0 Battery and Load Status Indicator

This circuit is another simple led flasher, but this time its main purpose is for load and battery status indicator. This circuit is connected in parallel across the load and the led flashes in every second. These flashes will keep as aware that the load is not removed from the battery thus protecting battery from draining unintentionally. The circuit consume very low current and operate from 12V down to 6V, thus it's okay to keep it installed all the time.

schematic diagram

Part List:
R1 - 10 kilo ohms 1/4W
R2, R7 - 120 kilo ohms 1/4W
R3 - 39 kilo ohms 1/4W
R4 - 560 kilo ohms 1/4W
R5, R6, R8 - 330 ohms 1/4W
C1 - 10uF electrolytic capacitor rated 16V
C2 - 220uF electrolytic capacitor rated 16V
D1 - 1N4001 or similar diode ( i recommend use schottcky)
Q1 - 2N2222 or similar NPN transistor
Q2 - 2N3906 or similar PNP transistor
LED - red or any low power LED (see LED pinout if you forgot)

2N3906 pinout

2N2222 pinout

Other Useful Flasher:
1.5V led flasher - uses two transistor at very low input voltage
Lamp flasher by FET -  high current and power  flasher
two transistor flasher - powered from 3V to 12V with two LEDs
Led chaser - 10 led chaser that turns on one after the other

0 1.5V LED Flasher using Transistor

Another LED flasher, but this time powered only by 1.5V (take note that the minimum voltage to light up LED is 1.8V or higher). Q1 and Q2 will start to generate pulses that charge the C2. When C2 is charged, the voltage across the LED is around 1.5V plus the charge in the capacitor. This voltage is enough to light up the LED.

2N4403 pins

2N2222, 9013 pins

Part List:

R1 - 1.2 Mega ohms 1/4W

R2 - 1.2 kilo ohms 1/4W

R3, R4 - 390 ohms 1/4W

Q1, Q3 - 2N2222 or CS9013 NPN transistor

Q2  - 2N4403 or  similar PNP transistor

C1 - 1uF electrolytic capacitor

C2 - 220uF electrolytic capacitor

LED - red (see LED pinout or LED info)

Other LED Flasher Circuit:

Two transistor Flasher - two LEDs flasher

Flasher by 555 - bright flasher uses 20 or more LEDs

Fading LED - fading effect of two LED

2 LM317 lamp flasher

Another simple flasher circuit that is good for car or vehicle use since its powered by 12V car battery.

Part List:
C1 - 4.7uF electrolytic capacitor rated 16V
C2, C3, C4 - see Flash Rate vs RC table
R1, R2, R3 - see Flash Rate vs RC table
Lamp - 12V bulb maximum 15W power
317 - LM317 or similar regulator IC

Flash Rate vs RC table

Rate is the frequency of the flasher. Changing the values of RC changes the rate. R is the resistance value of R1, R2, R3; and C is the value of C2, C3, and C4.

Similar Flashers:
Bulb Flasher - 12W bulb flasher using power BJT
LED Flasher using 555
Lamp Flasher using FET - high current flasher for bulb or LED

0 Two transistor LED Flasher

One of the simplest led flasher circuit and that can be used as indicator circuit and decoration lighting.  Has a wide range of voltage supply ranges from 3V up to 12V DC. The circuit draws about 10mA from a 6V battery, thus consumes very low power. The parts also are minimal and very cheap. The drawback of this flasher is its good only for LEDs unlike the power Mosfet flasher that can power high power LEDs and even a 30W bulb (30W @ 12V).

Flasher Schematic

Part List:
R1 - 390 ohms 1/4W
R2 - 56 kilo ohms 1/4W
C - see Time vs capacitance table below
Q - 2N2222, CS9013 or any similar NPN transistor
LED - RED or any 3mm or 5mm low power LED
Bat - preferably 6V battery (3V to 12V will do also)

2N2222 or CS9013 pins

Flash rate:
Based on trial an error using the parts used above, the approximate flash duration T of both LED is around 0.56*R2*C.

Flash duration T diagram of  both LED

Time vs capacitance table

0 Lamp Flasher Circuit using FET

It can be used as lighting indicator and flasher in vehicles. Unlike the BJT based flasher, this one has higher current capacity thus can power not only LED but also bulbs or lamp.

Circuit Schematic

Part List:
Bulb - 1W to 30W bulb  rated 12V
R -  see table below
C -  see table below
Q - IRF530, IRFZ44N, or similar N-channel Power MosFet

IRF530, IRFZ44N pins

Rate of the flash:
Both bulbs flashes at the same rate or duration T but not at the same time. The duration T is approximately 0.7RC.

Current in both MosFets

RC time constant table

0 Bulb Flasher

This flasher can be used as traffic alert or hazard indicator when repairing something on roads.The bulb flashes around 1.2Hz frequency, slow rate but enough to be noticed even at a distance. You can use 6V or 12v battery and any bulb with power rating of 5W to 12W.

Flasher schematic

TIP41 pinout

Part List:
C1-1000uF 16V
R1-5 kilo-ohms
Q1-2N3906, 2N2907  or any similar PNP transistor
R2-200 kilo-ohms
R3-33 kilo-ohms
D1-1N4002 or 1N4007
C2-22uF or 33uF 16V
Q2-TIP41c or TIP31c
Bulb-5W to 12W (6V/12V)
S1-any switch with minimum 1A rating
Bat-6V to 12V battery

7 Fading LED

This a dual fading led using 555 timer IC. When first LED (Red) starts to increase its light intensity, the other LED (Blue) starts  to get dim. See the fading sequence diagram of the two LEDs below to understand how it works.

fading sequence diagram 

schematic diagram

Part list:
1-555 IC
2-150 ohms resistor
1-20k ohms resistor
1-Red LED
1-Green LED (note :Blue in diagram)
1-220uF/16V electrolytic capacitor
1-NPN transistor (2N2222, 9013, other general purpose NPN)
1-PNP transistor (9012, other general purpose PNP)

1-9V battery

19 LED flasher circuit using 555 IC

This project is a flashing led circuit powered by 555 timer IC.This

flasher circuit is composed of two versions, the simple led flasher 

that uses only two LED, and big flasher that consists 20  LEDs.

Simple LED Flasher circuit is powered from a 6V to 12V

battery and delivers a current of about 20mA to LED. The 

frequency of the flashing on both LED is controlled by 100K

potentiometer connected between the discharge and trigger pin

of 555 timer IC. The rate of flash ranges from 1blink per 2 

seconds up to 10 flashes per sec.

simple LED flasher schematic

Big LED flasher circuit is composed of 20 LEDs and uses transistors

as the driver and amplifier of the pulses generated by the 555 IC. The 

npn  general purpose type (9013, 2N222, etc), so is the pnp transistor

(9012, BC557, etc) If the supply voltage is 6V, R1and R2 =27 ohms 

while R1 and R2 = 200 ohms if supply voltage is 12V.

Big Led Flasher schematic

You can change the frequency of the flashes by changing the values

of resistors and capacitor using the 555 timer calculator.

If you planning to build up to 300 LED per group just replace the part of the schematic above with this. See diagram below. Power supply used is 12V.

Note: The type of LED can be of any color such as red, green, orange, yellow but not blue or white LED.
          Blue or white LED requires much higher forward voltage to light.