The power supply is one of the main constraints when operating Wireless Sensor Networks (WSN). The most obvious energy source for a WSN node is a rechargeable or non-rechargeable battery. Batteries seriously limit WSNs usage and are associated to the increasing cost of large networks. Low cost networks will be achieved when battery consumption becomes substantially reduced or eliminated. Within this scope, powering WSN devices using mains power, is not an advantage since node installation requires complex and time consuming actions. Replacing batteries is therefore an important topic even in environments with mains power availability. In this paper, a battery-less device running an IEEE802.15.4/Zigbee protocol stack on harvested energy is proposed. Its operation mechanism and required software adaptation to sustain this complex protocol are described. The protocol compliant node uses a contact-less scavenger system that is able to power a WSN node from mains power lines thus providing an inexpensive and easily installable device even for non-skilled users.