For those starting out in DCC, CVs can be enough to cause your eyes to glaze over.  The decoder is simply a tiny computer which is able to remember how you want your model to perform and then do what you want when you want it to happen.

The beauty of the decoder is that it can be tailored to suit your taste.  The software is set up or configured by you and therefore varying of these configurations will be the means to do that.  Hence, Configuration Variables; or CVs.  I like to think of CVs as being like the knobs on your stereo.  You choose volume, tone, balance and the like to suit yourself.

Individual manufacturers set up their decoders  to be configured in many ways and choose CVs from the list and give the CVs a range of behaviours relative to the value you put in.  However there are a few CVs which are common for most decoders.  They are:-

CV 1     The short address.  By selecting CV1, you can enter any address up to 127

CV 2     The start voltage.  While the term voltage isn't exactly correct, it suffices to explain that the model can be set to start moving at the lowest throttle setting you require.

CV 3     Acceleration Time.  The higher the value you enter into CV 3, the longer the model will take to reach maximum speed.

CV 4     Deceleration Time.  The higher the value you enter into CV 4, the longer the model will take to slow down and stop.

CV 5     Maximum speed.  The higher the value you put in, the faster the model wil go on full throttle.

CV 6     Mid speed.  This CV is designed to give you a rough speed curve.  Set it halfway between CV 2 and CV 5 and then play with it from there.  It often depends on the characterisitcs of your model, as to where you like it to be.

CV 29    This is the one that worries most people at the start.  For reasons I don't really understand myself, CV 29 has been chopped up into 8 parts, or Bits.  Bits are more like switches than knobs; that is they are either ON or OFF.  The commonly used Bits are the first 6, the other two being left for individual manufacturers to use.

Here is a digram showing how to manage CV 29




You can see that Lenz have numbered their Bits differently, also TCS use letters; but the result is the same.  If you look at the "What it does" column, you can see the "Change" value for what ever you are trying to do.

I know that some DCC systems allow you to read the Bit values and change them individually on the screen, but I felt that it you understand the way it works, you can manage CV 29 if your system doesn't have that facility.

This thread may be of help if you are trying to decide if a cheap decoder is good value or not.  If the decoder manual shows that it doesn't at least support all of these CVs and bits, (Plus a reset CV), you may find frustration when you come to start tweaking.

Reset CV.     I've left this to last as it's important, but isn't always the same CV number.  It's usually CV 8 = 8.  That means if you call up CV 8 and put in 8, the decoder will reset itself to where the manufacturer put it.  In Lenz decoders it's CV 8 = 33, in NCE, Soundtraxx (other than Tsunami), DSD and TCS, it's CV 30 = 2.

If the decoder doesn't have a reset CV, avoid it like the plague.

I hope that this has been helpful.  My thanks to my co-collaborators, Ian Wade and Ron Solly.



 

very helpful.

Max, you explained it in simple language. Well done!

Yeah, exactly so Craig. Good one Max and it's going straight in the Index.

Thanks, Guys. :thumbs

We can't get too much of this kind of simple information that even I can understand.

That is super clear Max......thank you.............I am going to print it out

That's brilliant Max.  DCC explained in plain language - just what I need. :thumbs

Are you going to continue with more episodes along these lines in the future such as explaining in layman's terms exactly how DCC works etc. etc. ?

I always thought they were something to do with job interviews …………….:roll::roll::roll:

You're welcome, John.  I'll have a go, Peter. 

I think a lot of us will look forward to that Max. I know I will.