Passive infrared sensor | EPFL Graph Search

A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms and automatic lighting applications. PIR sensors detect general movement, but do not give information on who or what moved. For that purpose, an imaging IR sensor is required. PIR sensors are commonly called simply "PIR", or sometimes "PID", for "passive infrared detector". The term passive refers to the fact that PIR devices do not radiate energy for detection purposes. They work entirely by detecting infrared radiation (radiant heat) emitted by or reflected from objects. All objects with a temperature above absolute zero emit heat energy in the form of electromagnetic radiation. Usually this radiation isn't visible to the human eye because it radiates at infrared wavelengths, but it can be detected by electronic devices designed for such a purpose. A PIR-based motion detector is used to sense movement of people, animals, or other objects. They are commonly used in burglar alarms and automatically activated lighting systems. A PIR sensor can detect changes in the amount of infrared radiation impinging upon it, which varies depending on the temperature and surface characteristics of the objects in front of the sensor. When an object, such as a person, passes in front of the background, such as a wall, the temperature at that point in the sensor's field of view will rise from room temperature to body temperature, and then back again. The sensor converts the resulting change in the incoming infrared radiation into a change in the output voltage, and this triggers the detection. Objects of similar temperature but different surface characteristics may also have a different infrared emission pattern, and thus moving them with respect to the background may trigger the detector as well. PIRs come in many configurations for a wide variety of applications.

Development of a Monolithic Fiber-Based Electric Field Sensor

Mahdi Tamizifar

This project has been done on the development of a monolithic fiber-based electric field sensor, with a focus on establishing a reliable, cost-effective, and scalable production cycle to be implemented initially at a pilot and consequently at an industrial scale. The small scale and the low cost of these electrically passive sensors would enable their application where applying an external electric current is either forbidden (e.g. by the ATEX directive), or would distort the electric field and thus limit the possibility of monitoring sensitive assets. This electric field sensor works on the principles of electrostatic induction and translates the electric field to the displacement of an array of mirrors and holes suspended over a second array of mirrors. By shining the rays of light onto the suspended array, it would be possible to monitor the variations of the reflected light due to the displacement of the suspended array over the second array which is deposited on a transparent substrate. At the first phase of the project, by utilizing the COMSOL Multiphysics simulation software, the optimal parameters of the electric sensor were simulated. Based on the results of the simulations, a general process flow was drafted and received the approval from the experts at the EPFL Center of Micro/Nano Technology (CMi). Based on the finite element simulations, in order to maximize the displacement of the sensor along the electric field, it has been shown that reducing the thickness of the sensor would significantly increase the longitudinal displacement of the sensor. Additionally, in order to further decrease the stiffness of the springs connecting the suspended mass to the frames, the structural material of the sensor was selected to be Copper, which also has a high electrical permittivity and low fabrication cost. Next, the micro fabrications based on the optimized design and the process flow were carried out at the CMi ISO 5 cleanroom facilities. In order to adapt the process flows to the capabilities and the availability of the machines, several process flows have been tested and the result of which have all been documented in this report. Moreover, regarding the limited range of the available choices for having a process flow which is compatible with the CMi facilities, the recommendations for further simplifying the process and decreasing the final production costs are mentioned in this report.

2018

Development of a Monolithic Fiber-Based Electric Field Sensor

Mahdi Tamizifar

2018