Elite aux output

[Scotty73]

Hi,

I am currently in the process of wiring up my R8014 point motors, i was thinking of using the aux output on the elite to provide power, done a test wire and all works fine, know correct me if i am wrong but this should not effect the power going to the track to power my locos as it only operates the points for a split second, these will not be operated with the controller just a switch, just need the power to supply the point, if you know what i mean

 

Thanks 

Dave

[walkingthedog]

Generally it is thought to be better to use a completely separate power supply for points etc. 

[Rog RJ]

I use the auxillary output of my Elite with no problems at all, even operates two point motors at the same time.  It might not be so reliable if I had a lot of locos running at the same time.

[Chrissaf]

.....as it only operates the points for a split second,......

.

In principle you are correct, but at the point of operating the point then there will be a very sudden and very high instantaneous current draw on your Elite 4 amp power supply. A solenoid point motor has a very low DC resistance in the operating coil, typically about 5 to 7 ohms. For all intent and purposes this is near as damn it a short circuit. So although the current draw is brief, it still has the potential to disrupt the DCC signals from the controller because this high current draw will potentially cause the voltage output that is powering the DCC part of the Elite to briefly collapse.

.

If you are intent on using the Elite AUX output for your points, then I really would urge you to consider connecting the AUX output of your Elite to a CDU (Capacitor Discharge Unit). Only one CDU is required, as it is a shared resource.

.

With a CDU installed you get several benefits.

.

Firstly the way that a CDU works means that the CDU is a 'fail-safe' device that will 'shut-down' under a point wiring fault condition (short circuit) and protect your Elite 4 amp power supply, and therefore subsequently should not 'shut-down' your DCC control of the layout.

.

Secondly, it is the CDU capacitors that provide the high current kick that the solenoid motors require to operate. The CDU is then re-charged more sedately from the Elite AUX output, putting less stress on the Elite and the Elite 4 Amp power supply. Subject to the CDU brand / model purchased, the re-charge time should still be sub one second.

.

Thirdly, again due to the way that a CDU operates, point motor operation should be more reliable and robust, particularly if operating two or more point motors in parallel together.

.

Fourthly, again because of the way a CDU operates internally, it is immune from a situation where you hold the momentary operating switch 'closed' for too long.

.

I still agree with WTD though, I would dedicate ALL of the 4 amps of the Elite power supply for running DCC trains and use a separate power supply (preferably @ 19 volts DC) with a CDU to operate your point motors.

[Scotty73]

Hi walkingthedog,

I had thought about using a separate power supply, but not sure on the output and ampage of power supply to use, and as the elite has an output of 15v DC and it works fine i thought i could just use that, save messing about, and as i said they will be switch powered and not dcc operated 

[Scotty73]

Hi Chris,

Thank you for your feedback, much appreciated, okay so going down the route of a separate power supply, you say 19v should br okay, what about ampage?

I have got a spare power supply knocking about 12v dc 3amp, will this be okay or do i need something with a bit more kick?

[Chrissaf]

If you don't use a CDU then you need a power supply with an absolute minimum 2 amps and preferably 4 amps.

.

If you use a CDU, then a power supply from 0.5 amps will suffice, but preferably 1 amp. You can go higher than 1 amp, that is not an issue. I'm just stating the minimums.

.

The voltage is a more critical power supply specification parameter than the current.

.

12 volts DC is in my view borderline for robust solenoid point motor operation, 15 volts is OK, but my preference is for 19 volts DC. Personally I would avoid 12 volts, but there will be many on here who will say that they use 12 volts without issue. Well at least none that they observe......

.

19 volt @ 3 amp or higher switch mode Laptop power supplies are readily available and dirt cheap on eBay. I would still use a CDU with it, because of the technical benefits. Particularly the 'second benefit' in my original list, as that will put less stress on the power supply. The CDU is designed to see near short circuits when you operate a solenoid point motor. The power suppy is not.

.

For example:

/media/tinymce_upload/39a854f3f3d3942d2474e9347b0bef0e.jpg

[Scotty73]

Thank you Chris for your advice 

[Flashbang]

A few things... The Gaugemaster GMC-WM1 offers a 16 volts AC output which is ideal for feeding a CDU input.  It can be obtained at most GM stockists and in some cases cheaper than the GM listed price.

Secondly, try to avoid the Hornby R044 Black point lever when using a CDU. Its very old design and not an ideal operating method means it fires the CDU into the point motor already in the move from direction coil BEFORE it moves over to the other side and provides power to the opposite motors coil to move the point over. Problem is the CDU doesn't have time to recharge before its needed again. Here the R044 lever needs to be held top centre of its travel for a second or two to allow the CDU to fully recharge then continue on with its travel to the other end of the lever frame.  

If you really must use the 15v DC output of the Elite then ideally use it with a CDU. The CDU providing the 'Beefy' stored pulse of power to move one or more solenoids at once.  

 

A CDU is wired immediately after the power source.  Its Output + (Positive) goes to the common connection of the operating switch(s) or lever(s). The two other connections on each switch or lever go to the motor operation left and right connections. The motors common connection joins to all other motors common wires and one wire runs back to the CDU output terminal - (Negative).   Only one CDU is normally required for the whole layout and they also protect the solenoid coils from possible continual energising which will quickly burn out the coil if left powered On, as once the CDU has discharged in a few milliseconds it cannot recharge again until all levers or switches are in their Off positions.

