Difference between revisions of "Sensors"
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=== Temperature Sensor === | === Temperature Sensor === | ||
| − | Some are analog some are digital. All can use microcontroller interfaces again digital or analog. Two analog devices are LM34 and LM35, they are very easy to use because the voltage output is directly | + | Some are analog some are digital. All can use microcontroller interfaces again digital or analog. Two analog devices are LM34 and LM35, they are very easy to use because the voltage output is directly proportional to the temperature. Dallas semiconductor makes a line of sensors based on their one wire networking, cool. Temperature may also be sensed by thermistors ( temperature sensitive resistors ), the forward voltage on a diode ( or transistor ) or by thermocouples ( junctions of two different conductors ). Thermocouples can work up to almost the melting temperature of the conductors. You can also sense temperature based on the light emitted ( usually ir ) from the object. Many of the temperature sensors can be highly non-linear in their response, programming in a microcontroller can be used to linearize the readings. |
| + | |||
| + | === Stress Sensor === | ||
| + | Also know as strain gage. Often based on materials where the resistance varies when elongated. Typically have very small signal output that are measured in bridge configurations. | ||
| + | |||
| + | === Pressure and Barometric Sensor === | ||
| + | Solid state units have become available for this. We need more material here. They can be used for weather stations, measuring altitude, or measuring pressure. | ||
| + | |||
| + | === Capacitive Sensor === | ||
| + | These measure capacitance, but normally this is the means to measuring something else: for example moving your hand close to a metal plate increases its capacitance to ground. Measuring the capacitance thus measures the the touch ( or near touch ). Two insulated electrodes on either side of a glass tube can detect the presence of water in the tube by the change capacitance. | ||
== Further Reading == | == Further Reading == | ||
Revision as of 19:16, 30 March 2008
Accelerometers, Gyroscopes, Temperature Sensors, Pressure Sensors, ...
Contents
Accelerometer
These measure ( gasp ) acceleration. May be caused by gravity or the second derivative of position ( relative to an inertial frame ). Since acceleration is a vector to go the whole distace you need a 3 axis sensor, but often 1 or 2 D will do. Often the output is a voltage(s). Feed it to a microcontroller with an a to d converter, perhaps through an operational amplifier. Op amp
- Accelerometer Breakout Board - ADXL322 +/-2g SKU#: SEN-00849 Price: $29.95 From SparkFun. Also links to other info.
- Buffered ±2g Accelerometer Product ID: DE-ACCM2G Price: $22.95 Also other links.
- PIC Links Then search for Accelerometer.
Gas sensor
MiCS 4514 CO and NOx sensor
Knock Sensor
Magnetic Field Sensor
Photo Diode/Transistor
Rotary Encoder
A rotary encoder is a device that measure ( or encodes ) rotational motion. The old fashioned mice with a ball used dual rotery encoders one to measure motion in the x direction one to measure motion in the y direction. This may be done using switching technology or by using optical methods ( so some encoders may be considered optical electronics ). Even stepper motors may be used as rotary encoders. It normally requires a microcontroller ( or speciality chip ) to decode the signals. In addition to mice rotary encoders are used for the user control on volume controls ( finally coupled to say digital potentiaometrs ), measure the position of joints in robots, or measuring the speed and/or positon of motors ( as in some servo motors ).
- Reading Rotary Encoders
- An Electronic Counter Project for Digital and Analog Signals, including Quadrature Encoders
Linear Encoder
Like rotary encoders but for linear motion. Modern digital calipers are based on this technology ( i think ). Positioning of print heads in computers may also uses this to position the print head.
Temperature Sensor
Some are analog some are digital. All can use microcontroller interfaces again digital or analog. Two analog devices are LM34 and LM35, they are very easy to use because the voltage output is directly proportional to the temperature. Dallas semiconductor makes a line of sensors based on their one wire networking, cool. Temperature may also be sensed by thermistors ( temperature sensitive resistors ), the forward voltage on a diode ( or transistor ) or by thermocouples ( junctions of two different conductors ). Thermocouples can work up to almost the melting temperature of the conductors. You can also sense temperature based on the light emitted ( usually ir ) from the object. Many of the temperature sensors can be highly non-linear in their response, programming in a microcontroller can be used to linearize the readings.
Stress Sensor
Also know as strain gage. Often based on materials where the resistance varies when elongated. Typically have very small signal output that are measured in bridge configurations.
Pressure and Barometric Sensor
Solid state units have become available for this. We need more material here. They can be used for weather stations, measuring altitude, or measuring pressure.
Capacitive Sensor
These measure capacitance, but normally this is the means to measuring something else: for example moving your hand close to a metal plate increases its capacitance to ground. Measuring the capacitance thus measures the the touch ( or near touch ). Two insulated electrodes on either side of a glass tube can detect the presence of water in the tube by the change capacitance.
Further Reading
- WSN:Sensors
- Interfacing with Hardware See the section on "Input" Writtern for the arduino but usefull just for the info on sensors.
- Welcome to the ITP Sensor Workshop Wiki. A whole wiki on sensors, looks good.
