Creating a simple 1.5V LED Flasher circuit

Last updated on May 15th, 2022 at 10:48 pm

This is a 1.5V LED flasher circuit. It requires a low voltage of just one AA 1.2V/1.5V battery, it’s efficient enough to last for 1 year. And this circuit only uses a few components consisting of two transistors, four resistors, and three capacitors only.

1.5v-led-flasher-using-bc556-bc546

So, It makes this circuit easy to put together and cheap.

About decades ago, making the LED flasher was quite easy. Because it uses LM3909 with one resistor and one capacitor to get it to work. Also, it requires a low voltage of 1.5V to function.
However, this chip is not selling anymore, because the factory discontinued it.

But worry not, this presenting circuit is also easy. At least, we would not have a problem finding the components. Believe it or not, even 71 years old elderly can do it!

How does 1.5V LED Flasher works


As Figure 1 is 1.5V LED flasher using two type transistors NPN and PNP also can generate an oscillator can makes LED flash by use voltage 1.5V only. And also use current low of 2mA only.

The components list

0.25W metal/carbon film Resistors, tolerance: 5%

  • R1: 100K
  • R2, R4: 820Ω
  • R3: 56Ω

Semiconductors:

  • Q1: BC546, 45V 100mA NPN Transistor or Equivalent
  • Q2: BC556, 45V 100mA PNP Transistor or Equivalent
  • LED1: 3mm LED, any color you wish

Capacitors

  • C1: 0.01µF 50V Polyester
  • C2: 10µF 25V Electrolytic
  • C3: 100µF 25V Electrolytic


How to builds and testing

This circuit very simple you can assemble on Perforated board or bread board like me. Figure 2

testing 1.5V LED flasher on breadboard

Then, I test it with an Adjustable DC power supply as video below. Normally LED does not glow with 1.5V of power supply. It will glow up when the voltage exceeds 1.8V. But with this circuit, we make LED flashes by 1.2V voltage equal to a general AA Ni-MH battery.

I notice they will flash faster when lower voltage supply. So, we can adapt it as alarm low voltage batteries or other projects as you have ideas.

Here are three circuits similar to the circuit above.


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5 Comments

  1. simon

    hey the updates encouraging do you have electronic troubleshooting tips? thanks

  2. bhavesh

    how can i adjust duty cycle in this circuit

  3. MR OHM 1970

    The LM3909 was a Fun Chip To use…Too bad it’a Gone!!!

  4. Alena

    There are different rules out there, but these will be the most frequent ones you’ll come across.

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