Model railway power supply

[DP]

Did you mean 1K there? I have used LED's on 12v so often, that I don't even need to calculate it - 1K everytime.

I am quoting generic spec where the led drops 2 volts and consumes 20mA, not to say there will be others that have different operating parameters and inbuilt ballast resistor
The calculator in following link makes the task easy
I have even encountered leds in optoisolators running off 240 volts ac, voltage obviously reduced, rectified and cleaned to acceptable parameters

 

[DP]

Easy LED Current Limiting Resistor Calculator In 3 Steps

Online Calculator Enter LED supply voltage, LED forward voltage and forward current to identify the series resistor value for safe LED operation.

www.make-it.ca

More info on these

 

[DP]

I believe your maths may be slightly out with this one

You don’t say Mr Watson
Nothing wrong with maths. Just out by factor of 10 correct value 470 ohms or 510

 

[Harry Bloomfield]

I am quoting generic spec where the led drops 2 volts and consumes 20mA, not to say there will be others that have different operating parameters and inbuilt ballast resistor
The calculator in following link makes the task easy
I have even encountered leds in optoisolators running off 240 volts ac, voltage obviously reduced, rectified and cleaned to acceptable parameters

Which confirms 1K, for a very safe 10mA.

 

[DP]

Which confirms 1K, for a very safe 10mA.

The led may not be bright enough if current flow is substandard.

 

[ericmark]

I would go further and suggest that the power supplies have a wound transformer at 50Hz to ensure there is assured isolation from the mains supply.

Can you still get them? I must admit I love watching the trains going around the track, but it seems to be all lighter fluid or battery powered, gone it seems are the days when power went along the rails. I have been watching with interest my next door neighbour setting out his railway in his garden, there are still signs in this house where the trains ran around the house, and through the garage.

In the main I play with slightly bigger versions, 2'6" between the rails, but many also have garden railways at home, I think if I wanted to spend £50k on a railway engine my wife would object.

 

[RandomGrinch]

but it seems to be all lighter fluid or battery powered, gone it seems are the days when power went along the rails

With the smaller scales, 'N' and 'OO', power still very much goes to the rails.

Although issues with track continuity are much reduced these days.
Nearly all track is Nickel-silver rather than steel, so there is no need to worry about cleaning up rust. A light wipe over with some IPA will leave a clean track.

Also, with the take-up of DCC, it is straightforward to connect a super capacitor to the rectified side of the decoder. This can keep the loco and sound going for a significant distance, even with no power to the track - this may however lead to the odd SPAD!

 

[ericmark]

Seems a waste of IPA, I would drink it. I do remember one lad had third rail and pantograph so he could have multi engines independently controlled on one line, he loved to show banking up the incline, I was really jealous, no way in my parents house was there enough room for that.

I suppose things have moved on, and even with power taken from the track likely now engine radio controlled, which means one can fit capacitors or batteries on the engine, in my day it was hard enough to get the motor to fit in the engines shell. Do remember some with smoke generators, not that I had one.

Anyway that reminds me, I have 40 pints to bottle and another beer brew to start, not IPA but Scottish Heavy.

 

[Harry Bloomfield]

Anyway that reminds me, I have 40 pints to bottle and another beer brew to start, not IPA but Scottish Heavy.

I've just bottled in the past few weeks. I've not tried it yet, still a few bottles left, of last batch.

 

[FiremanT]

@JohnD

I forgot that I started this thread.

Thanks to all responders, although it did get a little technical and well above my head.

In the end, I took JohnD ‘s advice and opted to use a few separate battery packs to power the differing voltaged units and LEDS. More sensible than my original plan, and did not have to change batteries over Xmas.

I fitted LV rocker switches to each group so the kids were able to turn them on and off. I fitted normal 240v switches to interrupt the supply to the working models, train set and tree lights voltage adapters, again so they could control them independently.

On the whole, it worked well, but I will make some changes before next Xmas, and will try to remember to post a pic.

You can run a few dozen LEDs off battery supplies with safety and ease.

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