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
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.
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.
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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.
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:
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:
- or use a power supply with an ATX power connector.
Those usually don't start up all the power lines until a signal is seen
from the PC.
You can get one of these:
for similar money.
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.
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
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.
OK. Look here, which may explain other questions I have asked, such as
stripping cable, staplers, carpets and more. Scroll right down :
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.
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.
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.
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.
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
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...
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