Valley Depot booster won’t pass the service mode program-
ming onto the track.
There is an accessory from NCE that can be used in either
of these situations. The Auto-Switch has three connec-
tors: one to go to the track output of either the DB150 or
the PowerCab; and one each for the DCC bus and the pro-
gramming track. When either unit goes into service mode
programming, a relay inside the Auto-Switch picks and dis-
connects the DCC bus from the track output, preventing pro-
gramming what is on the layout.
9. CV 29 is different among different
decoders
Here is another ditty from Ross.
There are only four CVs that are mandatory in the NMRA
Recommended Practice 9.2.2 document:
Primary (short)
Address
(CV 1),
Manufacturer’s Version
(CV 7, selected by
the manufacturer),
Manufacturer’s ID
(CV 8, assigned by the
NMRA) and
Configuration Data #1
(CV 29). RP 9.2.2 also speci-
fies exactly what every bit in the CV29 must control and how.
If you want to check this out, you can read NMRA RP 9.2.2 on
the NMRA web site
10. Knowing the stall current is neces-
sary to select a decoder
Mark Gurries, an electronics engineer who maintains an exten-
sive website on DCC topics, raised this one.
DCC Impulses Column - 9
Folks who have followed my column know that I have long dis-
cussed the use of stall current to safely size decoders. No, I’m
not backing down on my stand there, but let’s look at Mark’s
viewpoint, explained on his web site
Current generation HO and N scale locomotives are far more
efficient than those built as recently as a decade ago. Modern
locos rarely stall above one amp. Many stall well below one
amp. Most operate at a small fraction (1/4 or so) of an amp.
Modern decoders in all sizes can handle at least one amp on
a continuous basis and most have thermal protection to shut
themselves down before the internal temperatures get too high.
“Any decoder from any manufacturer that
pretends to meet NMRA standards must
have CV29 defined per RP 9.2.2.”
9: DecoderPro - CV 29 collects data (orange background)
from several tabs in DecoderPro – but it is the same data
for all decoders.
9
MRH-Mar 2014
