TILI Automation

 PLC outputs are of two general types: (1) relay (2) solid state Relay outputs are mechanical contacts and solid state outputs may take the form of transistor or TTL logic (DC) and triac (AC). Relay outputs are usually used to control up to 2 amps or when a very low resistance is required. Transistor outputs are open collector common emitter or emitter follower. This type of output can control lamps and low power DC circuitry such as small DC relays. TTL logic outputs are available to drive logic circuitry. Triac outputs are used to control low power AC loads such as lighting, motor starters and contactors. As with input units, output units are available with a common terminal and isolated from each other. The type of output unit selected will depend upon the outputs being controlled and the power available for controlling those devices. Typically, power for driving output devices must be separately provided since there can be a wide range of requirements depending upon the device....

At this post, we will understand how to filter digital and analog inputs in a PLC. As the topic says, filtering is a means to remove unwanted spikes in the signals received in PLC. Its role is to eliminate the fluctuations and pass only proper signal changes at a particular time to the PLC. Inside a PLC, the filter circuitry comes first and then comes the PLC input processing circuitry, which accepts the final filtered input and uses it for its logic. PLC Digital Input Filters Let us first consider the digital input. The role of input with a filter is to accept a digital field input and pass it to a processing circuit through the filter. If you see the below image, there are two parts. First of all, the green circle indicates that the input change will be passed and the red circle shows that the input change will not be passed. In the first  part, there are two changes where there are many fluctuations and that input changes will be bypassed. There are two changes where there are n...

 PLC Multiple Outputs Configuration PLC Multiple Outputs Configuration useful for PLC Sequence of Outputs or Sequence Logic, PLC Ladder Rung with Two Outputs, PLC Ladder Rung with two inputs & two outputs. PLC Ladder Rung with Two Outputs : With ladder diagrams, there can be more than one output connected to a contact. Figure 1.20 shows a ladder program with two output coils. When the input contacts close, both the coils give outputs. Example: In Some cases it is required to start two pumps in parallel by pressing a single start button then the above logic may be useful. PLC Ladder Rung with two inputs & two outputs : For the ladder rung shown in Figure 1.21, output A occurs when input A occurs. Output B only occurs when both input A and input B occur. Example: Say we have a Single Start button to Start two pumps in parallel. But we have extra Start Permissive for Pump B only and it must be started on satisfying the permissive only. Note that there is no permissive for Pump...

 Today we are going to discuss about Relay Noise reduction method. Sometimes we observe more noise is generating by relay output switching. In such case , a Noise filter must be connected to the load side or other appropriate countermeasures must be provided external to the PLC. How to Reduce Relay Noise in PLC Systems Countermeasures are not required if the frequency of load switching for the whole system with the PLC included is less than 5 times per minute means required after more than 5 times per minute. Countermeasure Example When switching an inductive load,connect an surge protector, diodes,etc in parallel with the load or contact as shown below: When switching a load with a high inrush current such as an incandescent lamp, Suppress the inrush current as shown below:

At this post i will give some basic instructions which are from my personal experience in order to give you a guide for how troubleshooting in automation systems (PLC/DCS) is : Automation systems troubleshooting has in general the same tactic in order to find the solution of system’s fault. Nevertheless, depends the complexity and the size of application and the specific automation system, the troubleshooting steps would be a little different or more complicated. The best knowledge is obtained through practice and actual troubleshooting conditions. Practice again and again is the solution in my opinion. Any supplement and comments are welcome!! How to Troubleshoot a PLC System  Before we proceed, we agree that modern automation systems have PLCs for controlling the application. If we have a small application then the system possibly has a microPLC (or nanoPLC) or another type of compact controller (many times this depends of the application). I said modern automation systems becaus...

 Electrical Switches have mechanical contacts or relays. These types of switches can control a wider range of current and voltage options. They are not affected by dirt, mist, magnetic fields or temperature ranges from near absolute zero to 1000°. Electro-mechanical switches can adapt to misalignment in installation/application to ensure there is no leakage current and making it available in many circuitry, actuator, and housing styles. Disadvantages include their price, limited contact life cycle, large size and slow response. Solid-state switch Solid-state switches are electric devices that do not have moving parts to wear out. They are able to switch faster without sparking between contacts or problems with contact corrosion. Their disadvantages include a high cost to build in very highcurrent ratings. Configuration When selecting a level switch, the user needs to determine if the electric circuit requires a normally open or normally closed switch. Normally open (NO) switches do...

 Before the advent of electronic circuitry, process control was a wholly mechanical endeavor. Facilities used pneumatic control signals where controllers were powered by varying pressures of compressed air. Ultimately, air compression of 3-15 psi became the standard for a few reasons: Very expensive to engineer systems detecting pressure signals under 3 psi Signals below 3 psi would be unrecognizable Easier to differentiate a live zero (3 psi) signal from a failure in the system (0 psi) In the 1950s, as electronic systems became less expensive, current input became the preferred and more efficient process control signal. The 4-20 mA range later became the standard for similar reasons as 3-15 psi did. Introduction In the world of process control, there are a myriad of different types of process inputs. Thermocouples and RTDs provide direct temperature reading while digital signals such as Modbus® provide exacting control over process variables and display. Analog signals, where info...