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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
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Message has 2 Replies:
 | | Re: DCC for the RCX
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| (...) 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
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| (...) 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)
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Message is in Reply To:
| | Re: DCC for the RCX
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| (...) 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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