• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Sensor Project

Extracts from this document...

Introduction

Sensor Project

I have decided to measure the temperature of a greenhouse using a thermistor in a potential divider circuit, and then when the temperature gets too cold, the relay will activate and turn on a heater. A thermistor is a temperature sensor in which its resistance will increase or decrease with temperature change depending on what type of resistor.

An alternative for this experiment could have been measuring light levels in a greenhouse using an LDR. A light sensor in a green house could tell you when and where in the greenhouse the most intense sunlight is, which you could you use to aid your growing skills.

I decided to design a temperature sensor for a greenhouse using a thermistor, as temperature can be critical in growing plants especially if it gets too hot or too cold.

As my thermistor is an NTC this means that as temperature decreases its resistance increases, and when temperature increases its resistance decreases.

Plan:

Circuit –

image00.png

Explanation –

The water is boiled until it reaches a temperature of just above 90° Celsius.

...read more.

Middle

image09.png

1.93 (R1+124.8) = 124.8 x 5.0

1.93 (R1) + 240.864 = 624

1.93 (R1) = 624 – 240.864

1.93 (R1) = 383.136

R1 = image02.pngimage02.png = 198.516Ω

TEMPERATURE (˚C)

 VOLTAGE (V)

1st V

2nd V

Av. V

20

247.0

251.0

249.0

30

181.7

181.9

181.8

40

131.8

131.8

131.8

50

98.0

99.2

98.6

60

75.0

75.6

75.3

70

60.3

60.5

60.4

80

49.1

49.1

49.1

90

37.8

38.3

38.1

Temperature-Voltage Graph

image03.png

...read more.

Conclusion

Safety –

The issue of safety is very important in any experiment. In this experiment there is no really serious risk. However even minor concerns cannot be overlooked.

The major safety points considered include

  • Avoiding the use of wet hands to handle electrical apparatus so as to reduce/eliminate the risk of electric shocks.
  • Being careful and conscientious with the hot water as hot water is potentially dangerous.
  • Ensuring proper electrical wiring (avoid using faulty equipment, use insulated wires etc.) so as to reduce/eliminate the risk of electrical injury and damage to electrical equipment.

Apart from these few points there is nothing serious to be considered.

Improvements –

My sensor could be improved in a number of ways. Firstly, I could have measured the change in resistance with temperature and not voltage. This is because using resistance as my variable would have given me a much clearer linear logarithmic graph making deducing values much easier and reliable.

Also, most textbooks relate the change in resistance of thermistors with temperature and not the change in voltage that occurs as a consequence of the change in resistance. Therefore, I would have had more formulae at my disposal.

References –

Advancing Physics AS textbook

Advancing Physics website

Student Notes

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Investigate how the temperature affects the resistance of a thermistor.

    When it has reach this temperature I will record the first resistance using the ohmmeter and then I will continue to heat the thermistor will the Bunsen burner, record the resistance every 50C . I will repeat this experiment twice more to ensure that my results are reliable and so

  2. Experiments with a thermistor

    The thermistor is very sensitive as it is able to detect very small changes in resistance. Using more sensitive output devices like a Wheatstone bridge circuit would illustrate its sensitivity. In quantitative terms, the sensitivity of the thermistor is:- Sensitivity = change of output / change of input = 5.01

  1. Using an LDR to detect the intensity of plane polarised light allowed through a ...

    Since I am using a resistance substitution box, I am limited to certain values. However, given the values of the resistor that are possible, and the EMF of 12V which we would achieve for a perfect battery, I can form the following formulae for the output potential difference, in terms of the values of resistance in the LDR, R.

  2. To investigate how the temperature affects the resistance of a thermistor.

    In my data I did have one anomaly which was the resistance at 400C and I can only think of one factor that could have affected this piece of data. The resistance seems to be smaller than it should be in which case one thing that could have affected it

  1. Sensors Project Report

    Then results can be recorded. The experiment is done 3 at least 3 times, and then produces a calibration curve. Variables - A variable resistor which will affect the sensitivity of the whole experiment - Number of pieces of paper varies from 1 - 200 pieces and is measured

  2. Light notes

    The distance from the focus to the centre of the mirror is the focal length. The more curved the mirror, the shorter the focal length. All objects regardless of distance have images that are virtual, upright, diminished that form behind the mirror between the mirror and the focus.

  1. Light and matter notes

    Orbiting electrons only accept the energy from a collision with another electron that will take it up to one of the allowed energy levels. When an electron in a high energy level returns to the lowest level it may do so in one step or go temporarily to any of

  2. Making, Calibrating and Testing a Sensor

    light, then the piece of car will be moved forwards at 1cm intervals until it is 1cm away from the LDR, this will replicate the car moving forwards. I have chosen to start at 30cm because this is the point at which a driver will no longer be able to

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work