by While working on this, I have gotten a bunch of questions, regarding all things Octoprint, ATX conversion, etc. So I figured I would post some links to handle some basic questions.
Thomas Sanladerer has what I would consider the best guide to setting up Octoprint. I had to modify the configuration a bit to handle the network in my workshop, but outside of that it worked out of the box.
I have also become a fan of Adafruit and everything that they have. Their instructions are very good and very detailed.
After you download whatever the newest image is, just follow either Tom or Adafruit and you should be fine.
After installing and connecting the PI/Octoprint to your network, it will most likely want an update to the latest release, just do it. Again, I did not have any issues with this.
Once installed and connected to your printer, and you have been able to control the device properly, install the PSU Control plugin. Follow the links off the control panel. Click on the 
on the top of the menu and select “Plugin Manager”, click “Get More…” 
and search for PSU Control. For the more advanced user, you can download this at Github from Shawn Bruce directly. I am not the author, he is and it is a great plugin. The instructions provided at the bottom of the Github page worked for me out of the box.
The pinouts for the ATX-RP-3DP board are as follows, if you are participating the beta test, the wiring between the board and the PI are included. All of the ATX pins are coming from the ATX 20 (or 24) pin molex connector.
Here is the pinout of the ATX connector.
Now it goes without saying, please have the power supply unplugged while doing this work. Do not over tighten the screws, these will strip easily, Make sure that they are snug.
As for the required power for the Anet board, you can use pins 10 and 11 coming from the ATX connector, or use one of the PCI-E connector. The yellow cables are always 12v, 5v is red, 3.3v are orange and the ground is always black. I would use at least two yellow cables for each of the 12v runs. There are more than enough cables to be able to do this. I would also do the same with the black ground wires. For my build, I went the extra step and opened the power supply open and de-soldered the cables and replaced them with silicon cables purchased from Amazon. Review the original post to follow the work. The 10 awg is for the 2 mosfets (hotend and heatbed), 14 awg was for Anet board input power directly. The extra 5v was terminated using 12 awg and not used. The busbar was purchased at Home Depot.
The GPIO plugin configuration for the PSU plugin should be defaulted to 40 for signal, 39 for GND and 38 for 3.3v monitor.
The case is posted on Thingiverse if you would like to download it. If you are participating in the beta, I have included one.
If you have any questions, please either get with me directly, or post a comment. All of the comments are moderated to cut down on the junk. But if it is a legitimate questions, they will get posted and replied to.
Please note, customizing 3d printers, custom electronics, etc are done at your own risk. This is provided as an approach to solving a problem. I am not responsible for any issues that a user runs into during the use of this equipment.
Reference material
- http://reprap.org/wiki/Choosing_a_Power_Supply_for_your_RepRap
- http://www.instructables.com/id/Using-the-Raspberry-Pi-to-control-an-ATX-power-sup/
- http://plugins.octoprint.org/plugins/psucontrol/
- https://toms3d.org/
- ATX PSU control board for Reprap Printer
- http://octoprint.org/
- https://github.com/kantlivelong
- Silicon wire bundle
- ATX PSU Case
