Wire in a resisitor between the decoder output and the unit as you would an led is what I would do.

Hi Ben
You don't need to IF you connect the smoke unit to one of the decoder outputs.
Why? Because, in most cases the return wire is the loco ground return, so only half-wave so the avarage current is lower.

THIS IS NOT TRUE when the smoke unit is connected directly to the digital current. In that case:
- smoke production and current is significantly larger
- life of the smoke unit is significantly reduced by larger-than-specified voltage (18 VAC instead of 12-14 VAC average voltage value in analog mode).
- in all cases, the smoke unit must be turned OFF in prolonged absence of smoke liquid.

In Digital one simple way is to insert a diode (anode to the smoke unit) 1N4001 to 1N4007 to reduce the current and behave EXACTLY as if driven by a decoder
You can further with a CS3 or CS2 configure the output as a smoke unit (pulsating and reduced intensity when stopped).

Be aware that a smoke unit needs additional current
- a regular smoke unit controlled by a decoder 80mA
- pulsated smoke unit 300 to 400 mA like on my BR06 (39662)

By comparison, a modern Märklin motor (CAN) needs 150mA to 180 mA
Sound and LEDs give no noticeable current (1 mA or less)

So if you plan to have many smoke units, be sure to have plenty of power available.
Cheers
Jean

Edited by user 04 January 2023 11:29:49(UTC)  | Reason: Not specified