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 Robotics / RCX / 2092
2091  |  2093
Subject: 
Re: DCC for the RCX
Newsgroups: 
lugnet.robotics.rcx, lugnet.trains
Date: 
Thu, 29 May 2003 18:57:48 GMT
Viewed: 
4639 times
  
In lugnet.robotics.rcx, James Powell wrote:

When I installed my first decoders (Digitrax DN121), I omitted
the capacitors, figuring if the buzzing was annoying, I could always
add them later.  As it turns out, there is a little buzzing at low
speeds, but it is not annoying to me (YMMV).  In fact, for my
diesels, it sounds like a low grumbling which reminds me of the low
"thrumming" you get as the prototype leaves the yard.  I just
installed a DZ143, and it buzzes at about half the volume of the
DN121s.


I don't install them either, and I have done something like 30 motors so far.

If you are referring to Tom's L-Gauge page, the resistor is
used for the headlight to lower the ~12V DCC voltage to 9V
for use with a standard Lego lamp brick.  I didn't need to
use this resistor since the RCX is already putting out about
9V.


True, but ONLY if you are just going to use the RCX as a output.  You can dial
the voltage that DB100's (and most other Digitrax) boosters put out to a exact
voltage as well, however it is something I haven't worried about yet.  For the
most part, this does limit the range of useable speed with a unprogrammed
decoder to the lower 1/2 of the scale.

I did however, add a diode in parallel with the lamp output
in case I decide to run an inductive load such as a
relay or motor on the lamp output.

I have gotten away with the lego motors so far.  However, YMMV :)  and no, I
don't put diodes on them.

James P

I'm no electronics engineer by any stretch--

A diode, iirc, allows DC current to 'flow thru' in only one direction.  What
would a diode do across the output on the top of the train motor?  And why would
one be good for 'inductive' loads such as a LEGO motor?

I like learning--use small words so i unnerstand please :)

Dave K



Message has 2 Replies:
  Re: DCC for the RCX
 
(...) The problem with inductive load is that when current is interrupted, they generate large voltage spikes with reverse polarity. The diode absorbs these spikes and avoids destroying the driver... Philo (21 years ago, 29-May-03, to lugnet.robotics.rcx, lugnet.trains)
  Re: DCC for the RCX
 
(...) Sorry, my earlier post should have been more clear. I was just commenting on the fact that in general a resistor is _not_ a good way to reduce voltage to a train motor. And you recalled correctly: diode's are "one-way". Thats why you need to (...) (21 years ago, 29-May-03, to lugnet.robotics.rcx, lugnet.trains)

Message is in Reply To:
  Re: DCC for the RCX
 
(...) I don't install them either, and I have done something like 30 motors so far. (...) True, but ONLY if you are just going to use the RCX as a output. You can dial the voltage that DB100's (and most other Digitrax) boosters put out to a exact (...) (21 years ago, 29-May-03, to lugnet.robotics.rcx, lugnet.trains)

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