Separate power supply for point motors

[Tomathee]

Afternoon, my side project has taken a few steps in moving from my head into reality and I'm starting to put a shopping list together. I'm still debating DC or DCC, and if I go with DC it should be simple as I'll buy a power supply with an AC output for the point motors. My question is in the option if I go with DCC, I don't plan on incorporating point control with it. Partly due to cost and complexity (of the parts rather than wiring, which I understand should(?) be easier), and partly as it's a small layout that the initial plan only includes 4 points. Therefore what can I use to power the point motors (probably the underboard cheaper option from Peco etc. type). I don't want to splash out on a DC controller just for that feature, however when I sift through most of the unrelated search results I only see a couple of things that might fit the bill but seem expensive for what they are (Peco PL-202 or Gaugeamster WM1 in this case). Is there anything else to look at in this scenario? thanks

[MyRule1]

There are plenty of similar adaptors available on the internet but whereas once the price differential between peco / gaugemaster and others seems to have narrowed. However for reliability and extra power a capacitor discharge unit should be considered although this obviously adds to the cost. You can also often pick up suitable transformers at boot fairs or charity shops. Just check the amps and voltage.

 

Although not cheap the Hornby HM6010 accessory controller is worth looking at.

[smokebox]

Use an ex laptop power supply.  Anything from 15 volts to about 24 volts and 3 to 5 amps.  Quite cheap on eBay. 

 

Including a CDU in circuit is an insurance against point motors burning out if a switch sticks on.

[Pete the Elaner]

3 minutes ago, smokebox said:

Use an ex laptop power supply.  Anything from 15 volts to about 24 volts and 3 to 5 amps.  Quite cheap on eBay. 

 

Including a CDU in circuit is an insurance against point motors burning out if a switch sticks on.

 

It does indeed. It does a lot more too:

 

It provides instant current. A coil reacts against change of current. When operating solenoid point motors, there is a coil in the motor & another in the transformer. It may sound bonkers but this means the transformer is slightly working against itself. This is why a CDU gives the motor a short, sharp burst.

 

The short burst makes the point throw more reliably (although it can possibly be too fierce for fragile hand-built points).

 

Why would a switch stick on? It is usually because arcing has worn the contacts. Arcing occurs when a circuit with a current is suddenly opened (when the switch is set to off). As the contacts pull apart, the collapsing current causes a coil to generate a voltage, which creates a spark across the switch contacts. A capacitor discharges very quickly through a coil, so after the initial burst of current, it drops rapidly, so when the switch contacts are opened again, the arc is very weak. So with a CDU in the circuit, you can get away with using smaller, cheaper switches & the risk of a sticky switch is minimal.

 

If you decide to go instead with a 'stall' type of point motor like a tortoise, these works in a completely different way.

[Tomathee]

8 hours ago, MyRule1 said:

There are plenty of similar adaptors available on the internet but whereas once the price differential between peco / gaugemaster and others seems to have narrowed. However for reliability and extra power a capacitor discharge unit should be considered although this obviously adds to the cost. You can also often pick up suitable transformers at boot fairs or charity shops. Just check the amps and voltage.

 

Although not cheap the Hornby HM6010 accessory controller is worth looking at.

 

Thanks for all the responses, I have a CDU on the list, the HM6010 is a great suggestion that I hadn't thought of, I'll look further into.

 

5 hours ago, smokebox said:

Use an ex laptop power supply.  Anything from 15 volts to about 24 volts and 3 to 5 amps.  Quite cheap on eBay. 

 

Including a CDU in circuit is an insurance against point motors burning out if a switch sticks on.

 

I saw a laptop charger mentioned elsewhere but I wasn't sure how much thought to give it, in terms of the how and the safety side. Do you just cut the end off, strip the wires and hook up to the CDU>point motor feeds (forgive my ignorance)?

 

4 hours ago, Pete the Elaner said:

 

It does indeed. It does a lot more too:

 

It provides instant current. A coil reacts against change of current. When operating solenoid point motors, there is a coil in the motor & another in the transformer. It may sound bonkers but this means the transformer is slightly working against itself. This is why a CDU gives the motor a short, sharp burst.

 

The short burst makes the point throw more reliably (although it can possibly be too fierce for fragile hand-built points).

 

Why would a switch stick on? It is usually because arcing has worn the contacts. Arcing occurs when a circuit with a current is suddenly opened (when the switch is set to off). As the contacts pull apart, the collapsing current causes a coil to generate a voltage, which creates a spark across the switch contacts. A capacitor discharges very quickly through a coil, so after the initial burst of current, it drops rapidly, so when the switch contacts are opened again, the arc is very weak. So with a CDU in the circuit, you can get away with using smaller, cheaper switches & the risk of a sticky switch is minimal.

 

If you decide to go instead with a 'stall' type of point motor like a tortoise, these works in a completely different way.

 

Thanks, I have a CDU on my other layout which seems to do the job and it will be a feature of this one. I'll not be using the stall type motors as it's a bit cramped with the size I've set the layout at, along with previous cost/complexity/unfamiliarity reasons.

[DCB]

Deleted due to unhelpful comments

Edited January 30, 2023 by DCB

[97406]

My points are not DCC controlled. They are powered by a Gaugemaster 16V AC power supply linked through a Peco CDU. The lights on my layout have their own 3V DC supply too, along with some of the new Bachmann Just Plug stuff for the Scenecraft office, so there are 4 plugs powering the different aspects of the layout.

[jamesed]

There is an obvious answer here, especially if you are undecided as yet whether your layout will be dc or dcc.  Why not use Cobalt IP Digital motors?  Ok, your initial reaction to this suggestion may be to think that at £24 each that's a mad suggestion but let's think it through.   They will work just as well on a dc or dcc layout.  If you prefer to control them from simple switches or pushbuttons rather than dcc control you can. It's just a case of buying some cheap switches and wire them straight to the relevant terminals (no soldering or even screw terminals to be bothered with). They use hardly any power to run so if you are on dcc they can be powered from your bus or if you are running on dc then any old power supply giving between 7-23 volts will do the job. The ex-laptop psu mentioned earlier will do the job fine. You certainly won't need a cdu which is a cost saving. If you are on dcc then you'll almost certainly want live frog switching which is built in so nothing extra to buy. You can use the S2 relay terminals to drive your mimic panel (which answers your other thread) without buying anything extra.  If you decide to go dcc, either now or in the future, you don't need to buy decoders; they'll work straight from your dcc bus.  If you are using electrofrog points you don't need to carry out any modifications to how they are wired - they'll work out of the box because the frog polarity switching takes place at the centre of travel. All you have to remember is to remove the spring from the points before you lay them. This is an option which will simplify your wiring and futureproof your layout. If you've currently only got four sets of points then just under a hundred quid to achieve this is a good investment and they come with a lifetime warranty too, so keep your receipt!

Edited January 29, 2023 by jamesed

[RAF96]

I use the 15vAC Aux output from an old DC controller to power my CDU.

[KingEdwardII]

20 hours ago, DCB said:

computer PSU's more or less for free, but they deliver 12 volts max

Hmm, that is by no means true and it would be a dangerous assumption to make.

 

Computer PSUs can supply a wide range of voltages, some as high as 20V or more. The USB power supply standard, as used on my computer, can provide 5V, 9V, 15V or 20V, for example - and there are later versions of the USB standard that provide for even higher voltages. Similarly wide ranges of output current apply to these PSUs - my computer can draw 100W - 5amps @ 20V, for example.

 

The only way to be sure with a particular PSU is to check out its specification in some detail.

 

Yours, Mike.