Smoke Units

Most smoke units indicate how many drops of fluid to use. I have tested 3 smoke fluids with a syringe and found that they are 37-39 drops per ml / cc. (Aristo, ProtoSmoke, TAS) I used an Accucraft 5 ml syringe (#14224) , but they are all really the same, the droplet size is a function of the surface tension of the fluid.

I recommend you count out your droplets from your smoke bottle and get your drop/ml down and then just use a syringe.

Smoke Fluid

There's a number of manufacturers that sell smoke fluid. I have had good luck with Aristo fluid, but no bad experiences with any of the others. Here's a place that has scented fluid:

Aristo-Craft smoke units - no longer available

There are many different smoke units from Aristo, from the simple heater type that is used in the cabooses to the latest style, called the "Aristo Prime Mover" smoke unit with electronics and a fan.

CLICK HERE for a specific page on all the Aristo units under Aristo Motive power.

For adding to other locos and purposed of comparison, only consider the "Prime Mover" one, with the fan built in.

When these work, they usually put out a reasonable quantity of smoke, and have a reasonable run time. Figure on 20 minutes on a filling.

Do not overfill, even though the reservoir can handle 4.5 milliliter, the design allows fluid to slop or condense onto the circuit board, and it attacks the electrolytic caps, swelling the rubber ends and popping them off the circuit board. This is one cause of failure. There is no way to keep fluid from condensing on the circuit board, since the circuitry is in the chamber with the fan, and that chamber is connected to the fluid chamber.

I recommend 4 ml of fluid max normally.

They are very inconsistent and many will only run for a few minutes before shutting off. Just keep returning them to Aristo until you get a good one. (No malice intended here, check the Aristo forum about the ratio of good to bad units).

This one is the best one, used in the latest locomotives, fan driven and a small microprocessor to control the heater.

patent pending

Modifying for "Direct Smoke":

Note: for running in "direct smoke drive" where you need direct and independent connections to the motor and fan, as when controlling the fan and heater with a QSI, Zimo, ESU, etc.

To modify the unit, follow the instructions below:

First, unsolder the connector. This will also give you room to let the wires out without cutting the case. You can see 1 of the 3 solder blobs at the top center of the picture below.

Now on the bottom of the board (which faces up in the unit), cut one trace by the large hole as shown. A carbide disk works well.. make sure the copper is gone.

Now wires in the 4 spots as shown. The plus for the fan is the white wire in this case, you can use red instead. the 2 wires for the smoke unit don't  matter, i.e. there is no plus or minus.

On the top of the board, cut THREE traces.

  1. On the upper right, near the black diode with a blue band, just the upper 2 spots. I used a carbide blade in a dremel.
  2. On the lower left near the big black capacitor, you need to cut the trace that comes from the round land (which is where you soldered a wire on the other side. Again I used the dremel
  3. At the tip of the x-acto blade, there is a trace going "up" from that round land, I used an x-acto blade here because it was a cramped space. Be sure to get the copper trace cut through.

Seal the opening where the wires exit so all the fan pressure goes out the smoke exit, you can use some duct tape or maybe a blob of silicon seal.

IMPORTANT: test with an ohmmeter, neither of the smoke wires should have ANY continuity to either of the fan wires, and vice versa. This is important!

Harbor Models

I don't know much about it, but the output looks fantastic. It draws 2 amps at 12 volts though! Several people have posted using it, but they have not modulated the smoke output, most likely because of the large amp draw. In 2012 they announced you could vary the fan speed, have not tested this unit.

The dimensions on the web site are not correct, the dimensions from an actual owner are: about 2 inches on each side and 1.5 inches tall, but the fan adds another 1.5 inches, so the entire unit is 2 inches wide, 3.5 inches long and 1.5 inches tall.

this will be a tough fit in most locos. You might consider putting it in the tender and then running a hose to the front of the loco.



LGB made several different smoke units, just simple heaters with no voltage regulation, etc.


 Wire color

5 Black and White
18 Brown and Yellow
24 White and White


Train America Studios (TAS) - no longer available

This company made one of the nicest aftermarket units, and they have 2 modes, a diesel mode, where the fan speed increases with speed, and a "puff 'n chuff" mode, where you can pulse the fan to match the chuffs, usually tie to the chuff switch. Unfortunately, in 2009, they were bought by Lionel, and then deep sixed. You will find these units in USAT locos sometimes, like the Big Boy, the Hudson, etc. (not in the normal line of plastic bodied diesels). Too bad.

Here is a top view:


  • The three pin plug next to the the aluminum tank/reservoir is for power, ground and chuff.
    • The leftmost wire, furthest from the tank is the "chuff" input, grounding it makes the fan go full speed.
    • the middle wire is ground
    • the rightmost wire, nearest the reservoir is positive
  • The connector at the far left goes the to fan motor, as you can clearly see.
  • The jumper between these 2 connectors controls "steam chuff" mode vs. "diesel notch" mode. The jumper is in the "Steam chuff" mode in this picture



  • Many units are supplied with a full wave bridge wired to the ground and plus leads to avoid destruction due to reversed supply voltage.
  • The "DCC" versions may have different PIC code (that is the program in the microprocessor) and a "larger value" heating element. This note was from Mike Regan at TAStudios.
  • I did not measure the current draw of the "chuff" input, it's low current. Isolate from other leads if you are connecting more than one thing to your locmotive cam/reed switch. (use a diode)
  • Notice the jumper between the power connector and the motor connector. It is in the "steam loco" position, the other position is the diesel position.(Steam closest to the reservoir).
  • They made AC and DC versions. The internal circuitry is different. The AC ones use a Triac to turn the heating element on and off, the DC versions use a transistor. So beware if you come upon a used on, it could be an AC version, which will not operate properly on DC.
  • The unit can draw up to about 1.8 amps before it goes into overload protection.
  • DO NOT connect the chuff input to positive DC, it will destroy the unit (wow, but this info directly from TAS)
  • Paul Burch informs me that a replacement heater (usually 27 ohm) can be gotten from Lionel, part number 6008141055. Link to Lionel parts site:

Here's a TAS installation in an Aristo mallet by R.J. DeBerg:



I received mine recently, and will use the "puff 'n chuff" feature on my AML K4, which has a chuff cam. The model I got is the TAS-2004.

