Instructables

Solar Powered Amplifier

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Instrument amp powered only by the sun. This is an amplifier that was inspired by a little high school punk/jazz band that plays in the summer near a farmer's market close to home. They are always playing acoustic instruments and I thought what if they could play electric instruments at a reasonable volume without a generator. Thus the solar powered amp was conceived. It took all summer but I finally finished the guitar amp of the set. The bass amp will follow since I found a set of stereo speakers really cheap. I am trying to finish the bass amp this winter so if the group shows up next summer I can see if they'd play through them. I love the retro look of the speakers.

The amp is meant to be used outdoors in the sun so there was no need for a battery. Also even if I charged a 9VDC battery it would only last about 15-20 minutes inside anyway.

Comments as always are very welcome. This is my first time powering anything with the sun.
 
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Step 1: What you need

Picture of What you need
IMG_8892001.jpg
A single speaker in a cabinet:
I found these speaker boxes at a rummage sale, they cost me $4 for both. What a deal!! You should be able to use any detachable speakers for this. great if you have a dead boom box or have scrounged the parts out of one, say to use a tape head for a tape delay. (instructable coming soon as i can scrounge enough tape heads)

Amplifier circuit:
LM386 Amplifier chip
5K linear potentiometer
1M audio potentiometer
100uf capacitor
.1uf capacitor
.047uf capacitor
10 Ohm resistor

Solar panels/power section:
1N4001 diode
2 x 2200uf electrolytic capacitors
I found 9VDC at 100mA seemed to be the magic number for me. I got mine through American Science & Surplus at 4.5 VDC by 50 mA you need 4 of these.
A sheet of plexi to mount the panels to
A hollow ball joint to feed the power wires from the inside of the speaker housing
Lenny243 years ago
Hey!
Cool instructible! Well, It isnt' very Important which wire goes where on a speaker, because they are Powered by AC.
How about using an amplifier which is a bit more powerful? But then you'll have to store the energy out of the solar cells in a lead battery or so.
Sparklesam5 years ago
u say that u used a 1M audio potentiometer, but is that the same thing as a 1M potentiometer?
pstretz (author)  Sparklesam5 years ago
Sorry for the confusion, I meant audio taper. Pots are either tapered audio or linear, see link. http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
abadfart5 years ago
how loud is this i want to use it outside for a performance. in the sumer we do rock shows in empty fields any where we can but we have to stretch out really long power cords for the half stacks.
pstretz (author)  abadfart5 years ago
well, your half stack has probably a 50-100Watt amp attatched to it. this is about a 1Watt amp. :) no, it will not amplify your rock shows. ;) it is maybe as loud as a small portable boombox. Think an amplifier for folk music to a crowd of about 20. There is no way this would ever be able to cover up a drum rock set. You could maybe scale it up to blend with a jazz set if your drummer was using brushes. :)
maybe 6 car batterys hooked up in line with an inverter
pstretz (author)  abadfart5 years ago
except you'd blow up the board sending it that much power. If you looked at the power section from an amp and basically just used this as a pre-amp maybe. By the time you spent all that time and effort, you'd have been better off to just buy a cheap generator and put a wood wall between it and the stage. That's what we always did. :) Here is a 28W solid state amp that runs on 12V. http://www.ssguitar.com/index.php?topic=1143.0 though you'd have to find some way of regulating it and i couldn't tell you how fast the battery would drain. Maybe ask around in the forums about a car battery powered amp.
the 6 battery's and inverter were to run my half stack
pstretz (author)  abadfart5 years ago
yeah, I think it'd still be cheaper to buy a generator that could power your whole band than batteries for everyone.
ya
dcpalmer5 years ago
I can purchase a 12 volt, .120 amp solar panel for not much money. They sell them as trickle rechargers for car batteries. Would this amp design work with that or would that power level blow it out? How could I modify this desigh to work with a more powerful wattage? Thanks from Milwuakee, WI.
pstretz (author)  dcpalmer5 years ago
All you have to do is swap out my solar section for yours. You may need 2 of those panels depending on the day. Try 1 first and see how it does. If you find the sound cuts out when a cloud goes overhead add another panel in parallel or increase the values of that capacitors. You may want to put your panel in direct sunlight, pointed at the sun and check that the voltage does not exceed 18VDC, other than that, have fun.
I am actually getting ready to build one of these. I have a couple of questions that really show how ignorant of electonics I am. 1. I notice you call for a 1 m pot for gain control and a 5 k pot for volume control. How important are these values? Would a 1 k pot do just as well in either role, oe 5 K pots. What does that 1 meg pot get you? 2. There are different versions of the 386 op-amp. One of theme can handle high voltages. Would 12 volts at 150 ma get you much more volume? This is a matter of curiousity for now. I will be using 9V .110 amp for my first try. That's all for now. Thanks for putting this up and for answering my questions.
Sandisk1duo5 years ago
what's the difference between gain and volume?
pstretz (author)  Sandisk1duo5 years ago
gain controls distortion of the input, volume controls how much of the sound goes to the speaker. that way you can have lots of distortion and not annoy your roomates. not that it's that loud. :)
but gain also controls volume, right?
pstretz (author)  Sandisk1duo5 years ago
not if it's labeled correctly. Gain always controls how much of the signal gets through. if you want a clean signal but the input is really quiet, you turn up the gain. if your input is really loud or "hot" you turn down the gain.

