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LabVIEW based Temperature Control

Goal:

In this exercise, you will design a LabVIEW VI ( virtual instrument) to control the temperature of a heating element (low value resistor). The temperature desired is by the user. The VI will use the DAQ board installed in the PC to :

Such closed loop temperature control system is similar to the one used in heating and cooling  of our homes with a thermostat.  Following  figure shows different components of the temperature control system involved in the design.

Fig 1 Temperature Control  System

Principle of Operation and Design of the Control System :

External Components:

LabVIEW VI Design

The VI you will design will be similar to the previous LabVIEW exercise of measuring and generating DC voltages. Following are few helpful hints :


Below is shown a typical Front panel of the VI. Your could be different but it should show all the scales, displays, controls with correct color as shown below.

Design specification:
Temperature control range: 80 deg F to 95 deg  F

Prelab:

You must have the circuit diagram of the temperature control system ready when you come to the lab. The diagram should include the pin numbers of all the components and the value of resistors. Also calculate the resistance value of the heating element.

In-Lab assignment
Parts List
LM 34
LM741
Relay Schematic (5 V Relay 201A0500)
One 1/2 Watt resistor ( value to be determined ).
Procedure:
1. Build and verify the circuit : 2. Build and test the VI :
Note : Power the temperature sensor but do not POWER the op-amp. 3. Experiment :|
Note: The resistor ( heating element ) can become very hot. Take precautions while testing the circuit. Report :

written by George Hunka
last modified by Siddharth M. Deliwala on 2/8/04

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