Please read the description first. Essential info there. Needle pulse generator for the audio or higher frequency range on 0,9V-1.5 Volt.
Application: beeper, morning awaking sound. Use say a few solar cells in a row (each cell gives 0,8 V max by the way, so many (!) of them in series, lying on the window sill, say 6 cells, more info in the textbox) when the sun starts to shine in the morning there.
I tested this option. Supplying it via solar cells and it only worked with say 5 or 6 of them in series, that means (say) 6 x 0,8 V = say 4 Volt effective under load. And it did NOT work in the simple way that I expected, say with 2 or 3 Solar cells in series or so (strange but true).
I think: the supply current to make the earphone unit "beep" in a somewhat fierce way (audible) was too low, when supplied via that solar cell unit (4 Volt-100 mA in bright sunlight = 4 x 100 = 400 Milliwatt, that is not much, it was tested today).
So no advice to use this circuit with solar cells. Much better idea in that case: use a classical A-stabile Muvib, with 2 x a BC 547 b. It is on my YT channel, search it via the search option (magnifying glass, there), via keywords: "multivibrator" "astable" etc.
Or moisture indicator: use say a 2 V battery (perhaps even 3 Volt = 2 x 1.5 Volt with a series resistor in the order of 1 K (experiment with that 1K value, could be a lower value in the range between 1000 Ohm and say 50 Ohm) to limit the max. current to the oscillator and take 2 ground electrodes/probes in series into that supply lead. The frequency tells you: dry or wet sound.
Sensitivity/sound can be set via that 470 K potentiometer.
Easy to make, only 2 transistors and works on 0,9 Volts, also (thus) on a 1.5 Volt standard Carbon-Zink or Alkaline battery. The circuit can be used in many applications.
When you want to use this circuit on voltages higher than 1.5 Volt (max. 2.5 Volt or so): wild oscillations can start. Also a too high current can flow through the transistors. In that case the transistors can/will burn out.
Test, try, experiment! Everything important is told in the video.
Some small corrections:
Of course (on 1.51 in the video) the drops of bleach and (say) the teaspoon of salt are diluted in 200 mL of water, to make an electrolyte. Be careful with that bleach water (Sodium Hyposulfite)
2.18 in the video of course (when you know something about the differences of Germanium and Silicon transistors): the Si-transistor has a higher barrier voltage (in the order 0,7-0,8 V) compared to germanium transistor (in the order of 0,3 V-0,6 Volt).
My You Tube channel trailer is here: [ Ссылка ]
Type there the keywords that you like (e.g. radio/audio/amplifiers/test/filter/) in the “looking glass” = search function” and give “enter”. Via that you can find specific video’s (under the say 1500 published).
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. [ Ссылка ]...
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. Upload 30 July 2024.
Important: much better is the 2 transistor A-stable Muvib. Say with 2 x a BC 547 b. Make it? Means emitter to ground of both NPN transistors (-), the 2 collectors via a 1 K resistor to the (+) lead (6-12 V). And the two base connectons of each BC 547 b via a 10 K resistor to the (+). Connect a 470 N (=0.47 uF) cap from the collector of TS 1 to the base of TS 2. And a 470 N cap (=0.47 uF) from the collector of TS2 to the base of TS1. Now it oscillates (signal it at the colector of TS2), but sometimes the oscillation does not want to start! Only when you "tip" the (+) line to the circuit. When you slowly put up the voltage to the circuit: it does not want to oscillate. More video's to come, how to cure that.
