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A tether is the easiest way.  Failing that, we need to know if it's command or conventional.

 

There are some cheap remote control devices that could be pressed into service to send the light status to the dummy car,

 

Take one of these C:US:3160" target="_blank">4 Channel Wireless RF Remote units, rig a relay to push the button on the transmitter, and use the receiver in the trailing cars to operate the lights and other functions as well.

Originally Posted by stan2004:

Are the lights meant to turn on only when in reverse?

Yes, rear markers off and headlights on when the tail car becomes the front of the train (power car pushing from the rear, its headlights off and markers on - the board handles that)

 

Of course with the rear car as the tail car, red markers on, headlight off.

 

Right now I just have red lights connected to the in car lighting so they are on regardless.

Last edited by Former Member
Originally Posted by stan2004:

Are the lights meant to turn on only when in reverse?

Yes, rear markers off and headlights on when the tail car becomes the front of the train (power car pushing from the rear, its headlights off and markers on - the board handles that)

 

Of course with the rear car as the tail car, red markers on, headlight off.

 

Right now I just have red lights connected to the in car lighting so they are on regardless.

Actually, I think the lowest "out of pocket" approach is the tether, and it's also the simplest by far to implement.  Options #2 and #3 involve some custom circuitry.  The Minitronics 50-004-01 4 pin tether would seem to be the cheapest and simplest option at $13.95.  Also, it's just a simple wiring exercise to get it working.  The tether is so small that it's easily hidden under the couplers, so it's a very attractive option as well.

 

Well, he's running a subway so presumably this might be, say, 4 total cars (or more?).  That would be 3 inter-connects at $13.95 each or over $40 just for the wires/connectors.  Of course sourcing your own connectors and wires could save some coin.

 

There would still be some minor component level work - adding resistors or what not.  That is, I don't know how MTH does subway powered-unit lighting but if the headlights use bulbs and he uses LEDs in the tail-unit, then some fussing is still required.

 

The "problem" with a tether approach is it's like that potato-chip jingle from several decades ago - no one can eat just one.  That is, the first thing I'd be thinking if I installed tethers is how to add one more wire to put the interior lights of the trailing cars under powered unit control.  So when shutting down the engine, or turning off the Interior Lights under DCS control, all the lights in all the cars turn off.  Then, once I got that solved, I'd be thinking...

Yes, tethers would get expen$ive.  My R-17 is an eight car set (2 power cars at the head end) so that's seven sets of connectors and the R-142a set is another four.

 

Besides, these are not kept on a layout all the time, so each would have to be connected and disconnected for every use.

 

Before anyone asks why I don't just use the second powered car at the back end of the train, it's because I sometimes run less that eight cars and my rear car has a detailed cab end (safety chains, q-car H2A coupler, etc).

 

I wonder if you could use a small motor as a generator to power the lights, or at least let a circuit know which way the car is heading.

 

The power car in the R-17 set uses bulbs, the R-142a set uses LEDs.

For now I'll probably just wire 18v bulbs into the car light bar as I mostly use these with DCS so will have good track voltage.

 

 

 

Last edited by Former Member

Well, the bulbs vs. LED's for MTH are not an issue, a resistor solves the problem of driving the LED.

 

I agree that multiple cars does complicate the issue, I was thinking two cars.

 

I think for a multi-car solution, I'd be back to my little remote hacked up to do the job.  Detecting the direction of movement would involve wheel sensors and more mechanics, so I'd personally tend to lean the other way.

 

Of course, for a simple reversing light, only two wires are required, and you can "roll your own" perfectly acceptable tethers for peanuts from snappable headers.  Here's a sample, the mating connector is made with the snappable machine socket strips.  This brings the cost down to pennies a connector.  Obviously, for the tethers, you'd use all black heatshrink for the construction.

 

 

Last edited by gunrunnerjohn
Originally Posted by gunrunnerjohn:

I forgot about the friction based switch, that would be a simple thing to do!  You could use a latching relay and a simple leaf spring so that when it goes in one direction it contacts and flips the relay.  Then it would stay there until you went in the other direction long enough to flip it the other way.

 

Can you identify a specific part/switch that would fit the available space?  I think the issue is what's readily available.  Once the directional sensor is identified, the "electronics" to then drive the correct lights is the easy part (in my opinion). 

 

I only mention the quadrature encoder because it is a readily available mechanism that fits the available space.  It's overkill as it provides speed information as well as direction.  All that's needed is the direction.

The mouse sensor idea sounds good.  Plenty of male mice around (the ones with the balls).  I'm no good at the electronics side though.  I can build something if it's laid out for me, but have no idea how to design it.

 

The mechanical friction lever would probably also work.  My thoughts on the shortcomings of that would be the reliability of the friction surface.

Originally Posted by Quick Casey:

In HO, Marklin has a sleeve on a cab coach axle that is a loose friction fit. A wiper then touches contacts biased in the direction of travel. Reverse direction, and the wiper moves with the direction of the axle's rotation to touch the other contact changing the lights from red to white, or vice-versa.

