LM3909 Frequency generator | LED flasher circuit ideas

LM3909 is a famous integrated circuit. We often find them in the LED flasher circuit and oscillator generator. I do like it. Why? In the LM3909 datasheet, it is a very simple circuit. They are used instead of the original circuit that uses dozens of transistors easily. Just you add a capacitor and a resistor for each one only.

They can drive LED blinking fast or slow with a few parts. It is so great in DIP 8 pin same as the 555

LM3909 simplest LED flasher circuit


In addition, it has very low power consumption, for example, a 1.5V battery could drive the LED flashes. And also current is only 0.3mA. You so use it for many months.

Thus, I will show you with the LM3909 collection include 7 circuit ideas, as following.

  • Frequency generator circuit using LM3909
  • LED Flasher—1.5V or 3V Battery Monitor circuit
  • Fast LED flashing 1.5V
  • LED Display for power supply 6V or 15V using LM3909
  • One LED display flashing low volt
  • 3V Lamp flasher High Current using LM3909

Frequency generator circuit using LM3909

This is a simple frequency generator circuit using LM3909. LM3909 is famous for all you know it. Because there is a famous story a flashing light to save energy and external devices. But in fact, it can also be the same ICs frequency generator.

Frequency generator circuit using LM3909

Simple frequency generator circuit using LM3909

Because the LED flash by voltage as The output voltage time to time, thus creating a virtual frequency out there. As the circuit in Figure 1 can be made out in the frequency range of 100 Hz to 10 KHz.

Figure 1 The circuit diagram of the Frequency generators circuit using LM3909
For application to easily change the frequency We just have to adjust the VR1. The VR2 is used to adjust the characteristics of the waveform to be symmetric as possible. You are now a small compact Oscillator to use another machine.

How to builds

This project uses just one LM3909 and a few other components. Thus we can assemble on the universal PCB board. As Figure 2 But you should be careful about wiring, various components specific polarity of the electrolytic capacitors and Pin of the IC.


Figure 2 The components layout of this Frequency generators circuit using LM3909

The components List
Resistors size ¼W +5%
R1: 470 ohms
VR1: 1K, Single linear potentiometer
VR2: 50K, Single linear potentiometer
C1: 0.1uF 25V, Ceramic
C2: 47uF 16V, Electrolytic
IC1: LM3909 Led Flasher/oscillator
Others components.
socket IC 8 pin for LM3909
The universal PCB board.

Now, LM3909 is not easy to buy. I checked on ebay.com. You may use other ICs such as 555 timer. It is a popular series of all time. NE7555 (CMOS types) uses a low voltage power supply.

Learn: How to use 555 timer circuits

LED Flasher—1.5V or 3V Battery Monitor circuit

Battery 1.5V or 3V Monitor circuits using LM3909

Let’s add a blinking LED for Monitor the electric current of 1.5V or 3V battery. By use, the integrated circuit LED Flasher or Oscillator. By the rate something flasher equal to 2V.

This circuit eats electric a little current poor age the work of battery long can’t be like be usable. If friends use battery 3V as result liberate pin 1 float keep. I hope that a friend may apply with Battery 1.5V or 3V Monitor Circuit

Fast LED flashing 1.5V

Fast LED flashing 1.5V

The Fast LED flashing circuit. that apply to AA Cell 1.5V. By add resistor 1K size between pin 1 and 8 pin of IC number LM3909. It will rate winking expansion 3 again times. When build capacitor 330uF sizes suit 1 pin and 2 adaptation pin modify by the tow electronic part outside. It makes way for choose for resistor outside equal to 3K,6K, and 9K. Other detail, see in the circuit.

LED Display for power supply 6V or 15V using LM3909

LED Display for power supply 6V or 15V by LM3909

This circuit uses the integrated circuit LM3909 perform be LED Flasher and Oscillator. For Drive LED give Flasher on – off with Frequency 2Hz.

For a formed show of office equipment with Battery For battery 6V size Capacitors. CT be valuable 400uF, Rs be valuable 1000ohm and RFB be valuable 1500ohm. For voltage 15V size the value of, CT equal to 180uF Rs equal to 3900ohm and RFB equal to 1000ohm. The useful life of battery long because the circuit uses a little electricity.

One LED display flashing low volt

One LED display flashing low volt

This circuit is LED display flashing with one LED. By when you press Switch S1 to give wasp the circuit then to liberate. It, as a result, make LED1 bright about 0.5 second. By this circuit uses the integrated circuit of NS number LM3909.

It is build the mono stable multi vibrator circuit produce low frequency. It uses low power supply 3V only just.

3V Lamp flasher High Current using LM3909

3V Lamp flasher High Current by LM3909

If you like to use the integrated circuit LM3909 to build a Flasher Circuit. But may get into trouble about applying to Lamp at having the requirement Current tall no. I then introduce to see this circuit can apply to power supply 3V and apply to Lamp 3V 1A get.

The transistor helps to increase a current hight up for the rate something flasher of a lamp can then poor Lamp stick bright can be unfinished.

This circuit uses the integrated circuit makes flasher get. By build transistor a kind NPN that durable Current 1A or tall more build stay the outside. This circuit can use to is Lamp warn at fine the frequency of something Flasher get. For use advertise or show something.

Then, the lamp at have reflected large-sized stay within a darkroom will fine give wink with tall speed That will do see to is actor picture stops something K rumor can shake. Friends may get circuit this idea goes to apply please sir.

Bicycle turn signal light circuit

We should have bicycle turn signal light circuit. It will save your life. In usual a bicycle does not have a turn signal light. If you want to turn, it may be dangerous. Because the car drivers that follow you, do not know you will turn.

You should add the safety to your yourself with building bicycle turn signal light circuit link this.

Light turning bike using IC LM3909

The work of the circuit
This is circuit uses LM3909 flasher oscillator IC. It will drive LED to flash with a low power supply,1.5V only.

In normal time, the switch-S1 will be a position-OFF.

Then, If we want to turn right, we will slipe the switch S1/1 go to a position Right. There is the 1.5V power supply goes to IC1. So IC1 will generate oscillator out of pin 6, and flows through the contact switch S1/2.

The circuit makes LED3, LED4 to flash at the same time conversely.

In another way, when we turn to the left. Also, S1/1 go to at a position Left. The frequency signal that pin 6 of IC1 will flow to the contact of switch S1/2.

It makes LED1, LED2 blink at the same time.

Change speed! The speed in flasher depends on the value of C1.

This circuit can work a long time, save your battery. Because the circuit will work just when opening the signal light only.

Keep reading: ‘555 frequency generator circuit’ »


I always try to make Electronics Learning Easy.

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