I'm planning on using 20+ R Pi Model B+ to run animated videos on 20+ PC screens, for an exhibition. I'm using Pi Video Looper, which runs on start up, and detects movies on a USB stick. I would like to know how to safely power down the Pis at the end of the day, and restart them again the next day (this is a long-running exhibition). I've read plenty on forums where the general consensus seems to be that this is not best practise, for fear of corrupting the SD card (OS). I'm not talking unplugging the mini-usb power cable (this would certainly cause unnecessary wear-and-tear) - I'm talking one switch that kills power to all the Pis.
PS: I'm happy to leave the Pis running through the night, but I DO want to power down the screens, so would need 2 separate AC circuits if I were to switch one and not the other, an expense which I'm trying to avoid.
PPS: 20+ RPis is a lot of devices to power down/up one-by-one every day. I've read the "Is it okay to just pull the plug?" Q & A - it's one of many where the advice consensus seems to be NOT to just kill power, lest the card is being written to at that exact moment, resulting in possible corruption of the SD card.
Ideally, for practical purposes (and to avoid unnecessary, costly duplication, since the screens and RPis will be spread out over a large warehouse area), the RPis and the screens should be running off the same source of AC power, on the same (AC) circuit. Then to power the whole lot down and up is a simple process, involving one switch. But if this is potentially harmful to the SD card, then obviously it should be avoided. This involves installing a second, separate circuit - so one for RPis and one for screens. Then when I shut down for the night, I shut down only the screens.
Any advice would be most welcome!