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

Electronics AS project

Extracts from this document...

Introduction

Fire Alarm Aim: The aim of this project is to create a fire alarm which will detect fire or the effects of fire and as a result, with a buzzer, aware any occupants and persons in the surrounding area. To do this, I have researched how to construct this particular circuit. Fire is a major hazard and without the proper warning indications, can lead to devastating consequences. This is a device that can solve this life-threatening problem. Research > From reading through a basic guide to fire alarms from www.firesafe.com, I have learnt that a minimum of 65 dB is required for a fire alarm in general areas or 5 dB above any background noise which persists for more than 30 seconds. If the alarm is to be placed where people are sleeping and are to be woken then 75 dB is required at the bedhead. > A thermistor with a resistance of around 100 kilo-ohms at room temperature should be used to make it sensitive to the high temperatures of fire (about 100 C) but not anything much lower. When in high temperatures such as this, the resistance of the thermistor should drop to only a few ohms, drastically increases the current. ...read more.

Middle

The same thing happens with the LDR but as the brightness increases the resistance drops and the voltage travelling through the LDR is pulled high and is passed into the AND gate; switching on a \buzzer alarm. This is the system that I will investigate and use for my system. (Fig.1) Reason for preferred choice I decided to go with option B because I would like the circuit to be able to detect the heat and light of the fire, other then just the smoke as this can be accidently set-off by anything that may produce a little smoke but have no fire. Sub-system Development My complete fire alarm system will consist of the sub-systems previously shown in the block diagram (Fig.1). The LDR voltage comparitor Ratio 10:1 Therefore, trigger point = 100? Using resistors 100K? and 10K?, a 10:1 ratio was formed to work out the trigger point. With the 1K? as R1 the trigger point was made to be 100?, which is enough light from a fire to trigger the circuit. Resistor R1 forms a voltage divider with the LDR; the voltage to the non-inverting input being larger than the reference voltage when the LDR is in the light. ...read more.

Conclusion

x 100uF R1 + R2 = 1.5 seconds = 21.4K? => R1 = 7.1K? 0.7 x 100uF T-low = 0.7 R2 C 1.0s = 0.7 x R2 x 100uF R2 = 1.0 seconds = 14.3K? => R2 = 14.3K? 0.7 x 100uF Tests on Sub-Systems Voltage comparitor - LDR Inverting/non-inverting Voltage with light ON (V) Voltage with light OFF (V) Inverting 0.72 0.79 Non-inverting 0.51 5.20 Output 7.42 1.34 This shows that when the light is on the output becomes high (7.42V) as the inverting voltage is higher than the Non-inverting voltage.The sub-system is therefore working. Voltage comparitor - Thermistor Inverting/non-inverting Voltage with high temperature (V) Voltage with low temperature (V) Inverting 0.73 0.78 Non-inverting 0.70 1.60 Output 7.29 1.37 This shows that when the thermistor is in high temperature the output becomes high (7.29V) as the inverting voltage is higher than the Non-inverting voltage.The sub-system is therefore working. AND Gate Heat sensor input (V) Light sensor input (V) Output (V) 1.37 1.34 0 1.37 7.42 0 7.29 1.34 0 7.29 7.42 6.28 This shows that when both the inputs of the heat sensor and light sensor are HIGH the output voltage then also becomes HIGH. However, when either one of the sensors is LOW then the output voltage remains LOW. The sub-system is therefor working. Scott Jenkins ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Design and Technology 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 Design and Technology essays

  1. Bedside table development evaluation

    AESTHETICS: > The product must not be too modern as it would look out of place in an 'old-fashioned' bedroom, this because my target market would have more mature tastes and their houses would have not been recently, so they would not currently be keeping up with the latest fashion and trends.

  2. Were developing a shoe removal detector which identifies and notifies a person entering the ...

    2. Newcomer detecting part Human skin detecting part can only send true signal when a human skin touches it. It can't detect the shoes on it. So we need another part which detects the presence of human on the pad. 3.

  1. Devlopment evaluation of my bedside table.

    the fact that items can be stood up straight gives us even more space in the drawer which is always a plus This looks like more than enough space for other items so that fantastic, I think we can even fit both lamp and telephone on there and still have space.

  2. Light & artificial lighting systems

    By night, artificial lighting will be the sole illumination, natural light of the moon will not be enough for general working conditions, and this would cause disruptions to work during the periods where the availability of daylight is shorter or evening overtime or shifts that are required to beat crucial deadlines.

  1. Research in the uses of silicon

    of current carriers. Such control is necessary for transistors, solar cells, semiconductor detectors and other semiconductor devices which are used in electronics and other high-tech applications. > Photonics - Silicon can be used as a continuous wave raman laser to produce coherent light (though it is ineffective as a light source).

  2. It is important that Sarah is blind having access to speech and Braille output ...

    It can contain more than forty gigabytes of hard disk drive storage capacity but can cause problems and ruin the PDA, whereas a PDA for the blind might today support a mini disk drive with about five gigabytes. PDA also has a bad battery, it doesn't stay for long.

  1. In this part of the evaluation I have commented the good points about each ...

    I have made and answered a few questions tat I took into consideration before I made my decision. This piece of work helps me to decide which design to choose. I think this piece of work is done very nicely because word processing it made it look neat and tidy.

  2. The Characteristics and Development of RFID - Radio frequency identification.

    There are several methods of identifying items using RFID but most systems consist of a tag, which is made up of a microchip with a coiled antenna, and an interrogator or reader with an antenna. The reader sends out electromagnetic waves that form a magnetic field when they 'couple' with the antenna on the RFID tag.

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