# O-Gauge Automatic Smoke Controller



## gunrunnerjohn (Nov 10, 2010)

Recently, I converted this neat little MTH Docksider to TMCC using the Electric Railroad MiniCommander 2 board. Since I wanted electrocouplers, I was left with no way to control the smoke unit, except the chassis switch. That's not really satisfactory if you want to have smoke, but when you stop you don't want it to smoke you out of the place! So, I set about designing a method of running the smoke only when the locomotive was in motion.

The obvious way to deal with this is to sense motor voltage, so that's the route I took. The basic circuit is a diode bridge using Shottky diodes (for the low voltage drop) to feed an opto isolator that will trigger whenever voltage is detected on the motor. Since the motor can run in either polarity, and the opto isolator is obviously polarity sensitive, the diode bridge converts either polarity to a single polarity voltage.

The other side of the opto-isolator drives a 12V relay that is fed directly from track power rectified and filtered. The relay is a miniature model with a 12V 10ma coil and 2A SPST contacts. Whenever the motor has applied voltage, the opto-isolator conducts and closes the relay to run the smoke unit.

It was necessary to separate the circuit into two modules because of space limitations inside the small engine. the pictures tell the tale.

If you need to have a bit more voltage for some applications, a couple of pairs of series diodes will give you more voltage on the bridge, but less on the motor. That wasn't necessary here, the fan normally starts on TMCC step 1.

This same technique could be used with a normally-closed relay from the same family to turn on cab lights only when the locomotive is stopped.

I hope this little project is of use to someone, I know it solved an issue that I had and was a fun afternoon project to do.


*The Intended Victim*











*The Completed Modules Before Packaging*

The top module is the four diodes and the capacitor, the bottom module is the rest of the circuit.











*The Completed Modules Ready To Install*











*Left Side Module Placement*











*Right Side Module Placement*










*Automatic Smoke Control Schematic*


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## Big Ed (Jun 16, 2009)

Sounds good to me..........does it work?


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## gunrunnerjohn (Nov 10, 2010)

big ed said:


> Sounds good to me..........does it work?


Take a guess.


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## Big Ed (Jun 16, 2009)

gunrunnerjohn said:


> Take a guess.


No?

Looks good, Doctor ElectricailStein.:thumbsup:

A smoking hot video would work. 
Does it really pour out the smoke? 
Liquid smoke I guess? 
What flavor are you burning? 
Since it smokes real heavy I guess it uses the smoke quicker?


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## gunrunnerjohn (Nov 10, 2010)

The MTH PS/1 smoke unit is designed for conventional, so when you run it on 18 volts, it does crank out the smoke an vast quantities. I've actually thought of dropping the voltage a bit, but I'm not sure where I'd put the extra components, the little shell of this Docksider is getting pretty full!

It does go through the fluid a bit faster than some other locomotives. And yes, I've never seen a fan driven smoke unit that used pills. I actually don't have any pill units around anymore.


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## Big Ed (Jun 16, 2009)

gunrunnerjohn said:


> It does go through the fluid a bit faster than some other locomotives. And yes, I've never seen a fan driven smoke unit that used pills. I actually don't have any pill units around anymore.


Duh I forgot that small detail.
Even in your old Lionel's you converted them too?
Do you even have any old Lionel? 
Or are yours all newer. Out with the old and in with the new.
What did you do with the old pill units?

What flavor smoke do you use?
Different? If so what one do you like the best?


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## gunrunnerjohn (Nov 10, 2010)

I had one old Lionel with a pill unit, but it was not smoking all that well. So, I did upgrade it. It's my Ft. Knox Express gold engine.  I think the guts of the old pill unit are still in one of my parts boxes.

I have a number of flavors of smoke, but the one I'm using most is the JT Megasteam NADA scent, i.e. no scent.


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## tjcruiser (Jan 10, 2010)

The Amazing TechnoFlash strikes again! Neat gizmo ... Shottky whatchamacallits and all!


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## gunrunnerjohn (Nov 10, 2010)

Just another day at the "office". 

I just got some Arduino microprocessor modules, look for some upcoming neat stuff using them.


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