I was in the dollar store the other day and saw this tiny garden rock, once I looked closer I noticed it was more than a rock. It was a solar garden light. It only costed one dollar and out of curiosity I had to buy it. I was browsing the web the other day and came across a product review for a solar recharge flash light. A lot of the reviews claimed that the solar panel was fake. Now I bought this rock just to see if the panel was real. Stpid reason? Sure but hey I was curious. After I got home I quickly took it apart to find out it was indeed real. It was a small panel and produced 2.5 volts at whatever Mah. After testing its various componets I realized I had no purpose for it. No garden and if I had one, one rock would make it look sad. I modded the circuit a little bit and turned it into a suprisingly bright solar rechargeable flash light. Also for a dollar this rock light was very well made. I will show you how to turn this rock light or any garden light into a nice flash light. If I may borrow a few minutes of your time lets get started!
Step 1: Taking Apart Your Garden Light. Well My Rock Light. All Similar
Take apart your light and disconnect everything. I just snipped the wires to later use them as a guide when re-connecting.
If you happen to find the exact same light I have then this should be easy, if you are using a different light then it might be a little harder, depending on what brand. Some make others more secure and what not.
In the picture you will see a small circuit, a small 1.2 volt battery at 40mah, a small solar panel and a led/reflector. All pretty simple. Now before you ask, there is no blocking diode in this circuit. It was designed to not have one. it works the same as it would with one.
Who as ever heard of 40mah battery? So tiny. I think we can do better. Since it is rated at 1.2 volts alls you have to do is replace it with a rechargeable double a battery. Most rechargeable double a batteries are rated at 1.2 volts aswell. I upgraded to a 500 mah battery which may sound like a lot but trust me it really isn't. It is however a great battery for this project since it is just powering one led. Now Im sure some of you new to electronics are thinking "wait, 1.2 volts? How is that going to drive a white led normally rated at 3 volts?" If you haven't noticed almost all garden light operate off of one battery rated at 1.2 volts. Now how it runs the led lies within the circuitry. Most circuits will have an ic or an inductor. More than many will contain an inductor or two. The inductor is what helps boost the 1.2 volts into enough to drive the led. Here is something else, if you change the value of the inductor you can either make the led brighter or dimmer. I ended up changing the value of the inductor so it can make the led brighter. You might not have to do this with other lights. Some, i am sure are brighter than others but if yours is a little dim you can simply make it brighter! I will get into that in a bit.
Step 2: Making Some Modifications to the Circuit.
SO in the last step I mentioned modding the circuit. What I did to mine you might not have to do to yours! There are three things I did to mine to make it more usefull as a flash light.
1- I changed the value of the inductor to increase the brightness of the led.
2- I added a push button (tact switch) to replace the slide switch
3- Important. I upgraded the battery from a 1.2volt nickle based at 40 mah to a 1.2volt 500mah nickle based. This will increase the run time while also increasing the charge time.
The values of the inductors might differ in your case or they can even look different. inductors can look like resistos, or capacitors. There are a variety of inductors. Be sure to look up inductors and values.
Step 3: It Needs a New Case.
Since this circuit is rather small we wont need any bulky case. I was tempted to use an altoids small case but decided not to. I ended up using an old usb charger. I was all for taking this charger apart and putting it to better use. It was rated at 330 mah which is not a lot for usb devices. Kinda weak.
First thing I did was I took the charger apart and gutted the circuit and removed some plastic to create more room for the new.
Secondly I needed to make a battery holder. I took two springs off an old circuit board and hot glued them inside of the case slowly cutting it to make it shorter so I could fit the battery perfect. I then soldered two small leads to it so I can later solder the battery wires to it.
3rd- I cut a rough looking square into the top of the case for the solar panel. The wires adn solderjoints easily fit using this method.
4th- I drilled a small hole for the button, If you dont have a small enough drill bit just use a screw :)
5th- I reconnected everything and placed everything in its place. I hotglued the panel, the button and the circuit in place. I ended up using the USB port for the light reflector to fit, also hot glued it for extra security.
Now if you use an altoids tin the set up is pretty much the same.
Step 4: Finished! Some Extra Photos
You are now finished! My solar panel charges this battery in about 5 hours. Once the panel is exposed to sunlight it will turn of the led automaticaly. Here are some extra photos of it! Also the reflector piece makes a great stand for when its time to charge. Look at the picture to see how bright it is. Thanks for viewing and I hope you had fun! Feel free to leave a comment and let me know how I did or where I can better.