 The lube oil pump system, which is a great explanation as to how we can go ahead and use a pressure switch in a control circuit, in a motor control circuit. Here we have your typical lube oil pump motor circuit. You'll notice I have a set of normally closed contacts for the stop. I have some normally open for the push button for the start. I have an M1 coil, which is for my lube oil pump motor, and I have some M contacts, which are associated with this coil. So when this energizes these clothes, I have three overloads in series with each other. That's on the power line. If you need some explanation as to where those come from, watch the power versus control circuit video. And then down here I have a pressure switch, which is normally open, which will close upon pressure rising. And then we have our main drive motor, and again, it has its three phase system, so it has three overloads in series as well. Now the way the system works is with bigger motors, you'll sometimes have to inject lube or oil or grease into the motor bearings to keep it running and to keep it nice and cool. So what we do is we have a lube oil pump motor that injects that. The main drive motor itself won't run until there's sufficient pressure, meaning that there is grease in the motor to keep it cool and keep it running. So what we do is we have this pressure switch. What will happen is as this runs, injects oil or injects grease, it starts to build the pressure up. When the pressure finally reaches its setting, then the main drive motor can start. So let's take a look at this circuit. We'll go ahead, we'll press start, which will energize M1 coil, which will start the lube oil pump motor. These will close because they're associated with this coil so that when I lift up on the start or if I let go of the start push button, the lube oil pump motor will continue to run. So at this point, with the start is up in that position there, the M contacts the seal and circuit is working, holding in M1. M1 is running and is building up pressure for the main drive motor. At this point though, the pressure switch is still maintaining or not maintaining rather than just sensing pressure, but it hasn't reached full pressure yet. So you'll have to set the pressure to whatever PSI or pressure you need. Then we'll see that eventually it will hit pressure. And when the pressure switch engages, then M2, the main drive motor will run. As long as this motor here is running, M1 is running and maintaining pressure, the pressure switch will stay closed and then the main drive motor can run. If there's any issue at all with this main pump motor, so say it develops an overload and these open, this will shut down, this will lose pressure. If this loses pressure, then M2 will de-energize. Or if we hit stops, what will happen here if we press the stop button up top here, you'll notice there's nothing to stop this motor. What will happen is that will de-energize the M1 coil, which will de-energize the lead-boil pump motor, which will open these contacts, which will then kill the pressure here and then de-energize M2. Here I've hit the stop button, which opens up the circuit. Power will not get through to this, so that therefore M1 coil de-energizes, which will open up the M contact, so it will not hold in once the stop goes back up. But you notice here that this motor will keep running. It will run for only as long as this pressure is there. But with this lead-boil pump motor not running, this pressure will drop pretty rapidly and open up the pressure switch and then kill off M2. And now the pressure switch is open and the circuit is de-energized totally. So it's good to keep in mind that whatever happens to M1, this is kind of controlling the whole thing. If the lead-boil pump motor has stopped, the main drive motor cannot run because it does not have pressure built up in it to keep it safe and cool. And that is how a lead-boil circuit works with a pressure switch. And we have a normally open pressure switch here, which will close upon rising pressure.