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university:courses:electronics:electronics-lab-window-comp-tmp01 [07 Mar 2018 12:20]
Antoniu Miclaus add hardware setup and procedure
university:courses:electronics:electronics-lab-window-comp-tmp01 [03 Jan 2021 22:21]
Robin Getz fix links
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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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 ===== Window Comparator ===== ===== Window Comparator =====
 +
 ==== Background ==== ==== Background ====
  
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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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  On the plot the "​windows"​ can be noticed when the input voltage is between the upper and the lower voltage references.  On the plot the "​windows"​ can be noticed when the input voltage is between the upper and the lower voltage references.
 +
 +===== Temperature Control =====
 +
 +==== Background ====
 +
 +An example of a window comparator application is a simple temperature controller circuit (Figure 2). The temperature sensor, TMP01, has the dual comparator configuration of figure 1 built in. By choosing the proper values for R<​sub>​1</​sub>,​ R<​sub>​2</​sub>​ and R<​sub>​3</​sub>​ the circuit monitors if the temperature holds in the required range (25 ± ~10 °C).
 +
 +The TMP01 is a linear voltage-output temperature sensor, with a window comparator that can be programmed by the user to activate one of two open-collector outputs when a predetermined temperature set point voltage has been exceeded. A low drift voltage reference is available for set point programming. By connecting the two open collector outputs together as a single wire OR output we can obtain a signal which is at a logic high when the ambient temperature is within the target window.
 +
 +<WRAP centeralign>​{{:​university:​courses:​electronics:​tmp01_window_comp-sch.png|}}</​WRAP>​
 +
 +<WRAP centeralign>​ Figure 4 Temperature sensor window comparator </​WRAP>​
 +
 +==== Programming TMP01 ====
 +
 +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.
 +
 +2. Calculate the hysteresis current I<​sub>​VREF</​sub>​.
 +
 +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.
 +
 +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:
 +
 +V<​sub>​SETHIGH</​sub>​ = (T<​sub>​SETHIGH</​sub>​+ 273.15) (5 mV/°C)
 +
 +V<​sub>​SETLOW</​sub>​ = (T<​sub>​SETLOW</​sub>​ + 273.15) (5 mV/°C)
 +
 +R<​sub>​1</​sub>​ (in kΩ) = (V<​sub>​VREF</​sub>​−V<​sub>​SETHIGH</​sub>​)/​I<​sub>​VREF</​sub>​= (2.5 V −V<​sub>​SETHIGH</​sub>​)/​I<​sub>​VREF</​sub>​
 +
 +R<​sub>​2</​sub>​ (in kΩ) = (V<​sub>​SETHIGH</​sub>​−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>​.
 +
 +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]]**
 +
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university/courses/electronics/electronics-lab-window-comp-tmp01.txt · Last modified: 03 Jan 2021 22:21 by Robin Getz