DCC and Lighting

[Anonymous]

I'm have a few questions about lighting and DCC:

1) If I wi***o light passenger cars, should I use a bridge rectifier and a voltage regulator to cut the power down?

2)I built a gyrating headlight using a 555 chip and red and white LEDs. It works on 3 vdc. I wanted to try it on 12vdc, so I wired in a 470 ohm resistor. Should I use a limiting resistor to cut power from a decoder? If so, what is the output from a decoder to a bulb? If not, what else?

[ckape]

I think using a bridge rectifier and a voltage regulator for passenger car lighting on DCC would be overkill. DCC is all constant voltage, so there's no need to provide a constant voltage, although you will probably want to use limiting resistors to get the power through your lights down to the prescribed levels. With the next-generation DCC having the bridge rectifier will probably be a necessity, but otherwise no (although it wouldn't hurt). Of course, if you really want to be fancy (and expensive) you could always buy a function-only decoder and control the lighting that way.

The 555 itself should operate similarly at any voltage, but the output voltage will be voltage applied to the power of the 555. I would suggest replacing the limiting resistors for the LEDs for 12V instead of 3V. You generally don't want to limit the voltage to an IC with a limitng resistor, since the current draw won't be constant.

[der5997]

Here's a couple of sites that may go some way to giving you answers.

www.ngineering.com
http://mywebpages.comcast.net/mjmx/lights.htm

[nfmisso]

QUOTE: Originally posted by GaryA

I'm have a few questions about lighting and DCC:

1) If I wi***o light passenger cars, should I use a bridge rectifier and a voltage regulator to cut the power down?

Yes, and a large capacitor. An LM317 is incredibly cheap, and efficient (low heat).

QUOTE:
2)I built a gyrating headlight using a 555 chip and red and white LEDs. It works on 3 vdc. I wanted to try it on 12vdc, so I wired in a 470 ohm resistor. Should I use a limiting resistor to cut power from a decoder? If so, what is the output from a decoder to a bulb? If not, what else?

Again, I would go the LM317 route.

http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=LM317T&type=store