SPECIFICATIONS
Title of the project : accident prevention for electrical
machinery
Domain : Embedded Systems Design
Software : Embedded C, Keil, Proload
Microcontroller : AT89S52
Power Supply : +5V, 500mA Regulated Power Supply
Display : LED
5mm, Liquid Crystal Display
Sensors :
Tactile switches and LDR, skin
sensor
Crystal : 11.0592MHz
Applications : safety at homes, offices and
factories etc
ABSTRACT
While a fuse
protects a circuit, it is destroyed in the process of opening the circuit. Once
the problem that caused the increase in current flow or heat
is corrected, a new fuse must be placed in the circuit. A circuit protection device that can be used more than once solves the problems
of replacement fuses. Such a device is safe, reliable,
and tampers proof. It is also resettable, so it can be reused without replacing
any parts. This device is called a CIRCUIT BREAKER
because it breaks (opens) the circuit. The first
compact, workable circuit breaker was developed in 1923. It took 4 years to
design a device that would interrupt circuits of 5000
amperes at 120 volts ac or dc. In 1928 the first circuit breaker was placed on the market. A typical circuit breaker and the appropriate
schematic symbols are shown in figure
Each type of fuse ( and all other over current devices) has a
time-current characteristic which shows the time required to melt the fuse and
the time required to clear the circuit for any given level of overload current.
In common fuse selection, simple ratios between the fuse closest to the load
and the next fuse to the source can be used to prevent having several circuits
interrupted. In power system design, main and branch circuit over current
devices can be co-ordinate for best protection by plotting the time-current
characteristics on a consistent scale, making sure that the source curve never
crosses that of any of the branch circuits. To prevent damage to utilization
devices, both "maximum clearing" and "minimum melting" fuse
curves are plotted. Similar curves are used for all over current devices:
fuses, common circuit breakers and power circuit
breakers.
We propose to
design and develop an electronic circuit breaker which is programmable and
efficient. The circuit was designed as an additional safety for electrical
equipment like jig saw. It is observed that most of the accidents in using zig
saw results in loss of certain portion of the hand, many a times the fingers
are more vulnerable. The proposed circuit detects the current leakage to the
earth and stops the motor almost instantly with least possible damage.
BLOCK DIAGRAM
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