The Saturn 6 from Titan is a fuzzy logic co2 controller, enviro controller I use for dehuey, exhaust, etc. it’s not cheap for small rooms, but the tight 3% adjustment parameters can really keep your enviro perfect. I run positive pressure CEA, but if my humidity or temps get out of hand, the exhaust fan kicks on and the negative pressure opens a damper the opposite side the room and the heat gets evacuated and the co2 burner shuts off until desired levels are achieved. I’ve seen em as low at $427 online. If your only using 1 or 2 1000w HID lights, I would use a digital lamp timer from Home Depot. If you’re using 3 or more, get a lighting relay with a trigger cable like a Titan Helios 10 or 11 connected to the same wall mart digital lamp timer.