pulse a LED – duty cycle part 2 (LED flasher)

Part 2 of how to let a LED light up on maximum power by means of a squarewave generator and a driver-transistor. The square wave generator (a stabile multivibrator) is a useful and practical circuit. Useful to test an amplifier, make a tone generator, make a simple organ, drive a LED or a transistor etc. In many cases it can replace a 555 timer chip in astabile mode. Full version of the square generator (50 Hz – 16 KHz) is in my book “Schematics 1″, the circuit showed here is almost the same but the wave has a little bit rounded edges (operating with two 1 K collector resistors and two 10 K base resistors). But the circuit is useful enough for this simple application as LED flasher. If you watch this video on another channel/website, please check YouTube for the original content. Nb: the circuit works good on a lower voltage when the coupling capacitor is removed (shortcut) and the wire from the potentiometer is directly connected to the collector from transistor 2. In that case the circuit operates very well (high flash) on 2 Volt. You can also forget the driver transistor and take the LED in the collector wire of the second transistor. Take a suitable series current limiting resistor in the collector wire of transistor 2 in that case. If you use electrolytic capacitors from 50-100 uF the LED flashes between 1-5 x each second in that case. Please note that my digital camera is unable to record the correct flash rate of the LED, in real the flash rate is higher then on the video.

Duration : 0:4:7

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