Thanks Mike - a good idea, but as you can see the MTH trucks are pretty much a solid slug of metal.

 

-};>~

Originally Posted by David McC:
 
 but as you can see the MTH trucks are pretty much a solid slug of metal.

 

-};>~

-};>~.  Well that's being polite.  My first thought was, Oh xxxx.

 

OK, is it practical for you to take a photo of the guts of a trucks?  Or is that a solid block too?  On the motorized diesel trucks I've worked on, the "lid" of the solid block comes off to expose the guts but who knows what surprises lay ahead...

 

Last edited by stan2004

The only thing visible in the top of the dummy truck is the slot where a motor worm would go. Otherwise, it's a solid block where the axles go through--power is carried to the other axle via spur gears on the side of the block.

 

Another suggestion is to use an inexpensive electronic reverse unit to control the lights. I believe this idea was used on a set of Lionel LIRR M-7 cars.

 

---PCJ

Originally Posted by stan2004:
Originally Posted by David McC:
 
 but as you can see the MTH trucks are pretty much a solid slug of metal.

 

-};>~

-};>~.  Well that's being polite.  My first thought was, Oh xxxx.

 

OK, is it practical for you to take a photo of the guts of a trucks?  Or is that a solid block too?  On the motorized diesel trucks I've worked on, the "lid" of the solid block comes off to expose the guts but who knows what surprises lay ahead...

 

I'd have to pretty much strip the car down to do so.  The trucks fasten to the floor from the inside, under the interior casting.  I don't think there's anything to see, just a flat metal top with a hole in it and a mount point.  The axles are threaded through the block with the wheels pressed on afterwards - no way to remove them.

 

With that solid block with no access to the axle(s) some of the other alternatives start looking pretty good!

 

But to follow this trail to a conclusion, dead-end or otherwise, what would you think of mounting a few tiny optical components in the yellow box shown below.  They would shoot an optical beam at some white stickers you'd put on the inside face of the wheel as shown.  I took the liberty of marking up one of your photos showing the area in question.  Mine is from a diesel powered-truck but it looks like there's a similar amount of wheel "overhang" beyond the solid block for a reflective optical sensor to shoot a beam at the wheel and get a reflection.

 

ogr subway wheel sensor

This would be the same concept as the tach sensor and the striped flywheels in MTH engines except the sensors would operate in quadrature-mode to sense direction. A few wires would have to find their way to inside the chassis. The optical components would only be a couple dollars and you'd still need a few more dollars of components inside the chassis. 

 

 

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Originally Posted by RailRide:

The only thing visible in the top of the dummy truck is the slot where a motor worm would go. Otherwise, it's a solid block where the axles go through--power is carried to the other axle via spur gears on the side of the block.

 

Another suggestion is to use an inexpensive electronic reverse unit to control the lights. I believe this idea was used on a set of Lionel LIRR M-7 cars.

Does this mean all the gears are in there for the dummy trucks?  In other words could one install just a shaft (no motor) with the correct worm gear and you would now have a shaft that spins when the wheels turn?  That would be even better than accessing an axle since the gear ratio would mean the worm shaft would spin faster than the wheel making direction sensing virtually instantaneous.

 

WRT the reversing unit, wouldn't this be for conventional only? Or is there something special about Lionel M-7 sets that it can talk to separate electronic reverse units like the MTH Coors set that GGG mentions can magically talk to the trailing cars?

I don't believe there are any gears in the dummy truck. The center of the axle may be exposed in the casting where the worm would normally go. I only have a power truck exposed (it was swapped out from an R-21 set that was randomly jamming), so it's only speculation about what's actually exposed.

 

A friend of mine runs two power cars in a train, so that took care of the lights as the two were MU'ed in DCS, despite running at opposite corners of the train.

 

I had overlooked the part about doing this in a command environment when mentioning the Lionel M7's. For MTH subways in a command environment, I'd just tap the headlight/tailight of the lead car, and equip the intermediate cars with pass-through tethers running headlight power to the tail lights and vice-versa. Its not like one does switching with subway trains, and the real ones have cables hanging beneath their drawbars too.  

 

The only question mark is whether the PS2/3 headlight/ taillight power supplies will tolerate a couple of additional LED's running off them. What say our resident PS2/3 experts?

 

---PCJ

Originally Posted by stan2004:
Originally Posted by RailRide:

The only thing visible in the top of the dummy truck is the slot where a motor worm would go. Otherwise, it's a solid block where the axles go through--power is carried to the other axle via spur gears on the side of the block.

 

Another suggestion is to use an inexpensive electronic reverse unit to control the lights. I believe this idea was used on a set of Lionel LIRR M-7 cars.

Does this mean all the gears are in there for the dummy trucks?  In other words could one install just a shaft (no motor) with the correct worm gear and you would now have a shaft that spins when the wheels turn?  That would be even better than accessing an axle since the gear ratio would mean the worm shaft would spin faster than the wheel making direction sensing virtually instantaneous.

