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# Lab 1 - Orientation and LED

last edited by 7 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.

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

GREEN LED

V = Vin-Vf

R = V/I

R = (5-2.2)/0.025
R = 112 Ω

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.

Minimum. Lower resistance would likely cause the LED to fail.

c. What is the resistance range of the potentiometer?

0-10 kΩ

#### 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?

Yes. Although this is a serial circuit, the resistor must always be between the power source and the LED to limit the current running to it. The switch however, can be placed at any point in the circuit.
-0.5 hm... does the current change through 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?

GREEN LED

V = Vin-Vf

R = V/I

R = (9-2.2)/0.025
R = 272 Ω