WEEK 5

Titles : LM 35 Temperature Sensor for eggs incubator project


Introduction

Last week, we made a study of the types of temperature sensors. For this week, we will study the temperature sensor can be used for micro controller based eggs incubator project. Temperature sensor suitable for this project is  lm 35 dz temperature sensor.


Objectives

1. To compress all the information obtained from the research to make it as the best solution for a good .project.
2. To know the characteristics of the temperature sensor lm35 dz.

Problem Encountered

From this research, it not have much of a problem as the information used to make the best solution is from data gathered before and it will not give any problem to use a temperature sensor lm35 dz type of eggs incubation project.

Project Description

Selection of temperature sensor is very important for this incubator project because it requires an precise reading of the temperature data to ensure that the temperature inside the incubator care is in good condition. This is because, the unstable temperature will damage the embryo in the egg. So, LM35 DZ is the right choice for this project based on the characteristics available on this sensor.Further, there is little explanation of the LM35 temperature sensor operation.

LM35 is a precision IC temperature sensor with its output proportional to the temperature (in oC). The sensor circuitry is sealed and therefore it is not subjected to oxidation and other processes. With LM35, temperature can be measured more accurately than with a thermistor. It also possess low self heating and does not cause more than 0.1 oC temperature rise in still air.
The operating temperature range is from -55°C to 150°C. The output voltage varies by 10mV in response to every oC rise/fall in ambient temperature, i.e., its scale factor is 0.01V/ oC.

Pin Diagram:

Why Use LM35s To Measure Temperature?

• It's can measure temperature more accurately than a using a thermistor.
• The sensor circuitry is sealed and not subject to oxidation, etc.
• The LM35 generates a higher output voltage than thermocouples and may not require that the output voltage be amplified.

What Does an LM35 Do?  How does it work?

• It has an output voltage that is proportional to the Celsius temperature.
• The scale factor is .01V/oC
• The LM35 does not require any external calibration or trimming and maintains an accuracy of  +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to +100 oC.
• Another important characteristic of the LM35DZ is that it draws only 60 micro amps from its supply and possesses a low self-heating capability. The sensor self-heating causes less than 0.1 oC temperature rise in still air.

For more information about this, please click here.LM35 DZ Datasheet


Project Outcome

What can i expect when  use An LM35 is :-

• I will need to use a voltmeter to sense Vout.
• The output voltage is converted to temperature by  a simple conversion factor.
• The sensor has a sensitivity of 10mV / oC.
• Use a conversion factor that is the reciprocal, that is 100 oC/V.
• The general equation used to convert output voltage to temperature is:
• Temperature ( oC) = Vout * (100 oC/V)
• So if  Vout  is  1V , then, Temperature = 100 oC
• The output voltage varies linearly with temperature.

How do use  LM35?  

• Here is a commonly used circuit.  For connections refer to the picture below.
• In this circuit, parameter values commonly used are:

              -  Vc = 4 to 30v

              -  5v or 12 v are typical values used.

              -  Ra = Vc /10-6

              -  Actually, it can range from 80 KW to 600 KW , but most just use 80 KW.