Using LED power supply to run incandescent bulbs

I need to run multiple traditional 12v MES bulbs, 2 watts each, and use old toy train transformers, which can provide an amp or two, which rather limits the number of bulbs each transformer can power. Usually around ten bulbs each.
Seen on eBay for 10 - 15 pounds LED Switching Power Supplies, which output 12v 150w, and therefore capable of powering 75 of my little bulbs. Would that work? Any reason not to use an LED supply to light incandescent bulbs?
Thanks
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Graeme

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On 17/08/2017 16:00, Graeme wrote:

Probably not. Incandescent lamps have a much lower resistance when cold an therefore take a much higher startup current. The LED supply won't have been designed for this.
Cheers
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Clive

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On Thursday, 17 August 2017 16:05:35 UTC+1, Clive Arthur wrote:

You're looking at 8-10x initial current surge for filaments, but an LED PSU should be current limited. Whether it'll work at more than 1/8th load depends on how it behaves with overcurrent. If it can soft start that could minimise overcurrent.
You could 1/4 the current surge with a relay connecting the lamps in series, then changing to parallel after a second or 2.
75x12v >> 240v so you could also run them in series strings on 240v. If wanted a neon with R across each would indicate a dead bulb instantly.
NT
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Sounds like this is getting very complicated, He does not say all bulbs will be on all the time and whatever method is used may well affect brightness of the other bulbs ans different numbers are turned on and off. Brian
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On 17/08/17 16:05, Clive Arthur wrote:

If the LED supply is any good, it should have current limiting protection.
Personally I stay the hell away from ebay for mains things that are permanently live - I get mine from RS, so I can see the full data sheet and have some hope it's not a dangerous PoS.
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On 17/08/2017 17:01, Tim Watts wrote:

It'll likely be made down to a price, will just about achieve its specifications and not a penny more.

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Try a power supply from an old PC? Many of those can do 12V at 150W easily.
If you're buying, power supplies from old servers can do up to 3kW at 12V for a few pounds on ebay - if somewhat noisily!
Random example that does 25A @ 12V: http://www.ebay.co.uk/itm/HP-Compaq-Proliant-DL360-G3-Power-Supply-280127-001-305447-001-ESP128-PSU-/361994292216
The only snag is you have to work out which two pins on the connector you have to short to turn it on. Also you'll likely have to solder on some terminals. There are breakout boards if you don't want to do this:
http://www.ebay.co.uk/itm/DPS-1200FB-QB-A-6-Pin-Power-Supply-Breakout-Board-Adapter-For-Ethereum-Mining-H8-/282590340308
- or use a power supply with an ATX power connector.
Theo
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On 17/08/17 16:41, Theo wrote:

Those usually don't start up all the power lines until a signal is seen from the PC.
You can get one of these:
http://uk.rs-online.com/web/c/displays-optoelectronics/led-lighting-system-components/led-drivers/?searchTerm=powerled%2012v&sort-by=Output%20Current&sort-order=asc
for similar money.
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All you need is to short pin 16 (PS-ON, green wire) of the ATX power connector to ground, and the PSU will start. Put a mechanical switch on it as the 'on' switch.
On server PSUs it's a different pin, which will take a bit of probing to find out (eg take a resistor like 470 ohms, wire one end to ground and poke pins with the other end until the fan comes on)

RS' website is currently down so I can't look at that, but the OP seems to be asking for something to drive incandescent bulbs. The previous discussion suggested an LED PSU isn't suitable.
Theo
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On 17/08/17 17:41, Theo wrote:

OK - but why would you want to? Big lumpy and probably old (fire risk?) PSU with a noisy fan verses a few quid for a designed for purpose nice safe zero noise unit.
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On Thursday, 17 August 2017 18:44:05 UTC+1, Tim Watts wrote:

Where do you get the notion that server PSUs are more hazardous than PC PSUs?
NT
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The OP hasn't told us his application, so we don't know the cost v size v noise v availability v hassle tradeoffs. He also didn't say how many bulbs he actually wants to light.
Agreed if it's a small scale then a power brick or similar may be a better bet. However I'm just suggesting options if they do want scope to go larger.
Most desktop PC PSUs are fairly quiet BTW especially when not near peak load - it's only if you start wanting about a kilowatt or so then noisy server PSUs are in the frame. Which is probably way OTT for the OP, but can come in handy for other applications - they're popular with RC modellers for charging LiPo for instance.
Theo
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OK. Look here, which may explain other questions I have asked, such as stripping cable, staplers, carpets and more. Scroll right down :
http://www.binnsroad.co.uk/layouts/ogauge16/index.html
There are +/- 50 MES bulbs at present, with at least 20 more to add. Not all will be the same wattage, although similar (say 2.2). At present, there are four pairs of two bus bars of stripped copper wire under the boards, for supply and return. 8 altogether - two across each end, and two down each side. Each pair is powered by whatever old 12v train transformer/controller I have to hand, the more amps the better. Output is set a little under maximum, to prevent the bulbs being too bright.
The problem is, the more bulbs I add, the more likely the controllers are to overload and cut out. Roughly 8 bulbs per transformer. I cannot add more bulbs without adding more bus bars and transformers unless I can reasonably cheaply and simply up the power supply, i.e. more amps.
Although a private layout, it is open to the public 10 days per year, so I want to avoid mains voltage above baseboard level. I have never run mains voltage above the boards.
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Graeme

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Graeme formulated on Friday :

Have you given any thought to converting to using LED's in place of the bulbs? There would be much less current / amps needed for the same output, the LED's can be had cheaper and they can be really tiny.
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Harry, yes I have, but I probably have around 100 bulbs in use (including those not actually on the layout), and at least that many as spares. Plus, if replacing with LEDs, I would want the ones that are made to look exactly like the original incandescent bulbs. Add to that the variety of voltages for various applications (3.5, 4, 6, 12, 14, 18, 20 and 24) and it all gets complicated and expensive. Having said that, when I run out of spares, I may well switch to LEDs as required, rather than en masse.
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Graeme

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On Friday, 18 August 2017 10:13:32 UTC+1, Graeme wrote:

You'll never get that old fashioned under-run filament yellowy white from them. Unless there's a tinted varnish I don't know about.
NT
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snipped-for-privacy@gmail.com writes

Yes, I agree, which is another reason not to switch. I may buy one or two, just to experiment.
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Small LEDS can be bought by the bucket full for not a lot. You might need a mixture of red and 'white' to get closer to the colour you want.
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On Saturday, 19 August 2017 07:00:21 UTC+1, Graeme wrote:

You can get bagfuls for a dollar from China. If you can find the right tinted coating you're in business. A far better option is get RBG LEDs, then you can have any colour you like, including underrun white.
NT
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I understand now - I was thinking fairground illuminations to be a flippant example of a requirement for lots of bulbs, but wasn't expecting an actual fairground :)
One issue with using a PC power supply is you get 3.3V, 5V and 12V, but no voltage control. If you want to dim you can try using a resistor, but (depending on current/voltage drop required) it could end up getting hot, which might be tricky to mount in a confined space like a model house.
Also, if you have hundreds of watts of lighting make sure you have a window you can open...
Theo
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