DCC loco running on its own?

[jblackwelljr]

I went down to the train room for the first time in several weeks.  I turned on my Digitrax Zephyr, hit the power button, and whoosh - my Stewart FT (D12IP decoder) left the station.  The little people on the platform were all very confused, as well as the engineer!  The giant guy standing off in the distance (me) also had a look of surprise.

The speed control was at zero, directional control was on "brake" and a different loco # was displaying (probably the last one I ran).  Is this a memory thing or is something else going on?  No matter what I did to the controls, the FT just kept going - then I realized I didn't have control of it.  

I haven't seen this before.  It was corrected with a couple of reboots of the Zephyr, but for a few seconds I thought maybe those little guys had taken over (que Twilight Zone theme).

[simon1966]

Jim, the decoder in the loco is almost certainly a DCC/DC compatible decoder.  What can happen is that upon power up the decoder sees the track voltage before it sees any DCC commands and promptly takes off in analog DC mode.  Disable analog/DC mode in the decoder and it won't happen again.

[selector]

I have had this happen to me.  It occurs on power-up and is usually the result to two things in my experience, althought what Simon says makes sense, too (my decoders are all set for dual mode).

Sometimes the throttles are not zeroed properly, nor the locomotives dispatched at the end of a session.  When you next power up, whatever speed was left on the throttle will appear on the display, and the locomotive will begin to accelerate just as it would had you dialled in the speed just then.  When the loco begins its slow move, I merely twist the encoder counter-clockwise a bit and it comes to a halt with the newly zeroed throttle.

If your locomotive shoots off without acceleration, then Simon must have it nailed because it is thinking in DC as opposed to DCC...hmmm, I may have to consider altering CV 29 to fid out...although I have never had a locomotive jerk up to 30 scale mph over one second on start-up...not once.

[jblackwelljr]

I think Simon might be right, although it has never happened before.  It went from 0 to 40 in about 3 seconds - kinda funny to see your locomotive pop a wheelie!

I'll be looking through the manual a little later.  Thank you gentlemen, 

 

[jeffrey-wimberly]

I've had the same thing happen repeatedly with a Proto 2000 PA1 with a Bachmann decoder. Six times out of ten it would start moving when the system was first turned on. I took it to a friend of mine who has a NCE system and he set the decoder for DCC only. It's never happened again.

[simon1966]

I am almost positive it is what I suggested.  It happened once in my house.  My son, then age 7 turned on the power and 3 or 4 locos took off at full speed.  There was a nasty crash followed by sobbing and "I didn't do anything Dad".  Since then all decoders have had DC mode turned off and no more instances have occurred.