Multi purpose oscillator 20 KC - HF with 2 Darlingtons, usable as inverter/HV oscillator/LED driver



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Please read the textbox/description. In this video I did not want to focus on the say “joule thief effect”, but on a principal way/method via which you can make in a succesfull way a radio oscillator/voltage inverter/or whatever other oscillator.

So it is about the principles of this 2-Darlington transistor oscillator, the issue is in fact not about the (refurbished) garden lamp.

The key to success is the coil with that tap in the middle (!) combined with a Darlington, consisting of 2 transistors with a substantial current amplification.

Say each transistor in the range of 80 to 150 (minimum, try & test!).
The driver preferred 150, the end-transistor in the 80 – 150 Ohms range.

The combined amplification (say 250 of a BC 547 B x 150 of a BD 139 = 250 x 150=37500) is so extremely high that almost all coils can be brought into oscillation, also coils that are not ideal, say in this case with the 3 steel pins as a core.

Steel/iron is far from ideal to work in a HF application.

Important: for a High Voltage oscillator use real HV transistors with a good amplification factor (say minimum 70) that can withstand a high voltage.

Good choice is e.g. the 2N5296, say 2 of them used as a Darlington. But there are many other High Voltage NPN or PNP transistors with a suitable Hfe, say 70 or 80.

Ferrite is (of course) a “better” material when you want to go to higher frequencies, say from 1 MC to 30 MC, etc.

I made with this setup many succesfull circuits in the past. Say an oscillator on 16 KC that was used to drive a cathode ray tube on (say) 4000 Volts DC (via a diode tripler and a classic 16 KC analog TV HV coil unit). More info in my books, showed in this video, available on the website of LULU. Search there for author Ko Tilman.

Correction to the video: the showed oscillator works in the 18 KHZ – 25 KHZ range, depending on the load: 1 white (fierce) LED or a bunch of blue LEDS, the blue LED board was made to work on 12 Volt, it worked quite fierce and good with this steel pin inverter.

Only problem with this steel pin inverter is that it is not optimized to take all the juice out of the (solar charged) 3 NiCad or NiMH batteries in series. There is (some) loss in this inverter, but when the sun gives everything.....

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 "LULU”, search for author “Ko Tilman” there.

https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=Ko+Tilman

I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 4 May 2022.

Sorry for my dirty fingers, I worked with black polymax kit, not very easy to clean it off. Always a problem, though the black polymax kit is the best kit for electronic applications... And much more, sealing, etc.
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