Harold,
Whatever size bulb you use, you can use the DC side of the power Pack to "dial down" the voltage. I end up running my 12V exterior/interior lighting incandescent bulbs @ 55-60%. Even at that voltage it provides a very nice and pleasant glow:
As far as headlights, definitely consider the LEDs. As mentioned, they operate much cooler and the beam is much more directional with an LED than with an incandescent:
If you have light leakage in the cab, a piece of heat shrink (shroud) around the head of the LED does wonders:
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
MisterBeasleyI would strongly recommend selecting a power supply standard for all the structure lighting on your layout, and then buying bulbs to suit that supply. That way, you will not need to mess with resistors at all, and your installations will be much simpler. You also won't be wasting power heating up resistors. On my layout, I use a 12-volt supply and run 16-volt bulbs. Running the bulbs at well below their rated voltage greatly increases bulb life, and provides a softer, warmer glow than running them at full power. Install a fuse between your power supply and your lights, too. Most supplies are not fused, and they will burn out if you accidentally short the leads, or if you overload the supply by slowly increasing the number of bulbs until it's just too much. For locomotives,use LEDs. There are many advantages. First, LEDs last far longer than incandescents, and replacing bulbs in locomotives is a time-consuming job. LEDs use less power, and we always must be aware of how much of our precious DCC power we're using. LEDs generate virtually no heat, so they can be safely placed against plastic locomotive shells without worry about melting. LEDs are directional, too, and are therefore much more appropriate for headlights.
I would strongly recommend selecting a power supply standard for all the structure lighting on your layout, and then buying bulbs to suit that supply. That way, you will not need to mess with resistors at all, and your installations will be much simpler. You also won't be wasting power heating up resistors. On my layout, I use a 12-volt supply and run 16-volt bulbs. Running the bulbs at well below their rated voltage greatly increases bulb life, and provides a softer, warmer glow than running them at full power. Install a fuse between your power supply and your lights, too. Most supplies are not fused, and they will burn out if you accidentally short the leads, or if you overload the supply by slowly increasing the number of bulbs until it's just too much.
For locomotives,use LEDs. There are many advantages. First, LEDs last far longer than incandescents, and replacing bulbs in locomotives is a time-consuming job. LEDs use less power, and we always must be aware of how much of our precious DCC power we're using. LEDs generate virtually no heat, so they can be safely placed against plastic locomotive shells without worry about melting. LEDs are directional, too, and are therefore much more appropriate for headlights.
There's never time to do it right, but always time to do it over.....
It takes an iron man to play with a toy iron horse.
Miniatronics makes an extensive line of bulbs in various glass diameters and voltages. For DCC these bulbs are great as they only draw .030 mili amps. I've never seen one get hot enough to hurt anything. You can use 16 volt bulbs from this company to lower brilliance and often DCC track voltages run up to 15.1 volts.
see ya
Bo
DC or DCC for the locos? Do not use those bulbs for DCC, they will generate nearly 1 watt of heat and easily melt plastic shells. LEDs are a much better choice, but if you must use incandescent bulbs get some of the 1.5V 15ma type, with resistor of course. They won't get hot enough to melt anything.
For DC, the 12V bulbs won't need resistors.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Simple Ohms law formula: R (resistance) = E (Voltage) divided by I (current).
First, subtract desired voltage from applied voltage -- that's the amount of voltage drop required. Then divide by the amount of current draw to determine the resistance.
Example: Suppose you are going to apply 16 Volts DC. For your first example of a 5 Volt 80 mA bulb, the formula would be 16 - 5 = 11. Eleven divided by .080 (80 milliamps or 80/1000 Amp) = 137.5 Ohms resistance. Use the next higher standard resistance, which would be 150 Ohms.
This is for a single bulb. If you're going to wire multiple bulbs in series or parallel, the formula gets far more complicated and there is no chart that I know of that can help -- you must learn Ohms law.
For AC input voltage, it gets even more complicated because you will be dealing with reactance instead of resistance..
And there's also the added factor of the wattage rating of a resistor -- 1/8, 1/4, 1/2, 1 Watt, etc., depending on how many bulbs you connect through one resistor.
Avoid all of this hassle and use an old power pack with the lights connected to the DC track voltage output. That way, you can adjust the brightness with the throttle setting no matter how you have them wired, as long as you don't connect so many bulbs that you overload the power pack's rating.
An alternative is to type "Ohms Law" into Google or other search engine and then go to the Wikipedia entry and learn from there, or use this on-line calculator:
http://www.ohmslawcalculator.com/ohms_law_calculator.php