$3 Emergency Solar Radio

Picture of $3 Emergency Solar Radio
In honor of all my good friends still over in Japan I've decided to create an Instructable for a $3 Emergency Solar Radio.  It's a great thing in case of tsunami, nuclear melt down, or zombie invasion.  Plus it's really cute when put into an Altoids tin.

My plan is to send this as a (slightly) joke birthday gift to a good friend of mine living in California, who just so happens to be freaking out about possible nuclear clouds.  This will also be really nice for her when she starts going camping again this summer.

The design is very simple and only takes about 45 minutes to put together, less if you know what you're doing.

If you'd rather not make one yourself, I'll probably be throwing up a couple completed ones as well as most of the parts over at my website
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Step 1: What you need

Picture of What you need
I bought all the supplies I needed from my local $1 Store.  (If in Japan, a 100 Yen store.)

To buy:
1x FM Radio
2x Solar Garden Light
1x Diode ($1 for 100 of them online, or take one out of any random junk pile)

If your local $1 Store isn't as cool as mine, you can probably find these things locally, online (like at my website, or from a trash bin.

Soldering Iron
Wire Strippers

Altoids Tin
Hot Glue 
Mini Speakers ($1 Store, or take apart old headphones)

Support Me By Buying Some Parts...

If you can't find solar cells or cheap AAA batteries, I have quite a few on my website  The same solar cells I use to make my Solar Cockroach would work great for this project.  You could also slap on a bigger, more powerful cell onto the outside of the tin like these nice 4.5 volt cells.

I also some AAA battery holders and very cheap AAA batteries for sale that have a much higher capacity than the ones you'd find in your average solar light.

josuchav7 days ago

you misspelt goggles

ajensen2714 days ago
found 2 separate lights around the house. one has a 2/3 aa battery and its panel puts out 1.2v and the other has a AA battery and its panel puts out .95-.97 volts sitting under 40w bulb(it was night out). which panel do i use and how many. also do i need the diode?
Kirbsome!2 years ago
Quick tip:
When buying solar powered lights for this, look for blue solar panels.
They are usually higher quality than the dark brown ones.
thanks good to know
JoshuaZimmerman (author)  Kirbsome!2 years ago
Very true. Those CIS are dark brown and very high quality...
This has got to be one of the single most coolest things on instructables!
wazy8013 months ago
what kind of tap do I use o step 8???
wazy8013 months ago
why do you have to drill on step 7?????
Nhoj167 months ago
I just began making this when I realized I'm out of diodes. Will it still function without one?
Nhoj167 months ago
Cool project! I think I have all that I need to make this laying around so I'll definitely do it.
Jacky P1 year ago
What diode do I use?
i suggest a schematic diagram for the project. please to make things simple
Whatat does the diode do in the circuit? Just curious
Orkekum1 year ago
awesome idea and well written, i can buy cheap radio with a scan button and a return one
JoshuaZimmerman (author) 2 years ago
Just because I'm a teacher doesn't mean that I'm not human.

With feelings to be hurt...

teachers are awesome c:
deanes1 year ago
Altoid tins are neat, but maybe an easier more practical project would be to just add the charging panels directly to the radio case? Or, maybe the panels glued to a plastic pocket-shaped sheet and connected by a sturdy wire to the radio battery compartment. Then you would have a solar charging case for the radio.
JoshuaZimmerman (author)  deanes1 year ago
Probably, but this is rather bare bones. Plus cute. You gotta factor in the cute aspect.
DAND2 years ago
What type of diode did you use?
static DAND1 year ago
 The current carrying capability, the voltage rating and the voltage drop across the diode are considerations. Too much current can harm the diode, too much over voltage drop, the batteries may not fully charge. Nominal figures; for the silicon diode used here is .7 V, for the Schottky diode it's .2 V. In most solar application the Schottky is preferred, but one can't walk into radio shack and buy one. In low powered projects like this, it's easier to add an extra salvage solar cell, and used the more readily available silicone diode. No precision is required on the voltage rating here as long as it's higher than the battery voltage, the voltage rating is important if the diode will see a reverse bias as part as normal desired operation.
JoshuaZimmerman (author)  DAND2 years ago
1N914. Very common. You can find them everywhere.
Thanks for the great instructables!
quick question
Are there any differences if you use a 1n914, a 1n4005 or a 1n5819?
JoshuaZimmerman (author)  earm992 years ago
1N914 us just really really common and has a low voltage drop. It's very handy for low voltage low current systems like in this one.

Google the other diodes and check the voltage drop. They probably would work fine for this kind of setup.
Subo691 year ago
if you were to use capacitors instead, which one would you use?
JoshuaZimmerman (author)  Subo691 year ago
Well you'd want some super capacitors. Ones that have 1F or more of power at around 3V.

