ALERT  TIMER  PROJECT 

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

This timer is a useful tool for those who often forget to turn off the devices in time.  Super Pose You want to boil water in your electric kettle or cook something on your gas.  You switch on the kettle or gas and simultaneously press the S2 momentarily to enable the warning circuit.  The ten-minute buzzer reminds you of what you were doing.

The circuit is constructed using an N channel enhancement - mode field effect transistor BS170 (T1).  It does not attract any power at idle and is less than 15 micrograms when working.  In terms of simplicity, the car key 12V fob battery would be an ideal choice.

Fig1;circuit diagram

Momentarily pushing switch S2 charges capacitor C1 rapidly via resistor R1.  When the voltage on capacitor C1 exceeds the threshold voltage at the gate of T1, it starts charging the reservoir capacitor C2.  Transistor T1 remains in stored state as long as the voltage on C1 is greater than FET gate's threshold voltage.  The time period of the alarm depends on the value of capacitor C1 and resistor R2, which governs the capacitor's discharge current.

The component values ​​provided here give an on - time of about ten minutes.  You can increase or decrease the time period of alarm by changing the values ​​of capacitor C1 or resistor R1.

 Assemble the circuit on a general purpose PCB and enclose in a suitable cabinet.  Press switch S2 along with your electrical appliance's switch to enable the alert alarm.  Switch S1 is power - on switch.  • 

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