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 _________= 1 pcs.
Q2_____BC556___45V 100mA PNP Transistor or similar_________= 1 pcs.
C2_____0.01µF 50V Polyester Capacitor___________ = 1 pcs.
C2_____10µF 25V Electrolytic Capacitors________ = 1 pcs.
C3_____100µF 25V Electrolytic Capacitors_________= 1 pcs.
R1_____100K 1/4W Resistors_______________________ = 1 pcs.
R2,R4__820 ohms 1/4W Resistors___________________ = 2 pcs.
R3_____56 ohms 1/4W Resistors___________________ = 1 pcs.
LED1 any color as you want_______________________ = 1 pcs.
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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