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# Lab 1 report

last edited by 7 years, 4 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.

Hint: Make sure that you account for the forward voltage drop (Vf) of the LED that you're using.

I used the green LED. To calculate the resistance you use the equation V = IR so R = V/I. The voltage supplied by the power supply is 5 V and the Vf of the green LED is 2.2 V. Current is 25 mA which is .025 A.

R = (5 - 2.2)/.025 = 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 resistance is a minimum resistance. That is, lowering the resistance would likely cause the LED to fail as the current would increase past the LED's max.

c. What is the resistance range of the potentiometer?

The resistance range of the potentiometer is 1.0 Ohms to 10.4 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?

It does not matter what order the components of the circuit are arranged between power and ground because everything is in series.

#### 4. Battery-Powered LED with Switch on Breadboard

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

I used the green LED. To calculate the minimum resistance you use the equation V = IR so R = V/I. The voltage supplied by the battery is 9 V and the Vf of the green LED is 2.2 V. Current is 25 mA which is .025 A.

R = (9 - 2.2)/.025 = 272 ohms