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BME Laboratory Experiment Introduction

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					                          BME153 Laboratory Experiment 8:
                              Transformers and Diodes
                                   Claire Vinson
                             Lab Partner: Enping Hong
                                     Section 01
                                 November 28, 2007
    I have adhered to the Duke Community Standard in completing this assignment.


                                _____________________

       Objective
       In today’s lab we will build diode clamping and clipping circuits. We will also
construct a simple transformer. We will analyze the effects of the circuits on a sinusoidal
input waveform, and we will learn how to convert AC voltage to DC voltage.

       Apparatus
           Solderless breadboard
           BK Precision 1652 Triple Output DC power supply
           Fluke 45 Dual Display Bench Multimeter (also referred to as a Digital
             Multimeter, or DMM)
           Tektronix oscilloscope

        Procedure
        The procedure executed in this lab precisely followed the proced ure outlined in
the lab handout provided for this lab with an exception of a 5100 resistor used in place
of the recommended 5000 resistor.

       Data and Calculations

       Error = [(experimental – theoretical) / theoretical] * 100%
       Error = [(51 – 50.45) / 51] * 100% = 1.08%

       Voltage division:
       VA = 12V * (12kΩ / (12kΩ + 2.2kΩ)) = 10.4 V
Experime ntal Results
Table 1: Values for components used.
        Theoretical                Experime ntal                   % Error
            51                       50.45                        1.08%
           100                       99.99                        0.01%
           150                      148.33                        1.11%
           270                       267.5                        0.93%
           510                       506.4                        0.71%
           620                       617.9                        0.34%
          1000                       986.4                        1.36%
          5100                       5160                         1.18%
           22nF                      24.41nF                       10.95%
          470nF                      474.8nF                        1.02%

Table 2: Values for analysis of the half-wave rectifier circuit.
     R2 (load)             Vout (DC)              Vpp (ripple)       Iout (DC)
       1000                  3.56V                  360mV            3.560mA
        620                  2.98V                  400mV            4.806mA
        510                  2.70V                  440mV            5.294mA
        270                   1.9V                  480mV            7.037mA
        150                   1.3V                  520mV            8.667mA
         51                 560mV                   560mV            10.98mA




Figure 1: One-diode clipping circuit.
Figure 2: Four-diode clipping circuit.




Figure 3: Diode clamping circuit.




Figure 4: Simple transformer circuit.




Figure 5: Half wave rectifier circuit.
Figure 6: Input and output waveforms for Figure 1 with 10 Vpp input at 2 kHz with .7
threshold voltage.




Figure 7: Input and output waveforms for Figure 2 with 10 Vpp input at 2 kHz with .7
threshold voltage.




Figure 8: Input and output waveforms for Figure 3 with 2 Vpp input at 10 kHz.
Figure 9: Input and output waveforms for Figure 3 with diode reversed.




Figure 10: Voltage across R1 for the circuit shown in Figure 4.




Figure 11: Ratio of primary voltage versus load voltage for the circuit shown in Figure 4.
Figure 12: Ratio of primary voltage versus load voltage for the circuit shown in Figure 4
with the winding of the secondary coil reversed.




Figure 13: Plot of DC component of input and DC component of peak to peak ripple
voltage output waveforms for Figure 5 where Rload = 510.


        Analysis
        The threshold voltage is 0.7V for the diodes used in this lab. The plots of Vin and
Vout for the circuits shown in Figure 1 and Figure 2 are shown in Figure 6 and Figure 7
respectively. The maximum output voltage of the circuit shown in Figure 3 is 10Vpp, the
same as the output. For this same circuit, the voltage offset of Vout is -0.7V with respect
to Vin. The plots of Vin and Vout for the circuit shown in Figure 3 in shown in Figure 8
and Figure 9. This is proof that there is current through the diode.
        According to Figure 10, the voltage across R1 for the circuit shown in Figure 4 is
2.56V. The primary voltage, Vp, is related to the load voltage, Vs, by a ratio of 1 to 2.
…section on AC currents… When the windings of the transformer are re-wrapped on
the secondary coil, the output voltage becomes out of phase by half a period as seen in
Figure 12.
        When analyzing the ripple voltage of a half- wave rectifying circuit, we find that
the load resistance determines the amount of ripple in the output voltage.

				
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