wiring ditch lights
Good day to all of you,
I am kind of stuck with this project. I am not very good at electrical et electronic stuff, but I,m willing to learn so I am turning to you all, once more, for help.
I want to add ditch lights to a loco I have but my problem is that I'm not sure how to go about for what I want to do. I have a decoder with only two available functions and I'd like to wire the lights so that both front lights are on at the same and the same for the rear ones, meaning that they won't flash and one wire is needed for each direction.
Now, I know I need to add a resistor since they are 1.5v bulbs, .015 amps but how do I wire two together? How do I calculate the value of needed resistor(s)? Will one resistor do or do I need two?
Thanks in advance,
Chris
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Use LEDs . . .
their life is measured in tens of thousands of hours, not hundreds, like 1.5 V bulbs!
See my March column:
http://model-railroad-hobbyist.com/magazine/mrh-2012-03-mar/dcc_impulses
Bruce Petrarca, DCC Impulses columnist
Learn about DCC at Mr. DCC's University:
www.MrDCCU.com
Depending on the Loco
Depending on the loco type, I would suggest simplifying things somewhat. If the loco is one of the "comfort cab" types that dominate modern railroading, I suggest just making the front ditch lights operational and leaving the back ones as "dummies".
-George
"And the sons of Pullman porters and the sons of engineers, ride their father's magic carpet made of steel..."
Modeling the Ogden River Railway in HO.
While I also usually use
While I also usually use LEDs, the answer to your question is the same. The decoder puts out around 13 volts on function leads but you need only 1.5 volts. The current will be 15mA or .015A so the resistor needs to resist whatever the bulb doesn't so in this case it's about 11.5 volts. Resistance can be calculated by dividing volts by amps so the math is 11.5V/.015A=766ohms. To check what size resistor, multiply volts and amps, in this case you get .17 so a 1/4 watt resistor would be fine. I put a resistor on each bulb and wire all the lights I want to work together to the same terminals. I usually go just a little higher resistor value than calculated so the light isn't operating at peak capacity and will hopefully last a little longer.
Thank you all
@kjd
That answers my question very well, thank you!
@Bruce
Since the bulbs are already installed on both end, I'm not willing to remove them to install LEDs but I will be installing LEDs on my other locos.
@George
This loco has a regular cab (Atlas R&S #206, GP40) and will operate on a switching layout so I want the lights to operate on both end of the loco and I'm willing to sacrifice the flashing.
Cheers,
Christian