My DCC-EX Prototype

[travis_farmer]

i have laid out my plans many times, and then changed them quite rapidly, so i will try to keep a running blog here of progress and ideas.

at present, my prototype runs off of a MEGA 2560 Core, development board. i use a Arduino Motor Shield, and a IBT-2 for the programming and main tracks. interface connection is via Ethernet, through a W5500 module, i think. power supply is a 16Vdc PSU for track voltage, and a buck converter for dropping the 16Vdc down to 5Vdc for the MCU power, and other logic and modules.
i have a 5U rack-mount steel project enclosure that i will house everything into. the main MCU, logic PCBs, and modules will mount on a piece of wood, via some plastic L-standoffs. it is my plan to get some sheet PVC and mount it on the front and back of the enclosure, after cutting out a large hole in both the back and front steel panels. that will aid in cutting holes for various connectors and such.

 

[travis_farmer]

so, my prototype is at a stage where i can alter it to make it electrically safe, without messing up too much.
track power will be provided by a RV PM3-? charger, adjusted to 15Vdc, fixed. this will pass into the enclosure with some sort of terminals. inside the enclosure, i will use a 12v-40v to 5v dc to dc converter to get VCC power. i will have fuses for various circuits, as well. master fuses for track power (one each for main and prog drivers), and 5v power, with sub-fuses for some 5v circuits.
this will eliminate the open power supply that is not super safe.

I have the PVC panel for the front panel, i just have to finalize some of the design before i cut any holes in the panel.

i have 3 screw terminals i can use for main and prog outputs, as well as the master power input, and i will need to properly label them. i will also need a hole to mount the 2004 LCD in place.

with there being zero AC line voltage inside the enclosure, it should be safer, and less likely to pickup interference.

i may use some of the 10awg wire (red + black bonded pair) to supply power to the enclosure, as well as carry it within the enclosure, where needed.

so i need to pickup the PM3-? charger, some fuse holders and fuses. sometime when i have some money available.

 

[travis_farmer]

I snapped a pic of my DCC-EX CS prototype. Mega2560 CORE main MCU board (bottom left), 2004 LCD (bottom right), Arduino motor shield for programing track (center right), IBT_2 motor driver for main track (upper right), and the W5500 Ethernet module (upper left).

 

[travis_farmer]

slight change, i think. i have an old radio cabinet that will work well for mounting my DCC-EX prototype into. though i am unsure of the best way to make it easy to work on. using my ISA back-plane would work, but it may also be quite over-kill. i think if i cut out the face of the radio cabinet, and make a sort of rack-mount frame, the different function boards could be removed as needed...
i could use the ISA back-plane for some things, but it may also just get in the way, in particular, i only need 3 power busses (5V, 12V, and 16V Track power), and two data lines for I2C connections.
i will need to source some large prototyping boards...
i have some weather-tight connectors i could use. 4-pin for power bus, and just a 2-pin for I2C. that way a board could be taken out of the enclosure for work, and replaced, with somewhat ease, i think.
if the prototyping boards are all the same size, i could kinda rack them in a wooden rack that simply has slots, and then the bus connectors.
i think for a power supply, i "could" use a PC ATX PSU for 5V and 12V, but Arduino boards don't like to start on a PSU power-on. they require a reset after power up, for some reason. but it may be my only option. the 16V track power would come from the open-cage PSU i have. the AC power-on would come from a relay powered by the PC PSU. plain and simple. i could use a 1/4 turn switch from my CNC stash to turn power on and off for the PC PSU (using the MB power-on signal, connected to ground). for ease of debugging, i could have a reset button on the front panel as well. if i use a 3-pin weather-tight connector for the I2C, i could include a master reset signal. just have the button pull to ground.
on the face panel, i want a single USB port for the master DCC-EX CS, so i can upgrade the software with ease. i would like an ethernet port, but only if i can find the spare i have kicking around somewhere. of course, the 20x04 LCD would have a place on the front panel.

i have not uploaded yet, but i will be running the Devel branch. this is so i can make use of the features of EX-IOExpander. that is a neat bit of wizardry that uses other Arduino boards (the supported ones), as an I/O expander. so i can in effect do away with the MQTT operated layout functions, and run it all, in theory, from the CS. this should be fine, as i really don't know how elaborate i will make the layout.

 

[travis_farmer]

i think rather than the old radio cabinet for my enclosure, i will go with the cabinet my father and i built for my HiFi system. i need to attach a panel to the front door. the power supplies can go on the bottom shelf, and the master Arduino board can go on the top shelf. that way the LCD screen can be mounted in the front door panel, at an easier to see height. the Fast Clock Arduino could also be located near or on the top shelf, so the LCD display, and buttons, can be easier to see and read. the digital clock display can be remote mounted.

 

[travis_farmer]

 

[travis_farmer]

schematics subject to change. last posted schematic is most current.

missing from the main board schematic, the connections for the Ethernet W5500 module.

 

[travis_farmer]

updated schematics