CS244 Introduction to Embedded Systems and Ubiquitous Computing Instructor Eli Bozorgzadeh Computer Science Department UC Irvine Winter 2010 CS244 Lecture 7 Sensors Actuators and Other hardware components Winter 2010 CS 244 2 Simplified Block Diagram actuators ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters Sensors and Actuators Sensors Capture physical stimulus e g heat light sound pressure magnetism or other mechanical motion Typical generate a proportional electrical current May require analog interface solenoid mic speaker Actuators Convert a command to a physical stimulus e g heat light sound pressure magnetism or other mechanical motion May require analog interface laser diode transistor compass dc motor accelerometer Sensors Processing of physical data starts with capturing this data Sensors can be designed for virtually every physical stimulus heat light sound weight velocity acceleration electrical current voltage pressure Many physical effects used for constructing sensors law of induction generation of voltages in an electric field light electric effects Example Acceleration Sensor MEMS device Small mass in center When accelerated Mass displaced from center Resistance of wires connected to mass change Detect change in resistance and model acceleration Courtesy S B tgenbach TU Braunschweig Charge coupled devices CCD Image ImageSensors Sensors Based Basedon oncharge chargetransfer transferto tonext nextpixel pixelcell cell CMOS Image Sensors Based on standard production process for CMOS chips allows integration with other components Source B Diericks CMOS image sensor concepts Photonics West 2000 Short course Web Comparison CCD CMOS sensors Example Biometric Sensors Example Example Fingerprint Fingerprint sensor sensor Siemens Siemens VDE VDE Integrated into ID mouse Example Artificial eyes Dobelle Institute www dobelle com Artificial eyes 2 Dobelle Institute www dobelle com He looks hale hearty and healthy except for the wires They run from the laptops into the signal processors then out again and across the table and up into the air flanking his face like curtains before disappearing into holes drilled through his skull Since his hair is dark and the wires are black it s hard to see the actual points of entry From a distance the wires look like long ponytails Other examples of sensors Heart monitoring sensors Managing Care Through the Air Rain sensors for wiper control Touch pads screens Proximity sensors High end autos Pressure sensors IEEE Spectrum Dec 2004 Collision avoidance Engine control sensors Audio sensors Motion sensors Thermal sensors SARS detection high fever Simplified Block Diagram actuators Sensors and Actuators Sensors Capture physical stimulus e g heat light sound pressure magnetism or other mechanical motion Typical generate a proportional electrical current May require analog interface solenoid mic speaker Actuators Convert a command to a physical stimulus e g heat light sound pressure magnetism or other mechanical motion May require analog interface laser diode transistor compass dc motor accelerometer Actuators Output physical stimulus varies in range and modality Large industrial control actuators Optical output Pneumatic systems physical motion IR Thermal output Small motor controllers stepper motors MEMS devices List goes on Stepper Motor Controller Stepper motor rotates fixed number of degrees when given a step signal In contrast DC motor simply rotates when power applied and coasts to stop Rotation achieved by applying specific voltage sequence to coils Controller greatly simplifies this MEMS Actuators Huge variety of actuators and output devices Microsystems motors as examples MCNC Dimensions in the order of several microns MCNC Actuators Courtesy and E Obermeier MAT TU Berlin Simplified Block Diagram actuators Sample and Hold Circuit Model Vx Ve when Clock 1 Sampling how often the signal is converted Quantization how many bits used for sampling Aliasing Potential Consequence of sampling e g Signal frequency 5 6 Hz Sampling frequency 9 Hz Analog to Digital Conversion Sampling how often is the signal converted Quantization how many bits used to represent a sample Twice as high as the highest frequency signal present in the input Sufficient to provide required dynamic range Under loading dynamic range not used properly Clipping input signal beyond the dynamic range Aliasing erroneous signals not present in analog domain but present in digital domain Use anti aliasing filters Sample at higher than necessary rate 5 0V 4 5V 4 0V 3 5V 3 0V 2 5V 2 0V 1 5V 1 0V 0 5V 0V 1111 1110 1101 1100 1011 1010 1001 1000 0111 0110 0101 0100 0011 0010 0001 0000 proportionality 4 4 3 3 analog output V Vmax 7 5V 7 0V 6 5V 6 0V 5 5V analog input V Analog to Digital Converter 2 1 t1 0100 t2 t3 t4 time 1000 0110 0101 Digital output analog to digital 2 1 t1 t2 0100 t3 1000 0110 Digital input digital to analog t4 time 0101 Flash A D Converter Parallel comparison with reference voltage Speed O 1 HW complexity O n ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters n of distinguished voltage levels Signal Processing Digital signal S0 S1 S2 Sn 1 What can we do with it Transpose e g Zi Si K Amplify e g Zi Si Compose e g Zi S1i 1 K1 S2i 2 K2 Filter e g Zi Si Si 1 2 Compress e g using Huffman codes Archive match against database etc Or process after converting to frequency domain Spectral analysis ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters Frequency Domain Any continuous time varying signal can be represented as the sum of cosine functions of different amplitude and frequency E g input signal captured as the sum of 4 cosine functions Once in frequency domain certain manipulations become trivial e g filtering ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters Simplified Block Diagram actuators ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters Digital to Analog D A Converters Various types can be quite simple e g ICS212 WQ05 Dutt Hardware Components Sensors Actuators Converters