When you order a DC unit, you need to tell them what operating voltage you use. I could not get them to give me a straight answer, but I think they set a regulator or dropping resistor somewhere. The DC unit comes with a full wave bridge rectifier (so the unit can be connected to the rails irrespective of polarity), so you can use them on DCC also.

It is a good looking unit, with the circuitry isolated from the smoke fluid. The fluid reservoir and the smoke chamber are in one metal casting, which is sealed to the circuit board.

They alsohave a TAS-1022 "Puff N Chuff" synchronized smoke upgrade. It is a control for a fan driven unit to pulse the fan in time with the chuff switch. It also includes a 5 volt power board (I assume that is needed to drive the logic circuitry) in addition to the Puff N Chuff board. I will have to try this out on the MTH fan when I try the MTH unit.



An inexpensive smoke unit, with just 4 connections, 2 to the fan, and 2 to the heater, ideal for use with a decoder that drives them directly. Originally Train-Li offered a rewired Aristo-Craft unit re-wired to bypass the original regulating mechanism and just connect directly to the fan and heater.

In theory you can also run the heater at a constant 5 volts.





They make a "Pulsed Smoke Generator", in 5v (8412101) and 19v (8412201) versions. They draw 500-650 ma and 120-150 ma, respectively, 50x28x30mm.

Update, summer 2011, the 19 volt unit has been discontinued, forcing people to either power the unit from the 5v output on a Massoth decoder, or to supply a separate 5v supply. A distributor has mentioned that the 5v output is regulated, but there are reports that the unit runs much better on 7 volts.

From the documentation, it's clear that Massoth is not very interested in using as a generic unit, for example the manual which shows many different connections to different hardware, does not show anywhere how to trigger the pulsed smoke from a simple reed switch.

Massoth had a presence in the US for a while, but as of May 2011, they terminated the contract the Klaus in Cumming GA. They are/were a major OEM supplier for LGB. It's not clear who is the main distributor for them.

I need to find videos of these in operations, because I have never used one.

There is a "pulse input" (which we would call a chuff input) that will produce 1 or 2 chuffs per pulse, and also a "diesel" mode. The "Pulse In" input is in the 3 pin connector that has "IMP / GND /  and U+" If you use a  reed swith, connect IMP and GND to the switch.U+ has 6.5V for the supply of a hallswitch.

When connected to a Massoth decoder, it will modulate the smoke output based on engine load (looks to be a SUSI interface).

It has overload and dry-run protection. They specify 30 minutes of operation per filling nominal.

Apparently by setting a DCC CV, you can compensate for track voltages over 19 volts in the now unavailable 19v version... interesting the detail they present on how to set CV's on a Massoth decoder if you are running DCC over 19v. This sort of implies that it's sensitive to over voltage.

The problem comes with how to connect it. The manual makes it clear on power, but the other connections use standard cables with no description other than "LGB Pluse Generator cable" with 3 wires.

You can figure out how to connect the pulse input, sort of, but then it tells you to set some CV's but it does not say why or what they do...

let me know if you play with one of these.

MTH (Mike's Train House) smoke units:

Many people are trying these in customizing, but they are really large: (the MTH is on top, the TAS below).


The MTH unit above measures about 3" long x 1-3/8" wide x 1-3/4" tall (thanks for the pictures and measurements Chuck!)

I don't know the MTH model above.

The motor and the heating element are directly connected to the 4 wires, no electronics involved, in the stock MTH systems, all the brains are on the mth board.

One negative, there is no local heat sensor to monitor the actual temperature of the heating element.

I have ordered the one from the Hudson  ( Proto-Sound 2.0® ) AA-0000032 50.00 ( 6.0x3.0x4.4mm brass cup )( 7.5mm long posts )

It's just under an inch wide, 1.4" long, and about 1.3" tall overall, not including the brass stack. It was $57 from MTH.

part number for the heating element: (MTH part # AI-0000018)


fan part number (MTH part # BE-0000041

USA Trains smoke units:

Again, like Aristo, there have been several variations. The early ones were a small square unit, very thin, no fan, just a heating element and a wick and did not work well.

The newer ones are metal bodied, have a fan and a separate circuit board that controls the motor and the heater. I have found these to be very reliable. The quantity of smoke is not great, but they work and come stock.

In stock form, i.e. running from the USAT power board, using 40 drops fo fluid, one quit about 9.5 minutes, the other 11.25 minutes, then turned itself back on and ran another few seconds, less than one minute

they both restarted when additional fluid was added (motors started, did not remove power, engine was shut down)

These units lend themselves very well to "direct smoke" setups where the decoder drives the fan and heater directly, like the QSI and Zimo.

Reservoir capacity seems to be about 2cc. The fan runs on 5 volts and the heater element gets around 6-7 volts.

Here is a USAT smoke unit in "direct smoke" mode via a QSI Titan decoder:

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