• 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. Marked by a teacher

    Sensing project

    5 star(s)

    Equipment * 12V power supply * Wires * Rotary potentiometer * Voltmeter * Fixed resistor * Crocodile clips * Protractor * Pointing device (Lego) Circuit diagrams Method and set-up This circuit is first constructed carefully and for safety reasons without the power supply switched on.

  2. 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

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

    This is because as the energy from the heat increases, more electrons jump the gap between the valence band and the conduction band so they increase the current. If you look at the equation I mentioned in my background information (Resistance (?)

  2. Experiments with a thermistor

    The voltage reading increases. CIRCUIT DESIGN OF APPLICATION OF THERMISTORS A thermistor has a wide range of commercial applications, and one of them is to control output devices such as water heaters and temperature alarms. One example of this is a water temperature control in swimming pools.

  1. An Investigation into the Resistance of a Thermistor, its Application as a Sensor and ...

    resistance at the same temperatures as before (but this time as the temperature decreased). Safety Issues Goggles were worn for safety. Another safety precaution was the use of distilled water. Because electrical components were being submerged in the water, pure water needed to be used as any impurities in water

  2. Investigate the relationship between temperature and resistance in a thermistor.

    This is a drop of 250 ohms. The temperature went from 250C to 1000C. By 500C the resistance has already dropped to about 50 ohms which is half the decrease in ohms under a third of the rise in temperature which proves that the resistance decreases most at lower temperatures and less at higher temperatures.

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

    The reason that I chose an LDR is because, most importantly, it is a passive sensor and this means that I am able to change its sensitivity by using whetstone networks, amplifiers or by inserting it into a potential divider.

  2. Measuring the temperature in a greenhouse using a thermistor.

    I am measuring the sensitivity by measuring the output voltage at every degree in my range. I will then look at the changes in output voltages from one degree to another and see if I can identify any patterns or anomalous results.

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