Energy harvesting for a smart sensor with NFC capability

Autor/Author: Javier Molina
Director/Supervisor: Guillermo Robles
Master Thesis Document in pdf.

 

Abstract – Modern life’s concerns regarding unnecessary energy wasting and the unstoppable development of electrical engineering gave birth to the concept of energy harvesting. All this, along with an overwhelming number of internet connected devices, make necessary new smart devices to make easier our lives not only at home but also in industrial environments. Throughout this project, the feasibility of using a Peltier cell as a thermoelectric generator is discussed in order to scavenge energy from a heat source. This project aims at using this system in dicult access locations to create a smart sustainable system that can keep track of relevant parameters such as temperature, pressure or radiation. By implementing this self-powered system, there is no need to replace batteries when fully discharged, it is only necessary collect the data when required. In particular, this Peltier cell supplies an energy harvester module that powers a standalone microcontroller to establish a communication with a NFC module. This device embedded with a NFC tag will store the parameters measured by a sensor. This novel approach is intended to allow any NFC enabled device such as any modern smartphone to access this data to be subsequently analised and take action when needed.

 

Resumen – Las preocupaciones de hoy en da con respecto al consumo abusivo energetico sumado al gran desarollo reciente de la ingeniera electrica y electronica han dado como fruto el concepto de energy harvesting. Ademas, el mundo en el que vivimos con un mayor numero de dispositivos conectados a internet hacen necesario dispositivos inteligentes para facilitar nuestras vidas, no solo en casa, si no tambien en el entorno industrial. En este proyecto se expone la viabilidad de usar una celula Peltier que es un dispositivo termoeléctrico para proporcionar energa a partir de una fuente de calor. Este proyecto persigue usar este sistema en sitios de difcil acceso y crear un sistema sostenible que lleve a cabo un sistema de recogida de datos, como temperatura o presion. La ventaja que ofrece un sistema como este es que no es necesario cambiar la batera, puesto que el sistema se autoalimenta. Concretamente, la celula Peltier suministra energa a un modulo de almacenamiento que establece una comunicacion con un modulo NFC. Este dispositivo contiene una etiqueta NFC que almacena los datos recogidos por un sensor. Este enfoque permite a cualquier operario con un dispostivo que permita la lectura de etiquetas NFC, como por ejemplo cualquier smartphone moderno, acceder a estos datos para analizarlos y tomar decisiones si es necesario.

 

Energy harvesting and NFC tag (LTC3108 -> STM32L433 -> M24SR)

The idea behind this work was to test the capabilities of using a near-field communication (NFC) tag to store the information acquired through an analogue input of a microprocessor powered by an energy harvesting source.

The setup includes these components:

  • Peltier cell
  • Energy harvesting system
  • Microprocessor
  • Dynamic NFC/RFID tag IC
  • Temperature sensor

Energy harvesting system

The capabilities of Peltier cells to harvest energy from differences of temperature between its two sides has already been studied in other posts starting with this link, so I will not develop this part of the work here.

The energy harvesting system used in this project is now based on the outstanding Linear Technologies (now part of Analog Devices) Ultralow Voltage Step-Up Converter and Power Manager LTC3108. This device can work with four selectable output voltages: 2.35 V, 3.3 V, 4. V or 5 V to power wireless transmitters or sensors and a low dropout voltage regulator output (VLDO) to power an external microprocessor. According to its datasheet it can start harvesting energy from voltages as low as 20 mV which is precisely indicated for applications that use thermo-electric generator (TEG) such as Peltier cells. The energy is stored in a bank of supercapacitors connected to two outputs of the LTC3108. Two 1 F supercapacitors in series are connected to VOUT and charged when VAUX has reached 2.5 V. Another two 1 F supercapacitors are connected to VSTORE supporting VOUT and preventing an unexpected drop of voltage due to a high power demand by the load. A picture of the setup for this integrated circuit (IC) is:

Continue reading Energy harvesting and NFC tag (LTC3108 -> STM32L433 -> M24SR)