Blog Week 4

In this week's activities, we will be using transistors to breadboard simple circuits.

1.       (Table and graph) Use the transistor by itself. The goal is to create the graph for I_C (y axis) versus V_BE (x axis). Connect base and collector. Use 10K potentiometer to generate the voltage. Use 5 V but DO NOT EXCEED 1 V for V_BE. Make sure you have the required voltage value set before applying it to the base. Transistor might get really hot. Do not TOUCH THE TRANSISTOR! Make sure to get enough data points to graph. (Suggestion: measure for V_BE = 0V, 0.5V, and 1V and fill the gaps if necessary by taking extra measurements). The circuit should look like below:

 

Circuit 1

 
          Table 1                                           Graph 1

2.       (Table and graph) Create the graph for I_C (y axis) versus V_CE (x axis). Vary VCE from 0 V to 5 V. Do this measurement for 3 different VBE values: 0V, 0.7V, and 0.8V. The circuit should look like below:

Circuit 2

       

      

                  Table 2                                                             Graph 2

  

1.       Apply 2 V to the DC motor and measure the current. Repeat this by increasing the load on the DC motor. Slightly pinching the shaft would do the trick.

     By increasing the load by pinching to the shaft of the DC motor, we were able to see a large increase of current to the motor. With the increased load the current was measured at 92.5 mA. Without the increased load on the DC motor the current measured to be 33.48 mA.

3.       (Table) Apply the following bias voltages and fill out the table. How is I_C and I_B related? Does your data support your theory?

VBE	VCE	IC	IB
0.7 V	2 V	40µA	7.28mA
0.75 V	2 V	40µA	48.8mA
0.8 V	2 V	40µA	66.8mA

Table 3

4.       (Table) Explain photocell outputs with different light settings. Create a table for the light conditions and photocell resistance.

Photo-sensor Light	Resistance
Blocked	9.45k Ohms
Partially Blocked	5.56k Ohms
Room Light	1.17k Ohms
Flash Light	.345k Ohms

Table 4

    (Table) Apply voltage (0 to 5 V with 1 V steps) to DC motor directly and measure the current using the DMM.
                                                                  

Voltage	Current
0	.38   mA
1	26.9 mA
2	33.2 mA
3	39.1 mA
4	44.6 mA
5	49.8 mA

                                               Table 5

     

6.       Apply 2 V to the DC motor and measure the current. Repeat this by increasing the load on the DC motor. Slightly pinching the shaft would do the trick. 

                                                                   
                                                                               Table 6

                                                                              

7.       (Video) Create the circuit below (same circuit from week 1). Explain the operation in detail.

 

Circuit 3

8.       Explain R₄’s role by changing its value to a smaller and bigger resistors and observing the voltage and the current at the collector of the transistor.

      R₄’s role for the circuit is if the resistance for the resistor in the circuit increases the motor gets much less power. Lower the resistance of R₄ and the motor will spin faster as it has more voltage going through it.

9.       (Video) Create your own Rube Goldberg setup.

If video does not show up.

https://www.youtube.com/watch?v=u_NePad6v9M&feature=youtu.be