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Here's a new way to generate the chuffs for TMCC upgrades and older TMCC locomotives where you want 4 chuffs/rev. 

 

I had this Lionel Cab Forward for upgrade with the Super-Chuffer, and part of the upgrade was 4-chuffs.  The drivers are so close that I couldn't mount the magnets there, and the recess for the wheels is barely visible around the frame, so sticking them in there was going to be REALLY difficult.  The wheels recess was also very deep, so the magnets would have to be sort of "floating" on the rim, making it even harder.

 

I decided to mount them on the leading pilot truck, the trailing truck didn't have room for the magnet.  That might have worked, but on corners and any sort of uneven spot on the track, the wheels wouldn't always rotate, so you'd skip chuffs.  Not acceptable!  I tinkered with the springs on the pilot truck, but I couldn't get it right.

 

Time for a totally fresh approach.  I ordered some reflective optical sensors and set about doing this optically.  It turned out to be easier than I thought.  I cleaned the inside of the wheel and stuck small squares of silver tape every 90 degrees, and then bonded the sensor to the frame.  A couple of resistors, one for load and one to limit the LED driver current, and everything connects to the Super-Chuffer, which already supplies the 5VDC power needed.

 

This may become a standard feature of my upgrades, it's much less likely to double triggering like the reed switch with magnets.  Unless you position the reed switch just right, it can get a "double-tap" as the magnet goes by.

 

 

Optical Chuff Switch

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  • Optical Chuff Switch
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Originally Posted by albrechtfutterer:

John,

 

it would be great, if you were publish a wiring diagram with parts.

 

There was an optical sensor at Dallee's. Can that be used ?

 

Thanks and regards

 

Albrecht

 

 

Albrecht, Digikey sells them. Here are the specs. Its an Optek OPB607A. You just need a current limiting resistor for the LED and note the polarity of the photo transistor.

 

http://optekinc.com/datasheets/OPB606-607.PDF

 

Pete

 

Pete is correct, it's the Optek OPB607A.  I had 5VDC available from the Super-Chuffer, so I just used a 270 ohm current limiting resistor for the emitter feed, and I also provided a 1K pullup resistor for the open collector of the Darlington output.  The output load was determined experimentally, I was initially letting the pull-ups in the Super-Chuffer and the TMCC board do it, but I was not getting reliable chuffs, it apparently needed a bit more current through the opto.  There was enough dark current through the opto to keep the voltage low.  There is another part, the Optek OPB606A that has a single transistor output and not the Darlington pair.  I have some of those as well, and I'm going to see if I can get enough drive out of them, maybe they'll end up being more suitable.

 

I ended up taking the spacing specifications with a grain of salt, when I tried to space them the .1 inches specified, it wasn't working at all, I was getting too much reflection from the wheel, even after blackening it.  I moved the emitter out to about 1/3", and then everything started working great.  I get about 4.5 volts black and around .8 volts when the reflective tape passes.  Fooling around with the sensor over various materials on the bench, I got similar results.  The spacing, at least for this application, has to be much greater than the spec sheet would suggest.  The bonus seems to be that it's not all that critical, anything from about 1/4" to 1/3" worked great.

 

Mounting these seems a bit less critical than reed switches with magnets.  This one is perched on a couple small pieces of fiberglass board to get it to the proper height to clear the frame recess and see the wheel.  I use CA adhesive to stick it there, it doesn't seem like it's going anywhere.  Getting the reed switch off the pilot truck took some effort, and I can tell you that Acetone is very lousy for actually debonding CA adhesive, contrary to what others might say.

 

I haven't thought about building kits yet, I just got the parts yesterday and worked on it to solve my problem with the job on the bench.  Now that I see that it works really well, I'll probably work to package it a bit neater. 

 

 

 

Ron, I like the idea of having two separate emitters on different engines to vary the timing, but there's one issue with most scale articulated locos.  There is only one motor driving both sets of drivers, so the timing won't really change.

 

Carl, it was created out of necessity, it was looking like magnets were going to be a messy solution.  I've actually been thinking about this for some time, it just seemed like a good time to give it a go.  I am pleased with the result, so I suspect that I'll be doing more of them like this.  It seems less "fiddly" than the reed switch and magnets.  As long as you have 5VDC available, it's actually easier to do than the reed switch as well.

 

No reason it won't work on any TMCC locomotive as long as you can find a place to mount it.  If the wheel flanges are visible from the inside of the shell, you can mount it there.  Many locomotives have to have it mounted under the frame to shine on the driver flanges.

 

The cam or axle would probably be too small to get the definition between light and dark, or at least That would be my thinking.

Interesting to see if it holds up under use.  The wheels can get dirty from grease, track gunk.

 

I am figuring out what I want to do on my Brass J.  There is plenty of access on the inside of the engine, this might be a nice method.  I also thought about the flywheel, but you would need some sort of divider circuit to account for the gear ration.  I wonder how hard that would be.  10 pulses in but 1 out.  G

I'm not anticipating any major issue with dirt, and if my metallic tape gets dirty, a wipe with a solvent rag will fix it.  If the wheels near the flanges are getting that dirty with grease, you need to change the lubrication intervals!   I looked at some stuff that has significant running time, and I don't think they're going to get so dirty on the inside as to cause an issue.

 

I originally thought about the flywheel, but the complexity of adding an adjustable counter for various locomotives made me decide to try this first.  Since these retrofits go into locomotives with varying gear ratios, you have to be able to tweak the counts.  If I had serial data capability for my Super-Chuffer, I'd probably have considered the flywheel and just divided the chuff input based on a configuration parameter.  That may be an option in the future, but it would take a new board design.

 

Originally Posted by gunrunnerjohn:
Originally Posted by Ron H:

John, I would put the optics on the TENDER wheels not the engines. ERGO, no auto sync.

 

Ron

I'm not sure why you want them on the tender, you get exactly four chuffs when they're on the drivers.  What is the perceived advantage to putting them on the tender?

John, mounted on separate tender trucks the 4 chuffs on each wheel on the respective trucks would randomly run in and out of sync due to different wheel drags, minute changes in track curvature and so on. I think it would be quite effective.

 

So, my question is, can two of these optical sensors run off the supper chuffer or directly off the cruise commander????

 

Best Regards,

Ron H

Last edited by Ron H

Ron, on separate tender wheels, that would probably work. 

 

Now comes the interesting part:

 

Articulated sound boards already have the extra chuffing enabled, so adding these two totally random triggers would be interesting to say the least.   I have no idea how it would sound, it might make sense to select a non-articulated sound board for what you contemplate.  If you were generating roughly four chuffs for each tender trigger, that would get the count right.  One problem with multiple sources of triggers is when they get close to overlapping, it would cause sound boards to drop chuffs, there is a window where a double-tap won't trigger the sound twice.

 

Having just finished a few minutes ago adjusting a reed switch to minimize the double trigger I appreciate the problem. The Super Chuffer elegantly varies the on time of the fan motor with changes in chuff rate. I have used a one shot (monostable multivibrator) to shorten the on time and give distinct puffs up to higher speeds before it appears as a steady stream. While simpler, it doesn't change the on time of the fan at slower speeds like the Super Chuffer. Neither does it fix overlap. That requires sufficient distance between the magnets and reed switch so its closed for the minimum amount of time.

The optical solution makes it much easier to do this. 

 

Pete

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