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Lorta_Lab 1: Orientation and LED

Page history last edited by xinyi xie 6 years 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.

 

I used a green LED. According to the datasheet, the forward voltage (VF) for the green LED is 2.2V. Therefore, Vtotal Vin-VF =5V-2.2V = 2.8V

 

Using Ohm’s law, we can now calculate the resistance needed for the green LED: V = IR => R = V2.8V/0.025Amperes = 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.

 

The LED would likely fail if we decreased the resistance from the answer to part (a), therefore the resistance is a minimum.

c. What is the resistance range of the potentiometer?

 

Resistance range of potentiometer was 0-10 kohms (measured using multimeter).

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?

 

Because the components are connected in series, it does not matter the order in which they are arranged between power and ground.

4. Battery-Powered LED with Switch on Breadboard

 

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

Accounting for the forward voltage of the green LED (same procedure as in question 2): Vtotal Vin VF = 9V - 2.2V = 6.8V

 

Then using Ohm’s law to calculate the minimum resistance needed:

R = V/=> 6.8V/0.025 Amperes = 272 Ohms

Fliqz has shut down their service. To access this video, email support with this video id: ea11d8901cb14d139987fab291e9da31

I realize now that the video is in portrait mode versus landscape. Also, there was no intro!

 

 

Comments (1)

xinyi xie said

at 2:13 pm on Jul 11, 2014

Great job!!

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