Please help me to design below circuit..
circuit which gives output HIGH for specific time (eg:120sec) and then goes LOW irrespective of the input until the circuit is reset.
Many ways to go about this, monostable 555, binary ripple counter, microprocessor. Easiest may be the 555. Most accurate the microprocessor. So if you put 555 timer in google there will be a bunch of examples. Please try one and if you have questions post questions.