Traffic Light Control

Sounds like the perfect place to try an arduino micro computer board. I have not used one of them myself but from the reading I have done this sounds like the perfect application. I hope some of the experts will add their .02$ worth.

I don't know if Greg will be able to build the syncing circuit for you, but awhile ago I ordered 1:48 traffic lights from Greg Leonard.  They are fabulous!!!!

http://miniature-traffic-lights.com/testimonials

George

What are you Syncing them to.  

In the real world traffic lights are on timed circuits that account for the variables encountered at that intersection.  Studies are done (car counts) to determine the optimum timing for rush hour traffic, holidays, weekends, school year, etc. and the lights are timed accordingly.  

If you have moving (electric cars) on your layout just stop the cars for a red light and start them again for a green.

If your little car drivers have insurance, don't stop them occasionally and see what happens! 

I'm sending this along to the Toronto Department of Transport.  I'm sure they'll get a big laugh out of it.

Bruce

I said in the real world!  What's Toronto got to do with it!

If I was doing this I would put an opto isolator's LED in series with each red light lead. The opto isolator's transistor output would control a relay that in turn cut power to the appropriate super street roadway.  Only real problem is that you might cut power with a car in intersection and the opposing car would T bone the stuck car.  Ways around that I am sure. But food for thought if you were electronically savvy and didn't want to learn microprocessor programming.

Thanks for the input folks.  rrman - I'd have a similar approach to your recommendations.  The sticking point is the traffic signals are red, yellow, green.  Timers are needed for the yellow to red combination.  There are several manufactures which have controller to address traffic light control.  Unfortunately I haven't found one that interfaces with the actual traffic.  I'm thinking maybe block controllers that support 3 aspic signaling may be the way to go if I can find one ? 

https://ogrforum.ogaugerr.com/t...enting-a-train-wreck

If it's simple go/no-go, it seems the above cross-over protection thread applies where the trigger to stop the cross-traffic comes from the red-light output of the controller rather than the other train.

Separately, if you put an opto-isolator in series with the signal going to the red-light (LED), the opto drops about 1V which may starve the red LED of sufficient voltage to light up.  I suppose the red-LED driving circuit may be a current-source which would maintain red LED brightness even with the opto in series, but I'd think most circuits are just some digital logic output with a resistor.  Since an opto only needs, say, 1 mA to operate, you could probably put it (plus a resistor) in parallel with the red-LED and not dim the red-LED.

Are you just trying to get something/anything to work...or do you want to go the extra mile and don't mind soldering and messing with components?  That is, how about having yellow slow down the approaching vehicles by, perhaps, reducing the voltage on the track (e.g., some relay-controlled voltage dropping diodes).   The yellow slowdown would only kick in if the traffic is sufficiently far from the light which could be implemented with an optical-triggered relay which are only a few dollars on eBay.

The 4 way dual lane intersection is going to be in front of Lionel's complete model of Grand Central Station.   The scene is just going to be a vignette.   All 4 streets are short maybe 30 inches each and dead end.  The traffic will go back and forth.  I'll probably use trolleys since cars would look silly going backwards.  The Superstreet vehicles run on AC but I believe the motors are DC.  If I can modify the vehicles to run on DC, they will be easy to reverse direction.  I plan on using relays for vehicle power control with sensors embedded in the roadbed adjacent to the intersection.  Since these vehicles have almost zero coast down when power is killed they immediately stop.  So a sensor close to the intersection should work fine.  There are lots of detectors on the market that will drive the relays.  I should be able to use spare poles on the relays to trip the light sequence.   When a car approaches the intersection the adjacent traffic light turns yellow then red and power is killed stopping the adjacent vehicle.  When the car passes the intersection, it hits the next sensor and turns the adjacent signal green restoring power.  When both cars arrive at the same time, I'm going to need a priority system.  Should work fine if the intersection is not cleared.  Need a timer to control the yellow to red sequence.   I plan to use MTH dual Traffic Lights.  Each light has 3 LEDs : red, yellow and green.  There is a MTH controller but it's meant for a static traffic display.  I'm going to take it apart to see if an input can be added to control the sequence.  Better yet, maybe there is a controller out there that will do the whole job but I haven't found it yet.

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If it's an approaching car that triggers the yellow-then-red in the adjacent light, does that mean both directions are normally green?  I'm not sure how many signaling systems use this protocol but it might limit your choices if you're trying to buy an off-the-shelf controller.

Unless you go down the Arduino path, I'd be surprised to find a plug-and-play controller that could do the whole job which presumably includes reversing the direction of the trolleys when they reach the end of the 30" sections.  I'd think you'd also want the trolleys to stop for a time...rather than simply reversing the DC voltage on the track thereby giving the passengers whiplash!

