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Old 04-01-2013, 02:56 PM   #1
DonR
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Passenger car lighting on DCC

Just finished installing the LED strip lights in
three of my HO passenger cars. Wow,
looks great.

Works great...not a flicker anywhere on
the layout. As expected the
capacitor in the circuit keeps 'em on.

But my addled brain is totally confused.

With the car taking power from the DCC (Bachmann EZ)
track, I measure 16.95 Volts DC across the capacitor
after the bridge rectifier with the LEDs burning.
I was anticipating a lower
voltage. Anyway...to get the desired low brightness level
it was necessary to use 1410 ohms of resistance between
the cap and the LED strip. That results in 8.6 Volts DC
across the LED input terminals when they are burning.

That's a voltage drop of 8.35.

Using the rule, 1 volt drop for each 50 ohm resistance,
I should achieve 8.35 with one 470 ohm resistor. 50 X 8.35 = 417.5.

So why did it take 3-470s in series (1410 ohms) to get to 8.6 v?

Is the LED 'load' so light as to not get the full voltage drop
from the resistors?

Ain't it fun the work on trains? Helps to start out addled.

Don
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Old 04-01-2013, 04:06 PM   #2
gunrunnerjohn
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If you're dropping 8.35 volts across 1410 ohms, you're only drawing about 6 milli-amps to light the LED's. That's obviously fine, but you mention "the brightness desired", apparently you didn't need the full brightness of the LED's for the application.
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Old 04-01-2013, 05:33 PM   #3
NIMT
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I use as many 5k for my interior lighting.
Useing higher value resistors will not hurt anything.
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Old 04-02-2013, 08:56 AM   #4
DonR
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John & Sean

Gotta thank you both for guiding me on this car lighting
project...

I didn't like the extremely bright effect of the strip LEDs
at full 12 volts...So started adding 470's in series until
I got what I wanted with 3 of 'em. Looks like the
old florescent tubes that were used in these old Silver Side
cars.

Do have a problem with the Intermountain metal 36" wheels
used for power pickup...they are excellent quality BUT the
flange is much finer than normal wheels...these cars have
talgo trucks and that seems to pull the wheels off the track.
Gotta go back to the regular metal wheels...pshaw. Never
had a problem with their old plastic wheels with the deeper
flange.

I plan to light up some cabooses next...will want them to
be substantially dimmer still.

Main headache...can't figure out how to take the shell of
the frame on any of the various Cabooses

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Old 04-02-2013, 02:32 PM   #5
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I have found that if the car is too light adding weights over the trucks will really help out keeping it on track.
Intermountain make 2 sets of wheels, .110 and semiscale wheels
Semi scale wheels do have much smaller flanges than the .110 wheels.
Tell me which ones you have and I'll get you the right ones.
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Old 04-03-2013, 08:49 AM   #6
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As usual, NIMT walks (runs) the last mile to help...and I didn't even
buy the wheels from him.

Thanks Sean...I've PM'd.

Don
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Old 04-04-2013, 12:26 PM   #7
DonR
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LED HO Passenger car video

Gonna try again.

It's just a short vid of Santa Fe Silver Side passenger
car train showing it's new LED strip lighting.

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Old 04-04-2013, 03:11 PM   #8
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They look great!
Now you need to put a better headlight in the loco!
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Old 04-05-2013, 09:24 AM   #9
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Thanks Sean

Yeah, that Bachmann F headlight looks like a small button...

What's available to dress it up?

Don
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