All About LEDs
Created by Tyler Cooper
Last updated on 2018-08-22 03:33:51 PM UTCGuide Contents
Guide Contents 2
Overview 4
What is an LED? 5
All the different sizes and colors 6
What are LEDs used for? 9
Changing the brightness with resistors 12
Which LED is brightest (what is the resistor)? 13
Which LED is dimmest (what is the resistor)? 13
If we had an LED with a resistor that was 5K ohms, which LED would it be brighter than? Which LED would it be
dimmer than? 13
Changing the brightness with voltage 13
Which LED is brightest (what is the voltage)? 14
Which LED is dimmest (what is the voltage)? 14
If we had an LED with a 1.0K resistor connected to a 4.2v supply, which LED would it be brighter than? Which
LED would it be dimmer than? 14
Max brightness!? 14
We connect our LED to the resistor, as we turn it from infinite to to zero, what happens? 14
We connect our LED through a 1K resistor, as we adjust the voltage from 0 volts to infinite volts, what happens?
What happened? 1515
The LED datasheet 16
Forward Voltage and KVL 18
Quick Quiz! 19
Let's say we have the same circuit above, except this time its a 5V battery and an LED with a forward voltage of
2.5V, how much voltage must be 'absorbed' by the resistor? 19
Let's say we have the same circuit above, except this time its a 5V battery and an LED with a forward voltage of
3.4V, how much voltage must be 'absorbed' by the resistor? 19
Ohm's Law 19
If I have a 3 ohm resistor (R) with a current of 0.5 Amperes (I) going through it. What is the voltage (V) across
the resistor? 19
Now I have a 1000 ohm resistor (R), and a voltage across it of 6.8V (V), what is the current (I) going through the
resistor? 19
Solving for the current 20
Revisiting Resistors 22
In the above breadboard, the voltage generator here is +5V, the forward voltage of the LEDs are 2.2V. What is
the voltage across the 10,000 ohm resistor? 22
Now that you know the voltage, how much current (I) is going through the 10,000 ohm resistor (R)? 22
In the same breadboard, the voltage generator is +5V, the forward voltage is 2.2V, what is the voltage across
the 1000 ohm resistor? 22
Now that you know the voltage, how much current (I) is going through the 1,000 ohm resistor (R)? 22
How much current (I) is going through the 100 ohm resistor (R)? 22
Revisiting Volts 24
Lets start with the 9V-powered LED. The forward voltage of the LED is 2.2V, what is the voltage across the
resistor? 24
Now that you know the voltage, how much current (I) is going through the 1,000 ohm resistor (R)? 24
Next, we will examine the 5V-powered LED. The forward voltage is 2.2V, what is the voltage across the resistor?
24
Now that you know the voltage, how much current (I) is going through the 1,000 ohm resistor (R)? 24
Finally, we will examine the 3.3V-powered LED. The forward voltage is 2.2V, what is the voltage across the
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