The Intel Galileo Microcontroller - Term Paper Example

Temperature Sensor Design With Intel Galileo Name of Student Institution affiliation Date Abstract A temperature sensor is an electronic device that detects continuous value of temperature at its surface and digitizes it through a signal conditioning process. This project was focused on the design of a temperature sensor and conditioning and processing using the intel galileo microcontroller development kit. Conversely, the project was aimed at developing a digital thermometer using a thermistor. Proper connection through a passive element network was developed, and the controller code written for the Galileo board using Arduino IDE. The values were read through the analog data input pin since temperature varies in a continuous spectrum as it changes in values with the environment. Since a thermistor isn’t designed to read standard temperature values, a few conversion parameters were incorporated in the coding so as to standardize the temperature and use the thermistor as a temperature thermometer or otherwise as a digital thermometer. Introduction Temperature is the degree of heat present on a surface of a body. It is transferred from one body to another owing to an existing gradient with two points of surfaces having a difference in the degree of heat. Temperature is measured in Kelvin as the SI unit. However, other measurement units are commonly employed depending with region and ease of application and understanding. For instance, the metric units that is most common for temperature measurement is the degree Celsius. Other unit of measurement is the degree Farenheight. The surface temperature need a transducer in order to be captured electronically. Such transducer that best befits temperature reading criteria is the thermistor. It forms the base component for converting heat energy to electrical energy. (Bailey, 2013) As it is with other sensor technologies, it is important to note that there exist other technologies used to record and process temperature digitally. One other such technology is the use of the bimetallic strip with connected electrodes that are used as terminals to transmit the electric signals generated at the junction of the two metal rods. Calibration of the measurement as it is with the thermistor is done by the code that is embedded on the controller chip. (John, 2011) Temperature sensors are classified according to the mechanism by which they obtain their values. There are two major classifications of the sensor type. Those that depend on change in impedance, also referred to as resistive and those that rely on change in voltage. The resistive type include the Thermistor and the Resistance Temperature Detectors (RTD). Those that are based on change in internal voltage include the thermocouple and the thermopile. Other types of sensors that are used to measure temperature are as enlisted below: Radiation pyrometer Optical pyrometer Bimetallic Thermometer Thermo wells Filled system Temperature Measurement The challenge that is posed therefore is to determine the best and most affordable design to use in the modelling process and one that would be easy to integrate with the Intel Galileo microcontroller programming kit and board. (Bailey, 2013) Literature Review To make a temperature sensor with the Intel Galileo board, it was presumed that it was prudent to use the thermistor. The choice of selection was based upon a number of temperature parameters that were considered, some of which are as follows: Range This refer to the maximum and minimum values that can be obtained or measured by the sensor device. By rule of thumb, the range should be determined such that the device can measure 50 – 70 % of the normal operating temperature. Span Also referred to as the calibrated range, the span is the difference between the maximum and the minimum values of temperature that can be obtained. Immersion length This refers to the distance between the free end or the tip of the measuring device and the point at which the probes are protruding. It dictates the area of impact and thus the effectiveness of temperature reading. Insertion length It is almost the same in definition as immersion length but with exclusion of the external threads. Turn down It refers to the ratio of the maximum measurable parameter to the minimum measurable parameter of the device. For the case of the thermistor, which was used for this project, the above criteria were found to be optimally operative and had the best finite parameters that can be used in both reading and calibration of the temperature values. From comparative analysis, the thermistor was also found to be exhibiting a fast response speed which can be shown from the table below: (Boise, 2016) The Thermistor The thermistor as earlier introduced is an impedance based device used to measure temperature. It is a type of resistor whose change in resistance is proportional to change in temperature. It was invented in 1930 by Samuel Reuben. It owes its name from the two words Thermal and resistor. It is symbolized as shown below: Thermistors are known to have an extensively higher affectability than most different sensors, yet they are likewise substantially less straight. Albeit extraordinary high-temperature sensors, for example, chromium oxide artistic thermistors made by GE Sensing can work up to 1000oC, ordinary gadgets have a generally contract temperature run and are not an ideal decision when long haul exactness is required. Be that as it may, thermistors are generally less costly than alternate sensors and respond speedier to temperature changes. (G., 2016) All sensors require linearization, yet each to an alternate degree. Likewise, to accomplish high exactness the circuit must be aligned with the real thermistor sensor associated. These two undertakings can be expert with simple conditioners and alignment circuits, however they can be very intricate and require manual adjustment. On the off chance that an advanced plan is utilized rather, the sensor flag is digitized by an Analog to Digital converter (ADC) and the linearization and alignment are done in programming with least human contribution. (Boise, 2016) Thermistors are solid state devices. They are made in two distinct types: the Negative Temperature Coefficient (NTC) and the Positive Temperature Coefficient (PTC). For the NTC, the Resistance is inversely proportional to Temperature. Changes with the terminal temperature could arise from ambient heat or from self-heating as a result of current excitation, or still it could be from both causes (H., 1984). The temperature curve for the NTC is as shown below: For the PTC, the resistance of the thermistor is directly proportional to the change in terminal temperature. As ambient heat or self heating action increases, so does the terminal temperature increase. The relationship for PTC is almost linear and thus helpful in using it as a measuring device (John, 2011). The images of the thermistor is as shown below: Where a. is the disc thermistor, b. is uncoated disc thermistor with radial leads, c. is coated thermistor with epoxy, d. is epoxy coated chip with insulated radial leads. Resistance for the thermistor is theoretically obtained from the equation: R = [RTM(RTL + RTH) – 2RTLRTH] / [RTL + RTH – 2RTM] Where: R = value of parallel resistor, Ω RTL = thermistor resistance at the lowest temperature TL, ? RTH = thermistor resistance at the highest temperature TH, Ω RTM = thermistor resistance at the midpoint temperature TM, Ω Midpoint temperature TM = (TL + TH) / 2, °C (Boise, 2016) Design Thermistors cannot be used effectively unless they are linearized. Linearization is done by adding a resistor in series with the thermistor (Bailey, 2013). This is as shown: In the implementation of the temperature sensor, The circuit was made as shown below with the breadboard connectivity as captured from the simulated diagram shown though in practice intel galileo was used: The data input was tapped at the center piece where the joint between the thermistor and the 100K Ohms resistor exists. It was then connected to the analog pin 0. In practice the connection was as shown with the yellow cable being the data input at pin 0, the red connected to Vcc while the black was connected to the common: Conclusion The use of thermistor to design the temperature sensor was successful and with ease due to a number of contributing factors. Suffice to say that the accuracy and sensitivity was excellent as viewed from the serial monitor that was run at display during the practical session. A few factors that oversaw the success of the project in using the thermistor include: High resistance: This plays a significant role in ensuring that the resistance of lead wires is effectively reduced. Also, only a single wire is used to relay data to the microcontroller kit hence less prone to stray resistances. Cost: the thermistor was the far most economical chip to obtain. With their mass market production and requiring no physical calibration, it was easy and cheap to acquire for the practical. Speed: The thermistor is small in size and hence relatively low thermal time constant. This therefore resulted in high speed response of the thermistor chip. References Bailey, D. (2013). Building Arduino Powered BBQ Thermometer. Safaribooks. Boise. (20 October 2016 г.). Quality Thermistor. thermistor.com: www.thermistor.com G., J. R. (17 October 2016 г.). Engineering Exchange. Engineeringexchange.com: www.designworldonline.com H., S. P. (1984). Transducers in Measurement and Control. Australia: CRC Press. John. (18 August 2011 г.). Temperature Sensors. Получено из IT Instrumentation Today: www.intrumentationtoday.com Read More

