DCC on & off

[EWBIV]

I have several Bachmann HO Spectrum DCC w/sound engines and they run great.  What function key (or other key) do I use to turn them off?  Right now they are all "on" as long as they are on the track.

Thanks for your help.

[ACY]

You will have to check the manual that came with your locomotive/decoder and your DCC system. If you can't find it there then check the website of the decoder manufacturer for info.

[Thomas1911]

Typically, you can turn the sound off (mute) with the F8 button, but this does not turn off the decoder completely.  In order to do that you will have to install an on/off switch to the track.

[jake_iv]

Hi;

Most decoders can be set to DC by programming the address to "00".  Different controllers have differing ways to do this. 

MRC Command 2000 controllers (an older starter system) calls for "...pushing button (7) in step 5 during programming. If you later want to use your decoder equipped loco on a DCC track you should program it for DCC again by following the program procedure without pushing button (7)."

I think I remember the EZ Command booklet saying that you could "program" a decoder equipped loco for EZ Command button "0" - that is the DC address on EZ Command.

Jake_iv

[Jim Banner]

jake_iv,

Close but no cigar.  Hitting the 7 key while programming with a C2k (Command 2000) sets bit 2 of CV29, turning analogue conversion on in the decoder.  This allows the decoder to operate on a dc track but does NOT prevent it from also operating on a DCC track.  Reprogramming without touching the 7 key clears bit 2 of CV29, turning analogue conversion off and preventing the decoder from operating on dc.  MRC recommended turning analogue conversion off when running on DCC because their early decoders sometimes misbehaved on DCC with analogue conversion left turned on.  For the record, setting bit 2 of CV29 adds 4 to the value already in CV29 while clearing bit 2 subtracts 4 from the value in CV29.

Secondly, the C2k can operate a dc only locomotive (one with no decoder on board) using throttle 1.  It operates dc locomotives by a process known as "zero stretching" which adds a dc component or bias to the DCC signal which is ac.  Throttle 1 is also able to operate a DCC locomotive with, I believe, address 01.  However, the relationship between addresses and throttle numbers, sets, and groups is rather weird in the C2k and without a great deal of mental gymnastics, one is never quite sure what address is actually being used.  Address 0 or 00 is the address you set the command station to in order to operate a dc (no decoder) locomotive when using Digitrax and a few other command stations.   Bachmann's E-Z Command implements zero stretching when button 10 is selected or when a dc throttle is connected to the command station.  Many DCC systems do not even bother with zero stretching these days.  Their manufacturers assume that if you are going DCC, then you will go all the way.

Perhaps there is some confusion about what "zero stretching" actually implies.  It has nothing to do with address zero.  The zero referred to is the binary bit value of zero.  In DCC commands, which consists of ones and zeros, the ones are short ac cycles to distinguish them from zeros which are longer ac cycles.  If the positive half cycle of the zeros are made extra long, there will be a positive dc bias on the ac signal.  If the negative half cycles are made extra long instead, there will be negative dc bias on the ac.  The motors in dc locomotives cannot respond fast enough to follow the ac part of the DCC signal but can respond to the dc bias imparted by the zero stretching.  The longer the stretch, the faster the locomotive will run.  And depending on the bias of the stretch, positive or negative, the locomotive will go forward or backward.  The only connection between address zero and zero stretching is that some systems use throttle address zero as a convenient way to signal the command station to turn on zero stretching, if otherwise allowed.  Throttle 1, button 10, or even a big toggle switch to turn zero stretching on or off would all work equally well.

Bottom line, there is no address or function key to turn decoders off.  If there were, then once you turned the decoder off, it would no longer be able to receive commands from the command station.  And there would be no way to turn the decoder back on.  The closest we can come to that is disconnecting the power from the track, either by a route selective turnout, a toggle switch, or if you really want to do it through your throttle, by using a relay operated by a decoder.

Jim

[EWBIV]

Maybe I'm trying to solve a problem that I don't have.  With some of my other DCC engines, I can press a function key (like 3 or 6) and the engine will appear to turn off (perhaps the decoder is still active).  With my Bachmann's (Climax, Shay, 4-6-0), they continue to give off sound (which I can of course mute).  Someone suggested that keeping them "on" is using up power.

Am I worrying about a problem I don't have?

Thanks.

[jward]

you are correct that even "sleeping" locomotives draw power on dcc. and sound locomotives draw more than regular dcc locomotives.

to keep them from drawing power you need to have a form of block wiring, where you have sidings you can park these locomotives out of the way and kill power to that track. this is done by inserting an on off switch between the ez command and the track. you will also need to insulate one rail on each track you'd like to control power to.