Final Update: Feb 10, 2017
This will be an ongoing project, I expect it to take several weeks to complete. A fellow on the Model Railroad Forum got me interested in the programmable Arduino micro computer controllers. I have been wanting to upgrade my existing signal controller and the Arduino MEGA will easily handle a 16 block control system. The MEGA has 54 digital I/O ports and 16 analog Inputs, I'm currently only using 8 blocks.
The Southern Pacific used three color single head signal heads in their signaling system. I'm currently using 3mm bi-color three lead common cathode LEDs in my signal heads so this project will drive those same LEDs.
The Arduino outputs have a maximum current of 20ma per port so I will include 500ma driver chips on an expansion board (the Arduino world calls an expansion board a "Shield") for my MEGA. I plan on adding 5mm LEDs paralleling the Arduino outputs on my control panel.
To my surprise there aren't any Arduino card shelves available and because I plan on using multiple Arduinos on my layout this project will include building a card shelf capable of holding 8 Arduinos with the ability to expand.
I have three Arduino UNOs with expansion Shields set up as 14 port random lighting controllers. They also have 500ma driver chips and and randomly turn on and off 12 volt 40 to 100 ma incandescent bulbs in my rural houses. The 7 channel 500ma driver chips have a max voltage input of 50 volts so they are very versatile. I operate my 12 volt bulbs at 8½ volts for a more realistic lighting effect and longer bulb life. I can easily change the brightness of the bulbs by increasing or decreasing the voltage to the driver chips.
This is an Arduino UNO programmed as a 14 port light driver using high current 7 channel driver chips on an Expansion Shield.
This is a MEGA with its high current driver chips on an Expansion Shield. Both the UNO and MEGA output connectors will need to be changed to fit the card shelf. A single dual row Arduino connector (40 pins) will handle all connection to the UNO and MEGA.
I have all the material to begin making my Arduino card shelves. This is a CAD drawing of my proposed card shelf project.
I was able to purchase a 24" x 36" piece of 16 gauge Aluminum at a local metal shop for $15 so I'm ready to start on my project. Earlier I found some 16 gauge Aluminum angle at Lowe's.
The sheet of Aluminum is large enough to build a couple of 4 card Arduino shelves as well as a new control panel for my layout. As they say, "two birds with one stone". That turned out to be the best price for sheet Aluminum I've seen in several years.
February 10th Update:
I finished a single Arduino UNO card shelf and it came out very nice as shown below.
After finishing the 4 slot shelf and experimenting a bit I decided to build single shelf that would hold three Arduino MEGAs and five UNOs. I have given a lot of thought towards micro controllers for my layout needs. I ended up with a total of eight for my layout. Six Arduinos should be sufficient for current and future needs so a single shelf with 8 slots should fill my need very well.
This is my 8 slot Arduino Card Shelf shown with a Arduino MEGA.
The 8 slot card shelf fits snug in the left side compartment in my control panel. When I built my control panel frame 28 years ago I left room for future expansion.
My multiple Arduino mounting project has worked out very nice.