Newbie Lighting Question

Newbie Lighting Question

Post by JP » Mon, 13 Dec 1999 04:00:00



I have 4 MTH street lights to wire.  Should they be wired in series or
parellel?  Does it really matter?  They will be driven by the accessory
power source.

Thank you.

 
 
 

Newbie Lighting Question

Post by Donald Lod » Mon, 13 Dec 1999 04:00:00


Quote:

>I have 4 MTH street lights to wire.  Should they be wired in series or
>parellel?  Does it really matter?  They will be driven by the accessory
>power source.

>Thank you.

It depends on the voltage of the bulbs and the voltage of the power
source.  With 12 volt bulbs and a 12 volt source you need to  wire  in
parallel.

1.5 volt bulbs and 12 volt power source needs series.  The bulbs will blow
if wired in parallel . And you would need at least eight bulbs in series.
12 volts/ 1.5 volts = 8 bulbs. More bulbs will cause the bulbs to burn
less brightly and therefore they will last longer. Less than eight bulbs
and you run the risk of blowing them.

I suspect these have 12 volt lamps as that what toy trains usually have.

Don Lodge

 
 
 

Newbie Lighting Question

Post by Jon P. Voge » Wed, 15 Dec 1999 04:00:00


Previously, JP wrote in rec.models.railroad:

Quote:
> I have 4 MTH street lights to wire.  Should they be wired in series or
> parellel?  Does it really matter?  They will be driven by the accessory
> power source.

Yes, it does matter.  If you wire in series, the lights will be dimmer than in parallel.  There's
a funny little equation involved here about adding resistors in series vs. parallel, but a simple,
though inaccurate, rule of thumb is as follows:

Pretend that the power supplied by the transformer can make x amount of light based on its power output.  Lights wired in series can be considered to make x / (# of lights) brightness.  In parallel, the light is still x bright, but you need the transformer to be able to output (# of lights) * x in power.  (Yes, I know that this is super simplified).

So, the question is as follows:

How many watts does each of your lights use and how many volts does your transformer put out?

What usually happens is that if you wire all of your lights in parallel, they will be too bright and will burn out faster.  If you wire all of your lights in series, they will be way too dim.  You need to reach a happy medium, with your lights wired in a parallel series, with maybe 2 lights per series and as many parallels as you need.  But, once again, this depends on the volts your transformer puts out (also the amps, but with just your 4 lights that should not be a problem ) and how may watts your lights use.

Sorry that it wasn't a simple answer, but it actually isn't a simple question.  But, I think most people do this by trial and error.  Put three of the lights in series, see how bright they are.  If they are too dim, take one out.  Stop taking them out when you have a nice, bright yellow light.  A really bright white light indicates that you are not putting enough resistance in the line and are risking burning out the bulbs quickly.  That's pretty much all there is to it.

Good Luck,

Jon

 
 
 

Newbie Lighting Question

Post by Tutor Helpe » Wed, 15 Dec 1999 04:00:00


There is one other consideration. Lights in series means that if one goes out they all go out and it becomes a bit of a chore to find the errant bulb. The best bet, wire them in parallel and add a dropping resistor. What size? Start at 10K and work backwards until you have a brightness you like.
Quote:

> Previously, JP wrote in rec.models.railroad:

> > I have 4 MTH street lights to wire.  Should they be wired in series or
> > parellel?  Does it really matter?  They will be driven by the accessory
> > power source.

> Yes, it does matter.  If you wire in series, the lights will be dimmer than in parallel.  There's
> a funny little equation involved here about adding resistors in series vs. parallel, but a simple,
> though inaccurate, rule of thumb is as follows:

> Pretend that the power supplied by the transformer can make x amount of light based on its power output.  Lights wired in series can be considered to make x / (# of lights) brightness.  In parallel, the light is still x bright, but you need the transformer to be able to output (# of lights) * x in power.  (Yes, I know that this is super simplified).

> So, the question is as follows:

> How many watts does each of your lights use and how many volts does your transformer put out?

> What usually happens is that if you wire all of your lights in parallel, they will be too bright and will burn out faster.  If you wire all of your lights in series, they will be way too dim.  You need to reach a happy medium, with your lights wired in a parallel series, with maybe 2 lights per series and as many parallels as you need.  But, once again, this depends on the volts your transformer puts out (also the amps, but with just your 4 lights that should not be a problem ) and how may watts your lights use.

> Sorry that it wasn't a simple answer, but it actually isn't a simple question.  But, I think most people do this by trial and error.  Put three of the lights in series, see how bright they are.  If they are too dim, take one out.  Stop taking them out when you have a nice, bright yellow light.  A really bright white light indicates that you are not putting enough resistance in the line and are risking burning out the bulbs quickly.  That's pretty much all there is to it.

> Good Luck,

> Jon

 
 
 

Newbie Lighting Question

Post by Jon Voge » Wed, 15 Dec 1999 04:00:00



Quote:
> There is one other consideration. Lights in series means that if one goes
>out they all go out and it becomes a bit of a chore to find the errant
bulb.
>The best bet, wire them in parallel and add a dropping resistor. What size?
>Start at 10K and work backwards until you have a brightness you like.

