Fox Valley ES44 GEVOs - Brightening The Ditchlights

[MetroRedLine]

I have locos from about every run.  The shell is typically very difficult to remove the first time.  I grind a bit off the "pimples" on the chassis which makes them come off easier.  I always take the fuel tank off first, and then simply continue to apply pressure until the shell lifts.  And yes, watch those sides carefully,  it's a beautiful jigsaw puzzle the first couple times.

I've taken off the fuel tank and even the radioator roof for good measure. Nothing budges! Argh!

[jereising]

Yep, the first shell removal can be daunting.  Just keep at it.  Little steps.

[MetroRedLine]

Those are 0604.  Were I doing it today I would use the Ngineering Nano in super white...I soldered my own leads.  One you get the hang of it, easily done...

The photo makes them look brighter than they really are.  In person, they're pretty close to the headlight.

Okay, I finally was able to take off the shell from my FVM GEVO. For your LEDs, did you have to use a different resistor? The voltage I'm getting for the stock dark amber LED is 2v. I actually happen to have some 0402 nano SMDs but they require 3v. How do I get them going?

[peteski]

Okay, I finally was able to take off the shell from my FVM GEVO. For your LEDs, did you have to use a different resistor? The voltage I'm getting for the stock dark amber LED is 2v. I actually happen to have some 0402 nano SMDs but they require 3v. How do I get them going?

What you are seeing is a voltage which develops across the LED. Yellow LEDs have around 2V and white LEDs will have around 3V.  The Decoder puts out around 10V to the function output. A series-connected resistor in the LED circuit  will regulate the current to the LED.  What I'm trying to say is once you replace the yellow LED with white LED, the LED will light up and there will be around 3V across it.  It won't burn up. If it is too bright, replace the series resistor with a larger value one.

[jdcolombo]

If you know the supply voltage, forward voltage drop and recommended current for an LED, you can use any of a number of handy calculators available on the web for calculating the dropping resistor value.

With DCC, you can assume an output of 12v at the function wires (it might be a tad lower, but for this purpose it doesn't matter much, and better to overestimate a bit than underestimate).  The Ngineering white nano LED specifies a 3.3v drop with a 20ma recommended operating current.  So if you plug those values into a calculator like the one available here:

https://www.pcboard.ca/led-dropping-resistor-calculator

it tells you to use a 1/4-watt 470-ohm resistor.  I usually find the recommended values too low, however - the resulting light is way too bright for me for locomotive lighting purposes.  Instead, I nearly always use a 1K resistor, which drops the operating current to 10ma and allows me to use a 1/8-watt resistor, instead of a 1/4-watt.

Most LED spec sheets will give the forward voltage drop and recommended operating current.  This allows you to calculate a "standard" dropping resistor value and wattage.  From there, you can try larger resistor values to "tone down" the brightness.  And notice that as the resistor value goes up, the current passed goes down, meaning you can often go from a 1/4-watt resistor to a 1/8 watt (smaller) at higher resistor values.

John C.

[peteski]

The Ngineering white nano LED specifies a 3.3v drop with a 20ma recommended operating current.

That is the problem with electrical specs - that is really the maximum safe current which they call "recommended current".

For our purposes White LEDs only need around 5mA or even less to produce the desired brightness.  If 5mA is used then you can calculate more realistic resistor value.

[jdcolombo]

That is the problem with electrical specs - that is really the maximum safe current which they call "recommended current".

For our purposes White LEDs only need around 5mA or even less to produce the desired brightness.  If 5mA is used then you can calculate more realistic resistor value.

Agree. 20ma is too high.  Most white LEDs have a 3.3v drop.  5ma from a 12v source would call for a 1.8K resistor, and would sink about .045 watts, which would be well within the tolerance of a 1/8-watt resistor. 

John C.

[peteski]

Agree. 20ma is too high.  Most white LEDs have a 3.3v drop.  5ma from a 12v source would call for a 1.8K resistor, and would sink about .045 watts, which would be well within the tolerance of a 1/8-watt resistor. 

John C.

Yes, white LEDs will have a voltage drop across them of around 2.6V to over 3V, depending on their chemistry and on the current.  The lower the current, the lower the forward voltage.  If you were to measure the Vf of a white LED with 5mA passing though it you will most likely see it dropping around 2.7V. But for our application using 3V as a general value for calculating the resistor value works fine.

[MetroRedLine]

Thanks everyone! I FINALLY DID IT!

I happen to have some 0402 SMD LEDs, so I decided to replace the stock front LED with two of these SMD LEDs stacked on top of each other, to allow the headlight and ditchlights to get equal illumination.

I started by clipping off the stock LED:



Then I got a piece of Evergreen #178 .100 x .188" strip styrene and cut it to the approximate height of the stock LED. The styrene block will function as a mount for the SMD LEDS. To seat the LEDs better on the mount, I got a small drill bit (the smallest bit in a standard drill set) in a pin vise and carved two dimples at the top center and the bottom center of the styrene block.



I glued each SMD LED into the dimple with CA, making sure the flat illuminated portion faces the front, and the back (where the wires meet the SMD) are what contacts the CA. It should look like this when both are attached:



In my first attempt at this, I accidentally broke off one of the wires off of the top SMD, so the best way to deal with the wires was to twist the pair together. Also with the way the wires are oriented when the SMDs are glued in, the wire orientation is opposite to where the + and - solder points are.

CA the back of the styrene block to the edge of the light board in the little nook where the original LED used to sit -- it is not necessary to glue it to the bottom of the nook, as you might want to remove the board to perform loco motor maintenance in the future.

Now solder the wires to the existing headlight solder pads. The + is the engineer's side of the locomotive and the - is the fireman's side. This is what it looks like when the wires are soldered in:



Time to test it out!



Looks good! Now, before I put the shell back on, it's best to secure the wires onto the light board with Kapton tape, to make sure the wires don't snap off when the shell is re-installed.



FINISHED!!!

[jdcolombo]

Excellent work.

Looks great!

John C.

[Scottl]

Nice work, a great and easy fix.

Is there some leakage below the front porch?  Maybe a touch up with paint on the light tubes?

[MetroRedLine]

Nice work, a great and easy fix.

Is there some leakage below the front porch?  Maybe a touch up with paint on the light tubes?

Yes, I noticed that. I'd have to disassemble the shell to get access to the light tubes as the opening is too small for even the smallest size paint brush.