DC controllers for points

[5113GBAK]

I have a Gauge master controller for my train.  I connect it to the mains via a transformer.  It's output claims to be 12 volts and I have no reason to doubt it.  The controller also has a separate out put position for 16 volts for the point motors.  As the controller output is 12 volts, logic would suggest it wont power a 16 volt point motor.  Am I right?
Thank you
Graham

[B.Meldon]

The usual power for solunoid point motors is 16v AC. (These are Peco PL10's and P1000's,  Gaugemaster Seep PM-1's etc.)
You need a monentary contact twoi way switch with a center off or two momentart contact press button switches. 
It is best through a capacitor discharge unit.
This will limit the power to the solunoid to a single quick pulse no mater how long you press the switch and not make the point motor buzz.

Obvioulsy if it is not a solunoid type point motor do let us know.

[Ian McAulay]

I use MTB MP1 point motors. They are actual motors not solenoids and will run on either AC or DC, taking very little current. For complicated reasons, I use DC on one of my modules and AC on others. (DC from 16V AC Gaugemaster power brick via RK Education DC power supply.) They are noticeably noisier on AC, probably because it's totally unsmoothed half-wave rectified AC via the internal diode. They take very little current either way.

Ian

[5113GBAK]

My question is, does a 12 volt input to the controller enable a 16 volt out put for the points?

[Hugh Norwood]

Firstly, you don't use the "12Vdc" output for point motors - as it is a variable d.c. power to drive the locos   {Note I may have mis-read your initial post here!}

The "16V ac" is a nominal a.c. voltage that most controllers use for their _input_ from transformers. (Internally it is converted to dc for the track power.

Point motors - is you are using the solenoid type (such as SEEP, PECO etc) {hey have a couple of electromagnet coils and alternately pull a metal armature one way or the other, which is used to change the points, then you can use either "16Vac" to drive them, PROVIDED you aply the voltage only for long enugh to throw the points. Prolonged application of power will burn out the point motor coils

The alternative (andbetter) way is to use the 16Vac to drive a CDU (Capacitor Discharge Unit) to power the point motors (once again a momentary application of power is enough, but at least CDUs will not short out the motors as they have built-in protection.

It woould be useful if you could say what sort of transformer you are using - is it perhaps a Gaugemaster unit - if so, could you say what its model number is, please? It would help me to say if the transformer would do the job. (I think it probably would, but it would be nice to have a bit more info.


Of course, you could just try experimanting! - Just heed my warning about aplying power to a point motor for too long...

Hope this helps

[Hugh Norwood]

PS which model Gaugemaster controller is it, please?

[5113GBAK]

All sounding very good.  So to continue, the controller is  Gaugemaster hand held Combi controller.  My interest is in where do I get the required 16 volts from?  The controller has a socket called 'Input' but I cant remember if the controller came with a transformer or whether I was expected to supply my own.  I have a second transformer and it says on it,  PRI.:230-240VAC, and SEC.:16VACMax 17VA, is this what I need?

[Graeme Dunbar]

Hugh got there before I did! I went upstairs to measure the output of the 'wall wart' transformer that is part of the Gaugemaster Combi that I bought from them.

The values given are nominal as Hugh says.

The label on the transformer says 15 V (AC) and measured with a meter set to AC volts the readings are 17.7 V. However this is with no load and when any sizable current is drawn it will drop.

The label on the Combi handheld controller itself under the two outputs are 0-12 V DC (well it actually says 1-12v DC, but I'm being a little pedantic about units) and 16-18v AC as printed.

The output of a transformer is not constant but varies depends on its load. If the transformer manufacturers are being truthful then perhaps they mean the output will be 15 V AC when the transformer is asked to supply the maximum current of 1500 mA that it is designed to supply.

As for the 12 V DC on the track output, perhaps it should be read as "compatible with 12 V locomotives". The Gaugemaster controller output is anything but 12 V DC but is a series of pulses with peaks of around 20 V at no load. The concept of a 12 V motor in a model train is also something of a concoction. The motor from a locomotive that is stalled when the speed is set to maximum will probably burn out but if it is run with no load (removed from the locomotive) it will probably survive a voltage rather higher than 12 V.

All this is a round about way of saying that the output of a controller from a reputable manufacturer such as Gaugemaster is appropriate for the task. You can control "12 V" trains from the track output and "16 V AC accessories" (as they are often named) from accessory output.

