Wiring for a roundhouse?


M

Myowngod

Pennsy Tuscan Red Blood
I am wiring lights in the roundhouse for my Dad's layout.
See schematic below. Click on it to see clearer.
View attachment 8564

The bulbs being used are 1.5v 15mA, grain of rice style(YELLOW circles). I was thinking of having 5 rows, 1 for each timber frame between tracks, with each row having 4 bulbs. The wire leads (RED) would drop down below the structure located at the front door and rear wall locations. They would hook up to a set of "buss" wires (ORANGE) under the structure, and then those busses would hook up to a power supply under layout (GREEN). The power supply will probably be an old transformer, maybe 12v.

There is a total of 20 bulbs in the circuit. My question is, should I put a resistor on each leg of 5 bulb rows or one larger one at the point where the wires run to the transformer? Also any ideas how many Ohms they should be? Each row would total 6v, the whole building 30v. I would rather the bulbs be dimmer then brighter, since there's so many in the building. I'll put a few bulbs on the outside of the structure near the back service doors as well

Thanks
 
Just wondering why you'd use series wiring for your lights and not parallel. With series when one lamp in a string fails they all go out. With parallel just run two buss lines from under the structure to each leg. That way if one goes out the rest stay on. Voltage taken across 2 rectifier diodes will give you close to the 1.5 volts and it'll be reasonably regulated. With a variable resistor across the diodes you can vary the light intensity to whatever suites you.
Just a thought.
Cheers Willis
 
I agree with Willis on the parallel vs series wiring question. That's why I always hated our old Christmas tree lights - you spent half of Christmas tracking down the burned out bulb in a string. :) I don't think you really want to do that with a roundhouse.

I also agree with the idea of a variable resistor or using the variable rheostat in a toy train power pack. 16 15mA lamps are, I think, going to be an awful lot of light for a relatively small structure and I think you'll need to dim them down considerably.
 
could this also be applied when using white led's? when i read this i thought it would make a great addition to the engine facility when i get it.
 
It's actually 5 series (4 bulbs each) in parallel. If I series 4 1.5v bulbs together, I can put a 1000 Ohm resistor on each series and they are just the right light, not bright, just a warm glow. I know if one goes out on the series they all go, but I don't want a bunch of wires coming down from the structure inside. The way I have it planned it would be 1 wire in the front and 1 in the back for each series, total 10 wires. Otherwise it would be 2 wires for each bulb, total 40 wires.

When I did the calculations for the resistor it came out to be 800 Ohms, so I put a 1000 Ohm resistor for longer life... I hope.;)

CBCNSfan - what is the difference between a regular resistor and a variable one? Or even a rectifier diode?
 
CBCNSfan - what is the difference between a regular resistor and a variable one? Or even a rectifier diode?
Click to expand...
Sorry it took a bit of time I decided to make a sketch.
Resistors, actually the only difference is the materials they are made of. Most common are the cylinder shaped with the colored bands, a variable resistor can have a carbon base but more common are the potentiometers like the volume controls on your stereo. These potentiometers have three terminals, the outer two have the total resistance with the center one being a wiper that allows you to select a portion of that resistance. You can accomplish what you want to do with a voltage divider of two fixed resistors.
A rectifier diode handle much more current than a signal diode and actually are the most common for our purposes. The 1N4000 series will be more than adequate for MR purposes.
In the diagram the power source can be any DC power pack, R1 (a carbon resistor) the value is not critical but keep in mind all the current for your lamps will flow through it. The two diodes connected in series will have a constant 1.5 volts across them therefor the terminals A and C have 1.5 volts for your lamps. R-2 and R-3 a divider network will divide the 1.5 volts according to the ratio of their resistive values. Like if R-2 were 5K ohms and R-3 was 10K ohms we could expect to have 1 volt between the B and C terminals. In this case the current for the lamps will be going through R-1 and R-2 but the voltage drop across R-1 will be equal to the (Power source) - 1.5 volts
Hope it helps the values I used are just to explain the diagram, the 1.5 volts is a good value though.
Cheers Willis
 
Last edited by a moderator:
You must log in or register to reply here.



Back
Top