Monday, February 20, 2012

LED Active Low and High



Picture to the left is a circuit of LED Active-Low, and the picture on the right are active-High LEDs circuit. Consisting of a resistor network that diseri with an LED. 

In the network-Low Active LED, the LED will light up if given the logic 0 (LOW) and will die if given a logic 1 (HIGH). When given the logic 0, then the LED anode voltage at the foot of a more positive compared to the cathode leg.

Voltage difference at the foot of anode and cathode LED LED exceeds the voltage falls, until the LED already sent (conducting electric current) and goes on. In contrast, when given the logic 1, then the LED anode foot is more positive than the cathode feet, therefore the LED does not send (not conducting electrical current) until the LED is not lit. In a network-High Active LED, the LED will light up if given a logic 1 (HIGH) and will die if given a logic 0 (LOW).

When given the logic 1, the voltage at the foot of the LED anode more positive compared to the LED cathode feet. Voltage difference at the foot of anode and cathode LED LED exceeds the voltage falls, until the LED already sent (conducting electric current) and goes on. In contrast, when given the logic 0, then the LED anode voltage on the feet is not more positive than the cathode foot LED, LED therefore not sent (not conducting electrical current) until the LED is not lit. Series resistor in the network function is as a constraint on the currents. You can use a resistor with a value of peace from 150 ohm, 180 ohm, 220 ohm, to 2K2 ohm depending on LED type that you use and how the brightness level you want.

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