Electronics and DCC

I recently installed a RRampmeter and noticed that my DCC-powered engines draw only between .02 and .04 amps, according to the meter.  Am I correct in assuming this is correct?  (Engines: Walthers H10-44, Stewart VO-1000 w/ ESU decoder, BLI SW-7, and Bachman 44 tonner with ESU decoder.)

TRNJ

 Absolutely correct.  The RRampmeter is designed with DCC in mind (although it will work with DC) and the readings you get are spot on.

David B

 Sounds about right, especially for the Stewart, Now put a decent size train behind them and check again - it will be higher, but not that much. Sorta confirms my overkill theory - no you do NOT need an 8 amp booster to run 4 HO or N scale trains. You don't even need a 5 amp booster.

                              --Randy

trnj:

I recently installed a RRampmeter and noticed that my DCC-powered engines draw only between .02 and .04 amps, according to the meter.  Am I correct in assuming this is correct? 

TRNJ

I could be wrong, but I suspect the decimal point is a typo/misread.  I would expect readings from 0.2 to 0.4 amps for most modern HO locomotives.  If the 0.02 and 0.04 amp readings are correct, then there is an error somewhere.

just my experiences

Fred W

Fred, you are wrong in this case, I am afraid.   The decimal is not in the wrong place as the meter reads to the 100th of an amp.

I have been a user of this product from it's inception.  You will see that Kato and Atlas units draw next to nothing, while Athearns will pull .2-.3 amps free and more under load.

There is a misconception about what a loco draws.  People tend to round up to the nearest tenth of an amp to err on the high side.  The fact is that modern locos with modern drives pull very little power.

David B

David

After doing some checking, I have concluded you are right and I was wrong.  I did not believe that newer drives had gotten below the 100ma threshold under normal conditions.  Doesn't matter whether on DC or DCC, the average current draw of the motor should be the same.  This analysis assumes decoder current is negligible in comparison, which should be correct for a non-sound decoder.  If decoder current was significant, decoder overheating would be an issue.

In checking, I noticed that Model Railroader reviews no longer include DC current draws while running - just slip and stall.  I had to go back to my '90s issues to find reviews that included current draws while running light.  And lo and behold, I came across several examples of reviews of locomotives drawing 20-40ma while running light.

my apologies

Fred W

 No problem.

Please note that a sound system doesnt add anything measurable to the current draw of the locomotive.  The only real factor is the motor and the number of lights.

David B

Very interesting information.  How, exactly, would I measure amp draw on a locomotive using a standard mulit-meter?

Put it in series with one rail and use AC mode. The values will not be precise due to the waveform but are OK for relative indications. You might want to borrow a DCC meter for comparison and create a conversion chart for your meter.