EE ternal Blinker Circuit Diagram
You occasionally see advertising signs in shops with a blinking LED that seems to blink forever while operating from a sin-gle battery cell. That’s naturally an irresistible challenge for a true electronics hobbyist. And here’s the circuit. It consists of an astable multivibrator with special proper-ties. A 100-µF electrolytic capacitor is charged relatively slowly at a low current and then discharged via the LED with a short pulse. The circuit also provides the necessary voltage boosting, since 1.5 V is certainly too low for an LED. EE-ternal Blinker Circuit Diagram The two oscillograms demonstrate how the circuit works. The voltage on the collector of the PNP transistor jumps to approximately 1.5 V after the electrolytic capacitor has been discharged to close to 0.3V at this point via a 10-kΩ resistor. It is charged to approximately 1.2 V on the other side. The difference voltage across the electrolytic capacitor is thus 0.9 V when the blink pulse appears. This voltage adds to ...