Student at IMEC-Infinity Management and Engineering College
Feb-2011 to Jun-2011
The circuit is built around Schmitt-trigger NAND gate IC CD4093 (IC1), timer IC CD4020 (IC2), transistors BC547, relay RL1 and buzzer. The Schmitt-trigger NAND gate (IC1) is configured as an astable multivibrator to generate clock for the timer (IC2). The time period can be calculated as T=1.38XRXC. This circuit saves both time and electricity for students. It helps to prevent them from dozing off while studying, by sounding a beep at a fixed time interval, say, 30 minutes. If the student is awake during the beep, he can reset the circuit to beep in the next 30 minutes As the output of gate N4 is connected to the clock input (pin 10) of IC2 through diode D3, further counting stops and relay RL1 energizes to deactivate all the appliances. This state changes only when IC2 is reset by pressing switch S1.