NAND gate monostable
555 timer IC is commonly used in monostable mode to generate a pulse every time a trigger is given. The project described here uses NAND gate for monostable operation and thereby avoiding the need of 555 timer.
If a logic level "0" pulse is now applied to the trigger input of gate U1the output of U1 will go high to logic "1". Since the voltage across the capacitor cannot change instantaneously this will cause the junction V1 and also the inputs of U2 to go high, which in turn will make the output of the NAND gate U2 go low. The circuit will remain in this state even if the trigger input pulse T is removed. This is known as the Meta-stable state.
The voltage across the capacitor will now increase as the capacitor C charges up from the output of U1 at a time constant determined by the resistance and capacitance combination, until the junction at V1 reaches a logic "0" level causing the output of U2 to switch high again, which in turn causes the output of U1 to go low and the capacitor discharges under the influence of resistor R. The circuit is now back to its original stable state.
The length of the output time period is determined by the capacitor/resistor combination and is given as the Time Constant T = 0.7RC of the circuit in seconds.
Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits....
Capacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycl...