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Developing a Fridge Add-On

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Research To help me with my design I need to find out information about - 555 timer- what does it do? What is it made from? What do the pins do? How will it go in my circuit? LDR What does it do? How does it work? How is it powered? "Anyone who uses a refrigerator will be able to use this product. This product is something useful which anybody can benefit from it is a product that can be of assistance to you in everyday life." It will be used in the kitchen inside a refrigerator so the circuitry will have to be concealed within a casing. This is because the refrigerator operates below room temperature and therefore the circuitry must be able to operate under these conditions. The casing is a vital part of the product because in a refrigerator many things can easily damage the circuitry. To operate this product there must be a power supply and the only thing, which could be used and concealed completely, is a battery. The battery though must be easily accessible for maintenance purposes. ...read more.


The Circuit The circuit above is a circuit which will be based on my final circuit; I am using a light dependant resistor because when a fridge is opened a light comes on and so when the light dependant resistor picks up the trace of light the 555 timer will start and after fifteen seconds of the light dependant resistor picking up light the buzzer will sound, so indicating that the fridge door has been left open. The Light Dependant Resistor If the control situation requires different levels of light this is likely to be the device used. The light dependant resistor is an analogue device and so its output is variable. However, it can be connected directly into the digital input connections of the interface. If different light levels need to be detected it must be connected to the analogue inputs of the interface. A battery can power the light dependant resistor and with my circuit that is the only possible way! The astable circuit will probably suit my circuit the best because when the fridge door is opened a beep is sounded until the door is shut. ...read more.


The main problem now is the fact that there is a continuous bleep, and if the person wanted to clean the fridge this would become very annoying so to prevent this a manual override switch should be placed in to allow this beeping to cease. To notify the person that they have turned off the circuit the best thing to do would be to have a led to light when the circuit is off but when the circuit is turned back on the led is automatically turned off. Switches Switches can direct the current around the circuit by re-routing or breaking the connections that make up the circuit. There are a large number of switches but the one which would probably be best with my circuit is the single pole double throw, this type of switch can offer a choice of two directions for the current to take depending on the position of the pole. The other alternative is the single pole throw, this type of switch can only make or break a circuit. The battery is not very expensive and allows maximum durability, which is why I do think it is best for my circuit. All the things I researched are all needed to produce my electronic product. ...read more.

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