EXPERIMENT – 7

OBJECTIVE: To implement Water level control using LabVIEW and analog input signals from

sensors.

APPARATUS USED: Arduino board, Relay switch, LABVIEW setup.

THEORY:

Introduction to LABVIEW: LabVIEW is an integrated development environment designed

specifically for engineers and scientists. Native to LabVIEW is a graphical programming

language (G) that uses a dataflow model instead of sequential lines of text code, empowering you

to write functional code using a visual layout that resembles your thought process. This means

you spend less time worrying about semicolons and syntax and more time solving the problems

that matter.

Relay Switch: A relay is an electrically operated switch. Many relays use an electromagnet to

mechanically operate a switch, but other operating principles are also used, such as solid-state

relays. Relays are used where it is necessary to control a circuit by a separate low-power signal,

or where several circuits must be controlled by one signal. The first relays were used in long

distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and

re-transmitted it on another circuit.

The input circuit is switched off and no current flows through it until something (either a

sensor or a switch closing) turns it on. The output circuit is also switched off.

When a small current flows in the input circuit, it activates the electromagnet, which

produces a magnetic field all around it.

The energized electromagnet pulls the metal bar in the output circuit toward it, closing the

switch and allowing a much bigger current to flow through the output circuit.

The output circuit operates a high-current appliance such as a lamp or an electric motor.

Connection of relay through BJT:

In the above figure shown a connection of relay with a BJT, in this system BJT is working as a

switch. When the high signal is read by it or it closes the switch relay coil get magnetize and

move it pin to NO. This connection completes the circuit and relay will off the AC switch which

controls the motor operations.

Interfacing Relay with Arduino:

In this circuit, the pins of seven-segment display are connected to Arduino pins 2-9, as shown in

the table below. Common pins (pin 3 and pin 8) are connected to GND and dp is left

unconnected, because it is not used in this experiment

U

N

O

Interface Arduino through LabVIEW:

Checks if LabVIEW sent a new value. If there is a new value, it converts it into integer byte with

the same value. This integer byte represents the delay interval used in sequence. That, the greater

the delay the lower the speed and vice versa. Else, Arduino continue running the motor at current

speed. This prevents the processor from overloading the serial port and pushes it to avoid

Arduino Serial port hanging.

RESULT: Study the operation of water level control with LabVIEW and close switch for tank.