CONTACT-LESS DIGITAL THERMOMETER USING MLX90614 or MLX90614n SENSOR WITH ARDUINO ECHO SENSOR & OLED DISPLAY

Handmade Contact Less Thermometer Using MLX-9061 or MLX-9061n Alongwith Arduino UNO or Nano, Echo Sensor Module HCSR-04 or US-100, 0.96 Inch I2C/IIC 4-Pin OLED Display Module.

ULTRA SENSITIVE TEMPERATURE SENSOR (SCHOOL PROJECTS WORKING MODELS)

TEMPERATURE SENSOR BY USING TRANSISTORS

NOTE: IF YOU WANT TO PURCHASE READYMADE WORKING MODELS PROJECTS, MODELS, CIRCUIT, FILES FOR YOUR SCHOOL COLLEGE ? CONTACT ME : (SONU MODEL MAKERS NOIDA : +91 9818479606).

INTRODUCTION: 

This is an Analogue Circuit based on Transistors and Resistances. The Project is best for School & College Students. CBSE ICSE All India Board Practical Examination. 

As the name indicates this is a Ultra Sensitive Heat or Temperature Sensor Circuit, best for measuring temperature of liquids, water, & gases etc. The best thing is that there is no use of "Poisonous Mercury" in this project.

NOTE: This is an analogue circuit hence there is no need to use Micro-controller or Arduino in this design or style, this is a "Non-digital Circuit" or Gadget.

As shown in the circuit diagram below the long tailed differential amplifier, amplifies and records the difference of the input voltage. Here the Thermistor is negative co-efficient type (NTC), i.e. resistance (R) falls with temperature. 

Big change in conductivity along-with temperature places a limitation upon the use of semiconductor devices in some circuits. The property of the Thermistor that is used to advantage. The Thermistor consists of sintered mixtures of oxides such as NiO, Mn₂O₂ and CO₂ and O₃. 

ABBREVIATIONS USED:  V=Volts, K=Kilo Ohms, Ohm=Ohms, R=Resistance, T=Transistor, (-ve)=Negative, ^oC = Degree Celsius, No.=Quantity in Numbers, 

Figure 1. Circuit Diagram for Transistor Based Analogue Thermometer

The use of thermistor in this circuit makes possibility to compare temperature range above a range as wide as 100^oC.

ASSEMBLY & SETTING: 

Set the Resistance 4.7K and 50K (R1) so that the voltmeter (0-5V) will show the needel at zero make sure keeping the thermistor in Ice.  Now immerse the thermistor in a hot water 100^oC,   now adjust the VR (Variable Resistance) 2K to get a full scale deflection. The thermistor is now set and ready for use. 

To measure any temperature, put the thermistor in contact with it - by doing that the thermal equilibrium is attained.  The temperature is obtained directly on the meter in realtime. However initial markings of the meter should be made to get accurate readings. For this measure the known temperatures, and mark them on the meter dial. 

PARTS USED:

1. RESISTANCE .........(R)........1.2K (2No), 1.5K, 3.3K, 10K, 12K(2No), 30K,
   .............................................47K (1/4Watt) VR, 1 Ohms, 00 Ohms, 680 Ohms (2No), 
   ..............................................50 Ohms, 2K VR.
2. DC METER .............(M)........ 0 - 5 Volts.
3. THERMISTOR ..................... NTC Type 10K  - t^oC.
4. TRANSISTORS  .....(T)......... AC125 (6 Nos).

Thermistor : Thermistor is a kind of Resistance whose resistance is directly dependent on

temperature either high or low, compare to normal/standard resistors. The word is a combination of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors (negative temperature coefficient or NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements (positive temperature coefficient or PTC type typically). An operational temperature range of a thermistor is dependent on the probe type and is typically in between −100 °C (173 K) and 300 °C (573 K).

NOTE: If you want to purchase these kind of WORKING MODELS / SCHOOL / COLLEGE PROJECTS - Please Contact Us : +91 0 - 9818479606, 9211878985.

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