What is Seal-in Circuit ?

A Seal-in circuit is a method of maintaining current flow after a momentary switch has been pressed and released.

Fig 1 : Start button not pressed

Note : Consider a Relay is used to control the power supply to a motor. Here we are calling this relay as ” Motor Starter Coil “. This Relay another NO contact is used to seal-in or latch the start signal.

As start push button is a push & Release type i.e. signal will be available for some time say momentarily and then signal will be lost.

so we have to latch this circuit in order to make motor run continuously even after release of start push button.

For this purpose we are using Relay (M) NO contact across Start push button such that it will take care of start signal after start button is released.

The seal-in auxiliary contact (NO Contact) of the starter (M) is connected in parallel with the start button to keep the starter coil (M) energized when the start button released.

After Start Push button pressed : The Motor starter coil energized and its NO contact becomes NC as shown in below figure.

Fig 2 : Start button pressed

PLC Latching Animation

Start Button Not Pressed :

Start Button Pressed & Released :

During Starting, Start push button will give the signal to energize the coil (M), after that coil NO contact which is connected across .

Start Push button will be used to latch the start signal as start push button will be released after pressing ( start button are momentary type ).

Comments

PLC Program for Mixing Tank

Create a ladder diagram for controlling a batch mixing process. Implement a PLC program for mixing tank or Mixing Process using PLC Ladder Logic. PLC Program for Mixing Tank Fig : Mixing tank A tank is used to mix two liquids. The required control circuit operates as follows: A. When the START button is pressed, solenoids A and B energize. This permits the two liquids to begin ﬁlling the tank. B. When the tank is ﬁlled, the ﬂoat switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together. C. The motor is permitted to run for 1 minute. After 1 minute has elapsed, the motor turns off and solenoid C energizes to drain the tank. D. When the tank is empty, the ﬂoat switch de- energizes solenoid C. E. A STOP button can be used to stop the process at any point. F. If the motor becomes overloaded, the action of the entire circuit will stop. G. Once the circuit has been energized, it will continue to operate until it is manually stopped. Solution : A

What is Relay? How it Works? Types, Applications, Testing

We use relays for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. But what is Relay? How a Relay Works? What are the Applications of Relays? Let us explore more about relays in this guide. What is a Relay? A Relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. Relays can be of different types like electromechanical, solid state. Electromechanical relays are frequently used. Let us see the internal parts of this relay before knowing about it working. Although many different types of relay were present, their working is same. Every electromechanical relay consists of an consists of an Electroma

Chlorine dioxide Analyzer Principle

Chlorine dioxide measurement Chlorine dioxide (ClO2) is an instable, non-storable, toxic gas with a characteristic scent. The molecule consists of one chlorine atom and two oxygen atoms – represented in the chemical formula ClO2. It is very reactive. To avoid the risk of spontaneous explosions of gaseous chlorine dioxide or concentrated solutions, it is generally handled in dilution with low concentrations. ClO2 is soluble in water, but tends to evaporate quickly. Typically it is prepared on site, for example from hydrochloric acid and sodium chlorite. The procedure provides solutions with approx. 2 g/l ClO2 that can be safely handled and stored for several days. Image Credits : krohne Sensor Parts : Reference electrode Applied chlorine dioxide specific potential Current needed to maintain the constant potential Counter electrode Measuring electrode The disinfection effect of ClO2 is due to the transfer of oxygen instead of chlorine, so that no chlorinated byproducts are formed. ClO2

TILI Automation

Search This Blog