Two transistor LED flasher with 1 Green/Yellow/Red LED that can be set to many flash frequencies HD
Please read the description/textbox. A very simple led flasher (demo circuit, can be elaborated) made with 1 NPN transistor (the BC 547 b or equivalent) and 1 PNP transistor (the BC 557 b or equivalent). Important correction, after elaboration and more experiments this evening: the circuit also works with a WHITE LED (!) even with a bunch of paralled WHITE LEDS. When Rx is too low (say shortcut), there is no flash effect with White LEDS. When R x = 820 Ohm the circuit also flashes with white LEDS. When the "upper" capacitor is 1 uF bipolar (base of the BC 547 to the 100 K resistor) it flashes every second. The amplification factor (say Hfe) is key for success, so be it 200-300. You can also try NPN and PNP Silicon transistors with a lower amplification factor, no problem with that. Limit is say 100-150. The circuit can drive 1 Green or 1 Red or 1 Yellow LED, at least in this configuration. Surely more LEDS when they are paralleled can be driven. In that case: experiment with the value of the 820 Ohm resistor, make that value smaller (say 470 Ohm or even smaller, say 100 Ohms) when the circuit has to supply a bunch of paralleled (read: identical) LEDS, be it green or red or yellow. On 12 Volt. In general: not white LEDS, their supply voltage is around 3.5 Volt, but don’t hesitate to do the experiment with 2 medium power transistors like the BD 139 and the BD 140 and some white LEDS, with a resistor in the 220 Ohms to 100 Ohms range at 12 Volt/300 mA supply voltage. When I have time I will test that setup in the future. The flash ratio depends on the capacitors, they are showed here: between 220 N (=0,22 uF) and 10 uF. But don’t think too small about this 2 transistor unit/basic setup. With medium power transistors (say the BD 139 NPN and the BD 140 PNP) you can get good/better results, say when you want to drive a coil or a bunch of white LEDS. Of course the circuit has to be adapted somewhat in that case, one of the aims of my You Tube Channel: do some experiments :-). When you have questions about (certain analog) electronic circuits and how to make them: go to my Channel trailer (Radiofun232 on You Tube) and go to the “looking glass”. Type there the keywords that you want/need like: “power supply”, audio amplifier, capacitor tester, oscillator, radio, shortwave, shortwave radio, or any keyword you like to find the essential info & schematics on my YT channel. You can contact me via email when you have questions about my published circuits. My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in. My books about electronics & analog radio technology are available via the website of