Point motor control

Basic electrical and electronics, such as DC/Analog control.
Jkelly
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Point motor control

Postby Jkelly » Tue Mar 24, 2020 5:20 pm

Hello everyone,
Hope you are all keeping well in these extraordinary times. Just wondering what you would all recommend- I'm trying to buy what I need before Hattons et all close down.. I use DCC on my layout but want to use analogue control for my point motors (Peco PL-10Es and a CDU). What power supply unit should I use to power the point motors? I am wondering as I need a separate circuit (analogue). Should I use a cased transformer?
Thanks for the help,
Jonathan

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Re: Point motor control

Postby RAF96 » Tue Mar 24, 2020 7:46 pm

I power my CDU from the 15vAC Aux output of a redundant DC controller (HM2000).
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Re: Point motor control

Postby Flashbang » Tue Mar 24, 2020 8:50 pm

Any power supply that can provide either 19 to 22 volts DC or 16 to 18 volts AC.

Gaugemaster sell one, its their part number GMC-WM3 16v AC plug in power supply.
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Jkelly
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Re: Point motor control

Postby Jkelly » Tue Mar 24, 2020 9:27 pm

So if I use the Gaugemaster wall transformer as you mentioned, that with relevant point motors and CDU is all I need?

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Re: Point motor control

Postby Bufferstop » Tue Mar 24, 2020 10:43 pm

The "wall wart" transformer has the advantage that you don't have to decide where to mount it. If you think you might throw a series of points one after another, you might want one of Gaugemaster's cased models for a bit more current. An old laptop power supply works well, there's a box under our stairs that has a collection of both AC and DC adaptors of various voltages and current ratings, that can usually provide one of the right rating even if it doesn't have the right plug on the end. I often wonder what became of the devices they came with.
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Flashbang
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Re: Point motor control

Postby Flashbang » Wed Mar 25, 2020 11:02 am

Jkelly wrote:So if I use the Gaugemaster wall transformer as you mentioned, that with relevant point motors and CDU is all I need?

Basically yes, but see second paragraph below. But now you will be very hard pressed to buy either, perhaps from ebay sellers, but most shops including GM are now closed UFN.
Don't forget you will need some switching method too. Here there are usually three options.. 1) Passing contact lever(s) such as the Peco PL26 (Note that the Hornby R044 Black lever doesn't work will with a CDU). 2) Sprung to centre Off toggle switches SPDT often referred to as (On)-Off-(On) switches or 3) Stud and Probe.
Use 16/0.2mm equipment wire for all feeds to the motors and where two or more motors are to move together from one switch/lever operation increase the return wire size to 32/0.2 or double up two 16/0.2mm wires.
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Re: Point motor control

Postby Suzie » Wed Mar 25, 2020 11:36 pm

You are best powering a CDU with a 24V DC power supply. This has advantages over a transformer:-
- Lighter (especially important for exhibition use.)
- More efficient (less heat and loss so will help save the planet.)
- Consistent operation regardless of mains voltage (important if your mains voltage varies, can be an issue for exhibition use or if you are in the country!)
- Cheaper (transformers are expensive items nowadays. The Gaugemaster one mentioned above is £20 therefore about twice as expensive)

Something like this should do nicely:-

24V 1A plugtop PSU from Rapid

You will be hard pressed to find a 16V AC transformer for under a tenner.
Last edited by Suzie on Fri Mar 27, 2020 2:54 pm, edited 1 time in total.

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Re: Point motor control

Postby Flashbang » Fri Mar 27, 2020 11:58 am

Suzie wrote:You are best powering a CDU from the mains with a 24V DC power supply. This has advantages over a transformer:-
- Lighter (especially important for exhibition use.)
- More efficient (less heat and loss so will help save the planet.)
- Consistent operation regardless of mains voltage (important if your mains voltage varies, can be an issue for exhibition use or if you are in the country!)
- Cheaper (transformers are expensive items nowadays. The Gaugemaster one mentioned above is £20 therefore about twice as expensive)

Something like this should do nicely:-

24V 1A plugtop PSU from Rapid

You will be hard pressed to find a 16V AC transformer for under a tenner.

I'm sure Suzie wouldn't wish to be misunderstood. But you don't want to be applying 240 volt (mains) to a CDU. I think the wording was not quite correct in line one and perhaps it should read.... You are best powering a CDU via a mains to a 24V DC power supply. ?? :D
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Re: Point motor control

Postby b308 » Fri Mar 27, 2020 12:19 pm

I suppose it depends on the point motor you use but I've never had to use a CDU with a Peco motor switching one motor or two together (crossing) using a 16vAC supply from the Aux supply on a GM controller... Perhaps to switch more it may be better.

