Blinking 1 LED using 8051
This is the first project regarding 8051 and of course one of the
simplest, blinking LED using 8051. The microcontroller used here
is AT89S51 In the circuit, push button switch S1, capacitor C3 and
resistor R3 forms the reset circuitry. When S1 is pressed, voltage
at the reset pin (pin9) goes high and this resets the chip. C1, C2
and X1 are related to the on chip oscillator which produces the
required clock frequency. P1.0 (pin1) is selected as the output pin.
When P1.o goes high the transistor Q1 is forward biased and LED
goes ON. When P1.0 goes low the transistor goes to cut off and
the LED extinguishes. The transistor driver circuit for the LED can
be avoided and the LED can be connected directly to the P1.0 pin
with a series current limiting resistor(~1K). The time for which
P1.o goes high and low (time period of the LED) is determined by
the program. The circuit diagram for blinking 1 LED is shown
below.
