LED lighting

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As there isn't a specific thread for lighting, I'm asking here…….

We have, over the years, built up a selection of those cheap Chinese made Christmas lights.

As one would expect, they don't last for more than two or three years, particularly in the case of the outdoor variety, usually failing where the thin wires exit the "multi-function controller - the box with the push-button offering any one of 8 or so different settings.

Another set failed last night - we had a storm and I assume that caused the failure for some reason.

After that long build up, I'm simply asking if the transformer which comes with each set could be used to power LEDs on the layout with some kind of regulation.

The input is naturally 240v AC and, in this case, the output is 24v with a maximum of 9.6 VA.  Can this voltage/current be reduced by resistors etc ?

On a similar theme, could old mobile phone chargers be used ?  I think they put out 12 volts but in milliamps …….



'Petermac
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I don’t see why not. There are resistor calculators online so you can reduce the load as appropriate. 
I would say you are better off with the mobile phone charger. They are already at a level more suited for leds. They are 5v not 12 (or at least my ones are). One is quite happily powering the Arduino and all of Teasel’s lights. I have a old usb charge cable I simply cut into and use to test before they move on to the arduino. 
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Thanks Chris.

You may well be right about the phone chargers being 5v - I didn't have one to hand when I wrote that.

I think, in the end, it may work out less complicated, and maybe cheaper, just to buy another power supply - they're not expensive in China ….. I just hate throwing things out !

'Petermac
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Ed
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I'm probably overcautious Peter, but I'd bin it and get something with a better pedigree.

Read too many stories about fires caused by overheating Chinese cheap clone laptop adaptors to feel comfortable with something that would remain plugged in for considerably longer than a couple of weeks a year.



Ed


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Not over cautious at all Ed.  I've experienced one major fire in my lifetime and don't ever want to see another !

Whilst it would appear most of the power supplies I have are made in PRC, I wouldn't buy one direct - all have come from what I'd assume to be reputable sources.

My layout is in a portable office unit (a sort of Portakabin) and the electrics are always killed at the main when I'm not in there.

'Petermac
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Peter,

my solution is to put to good use those old power bricks which come with a lot of mains powered or rechargeable battery devices.

Ideally it should have a regulated voltage output or a surge on connection would be problematic for LEDs. Typically rated 5V or 12V, these are ideal to power individual sets of series-connected LEDs, which can then be wired in parallel to the supply. A resistor is required in series with each LED set as current regulator.

The winter night photo you kindly proposed of Westown-Heathfield for POTM is entirely powered by just one such 12V 1A power brick with about 10 different parallel wired LED strings of 3 or 4 LEDs, one for each building / station. Each individual LED circuit is drawing about 15-20mA so more than enough resources from the supply.




Last edit: by Colin W

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