ELECTRICAL ENGINEERING TECHNOLOGY PROGRAM EET 331 – ELECTRONIC DESIGN LABORATORY EXPERIENCES LABORATORY EXPERIENCE: FREQUENCY AND LIGHT CONVERSION This laboratory experience introduces the concepts of frequency-to-voltage and light-to-frequency conversion. It also introduces students to working with new integrated circuits. PART 1.- THE FREQUENCY-TO-VOLTAGE CONVERTER Frequency-to-voltage (F/V) converters are devices that output a signal proportional to the frequency of the signal at their input. Therefore, they can be used to measure the frequency of an unknown signal with just a simple DMM. The F/V converter used in this laboratory experiment is the LM2907 from National Semiconductor. The LM2907 can be powered between 10 to 15 Volts and ground. 1.1 Design a frequency-to-voltage converter with the following transfer function: Vout = 10-3 fin (1) with Vout being the output voltage in Volts and fin the input frequency in Hz. 1.2 Test and verify your design using a square wave. You may have to modify the parameters of the test signal if necessary. Once it is working, repeat the process for a triangular and a sine signal. EET 331 – Frequency and light conversion 1/41.3 Complete the table below. The table represents the minimum voltage of the input signal that will trigger the F/V converter as well as the maximum DC offset, positive and negative for the converter to operate correctly. min Vin (peak) + Voffset - Voffset Square Triangular Sine 1.4 In order to characterize equation (1), create a table that represents the output voltage for different input frequencies. Use your best judgment to determine the range and number of frequencies that you will be testing. Justify your decisions. fin Vout 1.5 Plot the data from the table. Investigate the linearity the frequency-to-voltage conversion. What is the factor that limits the maximum frequency that can be used? 1.6 Set the function generator to produce a FM signal within the operating ranges of the converter. Use this signal as the input to the frequency-to-voltage converter. Verify that the output corresponds to the modulating signal. Do not disassemble your design as it will be used later in Part 3. PART 2.- THE LIGHT-TO-FREQUENCY CONVERTER The TSL230R manufactured by Texas Advanced Optoelectronic Solutions (TAOS) is a device that produces a square wave whose frequency is proportional to the intensity of the light received by the sensor. Note that the TSL230R has a control for its sensitivity and a frequency divider in order to maximize its operational range. 2.1 Set up the TSL230R to operate in the electronics laboratory. EET 331 – Frequency and light conversion 2/42.2 Measure the output frequency for the different scaling factors. The signal may be affected by phase jitter and difficult to measure. If this is the case, you will have to use the memory from the digital oscilloscope to make the measurement. 2.3 For the normal light in the electronics laboratory, what seems to be the best frequency scaling factor? What is its frequency? Use Figure 1 to estimate the irradiance in the electronics laboratory. 2.4 Repeat parts (2.2) and (2.3) by now illuminating the TSLR230R with a flashlight. PART 3.- LIGHT/FREQUENCY AND F/V CONVERTER The TSL230R generates a signal with a frequency proportional to the intensity of light. The LM2907 generates a voltage proportional to the frequency of the input signal. We can combine them in order to create a design that will produce a voltage proportional to the intensity of light. 3.1 Combine the two previous designs in order to have a circuit that will output a DC voltage proportional to the intensity of light. Verify that it works correctly. 3.2 If it does not work, you may want to revisit your data from the table from 1.3. Based on that table, modify your circuit to make it work. Explain your solution. 3.3 For a given sensitivity for the TSL230R, what is the change in DC voltage between the normal illumination in the electronics lab and a flashlight? 3.4 Without using the flashlight, observe the output signal with the oscilloscope. Couple the oscilloscope in AC. Increase the sensitivity until you observe an AC signal. What is its frequency? Where is this signal coming from? EET 331 – Frequency and light conversion 3/4EET 331 – Frequency and light conversion 4/4 PART 4. Laboratory report - Create an individual lab report using the guidelines provided in the course’s website. Include all the information that you believe is necessary. - Once again, please comment on the difficulties and challenges of this laboratory work (i.e. what worked, what did not work, what you liked, what you didn’t like, etc.). Be assured that the grade for your laboratory work or your course will not be affected at all by your positive or negative