if you have a loud signal, say from a guitar with the knobs all at maximum, and you turn the gain up, the signal will start distorting. because of this distortion, the signal gets compressed and sounds louder. see this wikipedia article, http://en.wikipedia.org/wiki/Clipping_(audio)

Volume, again assuming it is not mislabeled, only controls the output to the speaker. In most cases it is a variable resistor driving the between full out signal and ground. Turn the knob up and the resistance increases to ground so more signal goes to the speaker. Turn volume down and the resistance to ground decreases and more signal goes to ground than the speaker. Alternatively you can control how much input goes to the circuit, which is what I did. R3 on the schematic controls how much of the input goes to the amp. By controlling volume at the beginning, I could use cheaper parts since they wouldn't see the high wattage that goes to the speaker.

Does that help?
yes i understand the more gain the more hiss
WilderLust6 years ago
Nice... just one thought about your sourcing. i have purchased stuff from The Electronic Goldmine, www.goldmine-elec-products.com, which has solar panels that will be much cheaper... they have a 10V 150mA unit for just under $10. Most people on this site will find them an awesome source for goodies :-) no i don't work for them nor do i own the company. i am just sharing a great source for toys :-) Cheers, WL
pstretz (author)  WilderLust6 years ago
Thanks so much for the tip, there are so many sites and I'm new to all this stuff. I think 2 of those would be plenty of power for a compressor and amp.
well... actually you would only need one and then you would still have 1V and 50mA more out of it than in the four you are using. This is a good idea anyway because it will allow you to operate in less light intensity situations.

you are right that there are so many places to get things. through the years i have, through trial and error, found some to be better than others for certain things. it all depends on what you want and how much. i think it is great that people share their sources like you did on these pages because we can all learn from each other's experiences and in doing so benefit all of us which after all is the point of this whole site.

here are some of the main suppliers i use (depending on what i need):
http://www.jameco.com/
http://www.goldmine-elec-products.com/
http://www.futurecb.com/store/default.aspx
http://www.digikey.com/
http://www.mouser.com/
http://www.sparkfun.com/commerce/categories.php
http://www.elexp.com/
https://www.em.avnet.com/home/
http://www.opamp-electronics.com/
http://www.circuitspecialists.com/
http://www.futurlec.com/index.shtml
http://www.minute-man.com/acatalog/
http://www.alltronics.com/cgi-bin/category.cgi?category=0
http://www.surplussales.com/
http://www.electrospec.com/?cid=globalspec
https://www.onlinemetals.com/
http://www.chemsavers.com/
http://www.caswellplating.com/
http://www.harborfreight.com/

happy new year everyone :-)
WL
Ohm6 years ago
Not trying to be too nit picky, but could you redraw the circuit with the pins in the correct orientation for an op-amp? It is kinda confusing to look at with the input on the output and the gain on the input side. Otherwise cool, I think this is probably the first solar powered guitar amp I have ever seen.
pstretz (author)  Ohm6 years ago
new schematic posted from eagle, hope this makes it easier to understand. I'll post a perfboard layout later to really clear up any confusion.
Ohm pstretz6 years ago
Cool, that is even better with the pin diagram of the IC, you don't really need to bother with the perf-board diagram since it is drawn in planer fashion all one has to do is replace the symbols with components.
Have you considered trying the runoffgroove ruby circuits? or the Beavis audio research noisy cricket circuits, essentially a ruby on steroids? They both have a jfet buffer/booster on the input which helps the sound out a lot.
Here are the links to the different sites
http://www.runoffgroove.com/
http://www.beavisaudio.com/
pstretz (author)  Ohm6 years ago
I built a Little Gem/MKII/Ruby all-in-one amp for my dad. It has a switch to select which amp to use. I liked the Ruby best. I've looked at Beavis Audio but haven't built any of their circuits yet.
andrew_296 years ago
sick man I need this exact thing for wakeboarding in the summer and snowboarding behind my snowmobile in the winter
Awesome... I might do this for my brother and I, then we can jam wherever we go, maybe we'll go down to my middle school down the street and jam on the benches or something.. but I wouldn't really want to walk on the street with my B.C. Rich Warlock... Great Instructable! (favorited)
pstretz (author)  GorillazMiko6 years ago
Ha, I can see you walking down the street with the amp strapped to your back, solar panels on a hat rockin a Warlock. _ Awesome!!
Haha, if I do this, I'll do that. :-)
Okay.. I probably won't be able to do this because it is way too hard for me.. but still, great Instructable.
pstretz (author)  GorillazMiko6 years ago
might be simpler if you break it into parts. If you build the crackerbox amp from MAKE or go to the Run off Groove site I link to, they have easy perfboard layouts. Just use my power section and plug it in. If you can find a bigger cap you can get away with one really big value, like > 5000uF. I had to use two in parallel because that;s what I had. Hope this helps.