Wednesday 25 September 2013

Power supply for HO scale lighting

Have been wondering how to supply power to my street lights.

2 questions:

Battery or transformer/adaptor?

What power ratings should the supply have in order to properly light up the bulbs but not blow them?

A couple of days ago I declared my ignorance about the application of Ohm's Law (V = IR) to this issue.

In the mean time, I found this old adaptor in the back of a cupboard I was clearing out.

Had to get rid of the connecting socket

And soldered on two crocodile clips instead.
The beauty of this adaptor is that it delivers variable voltage - accessed by sliding a little switch at the back of the plug.

The little slide switch

3, 4.5, 6, 7.5, 9 or 12 volts

For 12 volts the output is 0.9 amps; for the lower voltages it is 1 amp.

That's useful information for when I learn how to apply Ohm's Law (as opposed to simply calculating the equation V=IR).

Temporarily rigged up a couple of brass tubes for supporting posts and dangled a street light between them. Clipped the crocodile clips to the base of each vertical tube.

The set up.

Turned out the room lights

And turned them on.
7.5 volts was selected (scared I'd blow the bulb) and there is a resistor in series with the bulb.

I think I could have gone to 12 volts because the bulb is rated 6 volts and the resistor should cut the supply from 12 v to 6v (I think).

But the bulb is also rated in terms of amps viz 0.07 amps. Would the 1 amp supply from the adaptor not have been too much for it???? That's the bit I can't quite work out.

Currently listening to:

Recorded 2005.

Over the decades, I have tried my best to like jazz. The only jazz that I do like is that emanating from Scandinavia eg Tord Gustavsen Trio.

Last night's dinner:

Potatoes, baked beans and a selection of  pretentious sausage rolls.
Currently reading:

Some of Freud's stories of sexual shenanigans in the catering industry and in the army are shocking (albeit hilariously related.)


Took the bikes to Tarbet and cycled the section of the West Loch Lomond cycle path that we had still to negotiate ie back down to Inverbeg. Negotiate is too strong a word - the path is flat.


  1. Those boats in the photo are run by my last neighbour owner of Cruise Loch Lomond.

  2. There was a continuous ferry service, a shuttle really, over to Inversnaid. Dozens of people using it.

  3. I think you call it a water bus, goes to Balmaha too.