Instructables
Picture of DIY Solar Powered radio for $5
This is another good use for the solar panel used on the huge amounts of garden LED lights around, coupled to a portable radio that runs off 2 or 3 AA cells.

Most of us have an old radio lying around, so I based the $5 price on the cost of purchasing/ acquiring a solar powered garden L.E.D light.

I suspect there are plenty of scrap ones lying around, not working because of slightly corroded battery terminals in damp environments - the solar panel will probably be perfect....

With this Instructable I have left my radio on now for 4 weeks, (12 hours a day) while I work and it has never let me down, even at a reasonable high volume level.

You could either leave the solar radio out on a sunny wind sill as I do or leave it in the sun outdoors - every so often to recharge the battery's.
 
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Step 1: Step 1

Picture of Step 1
What you will require:

1. A portable radio, AM/FM or DAB, (2AA or 3AA battery type).
2. One 4 or 4.5v 80 mA solar panel, prised off from a Solar Light.
3. ideally a BAT43 Schottky diode or Silicone IN4001 (more voltage loss)
4. soldering iron, solder and red and black cable 6" lengths.
5. 2 or 3 NiMh rechargeable batteries (NiCd are ok but not as good) minimum capacity 800 mAh per battery.

Optional - heat shrink sleeving, Adhesive foam strip

This is a very quick project, that can be made in about 2 hours, and helps save the planet :)

Step 2: Removing solar panel from Garden light

Picture of Removing solar panel from Garden light
Solar_Panel.jpg
Please choose a solar panel that has 8 solar strips that run the entire width of the panel - some cheaper panels only have 4 strips or are cut down, you will need the full 8 strips to provide the 4.5v 80 mA output.
Remove the clear plastic lens and metal rim from the garden light, it's usually a push fit and easy to get off.
Using a screwdriver, carefully prise the panel away from the lights body, it is adhered on with some type of glue - BE CAREFUL.
Cut the connector wire and remove the panel completely.

Step 3: Connecting up the radio.

Picture of Connecting up the radio.
Solar_Radio_Wires.jpg
Solar_Radio_Rear.jpg
Some radios have a power input socket for mains adapters, mine did but it was an odd size (Sony).
This option makes connecting the panel more easy, just connect a suitable jack plug to the solar panel (using a blocking diode) and that's it, check polarity is correct!

I decided to hard wire my solar panel, here is how I approached it.

1. Remove the rear panel of radio, and with the battery's in situ, using a multimeter identify the positive and negative connections (where the battery's would connect to). Make sure the multimeter doesn't indicate a negative value, you have the positive and negative probes the wrong way around if so.

2. Solder the 6" lengths of red (to positive) and black (to neutral).

3. drill a small hole in the plastic to allow the two wires to exit the back of the radios panel when reassembled.

Step 4: Solar Panel and blocking diode

Picture of Solar Panel and blocking diode
You will have to solder a BAT43 or IN4100 blocking diode to the positive terminal on the solar panel.
The BAT43 Schottky type diode is better because it has a lower voltage loss, (about 0.3v) particularly important if you are charging 3 battery's like me.

The diode prevents any reverse current from the battery's happening when there is low light.

Please make sure the white or black 'band' faces away from the solar panel, you can check if you have connected the diode the correct way around by using a multimeter set to mA's or volts and see if there is any output in bright light from the panel, if not the diode needs connecting the other way around.

Step 5: Final Assembly

Picture of Final Assembly
side.jpg
Using a piece of double sided foam adhesive tape you can position the solar panel centrally onto the radio.
Fortunately my Sony radio had a positionable stand that was ideal to mount the panel on, however if your radio doesn't you could position it on the top of the radio.

Solder up the positive and negative wires from the radio to the solar panel, and use heat shrink tubing or insulation tape to cover any bare joints.

Step 6: Final photos

Picture of Final photos
gotwind..org_Solar_radio2.jpg
There it is done,it works great, I used to work at my computer all day listening to my stand-alone stereo system that used over 40 watts of mains power just to listen to BBC radio 2 (U.K station).

This lasts forever and costs no energy........

