This article focuses on how to transfer sensor data in a typical IoT system in a secure and malicious attack-proof way, using microcontrollers to read temperature and light sensors. The objective is to transfer them using a blockchain protocol using a wireless sensor network as a platform, in which the nodes are formed by microcontroller systems. In this way, a low-cost, low-energy prototype system was created, capable of measuring over long distances and transmitting measurement data safely. Practical results on the bench and in the field demonstrated that the use of this technology is promising for use in various situations, specifically in photovoltaic solar plants for measuring voltage and current as economic assets. Field tests have shown that the system can be used at maximum distances between sensor nodes of 75 meters. Attempts were made to sabotage the system, but all proved ineffective.