ECEN 3010 Lab: Measuring Voltage and Current in Circuits using Resistors and Timers, Lab Reports of Electrical and Electronics Engineering

Download ECEN 3010 Lab: Measuring Voltage and Current in Circuits using Resistors and Timers and more Lab Reports Electrical and Electronics Engineering in PDF only on Docsity! ECEN 3010 Lab Circuits and Electronics University of Colorado at Boulder Lab #2 Resistors and Timers Names of All Participating Lab Partners: Lab Section (Circle One): M T W Th F Learning Objectives This lab gives you experience with:  Measuring voltage and current in a circuit  Calculating theoretical voltage and current using Ohm’s law, voltage division, current division, and equivalent resistance.  Comparing measured voltage and current with theoretical values  Astable 555 timer circuit Minimum Parts Required: One LM555; various LEDs, resistors, and capacitors. Part 1 – Basic Resistive Circuits 1.1) What are the resistance values (in ohms) of resistors with the following color codes? a) red red red b) brown black red c) yellow violet orange d) brown black green e) brown black gold f) green black yellow ECEN 3010 Lab 2 Page 1 of 8 Rev. 2008-08-24 This material is subject to copyright notice on last page. In the following experiments, you will use the multimeter at your lab bench. A multimeter measures voltage, current, resistance, and possibly other values depending upon how you have the multimeter set up  To measure current, the multimeter must be set to measure current, and the multimeter must be inserted in series with the conductor through which you want to measure the current. For the multimeter available in lab, use the bottom-right two terminals of the multimeter (see Figure 1). The meter measures current should from the bottom-right terminal (use a red cable at this terminal) to the middle-right terminal (use a black cable at this terminal).  To measure voltage, the multimeter must be set to measure voltage, and the terminals of the multimeter must be placed across (in parallel with) the component across which you want to measure the voltage. Use the top-right two terminals on the multimeter (see Figure 1). The positive side of your reference polarity should be connected to top terminal (use a red cable), and the negative side of your reference polarity should be connected to the middle-right terminal (use a black cable). To measure a node voltage, connect the black lead (middle- right terminal) to ground. Black Red Circuit Current Flow Multimeter For Current Black Red Ground of Circuit Multimeter For Voltage Voltage to Measure Figure 1. Measuring voltage and current with the multimeter available in lab. IMPORTANT: Measuring a VOLTAGE with the meter set to CURRENT mode will likely damage the meter. 1.2) Build the following circuit on your breadboard (see Figure 2). Use R1 = 1 Kohm and R2 = 2.2 Kohm. Assume the negative terminal of the supply is the reference node (ground). Calculate the node voltage V1. Measure the voltage V1 in the circuit. Does it match your calculated theoretical voltage? If not, why? ECEN 3010 Lab 2 Page 2 of 8 Rev. 2008-08-24 This material is subject to copyright notice on last page. Part 2 – Resistive Bridge Circuits 2.1) Build the following bridge circuit (see Figure 5). Use 1 Kohm resistors for R1 and R4. Use 2.2 Kohm resistors for R2 and R3. R2 2.2 k i1 V1 5 V R4 1k R3 2.2 k V2 R1 1k Figure 5. Resistor bridge circuit. 2.2) Calculate the current i1. Note: If you simplify the circuit into parallel circuits, you can no longer find i1. Consider instead finding node voltage V2 using node-voltage analysis. Assume the negative terminal of the power supply is the reference node (ground). Measure the current i1 using the digital multimeter. To measure this current, the ammeter will replace the horizontal bridge wire. Does the calculated value match the measured value? What is the percent error? If there is a discrepancy, explain the source. 2.3) Change R1 and R4 to 2.2 Kohm (see Figure 6). ECEN 3010 Lab 2 Page 5 of 8 Rev. 2008-08-24 This material is subject to copyright notice on last page. R2 2.2 k i1 V1 5 V R4 2,2 k R3 2.2 k V2 R1 2.2 k Figure 6. A second resistive bridge circuit. 2.4) Calculate the current i1. Measure the current using the digital multimeter. Does the measured value equal the theoretical value? What is the magnitude of the error? If there is a discrepancy, explain the source. ECEN 3010 Lab 2 Page 6 of 8 Rev. 2008-08-24 This material is subject to copyright notice on last page. Part 3 – Monostable Timer Circuit During the previous lab, you constructed a 555 timer circuit in the astable mode. The astable mode produces a periodic square waves at specific frequencies and duty cycles. During this lab, you will use the 555 timer IC in monostable mode. The monostable mode allows you to create a “one-shot” circuit; this circuit produces a single voltage pulse of a specific time duration. Using the 555 timer IC application note (see website), design and build a circuit that lights a red LED for five seconds. Use the LED and transistor circuit from Lab 1 to control the LED (see Figure 7 and replace the function generator with your monostable 555 circuit). Use a 0.1 uF capacitor in place of the 0.01 uF capacitor shown in the application note. You will need to create a trigger for input to pin 2 of the 555 IC. This input will trigger these start of the output voltage pulse. Attach a resistor (between 1 and 5 Kohm) between the +5V power supply and pin 2 of the 555. To trigger the timer circuit, touch a wire between ground and pin 2 of the 555 IC. Have a TA sign off below when you have your circuit operating correctly. Include the sign-off page with your lab report. vF(t) 2N3904 V = +5V R1 2.2KW R1 68W Function Generator Power Supply D1 LED B C E Figure 7. A transistor controls the LED. The function generator will be replaced by your monostable timer circuit. Instructor Sign-off ECEN 3010 Lab 2 Page 7 of 8 Rev. 2008-08-24 This material is subject to copyright notice on last page.