# USA Trains GP38-2 smoke units



## PhilP (Nov 21, 2015)

Hello

Has anyone worked out what the two circuit boards do in this model (for smoke), and how to drive them 'simply' with DCC?
I am using a DPDT relay to feed the original board for lights. A XXL decoder for motor etc. control, and a Phoenix Sound for er sound!

Am thinking of another relay to switch motor feed off/on to power wire to smoke. - will this potentially over-voltage the smoke system, reducing its' life?

TIA.
Phil Partridge.


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## Greg Elmassian (Jan 3, 2008)

If you have the newer type smoke units, with the motor, you can ignore that little board and feed the fan and heater from your decoder.

The fan is a 5v fan, and the heater is pretty much full output at 9v.

Drive them direct from your decoder, with the appropriate settings.

Greg


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## Treeman (Jan 6, 2008)

Greg, won't the smoke units draw more current than the rating of most function outputs.


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## PhilP (Nov 21, 2015)

The smoke units do seem to take a good amp..

I have seen one solution, where the two smoke units were wired in series to cut the current down.
Not sure I can do anything fancy with the function outputs on a Massoth decoder? Bar two differing divider settings to alter fan speed.. But it is how to trigger the change dependant on motor-speed?


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## Treeman (Jan 6, 2008)

They don't produce great smoke at full voltage, putting them in series will hurt the output.


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## Greg Elmassian (Jan 3, 2008)

It's simple physics, more smoke, more wattage needed. if you put 2 heating elements in series, then each will make half the smoke.

But if you put 2 Aristo units in series, for example, which run about 5 volts internally, then at 10 or 12 volts you will get double the smoke... 

It's the same idea as running LEDs in series when you have enough voltage.

But all of this is moot, since you are talking directly driving the fan and heater from the decoder...

Greg


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