Wednesday, February 1, 2017

Week 4

Week 4

1. (Table and graph) Use the transistor by itself. The goal is to create the graph for IC (y axis) versus VBE (x axis). Connect base and collector. DO NOT EXCEED 1 V for VBE. 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 VBE = 0V, 0.5V, and 1V and fill the gaps if necessary by taking extra measurements).

Table1.1 The table shows Base-Emitter voltage Vs. Collector current

Graph1.1: The graph  shows the relationship between  Vbe Vs. Ic

The data for the current across the collector and base-emitter voltage was collected and we used different values of voltage to see the relationship between the Vbe and Ic. We indicated that Ic will be at zero until the Vbe goes over 0.5 V and then Ic will increase exponentially as it is shown in the graph

2. (Table and graph) Create the graph for IC (y axis) versus VCE (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 table shows Vce and Vbe Vs Ic

Figure 2.1 Vce Vs Ic
In this experiment, we added one more voltage source which is collector-emitter voltage and we used three values of Vbe to measure the the collector current with 2 values of voltage across the Collector-emitter. When we used zero for both Vce and Vbe the collector current was still at zero. As it is seen in the table we used the same value for Vce which is 2V and we changed the Vbe values in both trials. We can see Ic increasing when Vce increases with the value of 0.7 for Vbe. Then we used the same value of Vce but we changed the the value of Vbe to 0.8 and still the collector current increased. This shows the relationship between Vbe and Ic is that when Vbe increases over 0.5, Ic will increase. I also think that we had to do more trials but we just did three , that's maybe we misunderstood the question.The graph above explains the results.

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

Table 3.1: The relationship between Ic and Ib

The table shows that the current of the collector increases higher than the current of the base. Our theory is that the ratio between Ic/Ib is called Beta and it should not change even if the voltage changes. In other word, Ic will be higher that Ib at the same rate which means Beta is the same for both. Also, That means the Beta will not change in the trials  even if Ib and Ic change.  Our data did not support our theory, I think we made an error that led us to these inaccurate results. 

4. (Table) Explain photocell outputs with different light settings. Create a table for the light conditions and photocell resistance.
Table 4.1 Shows the value of resistance that we got from the different amounts of light we allowed to hit the photocell. With more light the resistor gives less resistance.

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

Table 5.1 the table shows the different current given on the motor with different voltage source.
The table shows as we increase the voltage applied to the dc motor, the current increases which prove ohm's law.
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 6.1 shows the current acting on the DC motor with a constant voltage but different load on the motor.
We applied 2V to the motor and when there was no load on the motor,the current was 53.8mA but when the load was increased on the motor, the current starts to increase as it is shown in the table.
7. (Video) Create the circuit below (same circuit from week 1). Explain the operation in detail.

The video explains the operation of the circuit. 

we used a 1k photocell which is used to control the voltage at the base and when we cover the photocell the resistance will increase causing the motor to stop and when we shine on the photocell, its resistence will decrease causing the motor to move faster.

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 is to manage the amount of current that travels to the collector then to the motor from the second voltage source. By increasing the resistance of R4 the motor does not receive enough current to operate, and by lowering the resistance the motor out put increases.

9. (Video) Create your own Rube Goldberg setup.
Video shows our Rube Goldberg Project

In Our Rube Goldberg Setup, we used a strain to pull pieces of Dominos. We reduced the voltage so the motor will not move fast and when we used the iPhone flashlight on the photocell, the dc motor rotates and pull the dominos. 


  1. Great explanation on your video for #7, helps me to understand the circuit better. Just make to sure to include captions on your tables and videos.

  2. I notice that there is a lot of differences between our calculation and yours maybe it is depends on how we dealt with the transistor. Like in q2. the question ask you to use VCE from 0-5V and you used just 0 and 2. Also, may there is mistakes in our calculation not in yours.
    Good job.

  3. There is a big difference between your data and ours. For question 2 I believe we were supposed to take around 15 measurements. "Vary VCE from 0 V to 5 V. Do this measurement for 3 different VBE values: 0V, 0.7V, and 0.8V." I thing you misunderstood the question. I also don't see captions for some questions like #1, 2, 3, 7. Also, question #4 is asking you to "Explain" and you didn't. Other than that is clear and organized.
    Thank you..