Parts for this Instructable, a three light T-intersection with one advance green light Electronic parts for this Instructable, 4-green LEDs, 20,000mcd 3-yellow LEDs, 20,000mcd 3-red LEDs, 20,000mcd 2-220& ¼-watt ...
Every Christmas we set up a large LEGO train layout in a section of the living room. This year, I ended up winning an eBay auction for a number of older-model LEGO road plates, one of which included a T-intersection. At about the same time, I saw a web magazine article on how to get started programming an Arduino embedded microcontroller. I'm a computer programmer by trade.
It seemed obvious to me at this point that a perfect project would be to create an LED traffic light out of LEGO bricks, some LEDs and resistors and an Arduino Nano controller. The T-Intersection became the center-piece of the layout. This Instructable will lead you through building the traffic light, as well as illustrate how the Arduino program works.
This is my second attempt at building the traffic light. On the first attempt, my 9-year old son helped me. Being slightly impatient, as 9-year-olds are apt to be, I was left with no time to take detailed photographs. The LEDs I used, found in my parts bin, were also extremely dim: bright at night, but invisible in the day.
With this second attempt, I obtained much brighter LEDs from a string of LED Christmas Tree lights that only half lit up. I also took very detailed close-up photographs with a brand new Sony DSC-TX5 digital camera that can close focus down to 1cm. I've annotated many of the photos.
You can choose to build this Instructable as presented or just use it for inspiration for your own creation. I realize that LEGO T-intersection road plates have long since been discontinued and are hard to come by now. Cross-intersections are all that are available in LEGO stores now. You might choose to build a fourth light. I've supplied an alternate program that should drive a cross-intersection with four advance green-lights. It should work, but since I was testing the program only on my T-intersection, it might not work perfectly. You'll need more LEGO bricks and LEDs to build such a light.
Step 1: Part list
Parts for this Instructable, a three light T-intersection with one advance green light
Electronic parts for this Instructable,
4-green LEDs, 20,000mcd
3-yellow LEDs, 20,000mcd
3-red LEDs, 20,000mcd
2-220& ¼-watt resistors
2-150Ω ¼-watt resistors
1-Arduino Nano micro-controller
1-5 pin male header
2-4 pin male headers
2-2x15 long female headers
1-2x6 long female header
1-50 foot spool Kynar #30AWG wire
36-2x2 round grey bricks
3-1x2 grey brick
3-1x2 modified grey technic brick with hole
12-1x1 round grey brick with holes in the stud
3-2x2 round grey tile
1-1x2 yellow plate
1-1x3 yellow plate
1-1x1 yellow tile
3-1x4 yellow tiles
2-1x4 yellow plates
13-yellow head light bricks
1-T-interesection road plate
Miscellaneous things needed to build this Instructable:
1-utility knife2-wires with alligator clips at each end for testing LEDs
1-hot glue gun
25 Watt soldering iron
fine rosin core solder
heat shrink tubing
heat shrink gun (or use heat from a soldering iron)
Parts for a cross-intersection with four advance-green lights
Should you choose to build the alternate model, this is my best guess at the parts that are required.