I would like to know how to power an lm386 amplifier with solar panels. I designed a lm386 schematic. This schematic
works with a 9 volt battery but does not work with the solar panels in series or parallel configuration.

Please tell me what I am missing. Each solar panel is approximately 2 to 3 volts dc.

Thanks

 

What is the voltage output from the panels in series when connected to the LM386?

 

What is the voltage output from the panels in series when connected to the LM386?

approximately 7 Volts dc

 

Should work with 7 volts, what is connected to the input? What exactly is it not doing?

 

I connected an electric guitar at the input. There is a led which lights up in series with the output voltage of the panels. However, the circuit does not amplify the sounds of the guitar using the solar panels. It works fine with a 9 volt battery, amplifing the sound of the guitar.

 

There is a led which lights up in series with the output voltage of the panels.

Why? Remove the LED.

 

Why? Remove the LED.

The led lets me know if the circuit is on. The led lights up and the amp works with a 9 volt battery, why should the led be the problem?

 

The led lights up and the amp works with a 9 volt battery, why should the led be the problem?

From your description of the LED in series makes me wonder how it is actually connected. Show the LED in your schematic please.
The output maybe oscillating using the panels. Connect a .1uf cap in series with a 10 ohm resistor from pin 5 to ground.

 

From your description of the LED in series makes me wonder how it is actually connected. Show the LED in your schematic please.
The output maybe oscillating using the panels. Connect a .1uf cap in series with a 10 ohm resistor from pin 5 to ground.
View attachment 240932

Here is an updated schematic. I will make the changes you suggested and see what happens.

 

You were correct you have the LED in series. Probably dropping too much voltage through the LED. Remove LED and try again.

 

A 2V solar panel is usually used in a solar garden light. It produces 2V at about 40mA in bright sunlight or only a few mA in room lighting.
A blue or white LED uses 3.3V so it drops the voltage feeding the LM386 to 7 - 3.3V= 3.7V.
The datasheet for the LM386 shows that its minimum supply voltage is 4V for some or 5V for others. Of course it works with a 9V battery, 9V - 3.3V= 5.7V.

The output power of an LM386 is shown on its datasheet producing 0.25W at low distortion into 8 ohms when its supply is 6v. it shows that then its heating is 0.22W so the power supply must produce 0.25W = 0.22W= 0.47W. Then the maximum 6V power supply current is 0.47W/6V= 78mA which is impossible from the weak solar panels but possible for a couple of hours from a 9V battery.

An LED should never be connected in series with the supply of an audio power amplifier.
Edited. the decimal point was in the wrong spot.

 

Here is an updated schematic. I will make the changes you suggested and see what happens.

Well I made the changes you suggested and I hear a faint click each time I strum the guitar.

 

Did you remove the LED?

 

A 2V solar panel is usually used in a solar garden light. It produces 2V at about 40mA in bright sunlight or only a few mA in room lighting.
A blue or white LED uses 3.3V so it drops the voltage feeding the LM386 to 7 - 3.3V= 3.7V.
The datasheet for the LM386 shows that its minimum supply voltage is 4V for some or 5V for others. Of course it works with a 9V battery, 9V - 3.3V= 5.7V.

The output power of an LM386 is shown on its datasheet producing 0.25W at low distortion into 8 ohms when its supply is 6v. it shows that then its heating is 0.22W so the power supply must produce 2.5W = 2.2W= 4.7W. Then the maximum 6V power supply current is 4.7W/6V= 783mA which is impossible from the weak solar panel but possible the half an hour from a 9V battery.

An LED should never be connected in series with the supply of an audio power amplifier.

Should a put a resistor in series with the led so the led is not in series with the power supply directly as a rule of thumb? If so, what value resistor do you suggest?

 

LED should be wired as in this modified schematic.

 

Did you remove the LED?

Yes I removed the LED. It still doesn't work.

 

Again, read the voltage on pin 6 with the solar panels connected.

 

pin 6 measures at 2.24 volts dc and the voltage measured across the three solar panels alone unconnected from the circuit in series is 10 volts dc. The LED is no longer in the circuit. I hear some faint clicking but no sound. Is the supply voltage too low on pin 6?

 

pin 6 measures at 2.24 volts dc

That's your problem! The solar panels can't deliver enough current.
What type panels are you using?

 

Didn't you read my post #11? It had a math error than I fixed now.
Didn't you read the extremely important datasheet for the LM386?

Your solar panels are much too small to produce 78mA or more. Use them to charge a little battery for a couple of weeks.