DIY Solar Powered Radio for $5

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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.

Step 1: 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

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.

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

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

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

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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49 Discussions

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diogopimentel580

Question 10 months ago on Step 3

what are the best portable radios to use
for this project

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SHOE0007

1 year ago

Oops I ment two solar cells.

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ErtanE1

2 years ago

5v solar cell,

FM radio,

DC to DC Lm2576 module.

i did convert 5v to 2,4v by the Lm2576 module

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itsruthanitha

2 years ago

I bought this Solar Powered Radio with Flashlight and Charger, came up with hand strip and easy to carry. I love about this product is, can charge my mobile phone by solar power. I got this discount coupon. http://patriotdeal.com/collections/all/products/solar-powered-radio-flashlight-and-charger Use this code "PD10"and save 10%.

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sitarap2

2 years ago

hi there, does anyone know where i can find the soldering iron, solder and red and black cable 6" lengths?

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TravisM18

3 years ago

I found a 4.5 solar panel, It ran my radio just fine but the down side was when I tried to use it to charge a 100farad capacitor. It would play for about half and hour or so but that was with the solar panel hooked up to it. I decided to just use the solar panel. But I have since thought about making a regenerative crystal radio.

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PaleoDan

9 years ago on Step 6

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.

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5 replies
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mitchikoPaleoDan

Reply 7 years ago on Step 6

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.

sorry for the late comment , i just joined the site...


wattage is a result of the volts times the amps. V x A =
Watts. think about a 60 watt north american light bulb running on 120
volts. now you can find the answer for the amps by dividing the watts by
the volts... A=W / V which is one half amp of current running though a
60 watt bulb... so now you get a feel for our topic.


if a 3 watt radio [maximum 3 watt written on the back but usually
uses much less about half typical] has 4 batteries of 1.5 volts each for
a total of 6 volts, then the radio will typically be consuming 3W / 6V=
0.5 amps maximum OR about half that typically at lower volume levels
and no lights on it which is one quarter of an amp [ ironically and
comically and oddly enough, one quarter amp of bad news though the chest will kill you LOL]

now think back to the 60 watt
light bulb that also has one half amp of current flowing through it but
glows white hot and gets very very hot. one device converts to heat and
light while the other is magnetic and sound. ;-)

to continue, the radio will need a 3watt solar panel able to produce 0.5amp at 6volts to run the radio at maximum volume with no batteries in it. 6x0.5=3watt [in my experience this is about 3 cheapo solar garden light panels from the dollar store, each panel makes about 2 volts to charge the single battery in it]

you might be able to run it on a lower panel at lower volume settings maybe. a tiny solar panel will work if you use rechargeables and turn off the radio when the batteries are low and charging in direct sunlight. lastly, a 0.25amp panel of 6volts might work in sunlight mid volume and the batteries might never drain.


rechargeables have set limits to how fast you should recharge or drain
so as to not overly damage them. each type has a different parameter. i
think ni-cd are best charged at 0.1C which means capacity. so a 600mAh
ni-cd would need to be filled back up with .600 Ah of capacity at a rate
of 0.06amps for 10 hours but you lose some efficiency to heat and other
losses so 11 hours maybe... 0.06ampsx10hours=0.600Ah=600mAh

ni-mh are faster and so are lithium.


i have an empty 12 "amp"/"hour" AGM lead acid battery that
requires 6 "hours" of charging at 2"amp" "maximum"... see how that
equals 12 ........ it says 144 wattHour on the side of it, when it is
dead i have used the 144watt/hours... it is a 12volt ..... the
watts/hours that i have to pump back into it to "fill" it are expressed
as volts x amps x hours = 12[V]x2[A]x6[H] ... if i used a one amp
charger i would charge for 12hours.. if i used a 1.5amp charger i would
charge it for 8 hours.. if i used a 0.5 amp charger i would charge for
24hours, etc. etc. etc.

sorry for the late comment

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PaleoDanmitchiko

Reply 7 years ago on Step 6

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).

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mitchikoPaleoDan

Reply 7 years ago on Step 6

Ah okay thanks for giving me the idea cause I want to do the same also.
Thanks for your prompt answer.

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mitchikoPaleoDan

Reply 7 years ago on Introduction

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

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Colaris

4 years ago on Introduction

So is the solar panel powering the radio or charging the batteries that are THEN poweriing the radio?

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rbrewer5

5 years ago on Introduction

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?

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

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alights

7 years ago on Introduction

so with this project do we have to buy a solar panel?? or just the LED lights??