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university:courses:electronics:electronics-lab-window-comp-tmp01 [07 Mar 2018 12:36] Antoniu Miclaus add tmp01 background and programming |
university:courses:electronics:electronics-lab-window-comp-tmp01 [25 Jun 2020 22:07] external edit |
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===== Objective ===== | ===== Objective ===== | ||

- | The objective of this lab activity is to use two high speed voltage comparators as a Window-Comparator and program the [[http://www.analog.com/media/en/technical-documentation/data-sheets/TMP01.pdf|TMP01]] Low Power Programmable Temperature Controller using this approach. | + | The objective of this lab activity is to use two high speed voltage comparators as a Window-Comparator and program the TMP01 Low Power Programmable Temperature Controller using this approach. |

A Window-Comparator is a circuit configuration, usually consisting of a pair of voltage comparators (inverting and non-inverting), in which the output indicates whether an input signal is within the voltage range bounded by two different thresholds. One which triggers an op-amp comparator on detection of some upper voltage threshold, V<sub>REF(HIGH)</sub> and one which triggers an op-amp comparator on detection of a lower voltage threshold level, V<sub>REF(LOW)</sub>. The voltage levels between these two upper and lower reference voltages is called the “window”. | A Window-Comparator is a circuit configuration, usually consisting of a pair of voltage comparators (inverting and non-inverting), in which the output indicates whether an input signal is within the voltage range bounded by two different thresholds. One which triggers an op-amp comparator on detection of some upper voltage threshold, V<sub>REF(HIGH)</sub> and one which triggers an op-amp comparator on detection of a lower voltage threshold level, V<sub>REF(LOW)</sub>. The voltage levels between these two upper and lower reference voltages is called the “window”. | ||

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==== Procedure ==== | ==== Procedure ==== | ||

- | Use the first waveform generator (W1) as source to provide a Triangular signal with 5V amplitude, 100Hz frequency and 2.5V offset. | + | Use the first waveform generator (W1) as source to provide a Triangular signal with 5V amplitude peak-to-peak, 100Hz frequency and 2.5V offset. |

Use the second waveform generator (W2) as 5V constant reference voltage. | Use the second waveform generator (W2) as 5V constant reference voltage. | ||

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In the basic fixed set point application utilizing a simple resistor ladder voltage divider, the desired temperature set points are programmed in the following sequence: | In the basic fixed set point application utilizing a simple resistor ladder voltage divider, the desired temperature set points are programmed in the following sequence: | ||

+ | |||

1. Select the desired hysteresis temperature. | 1. Select the desired hysteresis temperature. | ||

+ | |||

2. Calculate the hysteresis current I<sub>VREF</sub>. | 2. Calculate the hysteresis current I<sub>VREF</sub>. | ||

+ | |||

3. Select the desired set point temperatures. | 3. Select the desired set point temperatures. | ||

+ | |||

4. Calculate the individual resistor divider ladder values needed to develop the desired comparator set point voltages at SET HIGH and SET LOW. | 4. Calculate the individual resistor divider ladder values needed to develop the desired comparator set point voltages at SET HIGH and SET LOW. | ||

+ | |||

The hysteresis current is readily calculated. For example, for 2 degrees of hysteresis, I<sub>VREF</sub> = 17 μA. Next, the set point voltages, V<sub>SETHIGH</sub> and V<sub>SETLOW</sub>, are determined using the VPTAT scale factor of 5 mV/K = 5 mV/(°C + 273.15), which is 1.49 V for 25°C. Then, calculate the divider resistors, based on those set points. The equations used to calculate the resistors are: | The hysteresis current is readily calculated. For example, for 2 degrees of hysteresis, I<sub>VREF</sub> = 17 μA. Next, the set point voltages, V<sub>SETHIGH</sub> and V<sub>SETLOW</sub>, are determined using the VPTAT scale factor of 5 mV/K = 5 mV/(°C + 273.15), which is 1.49 V for 25°C. Then, calculate the divider resistors, based on those set points. The equations used to calculate the resistors are: | ||

