Hi everyone, I’m working on an electropneumatics homework assignment and I’m having trouble understanding how the current flows in the circuit.
Could someone please explain or maybe highlight the current flow at each stage (starting from pressing START and then through the sequence J21 → J22 → J12 → J11)?

J21, 22, 12, 11 are hercon sensors and A 14, 12, B 14, 12 are relays as I understand.

 

current...?

conventionally current is assumed to go from positive supply terminal through the circuit to negative supply terminal. but in this question this is completely irrelevant - the same could be done with opposite sensor polarity or even make the circuit AC.


what you are asked about is determine how to accomplish sequence shown by timing diagram.
you have there 4 inductive proximity sensors or reed switches (J21, J22, J12, J11) that activate solenoid valves (A14, A21, B14, B12).

Note... A14 and B14 are solenoids of one pneumatic valve operating cylinder C14.
A12 and B12 are solenoids of another valve operating cylinder C12.

Assume that A means extend, B means retract, so you can see the sensor arrangement in the timing diagram.



when sensors are activated, they will activate solenoid allowing sequence to propagate.

assuming the timing diagram shows up as extended and down as retracted.

looking at electrical drawing A14 solenoid will only be energized when J21 sensor is on and start button is pressed. then it will take some time for cylinder to move and eventually reach J12...

Now you do the rest