Power lm386 with Solar Panels

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
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
 

Attachments

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
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.
 

sghioto

Joined Dec 31, 2017
2,363
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.
1623375036302.png
 

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
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.
 

Attachments

Audioguru again

Joined Oct 21, 2019
3,207
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.
 
Last edited:

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
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?
 
Last edited:

Thread Starter

Adam Monarch

Joined Mar 17, 2019
59
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?
 
Last edited:

Audioguru again

Joined Oct 21, 2019
3,207
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.
 
Top