TMCC Upgrade Smoke Chuff Solutions

GRJ.

Great stuff, I saved the images for future reference. 

Thanks!

Seconded and saved - What he said!

Glad you like it guys, hope it's helpful.

So, what happens when the locomotive isn't moving?  Is there a steady stream of smoke?  And how well does it work in conventional?

There is no provision for determine the state when stopped, it depends on the state of the chuff switch.  I'm working on a design using a PIC processor that will automatically transition to continuous fan at low speed when stopped.

I designed this for command, conventional would require a lower voltage relay and a regulator to insure reliable operation of the chuff output.

Hence the difficulty in doing this.  The design should account for both conventional and Command operation.   This is the elegance of the MTH design with integrated smoke and sounds controlled by the processor driven off the tach reader.

The TMCC has more variability because of the way the R2LC Smoke Triac handles power to smoke differently in the command versus conventional, let alone the differences in input voltage.  Part of the reason that early smoke units had 27 ohm resistors to handle the full wave AC that could get up to higher voltages when in conventional.

I am working on a Brass Williams J conversion for myself.  I have the fan smoke unit ready to mount, and it has independent AC input for the fan motor 5V circuit.  One thing I am toying with since I am installing a TAS system from a Weaver Northern and will have chuff generated from the tach reader is to use a reed switch not to interrupt input voltage, but rather place 5V on the negative return to stop the fan when the reed closes at chuff.  The problem is I will have to create a common DC buss and not allow the DC return to AC common the way Lionel does it or I risk shorting my 5V power supply.  G

I am thinking, for the next one of these I do, I'll use the other contact of the relay to short the motor to provide dynamic braking for stopping the motor faster.  I don't think you really need a negative shot to get this done. 

I'm having real difficulty imagine synchronizing the reed switch with the tach generated chuff, not sure quite how you visualize that working.

For conventional operation, using a lower voltage relay, say a 5V one with a regulator would do the trick for my design.  This module doesn't control the heater voltage, that is controlled the same as with any TMCC locomotive in conventional mode, so the variability there is the same as always.

FWIW, I wasn't presenting my designs as a solution to all such issues, just showing how this issue can be handled.  As I only run command, many of my solutions tend to be slanted in that direction.  Adding extra work and parts to handle conventional operation doesn't make much sense in my situation.

Great stuff John.

Have you made one of these ?

Just wondering how well the mechanical relay works

at high speeds. Also how long this relay might last.

That's a lot of cycling for a mechanical relay....

Would 2 SCR's work ? Might also give you a smaller foot print.

Yet we now have another reason why this is such a unique hobby.....

I've made several of them.  The relays are rated at 100,000,000 operations at low current, so I suspect they'll have a pretty long life, probably outlasting anything you install them in.

There are lots of other ways to do a circuit like this, however for the new RailSounds Commander with the isolated DC supply, it requires a bare dry contact as you can't have any common reference to frame ground for either side of the chuff input.  That presents a somewhat unique issue that led me to use the relay for the job.

I was just pointing out the difficulty in making all the various features work with TMCC based on Sinclair's question.  It becomes complex or you make concessions based on how you use the engine.

Not sure what you mean by negative shot?  I was going to use the 5V regulator on the smoke unit to drive the fan motor.  The reed would induce 5V on the return to stop motor.  Was going to use the regulator in the CV board on the boiler front, since the sleuth smoke is removed.

Synchronizing is certainly an issue.  One thing that is neat on the Williams J is that the drivers rise about a 1/4 to 3/8" above the frame.  You could easily place a magnet on each side (wheel) and use 2 reeds.  So if you used a ERR product one reed could do chuff and one puff.  The boiler will hide the reeds.

I am still in the design phase, not sure which way I will go.  G

Sinclair's idea of running the fan when stopped is a good one, it just takes extra parts.  That's the primary reason I'm working on a uP based solution that will recognize when the locomotive is stopped and handle that issue.  It'll also have provisions to control cab lights and Rule 17 lighting, since that's easy if you know the locomotive state.