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Cole Hoffer - Lab 1

Page history last edited by xinyi xie 6 years, 2 months ago

2. Controlling the Brightness of LEDs

 

 a. What resistance do you need to limit current to 30 mA (if using red LED) or 25 mA (if using yellow or green)? Be sure to state which color LED you               are using. This resistance refers to the total resistance in series with the LED.

 

Using a green LED (25mA)

Forward Voltage Drop = 2.2V

     Voltage = 5V - 2.2V = 2.8V

 

V = IR

R = V/I

R = 2.8 / .025

R = 112 Ohms

 b. Is the resistance from question (a) a maximum or minimum resistance? That is, in which direction if you change the resistance (higher or lower) would      the LED likely fail.

 

     It is the minimum resistance. The resistance and current are inversely proportional, meaning if one increases, the other will decrease. Lowering the      resistance any more would cause the current to increase above 25mA, causing the LED to fail.

 c. What is the resistance range of the potentiometer?

     

     0 - 10 kOhms  +-5% 

                              or .5 kOhms

 

 

3. Basic LED Circuit with Switch

 

 a. Does it matter what order the components of your circuit are arranged between power and ground? Why or why not? 

 

     No, all components of the circuit are in series, thus meaning all components will achieve their desired task regardless of their order. If one component      is not working properly, the entire circuit will not work because it is in series and the LED will not light. Resistors affect the entire circuit, meaning      their placement in the order is not important and the button simply acts as connecting/disconnection in the circuit.

 

4. Battery-Powered LED with Switch on Breadboard

 

 a. Using this battery, what is the minimum resistance required for use with your LED?

 

Using a green LED (25mA)

Forward Voltage Drop = 2.2V

     Voltage = 9V - 2.2V = 6.8V

 

V = IR

R = V/I

R = 6.8 / .025

R = 272 Ohms

 

 

 

 

 

 

     

 

Comments (1)

xinyi xie said

at 4:32 pm on Jul 10, 2014

Great job!!

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