What are pull up resistors? |

What are pull up resistors?

Light Emitting Diodes are often used in circuits to represent some a particular change. Each LED comes with a voltage rating and current that is can withstand. It is important to know how to calculate theresistanceneeded for LEDs so that you don’t destroy the LED.

You can useOhm’s law to findthe resistance require to wire an LED.This equation will give you the value the resistor should be

(Vs-Vf)/ I

where Vfis the forward voltage and I is the current intensity of the LED. It’s worth noting that the forward voltage is nearly the same for all LED’s regardless of the current. That value is usually 1.5 Volts.

When thepushbuttonis pressed, the LED is automatically connected to ground and has a low (0) output.When the pushbutton isn’t pressed, the LED is “pulled up” to high (1).

This is a chart to help with the resistor calculations. The chart shows the various current intensities for different 5mm LED colors.

Using the equation stated earlier with the corresponding LED you should be able to calculate the need resistance value.

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