How does the pressure switch on the compressor work?

To understand how the pressure switch on the compressor works, we need to first understand what the pressure switch is?(When the low pressure pressure switch is working inside, you can also refer to the principle in part)

The pressure switch is a pressure-driven electrical switch. This means that there is an electrical switch that is forced to open or close by air pressure.

The air pressure at the inlet acts on the flexible membrane. Pressure turns into strength. How much force depends on two things: the area of the membrane (square millimeters) and the pressure of the compressed air (bars). Since the area is constant, the force generated is proportional to the air pressure.

The other side of the diaphragm is connected to a spring and a lever acting on the electrical switch.As long as the downward force of the spring is greater than the upward force of the compressed air, the membrane (and lever) will remain downward.But when the pressure increases, the upward force of the compressed air is higher than the downward force of the spring.At this time the membrane (and lever) will move up. When the membrane moves upward, so does the lever. The lever opens the electrical contact again and the compressor stops.

Now this is not a direct connection, but there is a clever mechanism inside that makes the switch flip immediately under a certain pressure, rather than slowly ("quick action").The mechanism is also connected to a second fixing screw that sets the pressure difference.For the internal working principle of the pressure switch, this simply means that the switch is closed again at a lower pressure than the pressure at which the switch is closed (built-in hysteresis).

I will try to explain it with the pressure switch on my desk.I will use a screwdriver to simulate air pressure (instead of compressed air pushing up, I use a screwdriver to push up :).If you still want to use a pressure switch, it is not recommended because it will damage the membrane.

The pressure switch works internally at low pressure: the large spring forces the diaphragm (green circle) downward (red arrow), while the air pressure tries to push upward (yellow arrow).The spring part and the membrane remain lowered. Electrical contact closed (blue circle)

The internal workings of the pressure switch under high pressure: the large spring forces the diaphragm (green circle) downward (red arrow), while the air pressure tries to push upward (yellow arrow).Now that the pressure is high enough, the membrane moves upward. Electrical contacts open (blue circle)And the compressor stops.

In order to be able to change the pressure setting, the downward force of the large spring can be adjusted (red arrow in the figure above).The adjustment is done by compressing the spring with a long screw. When you turn the screw clockwise, the spring compresses more.It will now generate a greater downward force on the membrane, so we need higher air pressure to overcome this force. In other words: we increased the pressure setting.

When the screw is turned counterclockwise, the spring compresses less. Compressed air is now easier to push towards the spring. In other words: lower the pressure setting.Almost no main spring Compression. The pressure switch is set at a very low pressure.