Solar Charging Night Light
Instructables Electronics ProjectLike so many electronics projects in my life, I got this idea while randomly walking around Hobby Lobby. I came across these cute little glass "light bulbs." They have screw off tops, a flat bottom, and only cost $1.50. Who could pass that up? My original idea was to try to cram a LED, battery and switch in there. Yeah, that wasn't ever going to happen. My second idea was to make it solar powered because as we all know, everything is better with solar. (Yes, even puppies!) In a nutshell what I ended up making was a little side box that had a solar panel, Joule Thief circuit and a switch on it connected to the glass bulb. Oh yeah... I threw in a simple dark detecting circuit as well. Just cuz. This is a fun beginners project for anyone wanting to do some soldering. I have other light detecting solar circuit kits on my gadget website, Brown Dog Gadgets.
Hot Glue Gun
Breadboard (optional, but super handy.)
22 Gauge Wire
1 Zener diode
3 White LEDs
4.5V solar panel
AAA battery holder
AAA NiMh battery (you can also use AA)
Little Plastic Bead Box
Step 1: Making the CircuitIn addition to making the circuit (borrowed from evilmadscientist.com) I'm am also adding a switch between the LED and the battery. This will allow the battery to charge even if the switch is off.
The first transistor PNP 2N3906 acts as a dark detector. When power (sunlight) is hitting the solar panel, the transistor is off. When there is power (darkness) coming from the solar panel the pathway turns on and we get power.
If you decide, you can skip this step and control the LEDs via the switch. After the first transistor we get the famous Joule Thief Circuit.
Schematic Switch Placement
Step 2: Wire Up The Solar PanelSolder on wires as shown in the images below. When you're done, put some tape over the tabs – they break easily.
Step 3: Wrap Your ToroidWrap your toroid up with wire. Use two wires, coated of equal lengths. Wrap the wire around the toroid at least seven times. Lastly, take a wire from one "end" and hook it up with the opposite color from the other end.
Step 4: Breadboard TestingIt is highly recommend to use the breadboard to test everything out.
Image A: The LED is off because the solar panel is getting light.
Image B: I covered the panel and the light goes on. Darkness detected!
Step 5: Drill Baby DrillDrill three holes in the bead or plastic box. I placed one in front for the solar panel wires, one on top for the switch and one out the back for the LED wires. The size is up to you and depends on how big of a switch you're using.
Step 6: Soldering the Dark DetectingIf you're not going to be working on the dark detecting section, you can skip this section. Otherwise, read on!
First, don't forget to thread your solar panel wires through the hole first. Now solder the zener diode and the 5kΩ ohm resistor to the positive wire. Solder the resistor to the center leg (base) of the PNP transistor. Then solder the zener diode, as well as the positive side of the battery case, to the left leg (emitter) of the transistor. Solder the double twisted end of the toroid to the right leg (collector) of the transistor.
Step 7: Test the Connections AgainUse the breadboard and test everything again. It never hurts.
Step 8: Diffuse Your LEDsIf you're smart, you would be using diffused LEDs. If you only have clear LEDs, you'll have to diffuse them first. To do this you can either use a big ball of hot glue to cover the lens or use sandpaper to scuff it up.
Step 9: Joule ThiefOff of the toroid are two wires. Take one (doesn't matter which) and solder the 1KΩ resistor to it. Now solder the other end of the resistor to the middle leg (base) of your NPN transistor. Solder the other toroid wire onto the right leg (collector) of your NPN. The Joule Thief is nearly finished.
Step 10: LED ConnectionI used long pieces of thick magnet wire because of the look and I wanted to hide the box away from the bulb. Anything will do, provided it fits through the hole in the bulb cap. First step is to put the wires through the bulb cap. (You can always make it bigger by using your drill). Then hook up all positive legs of your LED to one wire and all negative to another.
Note: If you're using a 8mm or 10mm LED, you might want to start with two and see if they'll fit into the bulb. Then, maybe add a third while the other two are inside the bulb. It's just like working on a ship in a bottle.
Step 11: Hook Up the Wires in the BoxTake the other end of your LED wires and put them through the hole in the box. Solder the positive one to the far right NPN leg (collector) (the one you already soldered the toroid wire onto).Then run another wire off the switch. Last, solder the new wire off the switch, the negative battery wire and the negative solar wire all to the left leg (emitter) of the NPN transistor. Now you're done soldering.
Step 12: Warm Liquid Glue or Should We Say "GOO Phase"Now we have a big mess of wires and stuff that needs to go into the box, and we want to make sure to avoid the possibility of a random exposed wire touching random exposed wires.
Hot glue powers activate!
Covering all the random exposed bits with hot glue makes things much easier. Word on the street is that the technical term for this is "potting."
Step 13: Shove It All in the BoxBe careful to shove everything into the plastic box. Again BE CAREFUL. Breaking something now would be a big pain to fix.
Step 14: Enjoy!You have now created what amounts to a very fancy looking outdoor solar light, the kind you can buy for less than $5. Only this one looks very impressive and was built by you. This is a great project for those interested in a beginner's circuitry project and is inexpensive to make.
To really impress your friends, use two colors of lights inside the bulb that you control using a second toggle. Go from the NPN to a toggle switch with two positive lines running out. Use a common negative line back. You'll have three wires instead of two.
View complete project instructions here.