The exponential growth of population is leading to the need for the integration of Information and Communication Technology (ICT) and advanced equipment in farming. Either excess or lack of water leads to uneven crop development and may result in loss of yield. Therefore, there is a need to implement a smart irrigation system to monitor moisture levels. It helps in regulating water supply to the field and using resources effectively. This paper proposes a power-effective smart irrigation system with a hygrometer sensor to measure the moisture content in the soil. The proposed sensor is calibrated for its resistance and is proportional to the moisture level. The novelty of this work is in terms of low cost and low power consumption. We envision a smart IoT (Internet of Things) system with a large magnitude of sensor nodes monitoring the moisture levels of plants on the farm. The existing sensor nodes in the market are costly and consume excessive power. Thus, a system built with these sensors is not scalable. We propose a sensor node based on the Schmitt trigger, which takes the hygrometer sensor output resistance as the input and gives the output in terms of voltage. The sensor output can decide whether to turn OFF/ON the water supply to the soil. The output from this circuit can be sent to the farmer at a remote location using IoT.