Smoke unit question MTH-ERR upgrade

You will burn up the triac on the R2LC board using the dual resistors in the smoke unit.  Remove them and install a single  resistor in the 22-30 ohm range.  I'm sure Gunrunner has a resistor part number he can add from one of the electronic dealers.  Newark, Mouser, Digi-Key

I take the Stackpole CB5JB20R0 which is a 5W 20 ohm resistor.  I put it diagonally in my vise long ways and slightly tighten.  The outer square ceramic shell cracks away and I end up with a perfectly formed smoke resistor.  Much faster than cleaning the ceramic powder off the other offerings.

After a few bench tests and measuring the temperature rise in the smoke triac, I've determined that 20 ohms is the lowest you can go and still be relatively safe with the power dissipation of the smoke triac at 18 volts on the track.  I've talked to people that have used one of the 16 ohm MTH resistors, but when I tested with that value at 18 volts, the smoke triac got close to 100C, too hot for me to be comfortable with it.  With the 20 ohm, the triac never gets past the mid 60's in my testing.  I can live with that.

Thanks.

GRJ - I have got 20Ω 2 watt ceramics that you recommended for Lionel smoke units.  I'll clean off one of those the old fashioned way and order a few of the rectangular ones you suggested. 

@superwarp1 posted:

You will burn up the triac on the R2LC board using the dual resistors in the smoke unit.  Remove them and install a single  resistor in the 22-30 ohm range.  

is there any special wiring needed after doing this?

Just replace the two resistors with one of the proper value, 20 ohms or higher, in the holes closest to the stack.  I fill the other holes with solder.

Dan check your email

Alan

Thank you.

My conversion is almost finished.  All the lights are LED's and the smoke heater works great with a single 20Ω resistor wired through the feature channel.

What I am left with is how to power the 5vdc smoke fan motor using the Cruise Commander and Sound Commander boards.  I do not see a 5vdc connection anywhere.  Is there anyway to connect it that can be controlled via TMCC?  It would be great if the fan ran slowly at idle then sped up when the locomotive started to move, like GRJ's Super Chuffer without the chuff (it's a turbine).  I could use an AC/DC buck converter and a latching relay to turn it off and on, but that seems like an awful lot of hardware for one dinky little motor.

Any ideas?

You can actually power your fan power off the smoke output as well, that way the smoke fan run with the smoke.  No relays in sight.

Truthfully, since the smoke motor only draws 30-40ma, you can do it with three components, a diode, 220uf 35V cap, and the LM7805T regulator.  40ma isn't worth wasting a switcher on.   I use the TO-220 regulator as it will run nice and cool with 40ma, the TO-92 low power one actually gets a little toasty with 40ma.

Thanks, John.  I know have the diode and resistor but I have check inventory for a 7805.

They're cheap, and you'd have had to buy the buck power supply anyway.

Actually I have half a dozen buck converters, but I had to order the 7805.  You’re right, $0.35 each, for 20 pieces, and free shipping from Amazon.

And even cheaper if you buy them from China.

Amazon will deliver on Wednesday.  China post might deliver on a Wednesday of some future week.

There's always that.   I could have sent you one, but I guess you'll have a lifetime supply now.