Fixed Voltage Power Supply And Panic Alaram
1)Fixed Voltage PS:Voltage regulator is a device which provides fix output voltage in spite of the variable input voltage supplied. It is a three terminal device. Voltage regulator basically comes in two different series: 78XX and 79XX. Voltage regulator under 78XX series are designed for positive inputs i.e. if while 79XX series are designed for negative inputs. In market variety of voltage regulators are available with output as 6V, 9V, 12V, 15V etc. Voltage regulator can also withstand over current drawn due to short circuit or overheating. It will cut off the circuit before damage occurs. One must take care while mounting the regulator because reverse polarity may destroy the regulator.
2)Panic alarm-It works on timer IC 555. It works on SET, ATTEND, CALL principle.
When we touch the touch plate , then it will show the blue LED glowing , and shows SET function. Then it shows the green LED on for ATTEND, and finally alarm buzzes when red LED will be ON.It is used for security purpose like in hospitals.