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pekar 8th May 2007 09:06 PM

DIY solar powered boombox
This is a link to a simple solar boombox I've developed.
More advanced versions have been made, but I tried to keep this as simple as possible so more people can build it.


DigitalJunkie 8th May 2007 09:16 PM


I've been running my chip-amp (TDA7350) from my 10W panel,and a bank of batteries. No mains noise here. :D

kstagger 9th May 2007 02:44 PM

neat idea - now I'm imagining a solar panel on top of the house... used to charge batteries to drive a bigger class D amp, and a portable CD/MP3/whatever player... and even my DAC which doesn't draw much current at all. When the clouds/rain comes there should be enough juice in the batteries to last you the night/day.

zacster 9th May 2007 06:28 PM

Those panels put out 24v if I'm correct, in which case you could run a low voltage tube pre-amp too, using 6GM8 tubes. I have an Aikido built that way, but no solar panels to power it.

FastEddy 9th May 2007 07:20 PM

" ... in which case you could run a low voltage tube pre-amp too ..."

Not too likely. The tube heaters will be too inefficient for the cells to maintain a decent level of power except in full sun.

Solar cells do put out a nice voltage, but solar output power falls off dramatically as the load increases. Watts is Watts ... :apathic:

A very nice concept BTW: solar powered MP3 player through solid state "boom" box ... I like it, good show!!

zacster 10th May 2007 01:24 AM

1.2a* 6v total? That doesn't sound like that much. That isn't even as much as a small light bulb.

G4ME 10th May 2007 03:48 AM

what about a solar paneled flash light? :D

Pano 20th May 2007 12:18 AM

This is a very "Bright Idea!"

I have 2 of these panels now (thanks Pekar) and it works. Works pretty well, too.

Quick warning - DO NOT connect 2 or more panels in parallel, there isn't enough voltage drop.

In the mid day tropical sun, these panels put out about 23V without load. That's far too much for the little Tripath chips. But not to worry, as Pekar notes, once you put a load on the panel, the voltage drops right down. Mine drops down to about 10.5V at moderate music levels.

I am running a Lepai amp because it seems to have over-voltage protection - that's a good thing. With just one panel running, I can't go very loud on small inefficient speakers because the voltage then drops to <8V. 8V is the cut off. As the Lepai has a diode on the power input there is a 0.6V drop. That doesn't help max levels any.

Putting 2 panels in parallel brings the voltage up too high and the amp shuts down. Too bad, because the amp cold use the extra power. Guess a voltage regulator is needed for 2 panels.

Adding a stiffener cap really helps. I put on a giant 47000uF cap. Lets the amp play louder overall because it fills in the power on the bass hits. Also keeps the amp playing when a shadow crosses the panel. 47000 is huge, but it was on the self, so I tried it. Turning off the Bass boost on the CD player really helped get levels up. The speaker I was using can't really do much bass anyway (Radio Shack Optimus).

There you have it, sun worshipers. Fun in the sun for your summer project. Thanks Pekar!

Oh, how is the sound? Luminous - of course! :D

DigitalJunkie 20th May 2007 01:01 AM

A small SLA battery might be a good idea..but would add some weight.
It would also help keep the voltage (fairly) constant ~12-13V.

pekar 20th May 2007 12:29 PM

I cover most of this on instructables, but having a battery in the circuit is recommended for most applications as it regulates the voltage and keeps things Rockin' when the sun isn't present.

My preferred SLA is a 2.3 Ah bag phone battery like this one-
But better deals can be found.

For a smaller, lighter, higher voltage power pack, I assemble 10 cell AA NIMH packs.
I get 5.5 hours of top volume playback from a 2.5 Ah battery with no solar charging.
...actually that is with my amp6, so a Sonic Impact should play longer.

The HF solar panels put out 120 mA. If your battery is 1.2 AH (1/10C) or larger, you won't have any problems with overcharging and no charge control circuit is necessary.


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