• 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. Light & artificial lighting systems

    This is commonly used in museums, galleries and more commonly retail stores where artificial lighting is used to enhance the works or items on display. Office during the evening, natural daylight is not available therefore having to relay on the artificial lighting to enable work to continue.

  2. My aim for this project is to design and construct a fully functioning alarm ...

    Specification 1) Clock will display in the format hh:mm - 4 seven segment displays 2) Alarm clock will sound until the Stop Alarm button is pressed 3) The loudness of the alarm will be between 85 - 95 dB 4) The brightness of the alarm will be 0.80 lux 5)

  1. The proposed design project is to design, produce and evaluate an innovative recycled clock, ...

    Research Research developments needed to be identified and reviewed. This review simply summed up research and no unnecessary work done on the development. Paper crafts book Book used to acquire skill of decoupage. Machinery Was used to complete practical part of the project. For this project and the particular way in which I chose to construct this clock I

  2. Bedside table development evaluation

    they are all hardwearing and durable so should last more than the expect 4-5 years of standard bedside tables. All materials used are able to be recycled and reused, I will include a word document making customers aware materials are recyclable and reusable All materials are reasonably lightweight and all

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

    Precision, economical power usage, user- friendly, reliable, mobile. > The product should precisely detect the newcomer with shoes to avoid embarrassment. That means we try our best to build a product which is not vulnerable to other environmental facts. For example moisture of air, wet shoes, leather base shoes etc...

  2. Devlopment evaluation of my bedside table.

    > Must be relatively lightweight so that can product can be moved around the room at will, so the product must weigh no more than 16kg as this is the max range one woman adult can lift from elbow height , but preferably 10kg, taking into account my target market

  1. Research in the uses of silicon

    Hence, the empirical formula is 'SiO2. The giant structure is responsible for the high melting point and hardness of silicon (IV) oxide. When heated to about 870 0C, quartz passes into another crystalline form called tridynamite. At about 1740 0C a further change occurs, into cristobalite.

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

    Speech Synthesizer is a powerful text to voice converting application that is extremely useful for converting all types of her texts to speech. She is more independence and enables her to do things she usually wouldn't be able to do.

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