You are asked to design a controller for a printer as follows. this controller has 4 inputs, to, ti, t2, corresponding to 3 paper trays, and input j signaling a paper jam. the circuit has 3 outputs: e for error, fo, and fi. description of inputs: inputs to, tı, t2 show the status of paper trays. if there is no paper in any of the trays, the corresponding input (to, ti or t2) goes low (logical 0), indicating that there is no paper in the particular tray. otherwise, ti = 1. if paper gets jammed in the printer, input j is asserted high (j = 1), indicating a paper jam.
description of outputs: signal e should be set to high if a paper jam occurs or all trays run out of paper. signals fo and fi imply the tray from which papers should be fetched: {fo = 0, fı = 0} imply that tray ( is selected; {fo = 1, f1 = 0} imply that tray 1 is chosen; and {fo = 0, f1 = 1} indicates that papers will be fetched from tray 2; and finally {fo = 1, fi = 1} indicate that no tray is selected. to generate fo and fi, the controller should check the following conditions: • if there is a paper jam or all trays are empty, then no tray should be selected (fo = 1, and fi = 1). • trays are selected based on their priority. the lower the number, the higher the priority, i. e. to > tı > t2. in other words, first, the controller checks tray 0. if it has papers, tray 0 is selected. if tray ( is empty, the controller checks tray 1; and if both tray o and tray 1 run out of paper, then tray 2 is checked. your assignment: a) derive the truth table of this 4-input 3-output boolean function according to the above specifications. b) subsequently, derive a simplified boolean expression and draw the corresponding logic circuit.

Infrared sensor is most used sensor in wireless technology where remote controlling functions and detection of surrounding objects/ obstacles are involved. this post will discuss about what is infrared sensor, its working principle, how it works, types, applications, advantages and disadvantages. what is infrared sensor

ir sensor is a simple electronic device which emits and detects ir radiation in order to find out certain objects/obstacles in its range. some of its features are heat and motion sensing.

ir sensors use infrared radiation of wavelength between 0.75 to 1000µm which falls between visible and microwave regions of electromagnetic spectrum. ir region is not visible to human eyes. infrared spectrum is categorized into three regions based on its wavelength i.e. near infrared, mid infrared, far infrared.

wavelength regions of infrared spectrum

near ir – 0.75µm to 3 µm
mid ir – 3 µm to 6 µm
far ir – > 6 µm
1 introduction to infrared sensor

fig. 1 – introduction to infrared sensor

working principle of infrared sensor

infrared sensors works on three fundamental physics laws:

planck’s radiation law: any object whose temperature is not equal to absolute zero (0 kelvin) emits radiation.
stephan boltzmann law: the total energy emitted at all wavelengths by a black body is related to the absolute temperature.
wein’s displacement law: objects of different temperature emit spectra that peak at different wavelengths that is inversely proportional to temperature.
key elements of infrared detection system

the key elements of infrared detection system are:

ir transmitter

ir transmitter acts as source for ir radiation. according to plank’s radiation law, every object is a source of ir radiation at temp t above 0 kelvin. in most cases black body radiators, tungsten lamps, silicon carbide, infrared lasers, leds of infrared wavelength are used as sources.

transmission medium

as the name suggests, transmission medium provides passage for the radiation to reach from ir transmitter to ir receiver. vacuum, atmosphere and optical fibers are used as medium.

ir receiver

generally ir receivers are photo diode and photo transistors. they are capable of detecting infrared radiation. hence ir receiver is also called as ir detector. variety of receivers are available based on wavelength, voltage and package.

ir transmitter and receivers are selected with matching parameters. some of deciding specifications of receivers are photosensitivity or responsivity, noise equivalent power and detectivity.