Random Bulb Lighting

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Bru

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I've been asked by my local model railway club to build a circuit that will light up houses and shops randomly on the new layout currently under construction. My first reaction was to use a tested and working multi-aspect European road traffic light circuit, substituting the coloured LED's for white ones, and slow the sequence down a high value resistor.

Unfortunately, the builder is determined to use 12v grain of wheat bulbs; I don't have any design skills and I tend to build circuits from existing diagrams - but I don't have any circuits that will do this job. The only suggestion I can think of is to wire the bulbs to a series of mult-pole rotary switches and mechanically turn on and change the lighting. This seems a bit ham-fisted, though.

Anybody got any suggestions or links to a circuit?

Thanks. Bru
 
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hi,
Whats the 12V wheat bulb current rating.?
 
I'm not sure of the current rating of the bulbs available, but they're probably the ones I bought for the club some time ago - almost certainly 65mA or 85mA, but I can buy ones for the project with a known current rating. The building are in the design stage at present, but I gather there will be around 30 of them - obviously not all lit at the same time.

I agree about LED's and - as I said - I already have a schematic for something which would possibly work, but the builder is keen to use bulbs.

Bru
 
Last edited:
Ubergeek63 said:
you would be better off with LEDs but for your sequencer, you can use 74HC4017s

Dan
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hi Dan,
Looking at the 'wheat' bulbs, they appear to be rated about 60/80mA region.

Ive asked the OP for the actual rating.??
 
The grain of wheat bulbs color

is perhaps the deciding factor.
they have a yellow hue instead of bright white or pure yellow color of LEDs.
I was thinking perhaps several 4017s with transistors on the outputs.
use an emitter circuit for a fading effect.
will draw up something to start.
 
I'm thinking of a slow-latched, 30-bit random number generator with lamp drivers. I did see "random" as a requirement.
 
this circuit needs tweeking

here is a simple solution that should work.
the componet values may need tweeking a bit.
just arrange the diodes in various patterns etc.
 

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I'd use a PIC (or even PICAxe) and a handful of PN2222 or a ULN2803 to drive the bulbs. (I don't know how much current the grain of wheat bulbs draw but I assume its very small)
 
the 2803 would be nice

but then you need to use pnp or inverters.
a pic yes if you have the resources to program them.
I myself want to learn how.
see there is C and assembler to program them
just need to get my hands dirty and find a cheap version of a programmer unit.
can't put out $100+ for one.
much less $65 for programming coarse that I get Emails about.
what to do??
yes I looked over your site, nice but just need to take the plunge.
I need to build a reaction timer for our pinewood drag racing setup.
 
Thank you for the help, folks. Very much appreciated. I'll get busy with
MrDEB's schematic this weekend and see what I can get working.
 
slight revisions w/ PS added

I added a regulated PS as well as an unregulated one for the bulbs.
this should work??
 

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