No green in one direction and red in the other although green in both directions would make the traffic experience more interesting.   I found a Dual Traffic Light Controller manufactured by Galak Electronics  that may work.  The product description talks about a "digital control for Yellow".  I'm hoping this triggers the sequence ?

http://www.galakelectronics.com/VG-303.htm

Hmmm..... maybe I'm not looking at this right.   Maybe I should sync the traffic to the lights instead of the other way around ?  That sounds easy.

On the board is marked "Yellow light time multiplier" with what looks like a table showing you how to set the jumpers to the right to select from a discrete set of value.  I suppose that's what they mean by "digital" yellow as opposed to the overall cycle timing using that "analog" screwdriver adjustment.

That's quite a good value...and they only charge $3 to assemble it.

I see there are 4 screw-terminals for each signal...I assume 1 "common" and 1 each for R,Y,G.  I don't know how the MTH signals are wired but presumably also 4-wires?  If so, you may want to check if the common wire polarity matches the controller board...or common-anode vs. common-cathode for common + or - relevant for DC LED wiring.

Well, that's how I'd do it. 

I'm more interested in whether there's a simple way to make the yellow do something.  If you simply kill track voltage on red, then you run the risk of the previously discussed intersection collision.  OTOH with judiciously located sensors, I'm thinking the yellow could trigger one of two actions.  If the trolley is very near the intersection, yellow would accelerate (increase track voltage) to insure it makes it through the intersection before turning red.  If the trolley is further away, yellow would decelerate (decrease track voltage) to insure it does not reach the intersection before turning red.  I'd think this would add to viewer interest whether or not it's prototypical behavior.  In other words, if yellow does nothing, and you only have red/green stop/go action, then why bother with a 3-aspect signal and just use 2-aspect signals...in my opinion of course.

Thanks stan2004 - nice catch on the board labeling.  The MTH traffic signal has 2 parts:  the signal and the controller.  There are 4 wires off the the signal that go to the controller, I presume as you said for the common and the 3 RYG LEDs.   Not sure if the LED resistors are in the light or in the controller.  The Galak controller outputs the board supply voltage to the LEDs so I presume external resistors are needed.  Not sure what the common mode is yet.  Price is excellent.

I suspect the MTH controller will not drive external relays.  The Galak provides 500 ma at the LED outputs which can be used to sequence relays for controlling vehicle power.

Also nice thoughts on mechanizing the YELLOW, speeding up and slowing down based on traffic position when the YELLOW light illuminates.  I like it and it sounds easy to do.

Any ideas on vehicle selection ?

I don't have Superstreets so can't comment on vehicle choice though I get your point about something that is bi-directional for your situation.

Yes, if the Galak can drive 500mA, then it's likely there are no resistor on-board and you'll have to select and include them externally.  Likewise, I notice they speak of driving LEDs or incandescents...but not driving relays.  It looks from photo they use transistors to drive the outputs...but I don't see any clamping diodes you need if driving a relay coil.  So you might need to add external diodes too for any outputs that drive a relay coil.  And, if the common wire polarity for the controller is different that the signal heads, then you'll need to either re-wire the heads or install an external inverting circuit using, say, a transistor and a few resistors (~25 cents per line).

Tell me more about the position detectors you apparently have in mind.

You may be sorry you asked about position detectors !!  My layout is a work in progress.  The track is down, the 40 switches are operational, there is a elevated section with a grade to the base layout.  I have number of stations like a 155th street subway and Fenway Park.  Some signaling.  Major things to do are the city area to be populated with D56 CIC buildings and the farm area complete with a mountain winery and lake.  Not much landscaping to speak of at the moment but it will come.  I'm retired, so there's no rush to complete.

The big unknown are blocks and block detection.  I'm running MTH DCS and have wired for easy incorporation of block.  I run conventional and Command Control engines both MTH and Lionel.  They work fine under the DCS system.  However with command control engines you can't just turn the power on/off for station stop and blocking.  There are a number of products on the market to provide train detection but none that address the command control issue.  I'm familiar with a couple of the workarounds for command control blocking.  I'm hoping MTH will come out with a product which will support command control blocking.  Seems easy enough, not sure why it's not here yet ?  I've used Zstuff train detectors already on an extensive sequence consisting of a number of Lionel 450 signal bridges.  I've have Circuitron photo train detectors embedded in my subway station for station stops/signaling but are not operational yet due to the command control issue.  Not sure what I would use for the Superstreets we have been discussing, although commonalty across the layout would be nice. Ideas are welcome.