Designing and building a digital thermometer - Revision history

Mariush: /* Source code */

2014-07-27T23:46:09Z

‎Source code

Mariush at 23:38, 27 July 2014

2014-07-27T23:38:57Z

Mariush at 23:38, 27 July 2014

2014-07-27T23:38:30Z

Mariush at 23:38, 27 July 2014

2014-07-27T23:38:12Z

Mariush at 23:36, 27 July 2014

2014-07-27T23:36:54Z

Mariush at 20:22, 4 June 2014

2014-06-04T20:22:25Z

Mariush at 19:43, 4 June 2014

2014-06-04T19:43:49Z

Mariush at 18:41, 4 June 2014

2014-06-04T18:41:04Z

Mariush at 17:34, 4 June 2014

2014-06-04T17:34:40Z

Mariush at 17:34, 4 June 2014

2014-06-04T17:34:01Z

← Older revision		Revision as of 23:46, 27 July 2014
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	Both MPLAB X and XC8 were installed in C:\Programs\Microchip (the project should not care about paths).		Both MPLAB X and XC8 were installed in C:\Programs\Microchip (the project should not care about paths).

		+	==Further Reading==
		+
		+	* [http://forum.allaboutcircuits.com/showthread.php?t=80018 Why ADC/1024 is correct, and ADC/1023 is just plain wrong!]
		+	* [http://electronics.stackexchange.com/questions/26356/how-can-high-temperatures-be-measured-with-arduino-uno-and-type-k-thermocouple-w AD595 related questions and answers, ADC impedance, using AD595 with microcontrollers]

	==Components==		==Components==

← Older revision		Revision as of 23:38, 27 July 2014
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	__NOTOC__		__NOTOC__

−	[[File:Icon information mini.png\|left]] This project was updated on the 28<sup>th</sup> of July. Please scroll down to see the new additions.	+	[[File:Icon information mini.png\|left]] This project page was updated on the 28<sup>th</sup> of July, 2014. Please scroll down to see the new additions.

← Older revision		Revision as of 23:38, 27 July 2014
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	__NOTOC__		__NOTOC__
		+
	[[File:Icon information mini.png\|left]] This project was updated on the 28<sup>th</sup> of July. Please scroll down to see the new additions.		[[File:Icon information mini.png\|left]] This project was updated on the 28<sup>th</sup> of July. Please scroll down to see the new additions.

@@ Line 1: / Line 1: @@
 __NOTOC__
 [[File:Icon information mini.png|left]] This project was updated on the 28<sup>th</sup> of July. Please scroll down to see the new additions.
 ==Introduction==

@@ Line 1: / Line 1: @@
 __NOTOC__
 ==Introduction==
-In this video tutorial, a digital thermometer is designed and built.
+In this video tutorial, a digital thermometer is designed and built using the commonly available AD595 thermocouple amplifier and an 8bit PIC16F1519 microcontroller.
 ==Description==
@@ Line 65: / Line 67: @@
 In '''Part 3''', the source code is explained in detail, along with suggestions regarding optimizing the project for use with other microcontrollers that may not have as many input-output pins or may have less resources available.
 ==Source code==
-The source code is available [http://www.helpedia.com/downloads/articles/digital_thermometer/digital_thermometer.zip here (ZIP, 263 KB)]. You can also view a basic [http://www.helpedia.com/downloads/articles/digital_thermometer/circuit.png circuit schematic].
+The source code is available [http://www.helpedia.com/downloads/articles/digital_thermometer/thermometer.revisited.zip here (ZIP, 263 KB)]. You can also view a basic [http://www.helpedia.com/downloads/articles/digital_thermometer/circuit.png circuit schematic].
 The project was created using MPLAB X 2.05 and it uses the XC8 Free compiler, both available on [http://www.microchip.com/ Microchip]'s website.

@@ Line 30: / Line 30: @@
 The first part chosen for this thermometer is a cheap [http://en.wikipedia.org/wiki/Thermocouple#Type_K K type thermocouple] supplied by Labfacility.
 The part is only rated for up to 250°C but the author suspects this low rating is simply due to the isolating material used and due to the small diameter of the wire. For designing, testing and building this project, this thermocouple is good enough - if it turns out the thermocouple can not handle temperatures higher than 250°C, it's always possible to purchase one of those more expensive high temperature thermocouples that can measure up to 800-1350°C.
@@ Line 50: / Line 52: @@
 It is possible to use other microcontrollers - for example Arduino - but an external voltage reference may be needed in that case, which increases complexity and cost of this project.
 Instead of using cheap LCD 2x16 displays, a seven segment LED display is used, giving the opportunity to explain how these displays work and make the tutorial more interesting.
-The only seven segment display found in the box of spare parts is an Avago Technologies HDSP-B03E 4-digit LED display. The clock style arrangement of the segments is just a minor inconvenience which can be worked around, the principles of operation are the same for other seven segment LED displays.
+The only suitable seven segment display recycled from other projects is an Avago Technologies HDSP-B03E 4-digit LED display. The clock style arrangement of the segments is just a minor inconvenience which can be worked around, the principles of operation are the same for other seven segment LED displays.
 Four BC337-25 NPN transistors help the microcontroller switch each LED digit on or off, and a 5v ST Micro L7805ABP linear regulator makes sure the microcontroller receives clean power, no matter what type of battery is used to power the AD595 thermocouple amplifier chip.
 '''Part 2''' shows viewers the build process along with explanations about various decisions made during the build process.
 There are also some small additions to the design, such as a DC input jack and a current sense resistor, used to measure the current consumption of the completed project.
 In '''Part 3''', the source code is explained in detail, along with suggestions regarding optimizing the project for use with other microcontrollers that may not have as many input-output pins or may have less resources available.
@@ Line 68: / Line 68: @@
 ==Source code==
-The source code is available here: (to be added later).
+The source code is available [http://www.helpedia.com/downloads/articles/digital_thermometer/digital_thermometer.zip here (ZIP, 263 KB)]. You can also view a basic [http://www.helpedia.com/downloads/articles/digital_thermometer/circuit.png circuit schematic].
 The project was created using MPLAB X 2.05 and it uses the XC8 Free compiler, both available on [http://www.microchip.com/ Microchip]'s website.

