Electro-pneumatic systems basically works on the basis of electric signal. In this system electric signals are used to operate control valves.
The electronic control valves are made up of solenoid valves, which due to magnetic field effects controls the direction of flow of compressed air, or control its supply.
Let's understand how a solenoid valve works. A solenoid valve converts electrical energy into mechanical energy to do desired operation.
Let's say we need a switch which is when pressed then the cylinder will move in forward direction, there is another switch when pressed it causes motion of cylinder in reverse direction. The solenoid valve has mainly two parts, one is the solenoid(electromagnet) valve and the other is openings, which has a plunger or a mechanism which is operated by solenoid.
When we need a forward stroke, the air should enter in piston from opening 1 and for reverse stroke air should enter from opening two in the cylinder. To do so the air should flow from respective openings of the valve, it is done by giving a electrical signal to the solenoid(electromagnet) which removes(or lowers/lifts) the plunger from the opening according to the signal. A solenoid valve can have two or more than two openings controlled by different switches. So for forward stroke we need a switch which activates the opening which is connected to forward stroke opening of cylinder and vice-versa.
There are various sensors available which are used to control these valve. Also solenoid valves are of different types. We will learn about them later.