I purchased an old train signal at a Flea Market over the spring (essentially the same thing as a traffic signal, except bigger). It uses arrays of LEDs for each of the lights - and for the sake of argument, let's say each light has 40 rows of LEDs (120 rows total).
I don't know the exact row count because I've yet to actually crack open one of the individual lights, I want to be sure what I want to do is possible before I do that. But (and correct me if I'm wrong), that shouldn't make too much of a difference.

What I want to see if I can do is get the light to light up like an Hourglass, lighting rows at regular intervals (the this case, one every 10 minutes).

Any thoughts?

 

Sure. You could turn each array into an LED MATRIX.

Those signs you see out front of stores. That way, you could scroll text for warnings, i.e. The red light could have a message scrolling in the middle saying "This light is red, and you are waiting because some sucker got creamed at the crossing because he tried to drive around the gates."

 

I purchased an old train signal at a Flea Market

If it's LEDs then it can't be that old. That aside, please elaborate further.

 

You're right - I suspect it's only from mid 2000's, but it's pretty beat up an needs some serious TLC (sanding and repainting mostly, there is one hole in the bottom, but that's all pretty irrelevant).

It runs off of standard wall voltage (120v 60Hz), in fact the previous owner had just wired wall plugs into each individual unit and they ran straight like that.

What would wiring them up as an array entail and how complicated would it be? I suspect that they are currently in either series or series-parallel.

 

They're, more than likely, a series string but we need some good photos before any accurate advice can be dispensed.

 

I have an 8" traffic ball signal that had 84 LEDs wired in series and powered by 120VAC. It had a high voltage switch mode power supply built into the display PCB. I had to remove all components from the PCB except the LEDs then make some trace cuts and attach wires to create a series/parallel circuit that I could drive with DC. It is now the mother of all bicycle safety blinkers having more than 20 times the number of LEDs of a typical blinker.

If your display is a similar product, it would require a more radical modification to isolate each LED. It might be easier to build your own board to go in the housing.

 

And we're going to have to insist that the project be run on low voltage DC from a step down transformer for galvanic isolation.