I am currently using 1.5 Volt bulbs (with resisters) in the cabs of my HO diesels. When I first put an engine on the track and start up the DCC power, sometimes those bulb lights come on extremely “bright”, and I must remember to hit the light button to turn them off for a second… otherwise they can burn up rather quickly. What causes that surge? Is there a method to keep the start up from turning on those lights at the same time? Note: Once the lights are off, I can go back and turn them on low or hit the #7 button to brighten them if I choose…but even then they are not super bright as that first power on. Thanks. JRP Great Southwest and Pacific RR
Sounds like a good question.
However, I haven’t noticed any surge on start-up from my DCC system. NCE Power Pro.
What is the resistor value you are using? I use a 1.5 volt bulb in a decoder equipped loco and use a 470 ohm resistor. Never noticed any flaring but the bulb is for a beacon. The voltage is around 1.1 volts at the bulb. I use a NCE power Cab at home and NCE Power Pro at the club. Both have a DCC voltage of about 13.8 volts.
Rich
It sounds like you don’t have a proper resistor connected to your lights. I always use a 1,000 Ohm resistor regardless of Ohms law calculations with an LED or 1.5 Volt bulb and have never had any problems with them.
Light bulbs have different resistance when the filament is cold vs when it is hot, this is probbaly the causeof the ‘surge’ you see. If it’s too high and burns out the bulbs, then you have too small a resistor.
470 ohm is too small for a 15ma 1.5V bulb, just about right for a 30ma 1.5V. For all esle being equal, a closer ‘exact’ value for a 15ma ulb is 940 ohms - but they don;t make such a resistor in common 10% tolerance types. 1K is the closest without going under - but remember there is a 10% tolerace, so that 1K can be anywhere from 900 to 1100 ohms. Likewise the smaller ones - that 470 ohm can be as low as 420 ohms which is too small and runs the bulbs with too much voltage.
–Randy