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Reply to "Decoders, Smoke, and Couplers"

Decoder Configuration

Getting all of the above hardware working nicely requires that the decoder be configured correctly to use it. The Loksound decoders are very configurable, so they work really well for an install with a bunch of extras like this. Getting them set up falls into two main areas:

  • Configuring the function outputs, that is, how the decoder interacts physically with the attached hardware.
  • Configuring the function mapping, or the logic of when and how the function outputs are controlled.

There are a few other items needed as well, in certain cases.

Configuring Function Outputs

Decoder function outputs have a lot of different effects available (dimmable headlight, ditch light, firebox, etc.), but for the most part, the actual output is simply a PWM signal. It's either on (100% duty cycle), off (0% duty cycle), or somewhere in between (dimmed, flashing, etc.). So a lot of getting the decoder set up right is just a matter of getting the PWM output needed to control a load in the desired manner.

1. Basic On/Off

This is the simplest function output configuration - simply 100% duty cycle, so that the output is fully on or off. This is the setup to use for controlling a smoke unit heater or some other load that you want to just turn on and off. Use the 'dimmable headlight' output mode, set it to full brightness (100% duty cycle), and disable all 'special functions' in the Lokprammer, like so:


This will work to control any of the power switches described previously.

2. Electrocouplers

The setup for electrocouplers is basically just an on/off output, but with a timeout, so that the couplers are pulsed briefly when the output is turned on, rather than being powered continuously. Configure as in (1), and then enable the function timeout and set it to the minimum, as shown below:


 3. Smoke heater

Now things get a little more interesting. A smoke heater can be controlled in an on/off manner, operating at a fixed voltage, or it can be controlled with a variable PWM duty cycle, so that the heating can be varied by the decoder during operation.

3.a. For on/off control, simply configure the output as described in (1) above. This is the approach to use with non-PWM compatible power switches. The voltage applied to the heater can be altered by adjusting the regulator output during installation. Electrocouplers will fire on anything from around 3V and up, so there is room to tweak the heater voltage if you are using a common regulator for both.

3.b. For variable control, a good option in the Lokprogrammer is the 'Seuthe smoke unit'. This provides three heat (PWM duty cycle) settings - an idle setting and min and max operational settings. You will want duty cycles around 60% and up for decent smoke output. Use this setup with a PWM compatible MOSFET switch. Here is an example from one of mine:


4. Smoke fan (diesel)

For the fan control for diesel smoke, the 'Seuth smoke unit' effect also works well, providing idle, min and max settings for driving the fan motor. This works well with either of the heater configurations described in (3). Since the decoder can drive the fan directly, there is no need for a power switch, and any PWM output can be used. As opposed to the heater, the duty cycles for the fan will likely be pretty small. See this pic for settings that work well for one of mine:


Keep in mind that, although the settings all refer to 'heat', it's really just setting the duty cycle of the PWM output, and that it can be used to run a fan motor just as well as a heater.

5. Smoke fan (steam)

Now for the fun one! Steam engine smoke is the most involved to configure, but also the most fun, because the options available and the effects you can achieve are pretty amazing.

5.a. Configure the chuff output using the 'trigger smoke chuff' output mode in the Lokprogrammer. The only setting that I have observed making any difference is the 'chuff power', which sets the speed of the fan while chuffing (it would be nice if the 'fan power' setting set the fan speed in between chuffs, but it does not appear to do so).


But, this is not enough by itself! There is a 'Smoke Unit' tab in the decoder settings list. For the chuff to work, the settings for 'smoke chuffs' on this tab must be non-zero. The settings control how long the chuff lasts as a percentage of the time between chuffs, as well as min and max chuff durations for setting limits at low and high speeds. For example:

 smoke chuffs

If you don't set these, the chuff will not work regardless of the function output setting.

Note that the settings shown here do not have anything to do with syncing the sound (and hence chuffs) to the wheel rotation. That is set elsewhere in the Lokprogrammer, and is well documented in the manual, so I won't detail that here. Also note, the chuff signal for the deocder must be included in the sound file. Although I have not run into this, is it possible that older sound files may not have the correct flag in the sound file, in which case the chuff will not work.

5.b. To add some smoke while the loco is idle, or to add some smoke in between chuffs, configure another function output and wire it to the same physical output used for the chuff signal. As discussed previously, this will superimpose the effects of the two function outputs, which allows for some real flexibility. For example, to add in some smoke fan at idle, and just a little bit in between chuffs while running, configure this output as a 'Seuthe smoke unit' with settings like so:


Alternatively, configure it as 'ventilator', with ramp up and ramp down times when it is turned on and off, or just configure it as 'dimmable headlight' for a fixed, low output. Lots of options here!

Configuring Function Mapping

Having configured the function outputs, the next step is to set up the decoder logic to control them. In most cases, this consists of simply mapping an F-key to one or more function outputs. The options for mapping in the Loksound offer a lot of flexibility, so I'll show a few cases here, using F5 for the mapping.

Uncoupler: Map the function output created in (2) above to the F5 key. One keypress will trigger the uncoupler, and the next will reset it, as with MTH PS3 decoders.


Smoke, diesel: For diesel smoke with the fan and heater on simultaneously, map the heater and fan function outputs created in (3) and (4) above to the F5 key. Pressing the key once will turn them both on, pressing it again will turn them off. The fan (and heater, if using a PWM power switch) will both vary in conjunction with engine speed.


Smoke, steam (option 1): For steam engine smoke with chuffs, map the heater output from (3) and the fan output from (5a) to the F5 key. Pressing the key once will turn on the chuffs, synchronized with the sound and wheel rotation. Pressing it again will turn it off.


Smoke, steam (option 2): For chuffs with additional smoke, either at idle or in between chuffs, map the heater output (3), the fan output (5a), and the second fan output (5b) to the F5 key.


Smoke, steam (option 3): As a final example, here is how to configure steam engine smoke for chuffs while running, with smoke while idle, but without any smoke in between chuffs. Note the use of the additional conditions 'Drive' and 'Stop', in conjunction with the 'F5' condition.


As you can see, the combination of the effects available for the function outputs, the flexible logic of the function mapping, and the ability to superimpose the physical function outputs, gives you nearly limitless options for creating cool smoke effects.

In the next post, I'll show some specific examples of how this all comes together in the locomotive.


Images (12)
  • output1
  • output2
  • output3b
  • output4
  • output5a
  • smoke chuffs
  • output5b2
  • mapping1
  • mapping2
  • mapping3
  • mapping4
  • mapping5
Last edited by thor73
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