UC Berkeley EECS 100 Lab B Boser LAB1 Solar Power Supply NAME 1 SID NAME 2 SID Laboratory Organization The document you are looking at are the instructions for the first laboratory in EE 100 You will use similar instructions for all labs These instructions serve dual purpose as pre lab instructions and lab guide Here is what you have to do 1 Preparation pre lab Download the instructions and read them to be ready for the laboratory For many labs you will be asked to analyze and design the circuits you will be building Complete all these assignments before the lab and make sure to enter all your results into a printed copy of the lab instructions or on separate sheets appended to the instructions Please get help in office hours before the lab if you have questions 2 Prelab submission Answers to numerical and textual pre lab questions boxes are submitted at the beginning of the lab period Copy your answers to the prelab questions in the blue boxes to the Prelab Summary page at the end of the lab document 3 Laboratory Follow the instructions and perform all required measurements Ask the lab GSI for help if you have problems with equipment parts or your circuits The instructions also ask for the GSI to verify certain measurements Demonstrate your working circuit and ask the GSI to acknowledge its correct operation in the box provided 4 Report Collect your measurement results interpretations etc on the printed lab instructions and add additional sheets as needed Turn in the completed instructions with all questions answered to the lab GSI You can do this at the end of the laboratory or up to one week after the lab Power Supply Laboratory Electronic equipment needs power to operate Most systems require a specific supply voltage For example the power brick of my laptop supplies 20 V to my computer to operate Check the labels of supplies you own for the voltages used by different electronic devices In this laboratory we first familiarize ourselves with the programmable laboratory supply E3631A and then design a solar powered supply We will also learn how to use the digital multimeter DVM 34401A Download the instructions for these instruments from the EE 40 website section manuals DVM and Laboratory Power Supply The DVM measures voltage or current and is indispensable in the lab Most can also be set to measure resistance We use the DVM not only to check the output of circuits we design but also to verify our setup Does the voltage supplied to the circuit have the correct value Is the supply current in the expected range When set to measure resistance the DVM can be used to check wiring Are two components properly wired to one another Did I inadvertently short the supply Such simple checks can save hours debugging To try out the DVM program the laboratory supply to 5 V and set the maximum current to 20 mA In this as in future labs always set a current maximum when using the laboratory supply typically about 50 percent above the current you expect your circuit to draw This prevents your design from going up in smoke if you inadvertently make a wrong connection Verify the output voltage of the supply with the DVM Can you make the DVM display a negative voltage 1 February 4 2009 LAB1 v1251 Figure 1 A resistor with value 680 and 5 tolerance colors blue grey browngold Next we need to verify that the output voltage stays constant independent of the current flowing up to the set maximum We do this by connecting a resistor across the output terminals of the supply Figure 1 shows a picture of resistors like those we use in the lab The colored rings encode the value of the resistor You can find that code e g on Wikipedia under electronic color code or resistor Use the Ohmmeter multimeter set to measure resistance if you are not sure about the value of a resistor You will find that only certain resistor values are available Most resistor types are only made with values 10 12 15 18 22 27 33 39 47 56 68 82 and decimal multiples or fractions thereof In many situations the closest value can be substituted e g 4 7 k for 5 k Alternatively it is possible to combine two or more resistors in series and or parallel to synthesize a desired value e g two 10 k resistors connected in parallel produce exactly 5 k When you design a circuit you need to round calculated component values to available ones and decide if the rounding error is acceptable or a more precise value must be synthesized from several parts What is the value of the resistors shown in Figure 2 Include the unit in your answer e g mV MW kOhm Use 1 pt proper capitalization and include the correct unit even if the result is zero e g 0 V 0 Figure 2 Color coded resistors colors orange orange red gold Assume a 2 7 k resistor is connected across the supply 1 pt What is the the value of the current flowing 1 1 pt What is the power dissipated in the resistor 2 As the value of the resistor connected to the supply decreases the current increases up to the maximum programmed into the supply For lower resistance values the maximum current flows and the supply voltage drops below the programmed value With the laboratory supply programmed as indicated above what is the minimum 1 pt resistance value below which voltage drops 3 Assume a 85 resistor is connected across the supply 1 pt What is the value of the current flowing 4 1 pt What is the voltage across the resistor 5 Draw a circuit diagram showing how to connect volt and ampere meters to measure the voltage and current simultaneously Include the laboratory supply and load resistor R L in your diagram Use standard electronic circuit symbols for these devices not pictures 2 February 4 2009 LAB1 v1251 2 pts 6 Connect different resistors R L with values as indicated below to the supply and calculate and measure the voltage Vs across the resistor and current Is flowing Fill in the table below and compare calculated and measured results Explain differences measured Vs Is Vs Is for for for for RL RL RL RL 1 8 k 1 8 k 120 120 calculated 1 pt 1 pt 6 1 pt 6 1 pt 7 1 pt 7 1 pt 8 1 pt 8 1 pt 9 9 Solar Power Supply Our objective is to design solar power supply for a small appliance such as a cell phone One of the questions we need to investigate is the size of the panel that is required To answer this question we need to better understand the characteristics of the solar cell It s interface is just like that of a battery two leads that supply power But how much power can it deliver At what voltage Let s find out in the
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