Obviously inverting a pulsar is kind of redundant, since it goes on and off repeatedly... however, when I want it to stop, a lever would do just fine, but it would keep it powered on. but what if I wanted the object its connected to be by default off? I can't use an inverter because the second I'll turn on the pulsar the inverter would fry and stop working, cutting the circuit. so how do I make an inverter that can withstand a pulsar?
So, first off, here's what a basic pulser with an enabling switch looks like.
The problem with connecting a door – or anything – to this contraption via Redstone is that the relative torch will no longer be part of the pulser. I'm not going to think about why is that – this is a weird contraption anyway – so here's the workaround:
The door needs to replace one of the non-vital torches.
The vital torches are those connected by the middle Redstone cross. Everything else is non vital (= removing it won't break the pulser) and can be replaced by a door in place.
Another important thing to remember is that the switch must not be right next to the door, or the current will simply flow from the switch to the door directly, ignoring the pulser entirely.
In this unpolished proof of concept, I brought the switch forward and replaced one of the side torches with a door. Since the door is directly wired to the pulser, it pulses with it.
It is incidentally a little known fact that you can extend pulsers at will by adding more blocks with Redstone on them and non-vital torches on the sides.
I'd use a simple sticky piston clock myself, since a pulser isn't technically stable to begin with. The piston can never burn out, and I can set it to "off" by just powering the piston.
Here's a top-down view:
With a redstone torch underneath the solid block, and the repeater set to the desired delay (a 1-tick piston clock is still pretty fast).
This way, it never burns out, and the lever deactivates it.