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Help with a solar audio oscillator.

TheRedPlanet

New Member
Hello! This is my first post on this forum and I'm happy to be here.

A little bit of background..

A recent interest in solar energy paired with an interest in insects lead me to designing a solar cricket installation based on 74HC14/40106 integrated circuits, recycled solar panels from garden lights, and piezo speakers.

This project being somewhat successful made me wonder if a similar (more musical) installation could be possible.

The idea was to keep the same solar panel and piezo but replace the insect sound circuits with oscillators that hold a single tone while receiving adequate sunlight. The problem with using a 74HC14 for this is that the tone of the oscillator changes as the chip is starved from changes in lighting. Maybe I could use a voltage detector that turns the circuit off under certain conditions?

Obviously my electronics knowledge is limited but there's plenty of audio wizards on this forum that I'm sure could give me a sense of direction.

Apologies if that isn't enough information. I'm happy to elaborate if there's any questions. :)

Thank you!
 

audioguru

Well-Known Member
Most Helpful Member
Solar levels change with clouds so of course the supply voltage changes. Use a rechargeable battery?
The squarewave buzzing from a simple oscillator makes poor music.
The high pitched squeak from a piezo transducer also makes awful and poor music.
 

AnalogKid

Well-Known Member
Most Helpful Member
Without your schematic there is nothing to comment on. Also, it is not clear what the question is.

ak
 

audioguru

Well-Known Member
Most Helpful Member
Solar garden lights use a solar panel that produces about 2V at about 25mA in sunlight which is only 50 milliwatts. The power drops with clouds.
A 74HC14 has Schmitt-Trigger inputs which change their trigger voltages when the supply voltage changes which changes the oscillation frequency.
A simple Cmos Schmitt-Trigger oscillator produces a squarewave output sounding like a buzzer.
A piezo transducer produces high pitched awful squeaky sounds.
And he want it to make music!
 

dr pepper

Well-Known Member
Most Helpful Member
A 40106 oscillator would be the choice, being ratiometric the chip in the right circuit wouldnt give great changeing tone over supply voltage, I htink something else is occuring, maybe motorboat effect or soemthing.
One of the 40106's gates, a zener and a resistor might be arranged to give you a staop/start at a certain voltage.
Another thing maybe put together a acoustic resonator so the sounder is loud at one frequency, all others being less so.
 

audioguru

Well-Known Member
Most Helpful Member
Two or more solar panels from garden lights in series are needed to power a 40106 oscillator since its minimum supply is 3V. Also, at only 4V its output power is very low.
A piezo transducer has a few high frequency resonances that are loud but the frequencies between the resonances are faint.
 

TheRedPlanet

New Member
Maybe music isn't the word, I just wanted to create something I thought was sonically interesting. I understand the limitations of square waves and piezo speakers.

I ended up finding almost exactly what I was looking for with this schematic.

Now I just need to track down some 1381s or something to substitute for it. :rolleyes:
 

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dr pepper

Well-Known Member
Most Helpful Member
The 13811 is a voltage detector ic, it starts & stop the beeping at 2.2v.
Theres some on ebay that are 2.4v, not sure if they are genuine parts though.
 

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