Hi,
if PIR sense movement, then it will on supply voltage for another two circuit boards for the fan(12V) and light (5V),
until the person left (mean no movement sense) then the supply voltage will be cut off...fan and light will be off.
is it possible?
Anything is possible if you can imagine it.
To keep the light and fan on while a person is in the room, you'd need some delay, as the PIR only senses movement. If a person stands (or sits) still for even a second, there's no output from the PIR, so, without a delay, it would switch on and off repeatedly.
You didn't answer my question...
Is the 0.6V to 0.8V when it senses movement or at rest?
Is the PIR taken from something else, or is it a ready bought "canned" unit?
Do you have a link to it or could you post a couple of photos (the connections in particular)?
It's impossible to device a circuit when you don't know the signals that's going to control it, so you need to answer the above..