Electronic Eye Circuit using IC 4049

This project is for small Electronic Eye Circuit using IC 4049.

It can sense darkness or shadow.

When light falls on LDR the circuit stays OFF.

When light is blocked then LED and buzzer turns ON.

It is like a magic eye circuit used for security or door alarms.

Circuit Working:

The main brain of the circuit is NOT gate.

It comes from CD4049 CMOS IC.

This IC has six NOT gates.

In this circuit we have used only one gate

LDR and resistor R1 form a voltage divider.

LDR resistance is low in light and high in dark.

IC CD4049 is a hex inverter and it changes logic high to low and low to high.

Pin 14 of inverter gate is input.

Pin 15 is output.

When light falls on LDR, voltage at input is low and inverter output becomes high, so buzzer and LED are OFF.

When darkness comes, voltage at input increases, inverter output goes low and turning buzzer and LED ON.

So circuit works opposite of light presence.

Below is the formula for Electronic Eye Circuit using IC 4049 :

Voltage at input (Vinput) = (R1 / (R1 + RLDR)) * Vcc

If light is strong then RLDR is small (few hundred ohms) so Vinput is small.

If dark then RLDR is large few mega ohms, so Vinput is large.

IC 4049 changes this voltage to opposite logic.

To build an Electronic Eye Circuit using IC 4049 follow the below connection steps:

Assemble all the parts as shown in circuit diagram.
Connect +6V to pin 1 Vcc and pin 8 to ground.
Pin 14 input connect from junction of one end of LDR and one end of resistor R1.
Pin 15 output connect to one end of buzzer and other end to one end of LED.
And other end of LED connect to GND.
Connect other end of LDR to +6V.
Connect other end of resistor R1 100k to ground.

This Electronic Eye Circuit using IC 4049.

It detects light and dark easily.

Can use as door alarm, shadow detector or night sensor.

Few parts needed with low cost and is easy to make.

Works with 6V battery or DC adapter.