The choice of selection was based upon a number of temperature parameters that were considered, some of which are as follows: Range This refer to the maximum and minimum values that can be obtained or measured by the sensor device. By rule of thumb, the range should be determined such that the device can measure 50 – 70 % of the normal operating temperature. Span Also referred to as the calibrated range, the span is the difference between the maximum and the minimum values of temperature that can be obtained.

Immersion length This refers to the distance between the free end or the tip of the measuring device and the point at which the probes are protruding. It dictates the area of impact and thus the effectiveness of temperature reading. Insertion length It is almost the same in definition as immersion length but with exclusion of the external threads. Turn down It refers to the ratio of the maximum measurable parameter to the minimum measurable parameter of the device. For the case of the thermistor, which was used for this project, the above criteria were found to be optimally operative and had the best finite parameters that can be used in both reading and calibration of the temperature values.

From comparative analysis, the thermistor was also found to be exhibiting a fast response speed which can be shown from the table below: (Boise, 2016) The Thermistor The thermistor as earlier introduced is an impedance based device used to measure temperature. It is a type of resistor whose change in resistance is proportional to change in temperature. It was invented in 1930 by Samuel Reuben. It owes its name from the two words Thermal and resistor. It is symbolized as shown below: Thermistors are known to have an extensively higher affectability than most different sensors, yet they are likewise substantially less straight.

Albeit extraordinary high-temperature sensors, for example, chromium oxide artistic thermistors made by GE Sensing can work up to 1000oC, ordinary gadgets have a generally contract temperature run and are not an ideal decision when long haul exactness is required. Be that as it may, thermistors are generally less costly than alternate sensors and respond speedier to temperature changes. (G., 2016) All sensors require linearization, yet each to an alternate degree. Likewise, to accomplish high exactness the circuit must be aligned with the real thermistor sensor associated.

These two undertakings can be expert with simple conditioners and alignment circuits, however they can be very intricate and require manual adjustment. On the off chance that an advanced plan is utilized rather, the sensor flag is digitized by an Analog to Digital converter (ADC) and the linearization and alignment are done in programming with least human contribution. (Boise, 2016) Thermistors are solid state devices. They are made in two distinct types: the Negative Temperature Coefficient (NTC) and the Positive Temperature Coefficient (PTC).

For the NTC, the Resistance is inversely proportional to Temperature. Changes with the terminal temperature could arise from ambient heat or from self-heating as a result of current excitation, or still it could be from both causes (H., 1984). The temperature curve for the NTC is as shown below: For the PTC, the resistance of the thermistor is directly proportional to the change in terminal temperature. As ambient heat or self heating action increases, so does the terminal temperature increase.

The relationship for PTC is almost linear and thus helpful in using it as a measuring device (John, 2011). The images of the thermistor is as shown below: Where a. is the disc thermistor, b. is uncoated disc thermistor with radial leads, c. is coated thermistor with epoxy, d. is epoxy coated chip with insulated radial leads. Resistance for the thermistor is theoretically obtained from the equation: R = [RTM(RTL + RTH) – 2RTLRTH] / [RTL + RTH – 2RTM] Where: R = value of parallel resistor, Ω RTL = thermistor resistance at the lowest temperature TL, ?

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