Solar charging is easy, don't forget to prepare your solar panel and solder in the electrolytic capacitor beforehand!
Once you've done that, you can simply plug in the solar panel into the DC jack - look for the PWR GOOD LED to indicate that the solar panel is providing power and then plug the battery into the BATT slot in the left. Use only 3.7V/4.2V lithium ion/polymer batteries.
We have a tutorial about the batteries in case you have some questions about how to use them.
When the CHRG charging light is lit, the battery is being charged. Make sure to have the panel facing direct sunlight not shaded and not behind any glass or plastic! when the battery is full, you'll see the green DONE LED light up.
Of course, sometimes is just really dark out and you can't solar charger, so there's a USB port on the board as well. Use any mini-B cable to plug in and charge.
If there is something connected to the DC jack, it will mechanically disconnect the mini USB connector so be sure to unplug the solar panel when USB charging
There are three status LEDs on the charger, which you'll find very handy!
The red PWR LED indicates that there is good power connected to the charger. If this LED is not lit, something is wrong with the power supply
The orange CHRG LED indicates current charging status. When this LED is lit, the charger is working to charge up a battery! It also acts as a low battery indicator (fixed at 3.1V) when no power is connected. So, if you don't have USB/Solar wired up, when the battery voltage drops below 3.1V, the orange LED will come on.
The green DONE LED is pretty easy to understand as well - when it's lit the battery is charged up! Very handy for when you want to know that everything is done.
If you need to connect larger LEDs or a microcontroller up to these status pins, you can us the STATUS 0.1" breakout on the bottom edge of the PCB. The pins are open drain, so they will short to ground when 'active' and float when 'inactive' - you'll want to use a pullup resistor if you need a digital signal or connect LEDs just like shown below on the schematic, if you want bigger lights.
The MCP73871 chip in the usb/solar charger has a very nifty feature called 'load sharing.' Say you have an every day lipoly charger and you want to use the battery while its charging. To do this, you might connect the project directly to the battery output. This means, however, that the charger is both charging a battery and driving your project at the same time. The charger is working extra hard and the battery is being charged and discharged constantly.
If you plan to have your project outside or unattended, we suggest adding temperature sensing to keep the charger from overheating the battery or attempting to charge when the battery is too hot or cold.
The USB/Solar charger comes with a preset rate of 500mA which will work great for USB ports, USB wall adapters and solar panels up to 3 Watts. If you have a project that uses a larger panel, or perhaps some other sort of setup, you can easily adjust the current by soldering a resistor into the PROG pads.
If you are placing the charger in a box, you may want to have external LEDs for indicating charge state. This is easy! Simply use any 3mm, 5mm or 10mm LEDs you wish and 1K resistors and wire them like so: