The steam chuff is controlled by the DC track voltage or by the DCC motor output, whichever is being used. The voltage at which the loco starts moving, and therefore at which the chuff is to start, varies. Most modern models from the major manufacturers start at about 2 volts. Older and kit built models can start at about 4 volts. Option switch 5 lets you choose the starting voltage which is best for your particular locos.
When the voltage is below the starting voltage then the steam card will just produce the steam hiss of a static locomotive. Once the voltage increases above the starting voltage then the chuff will start and the rate will increase in proportion to the voltage.
Three chuff profiles are available which are intended to correspond to two, three and four cylinder locomotives. Option switch 4 is set off for 2 or 4 cylinder locos which produce 4 chuffs per wheel revolution and on for 3 cylinder locos with 6 chuffs per revolution.
When the loco is accelerating or running at a steady speed, a strong chuff will be heard. When the power is turned down and the loco is decelerating, this will change to a softer sound as in the prototype.
If a battery is not fitted then no chuff will be produced until the track voltage reaches about 6 volts.
Chuff now improved for older controllers
The steam soundcard is designed to chuff hard, with the beats increasing with wheel speed, when the loco is accelerating. It then switches to a softer “coasting” sound when slowing down. Recent feedback from some customers has shown that, on some controllers, the soundcard tends to drift between “chuffing” and “coasting” modes when running at a constant speed. This is caused by the fact that some controllers output a very rough DC voltage and the oscillations confuse the soundcard to the extent that it thinks it is decelerating when it is not.
We have been able to overcome the problem by modifying the soundcard software so that it will work properly with these controllers. As a result, we are able to offer free updates to customers who may have been affected by this problem. Please email us using the Contact Us button in the menu bar above.
