1. Introduction

In the previous blog, we talked about the basic circuit to automate a process. In this blog, we focused on creating and explaining the circuit for automating process that involves time-dependent control. Also, we used a scenario or a problem as our basis for the circuit. The problem is described as

A washing system used a hydraulic cylinder to dip a plastic component in and out of the bath. The cylinder extends to dip the component after pressing a start button. A delay of 10 seconds is set so that the there is a time to check if the component is clip properly in the cylinder. The component is dip in the cleaning bath for at least 10 seconds. The process is continuous unless a stop button is pressed.

The problem asked to create a circuit that enables a plastic component to be washed. The process is continuous unless manually deactivated by the operator. Extending and retracting the cylinder is set to a 10 second delay. In the next section, we present and discuss the circuit in details.

2. Circuit and Simulation

Figure 1: Electro-Hydraulic Circuit

In this blog, we used similar configuration of hydraulic actuation circuit as to the previous blog. The hydraulic circuit used a double solenoid 5/2 way directional control valve as the main control element for the hydraulic cylinder. For the electrical controller, we used a relay, two set of timer relay, a pair of solenoid, a pair of button and sensors. In the first and second ladder, we initialize the activation of the process. We connect the start button and latching contact K1 in parallel so that when start button is pressed, contact K1 sustains activation of relay K1. The combination is connected in series to the stop button and relay K1.

For ladder 3, we set up the timer to delay the extending of the cylinder after we pressed the start button. We connect contact K1 and K3 in series with the timer K2. Contacts K3 deactivates the timer when timer K3 is activated so that timer K2 reactivate after completing a cycle of the process.

On the other hand, timer K3 is connected with the sensor S1 and S0 so that when the cylinder is fully extended, it activates. The latching contact K3 is placed to sustain activation of relay K3. For the solenoids, timer K2 and sensor S1 is in series to solenoid Y1 while contact K3 is connected to solenoid Y2. The circuit is shown in Figure 1.

Figure 2: Start button is pressed.

Figure 3: Solenoid Y1 is activated.

When we pressed the start button, electricity flows through relay K1 that results to closing of latching contacts K1. At ladder 3, timer K2 is activated when K1 closes. Latching timer contacts K2 switched from open to close position after the time expires. Solenoid Y1 opens port B of the 5/2 way DCV after K2 closes. The step by step activation is shown in Figure 2 and Figure 3.

Figure 4: Cylinder reached full extended length.

Figure 5: Solenoid Y2 is activated.

Once the cylinder reaches the full extended length, timer K3 is activated because the sensor S1 send a signal to allow current to flow through it. Contact K3 closes as time expires and allow electricity to flow across solenoid Y2. As a result, solenoid Y2 opens port C of the 5/2 way DCV to retract the cylinder to initial state. Hence relay K1 is still activated, timer K2 restarts and extends the cylinder after 10 seconds. The process continues as long as K1 is activated. To stop the process, stop button is pressed to cut the electricity to relay K1. The simulation is shown in Figure 5.

Figure 5: Simulation

3. Conclusion

In this blog, we discussed on how to implement a time-dependent automation using electro-hydraulic. Similar to previous blog, we used a double solenoid control valve as the main control element for the cylinder. A on-delay timer was used in the circuit because it gives us an easier way to implement the scenario. The important points to remember in automating with timer is to make sure the timer activation is not sustained.

4. References

[1] Hydraulic Basic Level. online access

[2] Hydraulic Advance Level. online access

[3] Electro-Hydraulic Basic Level. online access

[4] Electro-Hydraulic Advance Level. online access

(Note: All images and diagram in the text are drawn by the author (@juecoree) except those with separate citation.)

If your are interested in pneumatic and hydraulic series, you can read:
Pneumatic and Electro-pneumatic
1. Pneumatic Basics: Direct Control
2. Pneumatic Basics: Indirect Control
3. Pneumatic Basics: AND and OR Logic
4. Pneumatic Basics: Memory Circuit and Speed Control
5. Pneumatic Basics: Dependent control
6. Pneumatic Basics: Multiple Actuators
7. Electro-pneumatic Basic: AND and OR Logic
8. Electro-pneumatic Basics: Interlocking, Latching and XOR logic
9. Electro-pneumatic Basics: Distribution of Workpiece
10. Electro-pneumatic Basic: Ejecting a workpiece
11. Electro-pneumatic Basics: Basic Automation
12. Electro-pneumatic Basics: Automation with Counter
12. Electro-pneumatic Basics: Automating with Timer
13. Electro-pneumatic Basics: Cementing Press (Time Dependent Control)
14. Electro-pneumatic Basics: Embossing Device
15. Electro-pneumatic Basics: Bending Device
16. Electro-pneumatic Basics: Introduction to Logic Module
17. Electro-pneumatic Basics: Automating with Logic Controller
18. Electro-pneumatic Basics: Logic Controller for Multiple Actuators
19.Electro-pneumatic Basics: Time-dependent control with Logic Controller.
Hydraulics and Electro-Hydraulic
20. Hydraulic Basics: Direct Control
21. Hydraulic Basics: Indirect Control
22. Hydraulic Basics: Dual Pressure Value and the AND Logic
23. Hydraulic Basics: Shuttle Valve and the OR Logic
24. Hydraulic Basics: Sequencing Multiple Cylinders (Actuators)
25. Hydraulic Basics: Automating Multiple Cylinders (Actuators)
26. Electro-Hydraulic Basics: Direct and Indirect Control (Part 1 of 2)
27. Electro-Hydraulic Basics: Direct and Indirect Control (Part 2 of 2)
28. Electro-Hydraulic Basics: Two ways in Implementing AND logic
29. Electro-Hydraulic Basics: Two ways in Implementing OR logic
30. Electro-Hydraulic Basics: Circuit with ON and OFF-delay Timer
31. Electro-Hydraulic Basics: Automating Processes (1 of 3)