 

WRT the reversing unit, wouldn't this be for conventional only? Or is there something special about Lionel M-7 sets that it can talk to separate electronic reverse units like the MTH Coors set that GGG mentions can magically talk to the trailing cars?

Stan, Lionel has a Small unit that receives TMCC commands and works in conventional also.  The original version was an LCRX.  It had directional lights, couplers and output for RailSounds.  Otherwise your correct, getting conventional to work is easy, but command changes won't work with a conventional reverse unit.  How about an accelerometer? G

Originally Posted by GGG:
Lionel has a Small unit that receives TMCC commands and works in conventional also.  The original version was an LCRX.  It had directional lights, couplers and output for RailSounds.
How much do/did these boards go for? They have far more capability (coupler, sound, etc.) than needed for simple direction indication.  So while expedient, I wonder if it would pass the "common-sense" test given they might still require some modification such as adding resistor(s) to drive red LEDs one way and white LEDs the other way.
And if we're strictly talking conventional-only, I'd wonder if different two reversing boards (one being the MTH PS board in the powered-unit) might somehow get out-of-sync with each other. If you press the DIRECTION button interrupting track power, it seems there might be situations where the two boards would differ in their interpretation of whether the interruption was a true direction change request. And once they get out of sequence with each other what a nuisance to re-cycle power and start again(?). 

Otherwise your correct, getting conventional to work is easy, but command changes won't work with a conventional reverse unit.
Without the "command" information from the powered-units PS2/3 board - whether from wired-tether(s) or wireless-link, I think it would be quite a hat-trick to come up with an electrical-only solution for an MTH subway.  As it stands, the proposed direction sensing methods whether a friction switch, optical quadrature detector, or even an accelerometer would be delayed as the car has to move before the sensor could do its thing and change the lighting.  The powered-unit would change lighting upon direction command before it starts moving.  So until the consist itself starts moving the trailing car would indicate the wrong direction in both command and conventional operation. I don't think this is a show-stopper but that's just my opinion.
How about an accelerometer?
These can be tricky to work with when the time intervals extends to minutes.  Small DC offsets in acceleration are integrated into velocity errors.  As the train approaches a station and slows down, the engine decelerates and the accelerometer output goes "negative". Differentiating this from departing a station in the reverse direction (where the accelerometer would also go "negative") might take some software embedded in a microcontroller chip.
Originally Posted by sinclair:

Going with the optical sensor, why not just read the ties of the track as the stripes?  Or would the contrast not be enough for the sensor to work?

This is a very interesting idea.  As discussed earlier, the current technology in computer mice uses "optical" technology rather than the rubber ball with rotating wheels.  They illuminate the mousepad or surface with a light (usually a red LED) and have a camera-like sensor that essentially takes pictures of the illuminated surface hundreds of times per second.  It's sophisticated pattern recognition software albeit integrated into a chip to analyze images looking for changes which reveals both speed and direction of motion.  All for less than $10 retail!  Pretty amazing stuff.

 

So, yes, I like the concept if that's where you were going but I think it would take some heavy-duty experimenting with lenses/optics to "focus" the camera on the rail ties...and then figure how to extract the direction info from the electronics.  I think it would might take all one's spare time for years to implement this from the ground-up.  And even then, the lights would disagree with the powered-unit until the consist starts moving.

 

OTOH if you meant the track ties are proxies for the black/white or on/off stripes on an MTH flywheel, then picking up on GRJ's comment, it too would take some experimentation to establish contrast levels for different track schemes and oddball cases such as how to ignore weird sensor data when going over, say, switches/turnouts.

I have opened up a couple of mice (the computer type) and I noticed that the scroll wheel sensor is small, compact, and easy to remove.  It would also be easy to mount with a small wheel running against the tread of the rail wheel.  I have NO idea how to power or use the output from this unit to do the direction sensing.  Does anyone here have enough knowledge to design the needed circuit?  I can build it if I have a schematic.

 

Alternately, can anyone point me to a page that explains how these sensors work and how to use them so I can muddle through the design process?

If you can extract the "sensor" part of the mouse and reliably couple it to the car's wheel via a rubber tire (or whatever), then I think the electronics side is within reach.

 

Since your persistence is admirable (many ideas here fade to black for whatever reason), I cobbled together this simple circuit.  It's somewhat half-baked using obsolete parts but it's what I had in my parts stash.  It demonstrates the idea of using an LED shooting a beam to 2 phototransistors.  The mechanical mouse probably integrates the LED and phototransistors into a single package but the circuitry to drive it is the same.  I hot-glued the parts to the truck of a diesel so it's kind of a mess but there's a 4-wire cable back to the circuit.  I only hooked up 1 Red LED and 1 white LED, a +5V supply needs to come from somewhere, and there are other short-cuts which make this more a proof-of-concept than a ready-to-build schematic.

 

A 10 sec video shows the circuit in action.  Note that this method operates at arbitrarily slow speeds.  Some of the "inertial" detection schemes including accelerometers or other momentum-based sensors can have problems with slow speeds if there's not enough "action" to trigger the detector.

 

ogr subway poc sch

ogr subway poc sensor

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