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Subject: 
Re: DCC for the RCX
Newsgroups: 
lugnet.trains
Date: 
Fri, 30 May 2003 04:33:17 GMT
Viewed: 
2548 times
  
   Huh??!? Your basic resistor can only handle 1/4 watt (0.25W), so your worst-case 2.8W is more than ten times the rated maximum current. Even dumping an “insignificant” 0.5W across a resistor is probably not adviseable unless you are also trying to heat your house. With fire. And don’t forget that all of this power is being supplied by the motor driver circuit of your precious RCX which has limits of its own.

I don’t know about you, but I tend towards .5W or bigger for most of my resistors, and diodes have exactly the same problem if you use them as a voltage drop. Load is not really signifigant on a 5A booster (soon to be 10 amps total...2 boosters). You would save 0% of your loss by using diodes vice using resistors:

E=RI regardless of anything else, and w=IE, so to get your 5V drop at 100 ma draw, you are loosing .5W regardless of if you use a diode, a resistor or a 2nd light.

   Is it worth trying to save a few pennies using a resistor to do a diode’s job at the risk of doing dammage to your RCX?

Yes, since it doesn’t make any difference whatsoever as to how the job is done. None. Not at all. So, use the cheaper resistor if you are dropping the voltage. Another thing to think about is that you only need 1 set of diodes if you are going to do this, since the acc leads are DC off a DCC decoder.

James (and if all else fails, show me your converted motors!)



Message is in Reply To:
  Re: DCC for the RCX
 
(...) Huh??!? Your basic resistor can only handle 1/4 watt (0.25W), so your worst-case 2.8W is more than ten times the rated maximum current. Even dumping an "insignificant" 0.5W across a resistor is probably not adviseable unless you are also (...) (21 years ago, 29-May-03, to lugnet.trains, FTX)

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