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R<sub>3</sub> (in kΩ) = V<sub>SETLOW</sub>/I<sub>VREF</sub> | R<sub>3</sub> (in kΩ) = V<sub>SETLOW</sub>/I<sub>VREF</sub> | ||

- | The total R<sub>1<sub> + R<sub>2</sub> + R<sub>3</sub> is equal to the load resistance needed to draw the desired hysteresis current from the reference, or I<sub>VREF</sub>. | + | The total R<sub>1</sub> + R<sub>2</sub> + R<sub>3</sub> is equal to the load resistance needed to draw the desired hysteresis current from the reference, or I<sub>VREF</sub>. |

+ | | ||

+ | I<sub>VREF</sub> = 2.5V/( R<sub>1</sub> + R<sub>2</sub> + R<sub>3</sub>) | ||

+ | | ||

+ | Since VREF = 2.5 V, with a reference load resistance of 357 kΩ or greater (output current 7 μA or less), the temperature setpoint hysteresis is zero degrees. Larger values of load resistance only decrease the output current below 7 μA and have no effect on the operation of the device. The amount of hysteresis is determined by selecting a value of load resistance for VREF. | ||

+ | | ||

+ | ==== Tasks ==== | ||

+ | | ||

+ | 1. Build the following circuit: | ||

+ | | ||

+ | <WRAP centeralign>{{:university:courses:electronics:tmp01-bb1.png|}}</WRAP> | ||

+ | | ||

+ | <WRAP centeralign> Figure 5 Temperature Measurement </WRAP> | ||

+ | | ||

+ | Measure VPTAT output value and compute the actual measured temperature in degrees Kelvin and degrees Celsius. | ||

+ | | ||

+ | 2. Build the following circuit: | ||

+ | | ||

+ | <WRAP centeralign>{{:university:courses:electronics:tmp01-bb2.png|}}</WRAP> | ||

+ | | ||

+ | <WRAP centeralign> Figure 6 Temperature Control </WRAP> | ||

+ | | ||

+ | 2.a. Identify the components and try to draw the circuit schematic. | ||

+ | | ||

+ | 2.b. Using the information provided by the breadboard circuit, compute the following parameters: | ||

+ | | ||

+ | * I<sub>VREF</sub> | ||

+ | * V<sub>SETHIGH</sub> | ||

+ | * V<sub>SETLOW</sub> | ||

+ | * T<sub>SETHIGH</sub> | ||

+ | * T<sub>SETLOW</sub> | ||

+ | | ||

+ | 2.c. How many degrees is the temperature setpoint hysteresis? How can you change this value? | ||

+ | | ||

+ | 2.d. How does the circuit work? When will LED1 (red) and LED2 (blue) turn on? Explain your answer. | ||

+ | | ||

+ | <WRAP round download> | ||

+ | **Lab Resources:** | ||

+ | * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/temp_ctrl_bb | temp_ctrl_bb]] | ||

+ | * LTspice files: [[downgit>education_tools/tree/master/m2k/fritzing/temp_ctrl_ltspice | temp_ctrl_ltspice]] | ||

+ | </WRAP> | ||

+ | ===== Further Reading ===== | ||

+ | | ||

+ | Additional resources: | ||

+ | | ||

+ | * [[http://www.analog.com/static/imported-files/data_sheets/TMP01.pdf|TMP01 Low Power Programmable Temperature Controller]] | ||

+ | * [[http://www.analog.com/library/analogdialogue/archives/42-10/testing_comparators.html|Adding Test Capability to a Window Comparator]] | ||

+ | | ||

+ | **Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]** | ||

+ | | ||

+ | | ||

+ | | ||

+ | | ||

+ | | ||

+ | | ||

+ | | ||

- | I<sub>VREF</sub> = 2.5/( R<sub>1</sub> + R<sub>2</sub> + R<sub>3</sub>) | ||

university/courses/electronics/electronics-lab-window-comp-tmp01.txt · Last modified: 03 Jan 2021 22:21 by Robin Getz