In this post I will explain how to take output from
microcontroller using LEDs. Before that lets check how actually a LED works ?
How LED works ?
LED
is a most suitable component to display an output status because it emits the
light when it is on. It is very cheap and comes in different size and colors. The
principal of working of a LED is equivalent to the p-n junction diode. The difference
is, it emits the light in visible spectrum instead of heat. The forward voltage
drop of LED is around 1.7v. it works around 10mA current supply.
The
circuit diagram for connection of LED is show below.
The
circuit diagram and microcontroller code for interfacing a LED with
microcontroller (AT89c51) is given below.
Component Required
:
1.
8 LEDs.
2.
Microcontroller AT89c51.
3.
8 registers.
4.
12MHz crystal oscillator.
5.
10 KΩ fixed register.
6.
10 μf (25v) capacitor.
Circuit Diagram
:
8
LEDs are connected with port P1 of AT89c51. Here LEDs are running of negative
logic means cathode of every LED is connected with Microcontroller port pin and
anode of all the LEDs are connected to +5v supply so we don’t required to give
+5v at the output of microcontroller in order to on the LEDs.
We are
sending the sequence of 0x055 and 0x0AA alternatively with some delay. Delay is
in the range of few milliseconds.
Code :
#include<reg51.h>
void delay(int time) //This function produces a delay in msec.
{
int i,j;
for(i=0;i<time;i++)
for(j=0;j<1275;j++);
}
void main()
{
while(1)
{
P1=0x00;
delay(100);
P1=0xff;
delay(100);
}
}