Please see all my other great renewable energy projects here:
http://www.gotwind.org/index.htm
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rbrewer51 year ago
OK, stupid newbie question - does the solar garden light already have a blocking diode? My understanding is that's to protect the panel from getting zapped by the battery when the light is low (current out from the battery exceeds current in from the solar panel). Wouldn't a solar garden light have the same problem and thus the same solution already built in? and I was wandering if I could take a few of these solar power squares as shown above and tie them together into one big solar panel?
trickster72 years ago
where i can get the garden light?
Tried to reply could not get passed the captcha so see post above
Trickster-the lights may be obtained at any Garden Center (Wal-Mart, Big K) Store or at Lowes/Home Dept, even $ General-just mk sure they have the 8 panels-some don't
You Can get a Solar Panel like this
At Minimum cost, Because Commercial Solar Panels are Expensive!
It will take you more than 10 years to pay back
If you Use Surplus Solar Cells You can get pay back in 1-2 years
There is an Engineer from Chicago his name is John Sommer
He explain it All in his Homemade Solar Panels Blog
alights2 years ago
so with this project do we have to buy a solar panel?? or just the LED lights??
lbruce lee2 years ago
mmmm. must little current ,,....
i plan on trying this for some beach visits this summer. is there a way to effectively patch in an auxiliary cord for ipod use?
BillBiker3 years ago
Hi,
This is really a sweet project! I am setting up a workshop in my garage and need to provide some sort of lighting to it. I have a couple options but honestly want to do it as cheap as possible. This idea occurred to me and I am like a very beginner in solar power. What I was wandering if I could take a few of these solar power squares as shown above and tie them together into one big solar panel?
PaleoDan4 years ago
Thank you for posting this. This was my first attempt to work with Solar Panels. I did not follow exactly as the materials I had at hand were a bit different. I had an old Panasonic radio that took 4 AA batteries. I took it apart and connected it to a scrap solar panel I had from an outdoor spotlight. I do not have batteries involved so my radio will only function in the sun but was still fun to start with.
DSCF4440.JPG
Hi,

How would it be possible to charge the battery? Can the circuitry work on that? I have placed a diode already on my radio but Im not sure that the current being supplied to my radio would be stored in the battery. Though it's still working on now because my battery is still new, but are we really sure that the battery is are being recharged by the solar?? How did you connect the solar to your battery series or parallel?

Thanks
Hi,

I'm wondering if the watt requirement of the radio is a function here? I mean is there any limitation in terms of what wattage should the radio has in order to be run by the solar panel model? Reply anyone please.
I do not know the answer to this in general but the radio I used is "AC 120V 60Hz 3 watts and uses 4 "AA" Batteries for 6V when run on battery. I had lost the AC plug long ago so was limited to the batteries when I made the modification. With the solar I have no limits (except the sun).
Ah okay thanks for giving me the idea cause I want to do the same also.
Thanks for your prompt answer.

my small transistor radio is 9volts can i just add a larger battery pack from radio shack, i wasn't trying to rhyme...
gotwind (author)  Yerboogieman7 years ago
No. The panel only outputs 4 volts, even two panels in series would only give 8 volts, so a 9 volt radio is not suitable. A 2AA (3volt) powered radio would be best.
pagray gotwind5 years ago
8v will work fine on a 9v radio
Fashim pagray3 years ago
Yep I've powered a Car Radio with a 9V Battery and they're 12 Volts
1 volt will have a very small difference, but it will work. 9v batteries actually output 10v for a little while, then settle down to 9, and drops to 7 before it dies. In short. It works...
PCvsMac gotwind6 years ago
Hello! You mention that you use a blocking diode, well living in the UK could you please tell me where to get the blocker (or alternative) I checked in my they just power one battery for the LED liglocal Maplins, however I dont know which one to get :S OK fair enough, but could this solar panel (that powers, let's say only one 1.2V battery) be used to power two rechargable batteries? And if so, is it cool to use NiMH batteries? OR Could work directly with the produce rather that charging batteries (Does it still need a blocking diode?)
Vissy PCvsMac3 years ago
The diode is just to prevent the panels from discharging the batteries when theres no sun. "Blocking" is just street slang for what the diode is used for. NiM batteries are about 1.2v and they charge at almost 3v, as compared to 1.5 volt alkaline.

Most small diodes that you can get at hobby shops/parts places are only 0.25 watts each. I also wouldnt go over 5v for a 3v system, and no more than 12 volts on a 9v system or it will get hot. Batteries will cook, too.

I got fifty 5W diodes from Digi-Key for five dollars, shipped an hour after I'd placed the order. I cant remember the name of the big elec online seller in the UK. You can make a voltage divider from those with some resistors (plans online)

Ignoring losses:
Watts = Volts * Amps
Amps =Watts/volts
Volts=Watts/amps
gotwind (author)  PCvsMac6 years ago
Yes, Maplin - IN4001 diode. Charging two 1.2 v NiMh Batteries is preferably. The radio will work directly from the solar panel in good light, a diode is always advised.
PCvsMac gotwind6 years ago
OK thanks dude. However, another question popped up. Oftenly a really cheap solar light powers a 1.2V battery, so would it be possible to power a 3V radio applience? If so please state. And if not also please state and it's back to the 'solar' drawing board. (hehe)
k thanks
knektek3 years ago
w00t! Same screwdriver and solar light!
ElectroBabe4 years ago
hey im doing something similar!!!! Im attaching a 4.5 volt panel to a baby swing but not getting enough current . how can I get more amps? more panels wired in parallel and then attached to the panel i already have in series????????????????????????????????????????????????????????????????????
oops, I meant most panels are far UNDERsized in IS projects.
Whats the voltage & rating on the baby swing? Is it battery operated?