 

Edit to correct error in typing

[Scotty73]

The switch i have wired in is a SPST (ON) OFF (ON) type

[Flashbang]

That is fine, but I feel they are SPDT.   The bracketed (On) means the switch cannot remain in that position when the operating toggle lever is released, as it returns to the middle Off position under internal spring operation.   DT or Double Throw means the switch makes connection to one of two places depending on its levers position.  Normally a toggle switches operating lever is opposite to the contacts.  i.e. if the lever is at the top then the middle and lower contacts make a connection.   They are also a lot cheaper than momentary levers too  😉     

Wire CDU Positive output to the switches middle tab, linking switch to switch middle to middle where more than one switch is needed. The outer two tabs on each switch run out to the appropriate point motors operation connections left and right.  Ideally use 16/0.2mm wire throughout and where two or more motors move together then consider increasing the return wire size to 24/0.2mm even 32./0.2mm (or double up using 2 x 16/0.2mm wires) as more current flows in this one wire where several motors all move at once.

[96RAF]

Switch types - basic guide

https://images.app.goo.gl/2VQ68Kc3bXa8a6hNA

 

Note that your SPST would be like  a car headlight flasher  i.e. Off until pulled (ON) against the spring. Upon release it springs Off again.

[Scotty73]

So unless i am not understanding what you guys are on about, the setup i am currently testing and tested is power supply 12v DC 3 AMP using a SPST switch (ON) OFF (ON) this all seems to be running just fine, the switch only powers the motor when i push the switch up or down, it returns to center no power. All looks good to me, this is all new to me, have never wired up anything apart from my track, 

[Chrissaf]

If that set up works for you, then that is just fine.......it just isn't necessarily the most optimum engineering solution........but if your happy with it.....then we're happy too.

.

Just as a picky point about correct terminology.

.

As Brian stated, the SPST is not the correct term for a (on) off (on) switch. A SPST switch is a simple on / off switch. Your (on) off (on) switch is a SPDT (DT = Double Throw) which means that it is a change-over switch. In this instance, a change-over switch with a sprung 'centre-off' position.

[96RAF]

Compare the first [sPST - normally open) and fourth (SPDT) switches on the top row of my link provided previously. Another obvious way to tell is how many terminals there are, 2 (SPST) or 3 (SPDT) or 4 (DPST) or 6 (DPDT) and if the toggle springs to Off from one way i.e. (ON)-OFF or both ways i.e. (ON)-OFF-(ON).

[Flashbang]

As Chris says... If it works for you then fine..

 

Now for some electrical theory... The switch(es) you have are not SPST they are SPDT = Single Pole (one electrical pole only) and are Double Throw - DT.  That means they can make a connection to two places (Double Throw) depending on the switches lever position, so when held over in one position the top connection tab makes to the middle tab. When held over in the opposite position the bottom connection tab makes to the middle tab. When the lever is released the switch returns under its own spring to the central Off position.  i.e. Single Pole Double Throw or SPDT with centre off  The (On)-Off-(On) reference is a typical example of this. 

12 volts DC is as previously stated considered to be a little on the low voltage side to operate solenoid motors 100%.  If DC is to be used then I would use a higher voltage of say around 18 to 19 volts and with a current output of at least 3.0Amp or more without a CDU.

For many years DC train controllers have offered additional power out connections over that of the controlled output for driving the trains.  Normally this additional supply is rated at 16 volts AC and is frequently used to operate solenoid motors and as its AC ideally via a CDU. 

Boring bit warning.... . Note; when 16v AC is fed into a CDU the capacitors charge to 1.41 times the AC RMS voltage, so 16v AC becomes around 22 volts which is fed to the solenoid coil when the switch contacts close.  A CDU also converts the AC into DC so the coil receives a "Beefy" pulse of DC power momentarily.     Next, If you feed a CDU with DC the capacitors will only charge to the same value as the DC input voltage, less a little bit due to the CDUs components. So 12v DC into a CDU will equal roughly 12v out (actually a little bit less).  Hence why AC is recommended for a CDU due to the input RMS voltage being increased by a factor of 1.41. 

Are you asleep yet??  No.. Then....

The original question was about using the Elite's auxiliary 15v DC output to power solenoids.   Yes, it can be used, but if used direct its at risk to the DCC voltage to track being robbed momentarily as the voltage is sent to the solenoid motors coil.   15v DC isn't too bad a voltage for solenoids, but is still a little on the low side!   If that 15v DC power is fed initially into a CDU then the CDU would take up the strain and the operation of a point motor shouldn't effect the DCC rail volts.   

 

So to recap.. Use the 15v DC from the Elite directly and be at risk of causing a blip on the DCC rail feed.  Use a CDU with either the Elite aux output or better still from a totally separate power source. The CDU then prevents accidental motor coil burn out and provides that momentary pulse that's really 'Beefy' in power.  If a separate power source is used then consider 16v AC as ideal or 18 to 19 v DC with or without a CDU, but ideally always with one.