IEEE 802.15.4 systems suffer from serious MAC unreliability problem due to contention based MAC protocol used for channel access and its default parameter values. Reliability issues arise on case of energy efficiency when power management is enabled; packet loss when number of contending nodes is increased. A method to use IEEE 802.15.4 MAC protocol with reduced unreliability as the number of nodes increases reliability decreases. The proposed WSN has central server and nodes, sink consists setting switches to fix the setting value of load through ZigBee communication using the microcontroller AT89C51. Controlling the node and monitoring them reduces the unreliability of receiving more number of packets from nodes to central server.