You need to use a rechargeable battery to charge when you arent using it, because people forget about voltage drop, and important things like no shadows on the panel at ALL.

You also need to use diodes (check watt rating too) to prevent the battery from discharging when theres low/no light or a shadow on the panel; its STILL a complete circuit and the battery will drain.

People overestimate solar. The dashboard chargers you plug in your cigarette lighter barely do anything (150mA in full sun).

You may want to experiment with rechargeable batteries, use them as you have this hooked up. You will NOT be able to move something like that with a tiny panel like in this IS. Get a panel from Northern, Newegg, other places. The 36" panels I have are 12v and 5watts each. (5w divided by 12volts = 410 milliamps, almost a half amp at 12 volts.

You could build a voltage divider to get the voltage down to what you need, but I cant remember how to calculate the loss in power from the resistors in a VD circuit. I think you can use Kirchhoff's law to calculate it and still have enough to run it without the batteries (but why?)

Most solar projects I see on here SHOULD have batteries in them, but dont. Most panels are FAR oversized, too. The current needed to start a motor can be 6 to 10 times the current needed to run. This could be overcome with a capacitor
Everyone should use batteries in anything solar they have.
nekoheehee5 years ago
Great little mod :D I have a question I was hoping you or anyone who reads this comment could answer. I have a portable cell phone charger that take 2 AA batteries. do you think this mod would work for something like that?
I know.. its been over a year. but yes, this should work in much the same way for your portable cell phone charger. I have harvested the guts from a couple of two battery garden lights just for that purpose. Its pretty much just a battery charging circuit. and you really only need a reversing diode wired into the panel for the purpose
Just wondering if It will be possible to get two 4.5 volt 40ma panels and wire them in parallel to acheive the same affect? They have half of the strips.
It will be possible.
gomiboy5 years ago
OK, stupid noob question - does the solar garden light already have a blocking diode? My understanding is that's to protect the panel from getting zapped by the battery when the light is low (current out from the battery exceeds current in from the solar panel). Wouldn't a solar garden light have the same problem and thus the same solution already built in?
dxguy776 years ago
Just built a solar panel that is 15.7 volts at peak and close to 200 ma of current. I did this by reclaiming the PV modules from 18 garden solar lights that had seen long service but Colorado winters are hard on these lights. Instead of tossing them out, I pulled the PV panels. Each PV panel puts out 2.2 volts, at peak. I supplemented the overall panel using 3 PV modules from LED lights that run at 4 volts. I glued them with silicone chaulk to a piece of particle board. I figured out the center of each panel, drilled holes for the wires and put them into 3 rows of 6. The very first row is wired in series for the voltage, and the next two rows were wired in parallel for current. I mounted a Radioshack 12V DC accessory outlet (270-1556) to the end of the board for quick access to 12V Cigarette Lighter Adapter (CLA) so I can power multiple items. Using a IGO CLA (it can go as low as 8 volts and high as 15) plugged into the outlet, I can charge my cell phone, iPod or any other small device. The voltage is regulated in the IGO unit to the appropriate voltage for the device (ie, 3.6 volts for most cell phones and 5 volts for the iPod). I have ran a HUGE GE Superradio AM/FM radio directly off this panel for hours. I have put this panel on my car's dash at lunch time to charge up my cell phone and it works great. Don't forget the one step about the switching diode! That's important if you don't want backflow and lose voltage if some devices are hooked up and the sun goes down.
twinklystar6 years ago
I've just done this with a sony minidisc player and a mp4 player a no name one from hong kong and its working great! I'm chuffed to bits.
Grady7 years ago
I bet even a dumb bunny like myself could do this one; it sounds great. Now, I wish someone could invent how to get good t.v. reception without the cable or satellite or high, lightning antennas.
PCvsMac7 years ago
A excellent project, I really wish I had thought it :)I have two questions, though. 1. How do I know what voltage it is for a solar light? 2. Where the evil batteries usually go, surely it must be easier to wire the postive side of the panel to the positive prong on the radio and (vice-versa for the negative sides)? Let me know, because I think that will work
i.am.mozman7 years ago
I was actually thinking about harvesting the panels to charge AAs while backpacking next week. I figured a couple of panels in series attached to a battery holder should be sufficient. This does reassure me that I wasn't completely off my trolley considering it.
fabiusX7 years ago
It happens to have 3 of those garden lamp idling witout a garden to be stick into and this project is so simple to do that it will worth a try.
Brennn107 years ago
Nice! I made this today! It works great! +1
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