Large Scale Central

Eggliner Lights

Electronics
#1

I am changing out the Marker Lights on an Eggliner. For now will be keeping the Front and Rear lights as incandescent. They only draw 60 ma. each.

But the marker lights total 240 ma. I have removed the incandescent lamps and wonder what colors to use for the markers.

Each side has two lamps so was thinking of either Green/RED or Green/Yellow or Yellow/RED. Where which one should indicate Coming towards you?

All LED’s will have a 20 ma current limiter and each side the LED’s will be in series.

BTW: This will also be DCC with 3 or 4 Functions.

Dennis

#2

Markers are usually red to the rear, and green to the front. Classification lights could be green or white (clear) So if you had red to the rear and green to the front, you could satisfy both functions.

#3

David Maynard said:

Markers are usually red to the rear, and green to the front. Classification lights could be green or white (clear) So if you had red to the rear and green to the front, you could satisfy both functions.

David: that was my first choice but wanted to see what others here on the forum recommended.

#4

Well, since there aren’t many responses, I guess you can just do what you want.

#5

David Maynard said:

Well, since there aren’t many responses, I guess you can just do what you want.

I guess it is my railroad and can do what i want. LOL.

#6

Dennis, now that’s the spirit.

#7

20ma lights give off a lot of light. You can reduce it to 12 ma esp for battery operations and with 2 in series save battery power/like.

However for dual leds, series operation is not easy for most but 12 ma instead of 20ma is a good way to go.

I would have front and rear as dual white/red leds and dual red/green on the sides. For the eggliner with 6 lights lit and 12ma per light, current would be minimal for battery operations

For DCC I would go with the full 20ma.

#8

Dan Pierce said:

20ma lights give off a lot of light. You can reduce it to 12 ma esp for battery operations and with 2 in series save battery power/like.

However for dual leds, series operation is not easy for most but 12 ma instead of 20ma is a good way to go.

I would have front and rear as dual white/red leds and dual red/green on the sides. For the eggliner with 6 lights lit and 12ma per light, current would be minimal for battery operations

For DCC I would go with the full 20ma.

Dan I agree. i posted as 20 ma as most people understand that value for LED’s, I was going to use between 10-15 ma current limiting with DCC. Reason is I want to use Rule 17 for the headlights so I need to pick a nominal value at full brightness that will give the dimming I want at stop. CV’s will be adjusted for the dimming and brightness.

it will be wired as 4 circuits, Front Light, Rear Light, Marker Lamps x2= 48 ma total. Each side the marker lamps, RED and Green, with be wire in series.

Before anyone comments, normally a RED LED voltage (~2.2 Volts) and the GREEN LED (~3.2 Volts) can still be wired in series and current limiting works best to prevent destroying the LED’s.

I am using 5 mm Cool White LED’s for the marker lamps and painting them with kids fingernail polish you find at Michael’s.

#9

I feel finding resistor values for 10 and 20 ma is simple. 10 ma is 100 ohms per volt dropped. So a 3 volt led on 24 volts is 21 volts times 100 ohms and the resistor would be 2200 ohms (resistors come in 2000 and 2200 ohms).

for 20 ma it would be 1100 in the example above 21 volts times 50 ohms and equals 1050 ohms).

Of course one can use an online calculator, but to me it is simple math that can be done in my head.

#10

Dan Pierce said:

I feel finding resistor values for 10 and 20 ma is simple. 10 ma is 100 ohms per volt dropped. So a 3 volt led on 24 volts is 21 volts times 100 ohms and the resistor would be 2200 ohms (resistors come in 2000 and 2200 ohms).

for 20 ma it would be 1100 in the example above 21 volts times 50 ohms and equals 1050 ohms).

Of course one can use an online calculator, but to me it is simple math that can be done in my head.

I understand that part, but by using a current limiting device you completely eliminate resistor calculations, that seems to be the issue I read about on the forums, members seem to shy away from using LED’s if they have to select resistors.

LED’s can be hard to figure out the exact voltage of each LED, they very slightly, and you need to know that all LED’s are not around 3.2 volts. Red, Yellow, Purple and orange can be in the 2.2 volt range.

Connecting one LED is easy to figure a resistor value with a fixed voltage, but when connecting LED’s in series or have a varying voltage, it gets more complicated. You can connect up 35 3.2 volt or up to 70 2.2 volt LED’s in a circuit that is powered by 120 Vac, but still need some current limiting device like a resistor or circuit. I prefer the current limiting circuit. Believe me I have repaired 1000,s of Christmas light strings from many suppliers.

What works well for me is using a LM317L (TO92 package) and one resistor of 68 ohms for 20 ma or 82 ohms for 15 ma and I am done. this is what I use on decoders that have DC connections. I can then put 3 using 12 volt DC or 4 using 14-16 volts DC, LED’s of any color in series with the current limiting circuit on a decoder and do not need to worry.

Dennis

#11

Dennis I was doing the same. In fact I still have a bunch of those regulators in my parts box. But the new CL2, LED driver chips, are so much easier to use.

#12

David Maynard said:

Dennis I was doing the same. In fact I still have a bunch of those regulators in my parts box. But the new CL2, LED driver chips, are so much easier to use.

Yes the CL2 works well but you are stuck at 20 ma. No way to reduce the current limit. But you can parallel the CL2 to increase the current limit in 20 ma increments.

I want something less than 20 ma. The LM317L has a maximum working voltage of 35 volts and can handle up to a 100 ma output. No heat sinks needed.

I am experimenting with another circuit that will not only give me current limiting but also dimming. That way I do not have to be concerned about the brightness of the LED’s. This will be adjustable dimming.

#13

Dennis, but that isn’t true. You can shunt some current past the LEDs with a resistor. If you have 3.2 volts across the LED, and you want to shunt 5 miliampers past the LED, a resistor value of 640 ohms would do that. 2 330 ohm resistors in series would give you 660 ohms, pretty close, and the 330 is pretty common.

#14

Or 2 10 ma leds in parallel with a CL2. To keep current balanced, add 100 ohm resistors to each led.

#15

See, there is a way.

#16

What Dan said, parallel 2 to get 10ma… I bought 100 CL2 a while ago. Makes stuff simple, and also brightness is perfect whether on my layout (24v) or others (sometimes as low as 18v).

Greg