favorite LED experiment

Published:2012/12/13 21:03:00 Author:muriel | Keyword: LED | From:SeekIC

Sequentially Off LED Pulser This circuit uses a series of transistors with an RC pair to pulse a string of LEDs. This the favorite LED experiment I performed this summer. This flasher circuit is different in that it turns off alternate LEDs for about 1 second in sequence. When you connect this circuit to the 9 volt battery, all of the transistors are usually placed in saturation and therefore all the LEDs are on. Closing the switch on the base terminal of Q1 for a moment initiates the correct pulse sequence. The pulse initiates in Q1 which turns off the LED connected to the Q1 collector for about 1 second. When Q1 turns back on (goes into saturation), Q2 turns off. When Q2 turns back on then Q3 turns off and so on. The circuit is a closed loop and many more stages may be added. You can experiment with different base resistor and coupling capacitor values to vary the speed of the LED string or to create a sense of randomness by varying each transistor's RC stage separately. This is a fun circuit!



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/LED_and_Light_Circuit/favorite_LED_experiment.html

Print this Page | Comments | Reading(3)