Quick Help - Connecting Smoke

Seuthe smoke generators are by far the most popular brand of smoke units available. Their #22 and #27 generators are commonly used in OO/HO models.

Connection to a Zimo decoder is very simple, as all current Zimo decoders provide enough power from a single function output to drive one. Typically, needing between 120mA and 180mA.

There are no additional components required - simply connect one wire of the Seuthe unit to the decoder's BLUE (common positive) and the other to one of the decoder's AUX function outputs. It is common practise to use the BROWN wire on Zimo decoders, but there's no reason in principle why any of the others couldn't be used instead e.g. GREEN, or a solder pad for one of the higher AUX/FA outputs where available.

You could even use the WHITE or YELLOW outputs, but you'd have to change additional CVs so that these became non-directional, as they are really intended for directional lighting!

Of course, whichever physical output you decide to use, there must be a Function Key defined that gives you control of it. YouChoos calls the GREEN output AUX3/FA1 and the BROWN output AUX4/FA2. If you are ordering a sound decoder, then it is worth checking that there is a Function Key defined to operate that output - we'll customise the project for you if you ask up-front of course!

It is easiest to control a smoke generator as a simple on/off feature, but it is also possible to make the amount of smoke produced dependent upon the speed or load on the motor. There are even safety features to automatically switch it off after a pre-defined period. See the Zimo decoder manuals for more information.

By way of more inspiration, below is a link to a customer video (thanks Steve B!) which shows the control of various custom-built smoke generators giving safety valve, draincocks and cylinder steam as well as synchronised chuffs from the chimney, all in O gauge locos. The installation, setup and configuration is obviously a lot more involved, but it goes to show just what is possible, so enjoy!

Synchronising Smoke to Chuffs Sounds

Zimo decoders also provide a feature to drive a fan to give the effect of synchronising smoke with steam chuff sounds.

Firstly you must have one of the outputs configured for the speed or load dependent smoke effect (value 72 for example is speed-dependent smoke effect), programmed into the appropriate lighting effect CV (CV#125 and similar). For example, using FO2 output for a smoke generator, set CV#128=72. Once this is done, the FO4 physical output needs to be configured to produce pulses with the chuff sounds, instead of being a normal physical output. This is done by setting CV#133=1.

For almost all Zimo decoders, it is output FO4 that is used for this purpose, except for special cases where a decoder has less outputs than 6, such as MX646, where FO2 is used instead.

For decoders where FO4 is a full-power normal output, simply connect your fan device between FO4 (negative side) and standard Common Positive (blue wire on wired decoder types).

For decoders where FO4 is a logic-level output, FO4 will essentially be a low-current positive connection, so you'll need to connect a wire to the decoder's Ground for the other side of the fan. In addition, you may need to configure FO4 to be a logic-level output rather than something like a SUSI connection - for example, on MS480, FO4 is by default used for SUSI, so you'll need to set CV#201=11 to convert that pad to be FO4 logic-level output rather than SUSI.

Note, on MS decoders, whichever output was configured to be the smoke generator (e.g. FO2 with CV#128=72), there must be a function key assigned to operate that output, and the function key must be switched on for the pulses to be generated on FO4.