Operational Amplifier Winking LED
Électronique / Electronic
Now we're going to make a winking LED circuit using a dual operational amplifier. In this circuit, an LED continues to light and turn off slowly.
Slide the switch to position OFF and connect the wires for this circuit. When you finish assembling the project, slide the switch to position ON to turn on the power.
After a few seconds you'll see the LED start to blink. Watch carefully and you should be able to see that its on and off periods are about equal.
The dual operational amplifier works as an astable multivibrator of a low frequency. You can change the period of oscillation, that is, the LED blinking rate, by using different values for R4 and C1.
See what happens to the blinking rate when you change the value of R4 to 220K ohms. One last thing-the dual operational amplifier has a high input impedance-resistance to input-so it loses very little input current. This means you can use it to build accurate blinkers and timers with longer intervals.