DCC and DC locos

[Alessio]

Hi All,

I used to know this so feel silly for asking but can someone just confirm I've got the following correct?

 

 'DCC-fitted locomotives will run on DC-controlled track, but unfitted, DC locos will not run on DCC controlled track.'

I'm considering a heavy 'refresh' of my collection, moving some locos on and replacing them with new models, and with that am considering whether to buy some DCC-fitted models with half an eye on a future switch to digital - a switch which I can't afford at the moment.

Either way I'd be buying second hand so it's just whether I bring DCC-fitted locos into the consideration or not.

 

Cheers!

 

 

 

[Fishmanoz]

Hi Alessio, DCC fitted locos may run on DC track.  However it is possible to turn this feature off by writing a value into the decoder at CV29.  So if buying second hand, you might ask about this and ensure the seller supplies the loco with this feature turned on.  On is the default setting, so it will only be off if it has been turned off by someone.

 

It is possible to run DC locos on a DCC track but strongly not recommended to do so.  The reason is it can burn out the motor, and possibly sooner rather then later.  Just sitting can be worse than running for them Too.

[Rog RJ]

Remember that many non DCC models can be converted to DCC quite easily, so some of your existing models could perhaps be converted at minimal cost.  If you have any DCC ready models, these just need a decoder to be plugged into a socket.

[Michael_A]

I read somewhere that even when running DCC locos on a DC system motor performance is improved through use of the decoder motor control circuitry functions, e.g. back emf. Also DCC decoders drive the motor using pulse width modulated high frequency, which in particular improves low speed performance. I am not entirely sure how this works though when driving the decoder with simple DC. Hmm, I feel a test coming on!

 

I'm confused and not too sure why you would want to (or in fact need to) turn off DC running in a DCC fitted loco if operating on a DC controlled system????? This comes later if you switch to and only intend to use DCC.

 

The statement to NEVER run standard DC locos on a DCC system is definitely true, in spite of what manufacturers may say.

[poliss]

 When running a DCC loco on DC, you will find that you will have to turn the control knob up higher to get them to start.

Fishy wasn't saying you should turn DC off. He was saying that, when you buy second-hand decoders, that you should check that the seller hasn't turned DC off.

[Fishmanoz]

Poliss is right Michael, they won't work on DC if DC running is turned off.  DCC users in the know do this with their locos to avoid DC runaway.

 

i don't believe PWM is used by a DCC decoder when a DC signal is detected, it just passes track volts straight through to the motor.  Hence the higher starting volts needed.