I think its better to keep the point control seperate from the train control.

Regards

[Dungrange]

My understanding of these units is that they take their power from the track as well as the DCC signal to operate them.  As such, I think there should be ten wires coming out of the unit, one pair going to the track and one pair to each of four point motors that are top be controlled from the decoder.  As such, I don't think that there is necessarily a connection directly to the layout controller.  However, on larger layouts with a lot of points, I understand that the current draw from operating accessories can use enough of the systems current to cause locomotives to slow.  However, this is probably only an issue when operating several locomotives at once and perhaps throwing multiple points simultaneously.  However, under such circumstances, I gather it is better to set up the accessories in a different power district or sub-district.  However, if you are likely to go down that route, you'd be better posting in the DCC part of the forum (since your issue isn't really the track).

[bill s]

David & Keith  -  thanks for your replies. I'm beginning to understand this a bit better now. 

One downside I can see would be the need for more controllers for four or more points which would be common on layouts. I think you're right David, any further queries on taking this further should be in the digital section. Thanks once again.............

[cpman46]

 

I'm new to rail modelling. I've started on a dcc layout and like what I've done to date. I've purchased two sets of Hornby point motors with the corresponding lever switches to operate them.

 

Snipped this from the Hornby site:

'Designed to be positioned either side of any Hornby point, this surface mounted point motor allows for the convenient electrical operation of points.  Can be be used with the Hornby R8216 Digital Point / Accessory decoder or for DC analogue operation, the R044 Lever Switch.'

 

Note the dc analogue notation. The switch is a passing contact one which suggests the point motors can be used with a 16V ac (not DCC) supply (i.e. a transformer with a 16V output or a controller with a 16V fixed output) and with or without a CDU as required.

 

Personally I agree with Grovenor, keep the point control separate from train control.

[Dungrange]

Snipped this from the Hornby site:

'Designed to be positioned either side of any Hornby point, this surface mounted point motor allows for the convenient electrical operation of points.  Can be be used with the Hornby R8216 Digital Point / Accessory decoder or for DC analogue operation, the R044 Lever Switch.'

 

Note the dc analogue notation. The switch is a passing contact one which suggests the point motors can be used with a 16V ac (not DCC) supply (i.e. a transformer with a 16V output or a controller with a 16V fixed output) and with or without a CDU as required.

 

Personally I agree with Grovenor, keep the point control separate from train control.

 

DC (Direct Current) and AC (Alternating Current) are both forms of analogue control (ie by varying the voltage rather than conveying a digital signal), but are quite different in practice.  The lever switch is no use for controlling points via the DCC (Digital Command Control) controller.  However, with Direct Current (DC), there will be a constant voltage difference difference between the two terminals, whereas with Alternating Current (AC), the voltage varies between plus and minus the stated voltage around 50 times per second (since mains power is usually supplied at 50 Hertz).  That is, the + and - terminals are constantly switching and it will usually have a sine waveform.  Whilst you can get electric motors that work with AC, I think solenoid type point motors only work with DC (but not DCC unless using an accessory decoder).  This means that you can't use the 16V AC terminal and why the DC analogue (as opposed to AC analogue) notation is important.

[Dungrange]

One downside I can see would be the need for more controllers for four or more points which would be common on layouts. 

 

Yes, on a large layout, you would need several accessory decoders.  These are broadly speaking the same as the decoders in the locomotives.  Whilst you will have a locomotive decoder in every locomotive, you would have an accessory decoder for every four points, although I think another manufacturer produces versions that can handle six points.

 

As Keith and Mike have said, I'd be inclined to keep point control separate (I've heard many say that), primarily because I'm not keen on the methods for changing points on some DCC controllers (ie selecting point 56 or whatever and changing it and then selecting whatever else you want to change).  A set of switches seems more intuitive to me.

[smokebox]

Solenoid point motors work perfectly well with AC. 16v AC is or was the norm.

[RailWest]

Solenoid point motors work perfectly well with AC. 16v AC is or was the norm.

I would agree. This does seem to be a case where 'analogue' and 'DC' are getting confused.

 

Let's go back to basics and, if the OP will excuse me, ask a few 'idiot questions' :-)

 

1. Have you tested your power unit to make sure that it is actually putting out power on the AC outlet? If so, what voltage are you getting out?

2. Were you trying to operate more than one point motor simultaneously? If so, have you tried it with just one?

3. Are the switches which you are using passing-contact or permanent contact (ie two-way)? I am assuming the former, as if the latter then I would expect a nice burning smell by now from your motors!

4. Are you sure that you've wired it all up correctly? Sorry, but one does have to ask.....:-)

[cpman46]

I would agree. This does seem to be a case where 'analogue' and 'DC' are getting confused.

 

Let's go back to basics and, if the OP will excuse me, ask a few 'idiot questions' :-)

 

1. Have you tested your power unit to make sure that it is actually putting out power on the AC outlet? If so, what voltage are you getting out?

2. Were you trying to operate more than one point motor simultaneously? If so, have you tried it with just one?

3. Are the switches which you are using passing-contact or permanent contact (ie two-way)? I am assuming the former, as if the latter then I would expect a nice burning smell by now from your motors!

4. Are you sure that you've wired it all up correctly? Sorry, but one does have to ask.....:-)

If you look at the OP he is using a Prodigy Express DCC Controller. This has no conventional 16V ac outlet, only connections for the programming track and main track. The outputs are a DCC ac waveform not a conventional 50Hz sinewave. You cannot connect the Hornby point motor directly to either output. It need to be driven from an accessory controller as previously mentioned and then controlled from the Prodigy Express not switches.

The OP has purchased the point motors and passing contact switches and therefore my suggestion that he runs them from a conventional transformer outputting 16V ac (NOT DCC) still stands.

[bill s]

Hey Guys  -   thanks all for your various inputs. I now know I cannot connect the point motors directly to the Prodigy controller. I know I need a separate controller like to Hornby R8247.

I'll investigate what other makes/arrangements are available. Thanks again and will advise when I get it working.

[RailWest]

cpman46, on 03 May 2016 - 09:24, said:

If you look at the OP he is using a Prodigy Express DCC Controller. This has no conventional 16V ac outlet, only connections for the programming track and main ......

Ah - all is clear now

[bill s]

Hello again guys  -  firstly thanks for all your various inputs to my initial queries. I'm pleased to say I have now succeeded in wiring and operating Hornby point motors on my layout!       The Prodigy Express doesn't allow accessory operation - well perhaps some limited ones but not my points. I obtained an NCE unit which seems to allow lots of accessory actions. Also fitted 4-way point accessory units with I believe CDUs in them.

These I wired up to the 'bus' power line and all the points work fine via the handset controller (hope you're following this).   

It's a big learning curve for me but I'm getting there. I'm particularly enjoying the modelling part of the hobby................will move onto the DCC section of the forum to find out about decoders in the engine. Would like a Britannia class engine with a wide selection of sound efx - but that's another story!

Thanks again!