Solar Powered Amplifier?

[earthtonesaudio]

Semi-related... I once saw a band that had the instruments charged up via bicycle-style generators.  About 6 audience members sat in stationary bikes and provided the power for the band.  I don't know if it would work for your friend, but just thought I'd throw it out, in the spirit of recharging...

[grapefruit]

I've used the LM4950 running from 12 volts and it put out about 6 watts into 8 ohms in bridge mode. We've played around with some MP7720DP class D amp chips. They are good but you have to make a SMD PCB to use them, and need 24 volts to get maximum power.

I've had good success using a Panasonic 7.2A/hr SLA battery. I used it to power a ghetto blaster that used to run off 8XD cellc. It would run every night for weeks without a problem. I used a plugpack type charger to charge it.

Cheers,
Stew.

[Mark Hammer]

1) Check the quiescent current ratings for whatever chip you use.  People forget that the amp consumes current even when you're NOT playing.

2) The supercapacitor idea is great.  Again, it's not the voltage so much as having that reservoir of available current to handle any sudden transient demands.

3) I am constantly impressed with how freaking loud my little 2W LM380-based amp is.  Six and a half inch speaker but the cabinet is bigger than you might normally find, and the extra bass that contributes makes the thing sound MUCH bigger and more powerful than it really is.  Two watts with the right cab/speaker combo, and the sort of gain structure and toneshaping that lets everything come through audibly can be surprisingly effective.  I run mine off an octet of rechargeable C-cells and it goes for quite a while.

[puretube]

These WIMA caps (brandnew...) can be cascaded! 

[Joe Hart]

Wow!  A ton of great info and ideas!!  Thank you, everyone!!!

Is this possible:

Can I build a Ruby (or something), have a solar powered battery charger with the battery hooked in like it's charging, and just tap the power off of the battery terminals?  In other words, panels to charger circuit (which includes a diode to prevent the battery from draining out the wrong way) to battery plus Ruby circuit (so the Ruby is wired in parallel with the battery).  Would this work?  I'm thinking that the amp would pull power from both the panel and the battery therefore keeping things somewhat constant and on a sunny day the battery would even be charging (perhaps slowly) while the amp is actually in use?  Or would I just have to charge the battery, then actually switch the battery out of the charging circuit and into the amp circuit (with a hard wired switch -- not physically moving the battery back and forth)?
-Joe
P.S. Mark, do you have a schematic for that LM380 amp or is it basically a Little Gem with that chip tossed in?

[earthtonesaudio]

Wow!  A ton of great info and ideas!!  Thank you, everyone!!!

Is this possible:

Can I build a Ruby (or something), have a solar powered battery charger with the battery hooked in like it's charging, and just tap the power off of the battery terminals? 

Seems like it should work.  But that is a very important question, I'd get a few opinions on the matter before connecting anything.

[demonstar]

Wow!  A ton of great info and ideas!!  Thank you, everyone!!!

Is this possible:

Can I build a Ruby (or something), have a solar powered battery charger with the battery hooked in like it's charging, and just tap the power off of the battery terminals? 

I don't see why this shouldn't work because it's the same principle as when a mobile plugged in charging while still turned on. So there shouldn't be a reason that I can see why any other battery can't charge and drain energy simultaneously if a lithium ion phone battery can. (I am just speaking from a commonsensical point of view it may be worth seeing what others with more know-how have to say.)

I'm not quite getting why not just plug the batteries into the mains when you get home to charge them and maybe occasionally if weather is suitable, into a solar charger. This would save hooking up the solar charger into the amp etc. It just seems a tad unnecessary. I guess you'd only be using an AA battery pack if it was a single ruby or other LM386 based project so they'd be dead easy to recharge virtually anywhere. It's not like if you were using a more powerful amp chip and needing to cart around a lead-acid monster were you maybe wouldn't want to leave one of them charging in the kitchen.   

If you do go for an LM386 based project look around because there of different variations.

Good luck with your project! Let us know what you decide on please.

