How To Make A Piston Repeat

You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.

Forums
Homework Help
Engineering and Comp Sci Homework Help

Help with triple piston circuit

Engineering
Thread starter Noob of the Maths
Start date Oct 26, 2021

Homework Statement:: cyclic

Relevant Equations:: ladder lenguage

HI! everyone :)

in today's electronics class the teacher asked us to make a simultaneous circuit of 3 pistons, with ladder language.

What am I supposed to do:
Upon energizing the circuit, they should expand one piston after the other; from A to C.

When piston C expands, it should return to its position by itself, and consecutively B and A in the same way.

At first the circuit works by expanding, but when piston C retracts, it does not contract completely and returns to its position again and again. The circuit is in a cyclic state of no return.

Captura de Pantalla 2021-10-26 a la(s) 17.33.09.png

Captura de Pantalla 2021-10-26 a la(s) 17.33.13.png

Thanks for read:)

Answers and Replies

There seems to be some very fuzzy thinking in the problem statement. Pistons do not expand; cylinder volumes do expand. Pistons do not return to the max volume condition by themselves; they are dragged there by the action of the crank and connecting rod. This looks like a case of confusion by analogy.

Homework Statement:: cyclic
Relevant Equations:: ladder lenguage
in today's electronics class the teacher asked us to make a simultaneous circuit of 3 pistons, with ladder language.

What am I supposed to do:
Upon energizing the circuit, they should expand one piston after the other; from A to C.

Am I missing seeing your ladder language solution? I'm not very familiar with ladder language control of PLCs, but maybe you have shown your work in the figures somewhere?

There seems to be some very fuzzy thinking in the problem statement. Pistons do not expand; cylinder volumes do expand. Pistons do not return to the max volume condition by themselves; they are dragged there by the action of the crank and connecting rod. This looks like a case of confusion by analogy.

Yes, I think it is a bit confusing.

The circuit is energized, then the pistons come out of the cylinder until they activate the sensors ahead of them. They come out one after the other, from A to C. However, piston C does not return to the cylinder, because it remains in a cyclic state; therefore, pistons A and B do not return either.

You speak of pistons coming out of cylinders and also returning to the cylinders, but in a real engine, the pistons always remain in the cylinders. The pistons move from one extreme position in the cylinder to a second extreme position (again, in the cylinder). What causes your piston to cycle unless you model the action of the crank and connecting rods?

You speak of pistons coming out of cylinders and also returning to the cylinders, but in a real engine, the pistons always remain in the cylinders. The pistons move from one extreme position in the cylinder to a second extreme position (again, in the cylinder). What causes your piston to cycle unless you model the action of the crank and connecting rods?

Yes, I understand that the piston does not come out of the cylinder. It just moves from position to position, language error.

The green button allows the pistons to reach their expansion position in the cylinder, but as I could not get them to return automatically, I put a new coil related to the blue button to press it and return them to the original position.

Am I missing seeing your ladder language solution? I'm not very familiar with ladder language control of PLCs, but maybe you have shown your work in the figures somewhere?

Its not really a solution, coils and interrupters are related by name literally

Do you want to exercise A, B, C then stop, or do you want a continuous repeating cycle ABCAB... ?
You will need to remember the last logical state, so you can steer the next activity. That needs three logical states.
If it is a once only sequence you will also need a logical "idle state" that prevents C repeating, while waiting for a trigger, that will enable A.

Do you want to exercise A, B, C then stop, or do you want a continuous repeating cycle ABCAB... ?
You will need to remember the last logical state, so you can steer the next activity. That needs three logical states.
If it is a once only sequence you will also need a logical "idle state" that prevents C repeating, while waiting for a trigger, that will enable A.

When A is in the maximum position to the right, it activates the sensor "a1", which in turn activates "B-". Thanks to this, piston B moves to the right, activating sensor "b1" and allowing piston C to move.

The movement of the piston allows to activate the sensor of the next piston allowing it to move.

When all 3 pistons are in the maximum outward position, piston C returns to its original state, activating sensor "c0". This allows sensors B and A to contract.

It is a cycle: A expands and activates B, B activates C.
C contracts and deactivates B, B deactivates A.

We have three hydraulic or pneumatic cylinders. A, B and C.
What follows is hopefully a symbolic way to define and think about the problem.
I leave it to you to find my errors and draw up the ladder diagram.
Language warning: I confuse; Off, reset, 0 and false. Also; On, set, 1, true and asserted.

Note that only one thing will actually be happening at the time.

We define the six control signals that will extend or retract each cylinder.
Those signals must occur in the following phases and order, then repeat cyclically.
Extension phase.
Xa extends A.
Xb extends B.
Xc extends C.
Retraction phase.
Rc retracts C.
Rb retracts B.
Ra retracts A.

We have six limit switches that are true when a cylinder is at the 'r' or 'x' limit.
Ar when A is retracted.
Ax when A is extended.
Br when B is retracted.
Bx when B is extended.
Cr when C is retracted.
Cx when C is extended.

Now we invent a direction bit, an RS flip-flop or latch called D, with it's invert ND.
The state of D controls the direction phase of all cylinders.
While in extension phase, D is on; ND is off.
While in retraction phase, D is off; ND is on.
There are only two turning points where the phase of D, ND changes.
D is set true, ND false, by momentary limit switch Ar.
D is reset to false, ND true, by momentary limit switch Cx.

The equations that determine the control signals are then as follows.
They are asynchronous, but listed here in the order they will be asserted.
Ax = Br & Cr & D;
Bx = Ax & Cr & D;
Cx = Ax & Bx & D;
Cr = Ax & Bx & ND;
Br = Ax & Cr & ND;
Ar = Br & Cr & ND;

I think that does it, except for the perennial questions.
What will happen if power is lost and then returns ?
Think also the state of D at restart ?
How can you reverse direction during testing or service ?
How can the system be started after construction or maintenance ?