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university:courses:electronics:electronics-lab-window-comp-tmp01 [07 Mar 2018 12:36] – add tmp01 background and programming Antoniu Miclausuniversity:courses:electronics:electronics-lab-window-comp-tmp01 [03 Jan 2021 22:21] (current) – fix links Robin Getz
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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: 
 + 
 +  * [[adi>static/imported-files/data_sheets/TMP01.pdf|TMP01 Low Power Programmable Temperature Controller]] 
 +  * [[adi>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

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