It sounds like you've already built your redstone contraptions. The simplest thing you can do, since spawn points keep the world loaded in a 128 block radius, is to use the /setworldspawn command to move the world spawn to the middle of your redstone devices. This should be enough to keep at least one device working at all times.
Unfortunately, if your device is unusually large, you cannot use command blocks to move the worldspawn along with the current. According to the Official Wiki: new spawn chunks won't be loaded by this command until a player moves within range. If you do have multiple or large devices that need to remain operational, I might recommend using bots/alts to keep the necessary chunks loaded.
Sources: This Reddit Thread