[Joe Hart]

Demonstar (and probably most of you)... why do it solar when a little battery-powered amp with rechargeable batteries can be bought on eBay for cheap?  Why do we do anything DIY?  To see if we can!  I just figure it would be neat (and green).

My only concern is that (theoretically) if I have 9V from a battery, and 9V from a solar panel/charger, would this now be feeding 18V into the circuit?  That may be too much?

I actually have a circuit that I'm hacking from one of those kiddie guitars with the speaker in the guitar.  It runs off 2 9V batteries and uses a KA2212 chip.  I hooked my "real" guitar to the circuit and tried it with an external raw speaker and it sounds okay.  So, I was planning on taking the circuit out, hooking it all up and then trying some different values for caps and whatnot to see where it takes me.

So would a solar panel to charge the batteries added in create too much current?
-Joe

[arawn]

Just my 2 cents but for this sort of project wouldn't it be ideal to run lower impedance speakers? say 2 or 4 ohm? Should be more efficient from what i understand, Part of the trick with the car audio guys They run lots of speakers at lower impedance and acheive much higher spl levels which is ultimately the concern here. More volume on a minimum of power!

[demonstar]

My only concern is that (theoretically) if I have 9V from a battery, and 9V from a solar panel/charger, would this now be feeding 18V into the circuit?  That may be too much?

I've been searching around it appears that the solar cell is paralled with the battery obviously with a diode in there to stop the battery discharing onto the solar cell and damaging it when there is no energy being created by the solar cell. The other big issue appears to be there needs to be a circuit there to stop the battery from over charging. These overcharging circuits seem to contain inductors. (arghhhhh!!!)

Demonstar (and probably most of you)... why do it solar when a little battery-powered amp with rechargeable batteries can be bought on eBay for cheap?  Why do we do anything DIY?  To see if we can!  I just figure it would be neat (and green).

Fair enough, sounds a good reason.

[Nasse]

http://www.treehugger.com/files/2006/09/20_solar_panel.php I found this link, not much useful info but interesting talk anyway. I think it might just be possible to keep small battery "topped up" with reasonable cost if you find suitable solar cells and circuitry, AC powered charger is needed anyway if battery is deep discharged I think. I found interesting links about solar charged bicycle lights, and a workmate´s brother had done a wind power generator from Shimano bicycle hub generator.

[rotylee]

Maxwell even sells a powerpack setup that may be just the thing.  One issue, though.  It seems that they cost about $140.00.  But maybe I'm missing something and they can be had much cheaper?

well you are talking about an expensive amp.
how much are the solar panels?
how much for/to build the power controller.
batteries...(what batteries?)
what if you want to plug in wind or hydrogen fuel cells or some other for of renewable energy.
even a generator would need noise suppression circuit.

[Mark Hammer]

P.S. Mark, do you have a schematic for that LM380 amp or is it basically a Little Gem with that chip tossed in?

http://hammer.ampage.org/files/Miniamp.zip

[Joe Hart]

Maxwell even sells a powerpack setup that may be just the thing.  One issue, though.  It seems that they cost about $140.00.  But maybe I'm missing something and they can be had much cheaper?

well you are talking about an expensive amp.
how much are the solar panels?
how much for/to build the power controller.
batteries...(what batteries?)
what if you want to plug in wind or hydrogen fuel cells or some other for of renewable energy.
even a generator would need noise suppression circuit.

I'm looking at an inexpensive type project.  Using recycled parts, home stereo speakers from the neighbors' trash, solar panels are less than $10.00 each, and even a solar rechargeable kit (with the battery included) is less than $20.00.  So, I'm going low budget here and the $140.00 would make me lean towards just buying a little portable amp -- but that takes all the fun out!!!
-Joe

[earthtonesaudio]

Zener regulation would work probably.  Just slap a power zener on there.  I'd go for one rated for the wattage of the solar panels.  Probably a 5W would handle most small panels, but you might be able to get away with a 1 watt or 1/2 watter.