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2nd request: Resistors for Athearn mini-bulbs

Didn't get a response to my question and will pose it again (remember please to answer the question rather than simply posing alternatives)...

I just wanted to make sure I'm using the right rating on my resistors that will be used inline with Athearn Genesis mini-bulbs (as found in their F units). I have calculated that the minimum I should use is 680 ohms, but is there a lower rating that would result in brighter bulbs, without severely shortening their lifespan?

Also, I've read that mini-bulbs don't handle special effects well (gyralights, etc.). Is my memory correct here? I have an F unit with 2 bulbs per lamp, and one of the lamps is supposed to be a vertical gyralight. If both bulbs were programmed as gyralights, would this make a decent looking emulation, or is it not worth the time? (I'm accustomed to replacing these bulbs with DCC compatibles, but want to try resistance for a change...)

Reply to
DCC Models
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No. Brighter light means higher wattage, which means hotter filament, which means shorter life. 5-10% overvoltage will cut their life in half or less (mini-bulbs are already rated at the hotter end of their operating range.) If anything, I would use 1000 ohm resistor, and accept a slightly dimmer light. A resistor reduces the working voltage of the lamp (see PS for explanation, if you want to know how it works.) Reducing the working voltage of a lamp by 10% or so will more than double its life. Reduce by 20-30%, and you'll increase their life tenfold or more.

A general rule is that at half its rated voltage, an incandescent lamp will last 100 to 1000 times longer than at its rated voltage. (It depends on how close to its limits the manufacturer has pushed the lamp when specifying its working voltage.) A slight over-voltage of 5-10% will cut its life roughly in half. And overvoltage of 50-100% will usually burn it out in seconds. BTW, most mini-lamps produce visible light at about half their rated voltage, but in a brightly lit room you may not notice it.

Incandescent (filament) bulbs have take a rather long time to turn off (== cool off), on the order of milliseconds. LEDs, however, turn on/off in microseconds, ie, about 1,000 times faster. Thus gyralight effects may not look right with filament bulbs. Experiment outside the engine before installing any such effects. IMO, alternating two lamps will likely give you the effect you want, but I haven't done it, so I can't advise you.

And, despite your objections to advising alternatives: I would explore LEDs if I were you.

HTH&GL

Reply to
Wolf Kirchmeir

I appreciate your answering my questions very much!

I have already tried SMD LEDs, with excellent results. It sounds like using the Athearn mini-bulbs only leads to problems, perhaps even much quicker than I had anticipated. The main reason I decided to try working with the factory-installed mini-bulbs is that the lamp holder does not have to be modified. However, if that ultimately leads to dim bulbs... or a very short life-span... I may have to stick with SMD LEDs.

Frank Eva

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DCC Models

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