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# Lab 1 Report (Hugo)

last edited by 7 years, 1 month 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 yellow LED. We know the voltage of the circuit (5V), the voltage drop of the LED (1.8V) and the current (25mA), so, from the Ohm Law:

U=R.I -> R=U/I -> R=(5-1.8)/25m -> R = 128 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's a minimum resistance. If you reduce the resistance the LED will fail.

c. What is the resistance range of the potentiometer?

The resistance range of the potentiometer is 0 to 10K (value of the potentiometer) ohms.

#### 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?

The order of the components doesn't matter, because the power will flow anyways in the circuit. But the LED must be in the right direction, because the power must flow from the "positive" side of the LED to the "negative" side of the LED. So, the positive part of the battery must be in the same side of the positive part of the LED and the negative part of the battery must be in the same side of the negative part of the LED.

#### 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 yellow LED. We know the voltage of the battery (9V), the voltage drop of the LED (1.8V) and the current (25mA), so, from the Ohm Law:

U=R.I -> R=U/I -> R=(9-1.8)/25m -> R = 288 ohms.

#### 5. Make a Video of Your LED Being Switched On and Off.

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