LED Flasher 1 transistor circuit

[gary350]

This circuit actually works. 9v battery will not flash LED unless battery is brand new and it is a good quality battery. I am using 6 AA batteries to get 9v. Also it will not flash unless you have .5 amps. This circuit flashes about 1 time per seconds. I changed cap to 470 uf & resistor to 2K it flashes the same speed but LED is not as bright. If i had to explain how it works I would say, cap charges up slow v & a are low but when voltage gets high enough transistor discharges capacitor through the LED. If I remove capacitor from circuit LED stays on all the time. I have several unknown transistors from old TVs I might try some in this circuit to see if they work. I think this circuit is a drain on the batteries they will probably never flash 12 months like other LED circuits. 3mm LEDs are easy to kill, 5mm are better.

There are other flasher circuits on this board look at the circuit in the center.

 

[AnalogKid]

The schematic is incorrect; the transistor is upside down (collector and emitter are reversed). Here is a link to the original:

Simplest_LED_Flasher_Circuit

The transistor is acting in an avalanche mode. It cannot be replaced with regular diodes.

The device in the photo is a thermistor, possibly a PTC current limiter.

ak

 

[gary350]

The schematic is incorrect; the transistor is upside down (collector and emitter are reversed). Here is a link to the original:

Simplest_LED_Flasher_Circuit

The transistor is acting in an avalanche mode. It cannot be replaced with regular diodes.

The device in the photo is a thermistor, possibly a PTC current limiter.

ak

YES your right but I can only get my circuit to work with the transistor backwards so I drew the circuit with the transistor backwards. Data sheet shows 2N2222 pin out to be CBE that is backwards most transistors are EBC. Ok my drawing is wrong but transistor is in the pc board correct. I tested the circuit you listed 330 uf blinks very fast, 1000uf is about 1 time per second. 100 ohm resistor does not appear to make circuit flash different or look different.

 

[gophert]

Your breadboard has the transistor in an orientation that works. Your hand-written schematic has the transistor reversed from how it is oriented on the breadboard.

 

[Willen]

As I tried, supply voltage is critical for the flash. I got it flashing around over 10V to 12V. With variable power supply, we can use different types of transistors.