Smoking Caboose 19807 resister use with Command Control

The Seuthe smoke unit in that caboose is a 12V unit.  I'm guessing for conventional operation, for which it was obviously designed, they just added the 1 ohm resistor to protect against direct shorts of the smoke unit.  Measure the resistance of the actual smoke unit, and you'll need a resistor of half that value to drop the 18V to 12V.   I have 6V units that measure 9-10 ohms, and an 18V unit that measures 30 ohms.  Given that range, I'm guessing yours should measure around 20 ohms and require a 5 watt 10 ohm resistor.  You could get away with a 2 watt resistor, but it's going to get pretty warm, that's the kiss of death for plastic.

Thanks so much for looking at this with me.     I measured the smoke unit and it measures 260 ohms --- not what I expected.  Did you mean .20k  ?  

260 ohms makes little sense to me.  That would produce no smoke at conventional voltages, and not even at command voltages.  At 12V, 260 ohms dissipates around half a watt, not enough to do anything.  even at 18 volts it would only be 1.2 watts, again not enough for a smoke unit.  My 6V units measure 10 ohms cold, and when they warm up they draw about .3 amps, that's 1.8 watts.

A Seuthe smoke unit that measures 260 ohms is bad IMO.

Yep -- I bet it got too hot -- running in command mode - or without fluid --- doesn't look like any melt damage  --- but maybe can't tell?    I haven't tried it on the track - so not sure if it works or not..  I should hook up my ZW and give it about 12v  and see what happens..  

Again thanks 

FWIW, I've tossed a few of these.  I get a lot of them doing fan driven smoke upgrades.  A significant number don't work, and they usually measure high resistance when checked.

I hooked up the ZW and gave it 15v on the tracks and it started smoking......?????  Checked the Ohms again -- 258 ohms....  go figure.   I ordered a 27 ohm 2w resister -- going to put it in instead of the 1 ohm guy and see if the voltage goes down to 14-16 under command-18v .....    Looks like this may work-      hope 2w will stay cool???  

A 27 ohm resistor in the standard tubular caboose smoke unit at 18 volts will very likely be way too hot.  18V through 27 ohms is 12 watts of power, that's way more than is typical for a TMCC fan driven smoke unit in TMCC equipment!  I'd be looking at a lot higher value for a static convention flow smoke unit!  I'd start with something like 56 to 68 ohms 2W and see how that performs.  You want visible smoke, not caboose on fire!

Thanks --- I've got a 51 ohm cement in the junk bin  --- I'll give it a try ( watch for smoke and measure Wattage)  and see which way to go 

Most important, make sure the side or top around the smoke unit don't get too hot and deform!   You do want a resistor in the 2-3 watt range maximum as the point of the exercise is to get the resistor hot enough to vaporize mineral oil, but not how enough to melt your caboose.

The 51 Ohm resister dropped the voltage down to 14.3 and getting lots of smoke ---- probably too hot and too much voltage? 

Outside wall of Seuthe smoke unit in the caboose is 130 F. 

Inside of Smoke Unit is 150F.....

Think I will get a56 and 68 Ohm resistor   to try---like u suggested at first

Yep, it's tricky to use those convection smoke units, that's why there are so many pictures of melted caboose sides and roofs!  I have modded a couple and put a small HO fan driven smoke unit in them, much cooler outside the smoke unit, and all the smoke you need for a caboose.

Thats a great suggestion...  Any tip or hints on the HO unit to use?  I think MTH has one?  I sure its first class

I use the MTH HO smoke unit.  I tune the voltage on the resistor for the desired smoke level, typically around 5-6 volts, and then use diodes to drop the voltage to the motor to around 2.5-3.0 volts.  I just use a little DC switching supply for the power.