Hi everyone, this is my first post, so bare with me if I am a bit ignorant. My electronics skills are squarely in the hobby category, so I'm pretty out of my depth on this.
What I am trying to do:
I have a 3D Printer that I am trying to turn on and off with a Raspberry Pi (running Octoprint). The printer is powered by a regular PC ATX PSU, on a P4 ATX connector (like one of these:
http://www.picco.nl/catalog/images/A65604.jpg ). I know I need either a MOSFET or relay to control a relatively high current source like this. I believe, after a lot of googling and research that I have found a workable solution, but I want to make sure it is adequate, and most importantly: safe.
I should also mention that I do not wish to turn the PSU itself on and off, as I am using it to power other things as well (such as a string of nice LED lighting for my bench). I know that's the easiest solution, but I need to be able to turn the printer off independently of the PSU.
Solution:
Using one of these:
http://www.amazon.com/gp/product/B0057OC5O8/I will wire up two of the relays to the positive lines of the P4 ATX connector. I will connect the relay board to the RPi. I believe that I can control two relays with a single RPi GPIO pin (shorting two of the relay INs together to the GPIO), which I think is the best idea so that both relays toggle on/off at the same time? I hope I am not wrong in the assumption that I can control both from a single pin.
I also want to make sure the current draw will be safe. Based on some sketchy specifications, I believe the printer draws, at most, around 8 amps (at 12V DC), and drops as the heating elements reach their set temperatures. By using two 10 amp relays, am I correct in assuming this would provide ample headroom to make this safe to use? Although I do not think the device will be drawing anywhere near 8 amps when the relays are actuated on or off, I do want to have the ability, as a failsafe mechanism if something goes wrong with the printer.
Finally, is there any other concerns that I should be made aware of with this? Thanks for your assistance!