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Have USA G Switcher hook up smoke generators

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ironacres:
I have my switcher running on battery 18.5 for a few months now, all working good.  Originally did not hook up smoke units being my first battery conversion and trying out.  Here is the problem it takes 7 to 8 volts to activate smoke at the board, LM puts out 5 volts.  I could run power from the battery output voltage on the LM would be 18.5 to a switch then to smoke board, but I would loose remote operation.  Or I thought of running a micro relay that I could energize the coil from the LM 5 volt output and feed power from the LM battery output to the smoke control board, that would be 18.5. I believe the smoke board will handle up to 24 volts G scale rated, the same if you were running track VDC. I tested using a veritable power supply to find start up voltage for smoke.  Has anyone else wired the same locomotive for smoke or am I missing something and over complicating things.     

Joel W:
You are on the right track - a 5 volt relay to turn the smoke on and off, and control the relay with one of the outputs from the LM.  Remember to attach a heat sink to the (3 wire) transistor attached to the smoke board, and put it somewhere where it has good ventilation.  Note that smoke units use a lot of power and will significantly shorten your run time.

Joel W:
Another possible solution is to explore the function of the transistor attached to the smoke unit and possibly trigger it directly from an output on the LN.  This will require more electronics knowledge than I have but it should be possible.  On mine it is a TIP122 which turns on when you ground the control voltage.

ironacres:
I still have the weight that the transistor was attached to in the locomotive,  have to order a relay that will operate on 5 volts.  I can make it work with an on off switch on the loco but that defeats the purpose of wireless control, and takes the fun out of it.

Alan:
Disclaimer: I have no experience with LM-3S-G. My experience is limited to HO LM-2 and LM-3.

I find it odd the LM outputs are only 5V when operating on a 18.5V supply. Are you certain of that measurement?

Smoke units will draw some serious juice because of the heating coils. Doubtful an LM can directly power. By your picture the original installation also required a driver circuit (the two transistors). Have you tried using the LM output to drive the base pin of the little transistor on the circuit board?

If you do go the relay route make sure to place a flyback diode across the relay coil otherwise you could damage the LM internal output transistor.

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