The simplest led flasher (one transistor)

Posted by Ilias-Man On Sunday, February 5, 2012 7 comments
This circuit consists of negative resistance in transistors.



A common NPN transistor is used.  In the circuit, a 1k resistor charged the 470u uf capacitor until the voltage became large enough to get the emitter-base junction to avalanche. At this point transistor turned on quickly and partially discharged the 470 uf capacitor through the LED and the 100 Ohm current limiting resistor. The current wavform, which is the voltage drop across the 100 Ohm resistor, Peak current was 26 milliamps, and the transistor continued to discharge the capacitor until conduction suddenly ceased at 6 milliamps. After the transistor stopped conducting, the capacitor began charging again, thus starting a new cycle.By changing C1 frequency change.


  A number of demonstratons of this circuit have appeared on YouTube.


Thanks





7 comments:

Unknown said...

why the base terminal is not connected and led does not flash it only glows
need your help.

Unknown said...

yes it cant flash untill u use a bc547

Unknown said...

does it work with 9v

Unknown said...

Beautiful message !...

Irfan said...

Change the value of R2 = 4.7k and C1 = 220Uf 25 volt, LED will flash beautifully

Irfan said...

Any NPN transitor will work, in my case i used C1815

Unknown said...

It is not working with 2n3904

Post a Comment

hostgator coupon