Digitrax voltage

[Anonymous]

I'm trying to think of some projects to do until I purchase my DCC system whch will be a Digitrax Super Chief. What I want to do is install resistors for my 1.5 volt ditchlights in my engines, but I'm not sure what voltage the "Chief" is to calculate which resistor I need.
I checked on their website but couldn't find a voltage value.
Thanks

[Anonymous]

Digitrax systems put out about 15 volts.

[mikebonellisr]

Is the 15v. the same on all settings?(ho, n,and g) I run my ho on the N setting because i recall reading someplace that it is more benefical for lights etc, but how does that affect sound,ops mode programing or anything else that is HO?

[rrinker]

N scale is about 12v, HO about 15v, O/G about 18v. Depending of course on your input power supply. If you are using a PS515 which is 15v, you can't get 18v out of the booster.

All voltages are within the ranges allowed by the decoders. There should be no problems programming or anything no matter what setting you use. Soundtraxx is a bit more picky with their upper voltage - 18v is too much. Plus if you design dropping resistors for 12v, switching to 18v will probably be too much current for LEDs and overvoltage a 1.5v light bulb.

--Randy

[Anonymous]

Thanks for the responses!
I just checked out some resistors on ebay
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=73147&item=3875594697&rd=1

From what I see if I'm using the 1.5 v lamps (15v power source) I'd need a 1K resistor. I'm rounding up , is this correct? Does the same also apply for a 1.5v LED ?

[rrinker]

You need to find the current rating of the light bulbs as well. And if they really are 1.5v lamps, try calculating the resistor so they get about 1.2 volts. Should be bright enough, and they'll last a lot longer. You need the current to calculate the power capacity of the resistor - and if it's too high you'll want to use different bulbs, because if you end up needing a 1 watt resistor a) it's big and b) the heat could damage the shell. There are all sorts of bulbs out there, but the usually recommended Miniatronics ones are fine.
For LEDs - 1K is great. Depending on the LED this leaves 10-14ma to the LED which is plenty bright on the ones I've used so far. I was playing the game and calculating each one exactly, but now I pretty much just put a 1k resistor in and go. A 1/4 watt resistor is fine.

--Randy

[Anonymous]

Thanks Randy, I just found the 1.5v miniatronics bulbs I have are rated at 15ma, so it looks like I'll need the same as the LED's. Would it be wise to experiment with a resistor value above and below 1K just to experiment with brightness?

[rrinker]

It could be worthwhile. But a) have a voltmeter hooked up across the bulb to see what voltage it's getting and b) buy some extra bulbs. Get too low and the bulb will be history.

--Randy