PLC can be interfaced with hundreds of input and output lines. Compare PLC and a computer on the basis of fluid power applications. So an interface is needed to connect the items which are not directly compatible.Дў2. Microprocessors usually works with different levels of voltages and currents than those used by sensors and actuators. Explain why interfacing is necessary in a microprocessor control of fluid power? (iii) Functional blocks (iv) High-level languages.Дў1. (ii) Low-level language based on Boolean expressions What are the various approaches for entering the program in PLC? (i) Central processing unit with an associated memory (ii) Input modules (iii) Output modules.Дў0. Programmable Logic Controller is defined as a digital electronic device that uses a programmable memory to store instructions such as logic, sequencing, timing, counting and arithmetic to control machine or processes. What is a Programmable Logic Controller (PLC)? So when the sequence changes, the program only has to be changed.ДЎ8. This is expensive, but microelectronic control is programmable. When the sequence changes, the hardwired electro-mechanical has to be changed. What is the advantage of using microelectronic control for fluid power compared to electro-mechanical control? The left leg of the ladder connected to the power and the right to the ground.ДЎ7. The ladder diagram is a representation of hardware connections between switches, relays and solenoids etc., which constitute the basic components of an electrical control system. In this way, a dwell can be provided when needed.

Timers are used to control the time duration of a working cycle. What is the purpose of an electrical timer? Relays are used for energising and de-energising solenoids.ДЎ5. But limit switches make or break contact permanently when they are actuated.Д®lectrical relay is a switch whose contacts open or close when its coil is energised. They make or break contact only as long as they are held pressed. Push button switches are momentary switches. How does a limit switch differ from a push button switch? Temperature switches senses change in temperature and open or close contacts when a predetermined temperature is reached.ДЎ3. Pressure switches open or close contacts based on the system pressure. What is the difference between pressure switch and a temperature switch? A stepping unit is built from memory valve and a preswitched AND valve with two inputs.ДЎ2. Combinational circuit design.ДЄ step counter is a digital modular counter constructed from stepping units. Name the common methods used for designing logic circuits?ДЎ.

Draw the symbol for fluidic OR element and write its truth table. (iv) Quite insensitive to temperature, vibration, shock, electric noise and radiation.ДЁ. (iii) Very little space needed for mounting. What are the advantages of fluidic elements? Fluidic elements have no mechanical moving parts.Д§. The elements use moving parts such as diaphragms, springs, disk, balls, poppets.ДЇluidics is fluid logics. These elements are available as AND, OR, NOT logic elements. The MPL elements are miniature pneumatic elements. What are moving part logic elements (MPL)? (i) Pneumatic limit valves (ii) Back pressure sensor (iii) Proximity sensor (iv) Gap sensor or Interruptible jet sensor (v) Limit switch.ДҐ. Name the different pneumatic position sensors. at any moment they can be in one of the two states. The components of logic control are sensors and switching elements called binary elements, i.e. The logic control is a control based on logic functions like AND, OR, NOT etc.

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