This is a low voltage LED flasher or 1.5V LED flasher circuit using BC556 and BC546 transistors. And other electronic devices is 4 resistor and 3 capacitors only. When about 15 years ago, making the LED flasher easy. because I use IC-LM3909 with an external device, only one resistor and one capacitor only got it to work. Also, use a low voltage 1.5V, it works now. However, IC is not selling because the factory discontinued.
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.
This circuit from we take them to use as many circuit below:
The components list.
Q1: BC546, 45V 100mA NPN Transistor or similar
Q2: BC556, 45V 100mA PNP Transistor or similar
C2: 0.01µF 50V Polyester Capacitor
C2: 10µF 25V Electrolytic Capacitors
C3: 100µF 25V Electrolytic Capacitors
R1: 100K 1/4W Resistors
R2,R4: 820 ohms 1/4W Resistors
R3: 56 ohms 1/4W Resistors
LED1 any color as you want
How to builds and testing.
This circuit very simple you can assemble on Perforated board or bread board like me. Figure 2
Then I test it with Adjustable DC power supply as a video below. normally we cannot apply 1.5V to LED glow it will on when the voltage exceeds than about 1.8V only. But with this circuit, we can cause LED flashes with voltage 1.2V like general AA nickel-cadmium battery.
I notice them will fast flasher when lower voltage supply. So can use to alarm low voltage battery or other projects as you have ideas.
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