Subject:
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Re: 12v Transformer
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Newsgroups:
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lugnet.trains
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Date:
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Tue, 20 Jan 2004 08:00:13 GMT
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Viewed:
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1210 times
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In lugnet.trains, Larry Pieniazek wrote:
> In lugnet.trains, Alan Muhl wrote:
> > I just acquired a 12v train set but it did not come with a transformer. Can
> > anyone provide advice about how to get one that works with a 110v outlet. The
> > ones listed on Bricklink all appear to be 220v. Can the 220v variety be adapted
> > to a 110v? I have had some reference to purchasing a 220v transformer and then
> > buying a converter. If that is the way to go then what type of converter? Thanks
> > for any help.
>
> I had good luck with a stepup transformer I bought at Radio Shack. You need to
> get a real transformer in my view, not one of those things that can run
> shavers... When you buy a 220V speed regulator, you will find some amperage or
> wattage requirements molded or printed on the case... hew to those in doing your
> stepup shopping. You can go larger but don't go too much smaller.
>
> Alternatively for a non LEGO solution, go with any reliable supply of 12V DC of
> sufficient amperage and splice it in to a power lead wire.
>
> Alternatively/alternatively, you can cut a 9V wire and splice a 12V connector on
> it...(1) the 12V trains will run on 9V, just not as fast. And if you operate 12V
> bulbs on 9V, they will last longer. I am not sure about operating accessories
> like remote switches though.
>
> 1 - I have done this, I got some 12V connectors (as service parts) from Conan
> and used a jeweler's screwdriver to mount them on a stripped 9V wire that I cut
> in half... one wire cut in half will give you 2 12V/9V power convertor leads. I
> will argue that it is almost not impure, but not quite. You're technically not
> supposed to cut 9V wires, although apparently if they sold 12V connectors you
> were supposed to at least be able to restrip 12V wires so I dunno.
A 12V transformer supplies full wave rectified power (humps on an oscilloscope).
Mine puts out up to 14.7 Volts no load to the track. The "DC" to the switches
is also 14.7 Volts max. There is an AC output that gives 17 Volts AC no load.
Therefore if you were to make your own transformer unit, use a 110V transformer
that has 18-21 Volt windings rated for at least 1.5 Amp (you might lose a bit in
regulation, but I haven't time here to calculate how much - other electronics
experts might like to say). The current rating should be well above your
expected constant load. Generally, don't skimp on the ratings or it'll get
rather warm and might be dangerous. Make sure your mains input is fused inside
the box if you make your own AC unit.
You could try feeding the 12V transformer's AC output with this 18VAC and test
whether the transformer produced enough DC - the AC output is connected to the
panel switch output but the train control output comes off other tappings of the
transformer. Therefore you'd lose efficiency by using the internal transformer
to tap off the 17V AC for the track output. If you upped the voltage to
compensate, the resulting DC voltage on the panel switches might be too much and
could blow bulbs etc..., so better leave this one for the test bench! Test
anything thoroughly before using expensive Lego components on it.
Regarding running 12V trains on a 9V controller, A 12V motor takes up to 12V at
2/3 Amp = 8Watts. A 9V controller gives up to 9V at 300mA = 2.7W, so there is a
serious power shortage! 9V gives half the power of 12V (proportional to V*V).
I think the 12V motors need the noisy full wave rectified unsmoothed DC to get
torque at low speed - you'd lose this with a smooth 9V controller. This is in
common with other model railways.
I have used the 12V trains with a beefy 3Amp smooth power supply at exhibitions,
but that's the expensive option. The PSU could easily handle multiple 12V or 9V
motors running for a long time. The advantage is that there was no need to
change PSU between the two systems.
I made some 9V-12V convertor wires so that I could use any old wiring for the
electrics and then convert it to the system for 9V track. Just put a 12V plug
on half a 9V lead. If you have any 1/0.6 bell wire you can shove the bare end
into the pins of a 12V plug. "Purity" for me means using only Lego in the
models (no glue, stickers or paint and minimal modification of parts, for
mechanisms only) - I'm not bothered about electrics beyond the feed wire as I
use a PSU to overcome the lack of power from Lego transformers (I'll stop
ranting before I start!). When you model wider than 6 you need more power and
more motors!
Mark
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Message is in Reply To:
 | | Re: 12v Transformer
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| (...) I had good luck with a stepup transformer I bought at Radio Shack. You need to get a real transformer in my view, not one of those things that can run shavers... When you buy a 220V speed regulator, you will find some amperage or wattage (...) (20 years ago, 19-Jan-04, to lugnet.trains)
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