That's a good point about the burned-out bulb.  I didn't mention the current
limiting resistors because that might be a bit much for a new person.  I was
also trying to remember the exact formula for calculating how much current
lights in a series will draw.  I get to the E = I * R part, then things get
all fuzzy.   Been too long.  I think I'll research it, though, and come up
with the exact equations.

Regards,

Jon

 
 
 

Newbie Lighting Question

Post by Greg Luk » Wed, 15 Dec 1999 04:00:00


Anyone who advises wiring lights in series is giving bad advise.  If you
wire in series, two lights will be half as  bright as one.  Four will be
1/4th as bright as one, if you are lucky enough to get any light at all.
And, as was said, if one light burns out, you open the circuit and all the
lights go out.

The correct way to wire small incandescent lights is in parallel, using DC
voltage.  You can figure that each light will draw about 100milliamps (or
.1amps).  So, your power supply should be able to deliver the required
power.  For 10 lights, you would need 1 amp DC power source.  An old power
pack (ie, transformer) from a cheap train set will give you about 1 amp, if
you are using 12 volt lights.  I highly recommend you use 12 or 14 volt
lights.  They will last forever if you crank down the power supply to give
the lights a nice warm yellow glow.

This is another reason to use parallel lighting -- you can control the
voltage, and get the exact brightness you want.  If you want to get a bit
more complicated, you can use one circuit for visible lights, such as street
lights and pourch lights.  These look best if they turned down a bit.
Lights inside structures will need to be brighter, so a second circuit can
be used for these lights.  Don't forget, if you have a circuit that is
designed to be bright, you can always dim two of them by connecting them in
series.  Or, experiment a bit with low resistance resistors to get a
variation between a structures -- bright for stores, less bright for houses.

Good Luck -- Greg

Quote:

>Previously, JP wrote in rec.models.railroad:

>> I have 4 MTH street lights to wire.  Should they be wired in series or
>> parellel?  Does it really matter?  They will be driven by the accessory
>> power source.

>Yes, it does matter.  If you wire in series, the lights will be dimmer than

in parallel.  There's
Quote:
>a funny little equation involved here about adding resistors in series vs.

parallel, but a simple,
Quote:
>though inaccurate, rule of thumb is as follows:

>Pretend that the power supplied by the transformer can make x amount of

light based on its power output.  Lights wired in series can be considered
to make x / (# of lights) brightness.  In parallel, the light is still x
bright, but you need the transformer to be able to output (# of lights) * x
in power.  (Yes, I know that this is super simplified).
Quote:

>So, the question is as follows:

>How many watts does each of your lights use and how many volts does your

transformer put out?
Quote:

>What usually happens is that if you wire all of your lights in parallel,

they will be too bright and will burn out faster.  If you wire all of your
lights in series, they will be way too dim.  You need to reach a happy
medium, with your lights wired in a parallel series, with maybe 2 lights per
series and as many parallels as you need.  But, once again, this depends on
the volts your transformer puts out (also the amps, but with just your 4
lights that should not be a problem ) and how may watts your lights use.
Quote:

>Sorry that it wasn't a simple answer, but it actually isn't a simple

question.  But, I think most people do this by trial and error.  Put three
of the lights in series, see how bright they are.  If they are too dim, take
one out.  Stop taking them out when you have a nice, bright yellow light.  A
really bright white light indicates that you are not putting enough
resistance in the line and are risking burning out the bulbs quickly.
That's pretty much all there is to it.
Quote:

>Good Luck,

>Jon

 
 
 

Newbie Lighting Question

Post by TOM » Thu, 16 Dec 1999 04:00:00


Quote:

> Anyone who advises wiring lights in series is giving bad advise.  If you
> wire in series, two lights will be half as  bright as one.  Four will be
> 1/4th as bright as one, if you are lucky enough to get any light at all.
> And, as was said, if one light burns out, you open the circuit and all the
> lights go out.

> The correct way to wire small incandescent lights is in parallel, using DC
> voltage.  You can figure that each light will draw about 100milliamps (or
> .1amps).  So, your power supply should be able to deliver the required
> power.  For 10 lights, you would need 1 amp DC power source.  An old power
> pack (ie, transformer) from a cheap train set will give you about 1 amp, if
> you are using 12 volt lights.  I highly recommend you use 12 or 14 volt
> lights.  They will last forever if you crank down the power supply to give
> the lights a nice warm yellow glow.

Low Voltage Snips

Quote:
> Good Luck -- Greg



AC is far better for the small filiment lamps you're talking about here.
Far better, as in about double the expected lamp life...

Before any flame wars start, take a look at the following site:
http://www.jansons.com.tw/ep2-3.htm

The lamp life estimates listed below are from that URL...

 Average Life (Hours)    AC       DC
                        7000     3500
                        5000     2500
                        5000     2500
                        1500     1000
                        5000     2500
                        6000     3000
                        1000      750
                        2000     1000
                        1500     1000
                         300      200
                       15000     7500
                         750      500
                        8000     4000
                       10000     5000

Generally, these are miniature 12 - 14 volt lamps.

    <><><> TOM <><><>
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