Making a basic solar powered string of led lights isn't too difficult. This instructable will require no electronics knowledge and no programing.
What were will be doing is upgrading some old battery powered mini lights to LEDs and then using some basic components, charging the batteries with a small solar panel. With the aid on 1 IC and 1 inductor, we can automate the string so it turns off and charges during the day and turns on at night.
Let's get started.
Step 1: Let's See What We Need to Get Started.
Step 2: What We Will Need.
I'll tell you what I used, but you can improvise your own parts.
1 Battery powered light set with battery box.
1 Solar Panel 2.0v @ 80mA (I'm using two 1.2v NiMHs in parallel. If you want to use one -then you need 2v @ > 20mA.
1 IC (QX5251F) Will discuss this one later on
1 Inductor 220uF (This is not exact and you can change it to meet your desires.)
10 LED's (White, Blue, Green or Pink) (Red and Yellow are a little different, but you can use them if you really want.)
A soldering iron.
Step 3: Let's Make an LED String.
You don't have to make your own string. You can buy battery powered LED string on Ebay for about $2 - $4 depending on the number of LEDs. Then you can just hack the battery box which you'll see in a few steps.
If you have an old Christmas string mini lights, they need to be Battery Operated. If you use AC powered ones, the wiring is not in parallel. You can cut up the AC strings and rewire them in parallel, or you can just get two long wires and solder on the LEDs.
Anyway here is a close up of the prep.
Step 4: Let's Start Putting the Circuit Together.
These are the connections we will need to make to properly have our circuit turn on and off automatically as well as properly charge the batteries and power the lights.
This is the entire layout. You can add 15 leds per QX5251F @ 20mAh per LED. The max current for the QX5251F is 300mA so you can play with different configurations.
I purchased my QX5251F from a vendor for $20 for 100pcs. He'll sell as little as 10pcs, but the shipping is still $9 plus $2 for paypal.
Here is the vendors contact info. firstname.lastname@example.org
If someone just really wants one or two, contact me and we'll see if we can work something out through paypal or something.
Here's the secret. You might be able to scavenge the entire circuit from any Chinese made solar lawn lamp. US ones use about a dozen different components, but I guess you could use that too.
Step 5: Working on the Housing Connections.
A few soldering points and we are almost done. So let's put it all together.
Step 6: That's It.
That it. I've tested this set up with two 1000mAh (The real capacity) and they ran all night. If you use a real 2000mAh battery you can obviously just use one. Just keep in mind that max output of your solar panel. If your solar panel can only put out 20mAh, in 8 hours of sunlight you'll only be able to charge your battery(ies) with 160mA so that's what it can put out. That's only enough to power 8 LEDs for about 1 hour at Full power. The circuit uses only a fraction, about 5ma per LED. Also you can't use the complete capacity of the battery. The QX5251F can use about 35%. It won't take the batteries down past 0.8volts.