Actually the best approach would be to get a couple of 1F 5V super caps and hook them up in Parallel. (5V so that you don't overcharge the caps, and can then use a 4V or 4.5V solar cell with the project.)

But you'd need several of them to be on the safe side. Really 3 or 4 if you want to use the radio out of the sun.
This reply is directed more to those that will read the comment made by the author than it is to the author. As science teacher none of the following shouldn't be new to him. F Farad is not a unit of power.  A capacitor can't be overcharged, but is susceptible to damage from over voltage.  Following the author's suggestions here  the capacitors wouldn't see a voltage over their rating. In my experience, there will be those who would read this and think they could wire lower voltage capacitors in parallel and they would be safe too hook up to a higher voltage source. However wiring the in series  can allow them to be used with a higher voltage source, but the total capacitance will be reduced.  Knowing how capacitors wired in parallel or series behave allows you make use of what you have in the junk box or otherwise can attain readily to come up with what you need.  For more details read .  Given the low current provided by the suggested salvage solar cells, I'd suggest doing the initial charge of a high capacitance bank from other power source. After that initial charge the solar cells should able to restore the charge in  available time of sunshine.
static1 year ago
Good instructable, but for my kit I have a AM/FM pocket radio that I bought from Radio shack for not much more than the cost here. Use 2 AA batteries, while I hive never tried rechargeable batteries I assume so the solar power should work.  At lower volume levels Alkaline batteries last well, so I'd take extra batteries. My guess is the  plastic radio case doesn't weigh much more than the tin is is more durable. Everyone seems to ignore AM, when AM will be received almost anywhere. Good tools for making holes in light weight metal are a hand metal punch http:// and a tapered reamer .  Links used for illustration purposes so shop around. The punches may cost less  from vendors serving those in the auto DIY crowd looking for bargains.
zinner3421 year ago
Hi Joshua,
I really like your solar powered radio and I am probably going to use it for a school project. But I am confused? How does it all work? My school says that you can use solar power, but is this radio actually using solar power or is it using batteries? When the sun shines on the solar cells, what happens? Does it charge the batteries or what? SORRY, I KNOW I'M ASKING TOO MANY QUESTIONS :P
~ a different joshua ~

the solar cells charge the batterys
hey I have a biz kind of like what you do and I have been looking for a place to create one your website looks great and I was wondering what site you made yours on?
Hey!This is a great Instructable and I have been planning to make one one these
but i got to know,how many volts do you use on your soldering iron because
they got a 25V,30V,40V,50V and 60V.So what do you suggest I use for this project
and your solar powered Altoids USB charger?
JoshuaZimmerman (author)  Ghosthost54681 year ago
I have no idea. My soldering iron isn't fancy enough to display "volts" used. It just has a temperature wheel with color coating.

Thanks,no sweat,I learnt a little bit about soldering so just do what you do!
Also,I'm on the cheap here cause I'm in Beijing Plus I'm a kid but i managed to fint the exact same radio,so at least I'll be able to complete some of it.
Felixninja1 year ago
Hey Joshua, I saw the exact same radio in a local dollars and sense store, but it says do noy use rechargeable batteries, have you had any problems with the 1st radio?
JoshuaZimmerman (author)  Felixninja1 year ago
I've had no problems. The issue is that regular AAAs give you 1.5V of power (so with 2 of them you get 3V) BUT rechargeables only give you 1.2V of power (so with 2 of them you get 2.4V).

As long as your project doesn't involve a motor or need a super specific voltage (for some reason) this really shouldn't be an issue. Yes, correct voltage is important, but for super simple little projects like the radio you're fine.

If you're really really really worried about voltage issues just wire up a third AAA battery to give you 3.6V and then limit it with a resistor so you get 3V inside the circuit (it may be fine with 3.6V anyways).
Doctor-X172 years ago
I like this project. Both versions look good, but you might be able to use speakers as you planned for the first version if you included an audio amplifier circuit. I'm not sure how small one could be made, though, or if it's feasible in terms of power consumption, but it might be a challenge for you to step up to! But internal speakers or not, this is a good Instructable. Keep up the good work :D

Also, anything in preparation for the Zombie Apocalypse is good.
JoshuaZimmerman (author)  Doctor-X171 year ago
Ooooo good idea! Headphones are alright, but speakers could get everyone rocking.

Then again, you could just build a more powerful solar setup and use a more powerful radio. It wouldn't be Altoids sized, but it would be more rocking.

Zombie killing rockin.
DoctorDv1 year ago
I made one and I was wondering if you know where the antennae is so I could make it bigger and make the sound clearer. Thanks!
JoshuaZimmerman (author)  DoctorDv1 year ago
In these simple FM radios the antennae could be anywhere. It depends on what type of radio you took apart. I wish I could help you out on that one.

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