If you are into remote controlled things you will know that they require batteries, which have to be charged. Many cheap chargers will overcharge LIPOs if not unplugged at the proper time. However, it is hard to have to constantly check your batteries and easy to forget. That is the inspiration for this project. I have found it to be very useful.

The only requirements for the charger is that it has a status light that turns off when it is finished charging. As an example I will be using the stock charger that came with the Hubsan H107L quad-copter.

Materials

Step 1: Software

Upload the following code to your board. Basically, all it does is wait for the light level to change and then beeps until light level is restored or it is turned off. The sensor is programmed to be on A0 and the buzzer on pin 11.

If you are getting inconsistent results adjust the threshold value for the light sensor or try a different resistor.

ChargerStatus.ino
Download

Step 2: Wiring the Photo-Resistor

The sensor we are using to detect light is a type of resistor. Different light levels change its resistance. Here is how to wire it. Refer to the picture above:

Wire one side to 5v through a resistor. It doesn't matter which value you use, I used a 100k
Attach another wire from that side to the Analog pin number zero on the LinkIt One
Wire the other side to Ground

Step 3: Wiring the Buzzer

This step is fairly easy. Wire one side to digital pin 11 and the other side to ground. This will act as our way of reminding that the battery is charged.

Step 4: Enclosure

An enclosure is necessary for this project. Not only does it make it look better but it prevents false alarms caused by other light sources such as ceiling lights and sunlight. Also, you will have to find a way to get the charger where your light sensor is. I made a hole in the box I used which worked perfectly.

Step 5: Use It!

Now when ever you have to charge your batteries you don't have to think about them until they are done! I have found this very useful having a couple of different RC models that all take LIPO batteries.

To improve on it, you could also add a smoke sensor to alarm you if your batteries catch fire. I did not have as much time as I would have liked to get a good enclosure and better pictures for this project because of a submission deadline. However, if you like it I can improve it! The project has self has kept my LIPO's in better shape because I for one have a very hard time remembering that they are charging!

I hope you liked it!