Time to put lights in my brass steam. What will look nice in the engins are those 1.5 volt, tiny little bulbs.
What resistors do I use? I’m and in HO and run digitrax. How do I read the colored bands on the resistors to know what it is? To be truthful, I haven’t used a resistor since 1950 in boy scouts. Please keep it simple.
The easiest way to read a resistor? With a multimeter…
http://xtronics.com/kits/rcode.htm
Here is a link to the color code. We has a somewhat more explicit version of the rhyme used in my electronics class at University. The only female engineer used to rattle it off with relish!
http://tonystrainexchange.com/technews/install-lamps-decoders.htm
Here is a discusion of resistor choice from Tonys
Here is a neat tool if you are using LED’s
I really like the golden-white 3mm LEDs, with a 1K resistor. LEDs run cool, consume very little power and last a very, very long time. They throw a very directional light beam, just like a headlight, and the golden-white colors have the proper yellow glow for older headlights.
Art,
I’m with Bruce on the 3mm golden-white LEDs. They really add realism to the headlight beam by putting out an incredible amount of direct light. As Bruce mentioned, it is very prototypical looking for the earlier steam and diesels.
The other plus to the LEDs is that the light is constant in DCC and doesn’t vary in intensity, like it does in DC. Art, you can buy a pack of 1K resistors directly from either Radio Shack or your LHS, if they stock them.
One thing to point out, which you may or may not already know. Resistors are non-directional so current can travel through them either way. However, LEDs are directional, so you need to be sure that you solder them in correctly.
The blue (common) wire from the decoder goes to the anode (+) or longer leg of the LED. The white (front headlight ) or yellow (rear headlight) wires from the decoder are soldered to the cathode (-) or shorter leg of the LED. The resistor can be soldered to either leg of the LED.
Hope that’s a help…
Tom
If you decide to go with LEDs, you can run optical fiber to the marker lights. I still have 1.5V bulbs in some steamers, and I’ll replace them when they fail. Until then, they look good. Use a constant lighting voltage circuit and you will solve the voltage reduction issue, too. I think this is right:
http://www.mrollins.com/constant.html
Thanks so far. How do you put the LEDs in the steamer light canisters and not look all bulky with those big leads sticking out some ackward place.??
Art, unfortunately LED’s do require some space. You can cut down the legs of the LED but I can tell you from experience that it is possible to destroy an LED by applying too much heat when soldering. When I cut the legs I like to leave enough so I can grasp the leg with a needle nose plyer between the LED bulb and where I am soldering to act as a heat sink. The resistor can be anywhere in the lead, so it can be in the wire at the decoder end, so you don’t have to have it there. The bottom line is, that you may not be able to fit an LED in your application. In Tom’s picture, there is tons of space as the LED can be inside the smokebox.
Simon makes a good point about room. All three of my steamers are newer (7 years and less) and were either DCC-equipped or DCC-ready - i.e. they already had a light board/resistor inside the shell to either add or replace the LED to.
Art, a couple of other tips for you. Black heat shrink around the LED will help concentrate the LED beam through the headlight lens better. Also, if the lens to your headlight is large enough and it doesn’t already have an opening, and you can drill the center of the lens with a #33 (0.113") or #32 (0.116") drill bit no deeper than 3/16" (0.1875") deep. A 3mm T1 LED will fit right up into that opening. I don’t glue mine in.
Tom
Art, the basic formula to use is R=V/I where R is the resistor value you are looking for, 1.5 is the voltage that the lamp requires, and I is the current that the lamp requires to illuminate to the proper brilliance. The max current is always specified on the data sheet for the lamp. Plus in the numbers in the formula and you will have the value resistor you need.
Hi Art.
An alternative would be to use a decoder that supplies 1.5V and doesn’t require any resistors, such as the ZIMO MX64V1.
Regards,
Art
ZIMO Agency of North America
http://www.mrsonline.net/
Thanks to all. It appears the answer to the question I was having trouble asking is Green/Blue/Brown. I need to go with bulbs because my decoder does not like LEDs and my engines have no room for them, thus the bulbs.
resistors for 1.5 volt little bulbs???
SINCE the topic was 1.5V lamps and resistors, not LED’s, I will answer accordingly.
Using resitors with DC track power will vary the intensity up and down. Better to use a bridge rectifier in series with the motor and run the bulb off the 1.4 voltage drop.
A 1.4 or 1.5V lamp will not only fit within most housings, comes on before the engine moves, but give you a realistic looking non variable headlight too. Adding 2 more diodes gives you ‘Directional’ characteristics’ for bi-directional diesels. Again, the motor acts as a ‘ballast’.
I have nothing against whiteLEDs but they are packages of RGB and generally require 5 volts to come on, and some of todays diesels start movinga at 2.5V.
I have mostly 1.4 15ma bulbs and have yet to replace one in 20 years. Check back with me in another 20?
Thanks, Don for actually answering the question that the original poster asked.
I still see one missing element. The resistor also depends on what voltage the DCC unit is set to put out onto the track and the current that the particular light bulb draws.
Our club runs 17.5 V. I lowered mine at home to 14.5V. So for my locomotives that are going to be run at the club need a different resistor than those for home.
I always try to use bulbs that only pull 15 ma. I also always try to run my light bulbs at 1.3 volts so that they last forever. In ummm 2006-1983=13 years have never burnt out a light bulb using this scheme.
We had so many questions about this at the club, I put together a spreadsheet for the members. I just threw it up on the web for everyone here.
http://www.walkersquawker.net/LightBulbs.htm
TZ great chart. It will come in very handy I am sure for many people.
I asked myself this very same question just today! I found on the Digitrax website, in the Decoder Manual, that 1.5V bulbs require 560 Ohm resistor. I’m not sure if a resistor of that exact rating is available, so you may have to put a resistor or two together to get that resistance rating. Oh, and they must be 1/4 Watt resistors (the smaller ones). When installing the resistor, they must be placed in series on the white/yellow lamp wires to each bulb.
Sorry everyone. When someone uses the term “bulbs” (as Art did in the original post), I automatically think of both incandescent and LEDs, not just incandescent. Sorry for the tangent, Art.
Tom
Actually the question asked was about bulbs with DCC, Don did a great job of providing excellent information on bulbs with DC.[}:)]