# What are CV's and why do I need to program them?



## santafealltheway (Nov 27, 2012)

I saw this come up alot while deciding which system to buy...


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## Cycleops (Dec 6, 2014)

Well in fact you don't need to, beyond the basics which covers the address, speed steps, direction etc, your controller will walk you through these. Some controllers are very basic and will only set the address. If you can set them you can fine tune the CVs that control the start voltage, top speed and acceleration to give smoother operation. You can also change the operation of the lights if you want them to perform in a particular way.

CVs really come into their own when using a sound decoder where the number of adjustments you can make is mind bending. But then again you can also just run it as it comes.


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## mesenteria (Oct 29, 2015)

Think of it this way: You purchase a Ferrari for going to church on Sundays. It gets no other use, and its path to and from Church has a strictly enforced speed limit of 50 kph (30 mph). Nice car. Yup, it's still a Ferarri. But........you know...........

The Configuration Variables are the instructions you assign to the decoder to help YOU to enjoy a more realistic railroading experience. For example, if you set your throttle, whether diesel or steam, at 50% of the maximum and wait for the locomotive to accelerate the trailing tonnage realistically, you can make the decoder do that. In DC ops, you have to keep your hand on the rheostat dial and gradually ramp up the voltage by hand. That's not how the prototype accelerates, although there are similarities.

The CV's control V-Start [CV2], or the lowest voltage it takes for the drive to just begin to turn over. They control Inertia [CV3], or how heavy the train is and how long it takes to accelerate it to the speed allowed. CV4 is the setting for Momentum, or the resistance of the moving tonnage to braking effort...that is, how long it takes the train to come to a shuddering halt, often many hundreds of yards down the tracks. You can fine tune the drive mechanism with other CV's, and you can alter the lighting, or control ditch lights, or switch horns and whistles, set chuff rate for the revolution rate of the drivers on a steamers, and so on.

You can control the effects of sounds, even their individual volumes on sound-equipped decoders. They come from the factory set at max, and they are most annoying at that volume, often sounding horribly distorted. There is a CV in most decoders to set the Master Volume, something I alter first when I get a new decoder or have to restore one to its factory defaults. I reduce my volume to about half, and then fiddle from there with other sounds.

CV's allow you to consist two or more locomotives, even a steamer and a diesel working together. You don't have to have two identical locomotives from the same manufacturer to do this. You can set the drives of each locomotive to work together, even if they aren't the same model or are from different makers.

I hope that helps a bit.


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## Cycleops (Dec 6, 2014)

Nice analogy with the Ferrari mesenteria. Are you saying if you don't fine tune the CVs you're holding the loco back in some way?

I have to comment about your statement that sound CVs come factory set to the max. I have several decoders and none have been so configured. Rather they are set to what the manufacturer considers will give you the best and most realistic experience.

There are of course many things you can do to adjust things to your liking and its been said before on here that configuring decoders, particularly sound ones, has become almost a hobby in itself. For me its something I greatly enjoy.


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## santafealltheway (Nov 27, 2012)

ahh. got it. Thanks guys!


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## D&J Railroad (Oct 4, 2013)

Configuration Variable. Sorta like that car illustration. In the car, a CV would be the seat adjustment, or the steering wheel adjustment or the radio volume adjustment or the speed of the windshield wipers or the headlights on or off etc. Each CV controls each of the functions of the decoder.


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## tkruger (Jan 18, 2009)

One of the uses I have found for configuring CV in non-sound decoders is when converting older DC locomotives. The motor may meet all of the amp draw requirements etc but require a bit more juice than a modern motor to start. Since I do not want to turn the throttler to 10 to start it moving I just set the starting voltage higher. Theoretically this also should give me better control since I now have the full range of steps to change the throttle and am not wasting the first 10. Reality is that the control is so much better with the DCC system that once everything is tuned in I cannot tell if starting at 10 or 0 is really better. 

On a side not my kids get real disappointed if I do not tune the locomotives to start at 0. There is a rule that noting is run at any number above 14 (50%) by them.


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## CTValleyRR (Jul 26, 2014)

In order to program them, you need a full featured DCC system or some form of PC interface. Basically, everything out there is going to do it except the very basic systems: Bachmann EZ Command and MRC Explorer are the two that come to mind.

I personally find it helpful to be able to program CV's on the main, without moving the loco to a programming track. The only time you really need to do that is to program the locomotive's address.


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