[Graeme Dunbar]

All sounding very good.  So to continue, the controller is  Gaugemaster hand held Combi controller.  My interest is in where do I get the required 16 volts from?  The controller has a socket called 'Input' but I cant remember if the controller came with a transformer or whether I was expected to supply my own.  I have a second transformer and it says on it,  PRI.:230-240VAC, and SEC.:16VACMax 17VA, is this what I need?

Gaugemaster sell suitable transformers. Unless you are confident you can source an equivalent from elsewhere, I would buy from Gaugemaster rather than rely on what some other seller might claim.

Edit: this one.
https://www.gaugemasterretail.com/gaugemaster-gmc-wm3-wall-mounted-transformer-16v-ac-uk-power-supply-0-point-75a.html

(It says it is out of stock, but the is an identical looking one that comes with a little diode board (that is not needed for the Combi).

Edit again: I see the label and spec on my transformer is a bit different, but I bought my controller many years ago and Gaugemaster may well have changed their supplier.

I should have read your post more thoroughly. It looks as if the transformer you have is the one. Compare it to the one on the Gaugemaster website.

[5113GBAK]

I've just looked on the GM site and the 16V transformer is exactly the same as the one I have.  So thankyou for your input, all of you and when I next see Angst Morepork, sorry Angsty Lesspork I'll introduce myself.  Did Sir TP really see your layout?

Regards

Graham

[Graeme Dunbar]

Also to echo what Hugh says, I'd go with a CDU unit to fire solenoid point motors. It is likely to be more reliable and safer than passing contact switches or (worse still) stud and probe switching. The CDU will produce a suitable pulse of current whereas there is a chance the passing contact switch may not be thrown completely and leave the power connected. I was talking to the owner of an 009 layout that used stud and probe point switching and he inadvertently left the probe dangling over the mimic panel and it was in contact with a stud. We noticed a smell and smoke rising from under the layout!

[JulienW]

Going a little off topic and taking a step back...

Changing the voltage of AC (alternating current) electricity is fairly easy. The transformer is in essence a pair of wire coils linked magnetically through an iron core, and the number of coils in each 'half' determine the ratio of incoming to outgoing voltage.

Converting AC to Direct Current (DC) is harder - I won't go into the various ways this can be done, and it's also harder to change the voltage (much more power loss compared to AC conversions).

As a result of this it is much easier (more efficient) to reduce the 240 volts AC mains to 16 volts AC via a simple transformer, then convert that 16 volts AC to 12 volts DC (the 4 volts essentially being 'used' in the process) rather than doing it the other way about (converting the 240 volts AC to DC, then reducing it to 12 volts)

Because of the way model railway transformers work (240 v AC to 16 v AC to 12 v DC) there is a readily available 16 v AC supply to power things other than the trains. Thus most solenoid point motors use 16 v AC.

Looking at a google search for "Gaugemaster Combi" a photo shows on the controllers bottom edge a socket (to the right with the control knob pointing up) for the wire from the wall socket / adaptor. There are also 4 screw terminals - the 2 to the left are the 12 volt output to the track ("0-12 v DC TRACK), the other pair are the 16 volt output you need to power your point motors ("16/18 v AC ACCESSORIES").

I would strongly suggest NOT taking the feed for your point motors from the bit you plug into the wall socket. It is not designed to do anything other than power the hand held unit, and it is this (the hand held bit) that can power both the trains on the track (12 v DC) and any point motors (16 v AC).

[B.Meldon]

I use transformers with seperate outputs for the controllers and the points, in the case of the controllers each controller uses a seperate transformer.
I do this so I can use common return wireing on the layouts reducing the wires needed by about half.

However, on a layout with one controller and a small number of points the need to reduce the number of wires is not an issue. 

[5113GBAK]

Julien
I'm not sure why you council against taking power from the transformer plug and I suspect it would be beyond me in any case.  I did consider a component the would permit a single 16Vac input to a two 16Vac output, just like any extension lead used in the home.  You suggest this would not be a good idea, but use the correct outlets on the controller.  Is that correct?
Graham

[Hugh Norwood]

I've just looked on the GM site and the 16V transformer is exactly the same as the one I have.  So thankyou for your input, all of you and when I next see Angst Morepork, sorry Angsty Lesspork I'll introduce myself.  Did Sir TP really see your layout?

Regards

Graham

Sadly, STP never got to see the layout in person - He did ask me to take it to the Convention in 2014 in Manchester, but he was too ill to attend. He did have a copy of the RM article, however.

The layout is next out at Narrow Gauge Now at Portland College on 25 Oct.