@@ Line 42: / Line 42: @@
 * it works powered from a simple, positive only power supply and with as little as 5V, if only positive temperatures need to be measured.
-By design, the IC is only capable to output a voltage that's 2V lower than the power supply voltage - with a small 5V power supply, the AD595 would only be able to correctly report temperatures up to about 300°C. As the requirements call for a maximum of 500°C, the IC will have to be powered using at least 7.1V, which limits the choices when it comes to what type of batteries can be used to power the whole project.
+By design, the IC is only capable to output a voltage that's 2V lower than the power supply voltage - with a small 5V power supply, the AD595 would only be able to correctly report temperatures up to about 300°C. As the requirements call for a maximum of 500°C, the IC will have to be powered using at least 7.1V, which makes choosing a battery for this project a bit easier.
 {{#ev:youtubehd|Vq3gZNG5loQ|480|right|Part 2 of 3}}
 '''Part 2''' shows viewers the build process along with explanations about various decisions made during the build process.
 There are also some small additions to the design, such as a DC input jack and a current sense resistor, used to measure the current consumption of the completed project.
 {{#ev:youtubehd|5q9RHUS1HB4|480|right|Part 3 of 3}}
 In '''Part 3''', the source code is explained in detail, along with suggestions regarding optimizing the project for use with other microcontrollers that may not have as many input-output pins or may have less resources available.
 ==Source code==
@@ Line 68: / Line 74: @@
 Both MPLAB X and XC8 were installed in C:\Programs\Microchip (the project should not care about paths).
-This section contains datasheets for the components used by this project:
+==Components==
-* Datasheet 1
+This section contains the components used in the project, along with links to their datasheets
 * Labfacility [http://uk.farnell.com/labfacility/z2-k-1m-iec/sensor-thermocouple-k-1m-ptfe/dp/7076150 Z2-K-1M (IEC)] - K type thermocouple, 1m, PTFE, -75c - +250c
+* Analog Devices [http://uk.farnell.com/analog-devices/ad595aq/amp-thermocouple-type-k-3-c-14dip/dp/409194 AD595AQ] - thermocouple amplifier, Type K, ± 3°C, 14DIP
 ==Online Stores==

@@ Line 33: / Line 33: @@
 The part is only rated for up to 250°C but the author suspects this low rating is simply due to the isolating material used and due to the small diameter of the wire. For designing, testing and building this project, this thermocouple is good enough - if it turns out the thermocouple can not handle temperatures higher than 250°C, it's always possible to purchase one of those more expensive high temperature thermocouples that can measure up to 800-1350°C.
-K type thermocouples output a small voltage as the temperature changes where the two different alloys are welded together - for K type thermocouples this voltage is about 41
+K type thermocouples output a small voltage as the temperature changes where the two different alloys are welded together - for K type thermocouples this voltage is 40.44 mV/°C. Such voltage is too low to be measured reliably using a regular multimeter and the output of a thermocouple so a thermocouple amplifier IC or a precision operational amplifier is required to boost this voltage to levels which can be measured easily.
 {{#ev:youtubehd|Vq3gZNG5loQ|480|right|Part 2 of 3}}

@@ Line 8: / Line 8: @@
 {{#ev:youtubehd|me1bqCAaraI|480|right|Part 1 of 3}}
-'''Part 1''' of this video tutorial introduces viewers to the reasons why a digital thermometer is useful for a hobbyist and how such a tool differs from others, such as infrared thermometers.
+'''Part 1''' of this video tutorial starts by introducing viewers to the reasons why a digital thermometer is useful for a hobbyist and why such a tool differs from other tools, such as infrared thermometers.
 Infrared thermometers have the advantage of being able to measure the temperature of a surface at a particular distance, but they some disadvantages:

← Older revision		Revision as of 17:34, 4 June 2014
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		+	__NOTOC__
	==Introduction==		==Introduction==