I've run into several situations where I needed a relay to switch smoke units that had more capacity than the native smoke output.
One issue is with the early Legacy parts no longer available, I needed to have something to replace defective Legacy smoke voltage regulators. My experience has been that a majority of them fail by simply dropping their output below what will produce smoke, but they still turn on/off with the command system keys. So, I reasoned that if I used that anemic output to simply switch a relay, I could still have smoke control, just not the three level smoke that Legacy offers. One level is a bunch better than no levels, so the quest was launched. I actually have a number of Legacy smoke regulators that all have the same failure, some were brand new from Lionel! Of course, I didn't think to test them when I ordered them, silly me, I assumed they would work properly! Now with my Relay, I can still get command controlled smoke from the early Legacy locomotives.
Next I ran into a TMCC upgrade of some MTH Centipedes, but with two PS/1 smoke units, I can't just connect them to the stock R2LC/R4LC smoke output. It occurred to me that the same functionality that I described above would solve this problem as well.
Finally, for A-A or A-B-A configurations with smoke units in all the units, you also run into a current limitation of the R2LC/R4LC smoke output, but the same board should neatly solve that problem as well. For those configurations, I use a tethered bridge on the ERR Cruise Commander to allow them to run four (or even six) motors, with the smoke relay board I can deal with the smoke unit control.
Here's my solution in a nutshell. This is the Smoke Regulator Assist Board R 1.0. The board is .6" x .75" and about .5" high. It can be simply encased in heatshrink and tucked in anywhere, similar to some of the Lionel modules.
The Wheels and Roller are obviously track power, the Smoke Input is the smoke control from the TMCC/Legacy logic, the Smoke Output is the output smoke voltage to the smoke unit.
The astute observer will notice I'm supplying track power through a diode to simulate what the TMCC R2LC does, so for smoke regulator equipped Legacy, you'll obviously have to change the smoke resistor to a higher value.
The FW SW 1 and FW SW 2 is just a feature that I tossed in to supply full wave track power to the smoke output if desired. I would use this for something like the Centipedes I mentioned before with the PS/1 smoke units. It ends up being a HI/LO switch for the smoke output.
Finally, since I had a relay with two FORM-C contact sets, I added a small header to optionally use the second set of contacts. Once again, like the HI/LO switch, it costs nothing to provide the option, and maybe it'll be useful for some application.
There is actually enough room with the header locations to use a standard connector if desired, I envision most of these would be soldered in and not have to be removable.