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Re: Point motor control

Postby Flashbang » Fri Mar 27, 2020 1:03 pm

We need to understand that 16 volts AC is the referenced RMS voltage - That which is read on a multi meter etc. When it is used to charge capacitors, as in a CDU, it is converted to DC and the RMS voltage becomes 1.41 times that inputted. So for example 16v AC would be 22.56 volts minus 0.7v loss in each diode used to convert the AC to DC. So using a 24 volt regulated DC power source is usually OK, so long as the CDUs capacitor(s) rated DC working voltage is greater than the DC input volts. e.g. over 25 volt and better if it has an even greater DC working voltage - DC Working voltage is printed on the capacitors casing. The Gaugemaster CDU has 40 volt capacitors fitted.
Note: I've underlined the word regulated. This means the DC output voltage of the power supply is held at that stated level regardless of loading - no load through to its rated maximum load. Using a mains fed non regulated DC supply could easily mean the output voltage is much greater than the rating under little load and drops below the rated approaching full load. The same will apply to an AC supply which will vary the voltage too. 16v AC can frequently be read up to or above 18v AC under no load. Hence an input of 16v AC is usually recommended for a CDU or 19 to 24 maximum volts DC.

Feeding a CDU with AC or DC of the correct voltage will allow one or several solenoid motors all to move at once.
Power supplies offering low current - 250ma/300ma outputs and of the correct voltage can be used, but this causes a noticeable delay in the recharge time. So usually a 1.0Amp or thereabouts supply is used, which will normally recharge in a few milli seconds.

You don't have to use a CDU with solenoid point motors, but it offers far more advantages than not having one. It prevents accidental coil burn out. It provides a rapid pulse of power beyond that available for a direct power supply and of course removes the need for larger current power supply.

My comment previously was about the wording used - I didn't want anyone thinking they could connect 240 volt directly to a CDU. :o
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Re: Point motor control

Postby Suzie » Fri Mar 27, 2020 2:58 pm

I'm sure Suzie wouldn't wish to be misunderstood. But you don't want to be applying 240 volt (mains) to a CDU. I think the wording was not quite correct in line one and perhaps it should read.... You are best powering a CDU via a mains to a 24V DC power supply. ?? :D


I think it is probably best to remove all mention of mains to avoid any consternation!

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Re: Point motor control

Postby Suzie » Fri Mar 27, 2020 3:02 pm

b308 wrote:I suppose it depends on the point motor you use but I've never had to use a CDU with a Peco motor switching one motor or two together (crossing) using a 16vAC supply from the Aux supply on a GM controller... Perhaps to switch more it may be better.


Each standard Peco PL10 motor draws about 4A, so a pair would draw 8A. It is usually best to not overload a 1A transformer to 800%!

It might work, and it might work for a while, but it is not a good idea to stress things to that extent. If you don't want to buy a CDU (they are not very expensive) then there are lower powered motors available that would be more suitable.

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Re: Point motor control

Postby b308 » Sat Mar 28, 2020 8:22 am

Then thousands of us have been getting away with it for decades! Suzie, it does work, and it doesn't overload the transformer. I'm not sure how to describe it (no doubt Flashbang will help!), but as it's a passing contact it's not a constant draw so if used correctly will not overload the transformer. Obviously if it was switched on constantly it wouldn't do anything any good! There is no need to scaremonger.

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Re: Point motor control

Postby Suzie » Sat Mar 28, 2020 9:02 am

You can drive your car everywhere in top gear all the time. If you don't drive far or often it might last for ever, but it does not make it a good idea and you should not be telling others to do it - some will damage their bearings and wear their clutch. Probably not many because not many would be stupid enough to take that advice.

There are right and wrong ways to do things. If the transformers were suitable for 8A operation they would be labeled as such and not marked 1A. Peco make the motors, and they make the CDUs to be used with them, not as a decorative ornament!

I am not scaremongering. I am just recommending the correct way to do things, and putting in the explanation that justifies it. I do not have blind faith. The 16V AC outlet on DC controllers stems from a time when point motors used to draw a lot less current than the Peco PL10.

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Re: Point motor control

Postby b308 » Sat Mar 28, 2020 12:11 pm

Please use a suitable comparison, that car one doesn't work.

The Peco point motors were launched well before the use of CDUs and were used for many years without them, they were designed to be used by the 16vAC output seen on many of the older controllers from the likes of Triang and H&M. It is not a necessity to use a CDU, I am not denying that it will help, but it isn't absolutely necessary, to say you have to use one as the "correct" way is wrong. The danger for point motors is continuous powering, where the power is held on continuously, if that is done the motor will be burnt out in no time. The CDU has the advantage that the voltage is reduced and so reducing the danger of a burnout. But if you use a "sprung to centre off" switch (most commercial switches such as Peco's or Hornby's are of this type) 16vAC can be used safely.


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