The past week I've started to use Twitter. Ironically, the reason is because this venture startup guy who reminds me a lot like a snake oil salesman, called me up and wanted to buy the liquidware.com domain name (I think he ended up getting liquidwarelabs.com instead, so more power to him). I kept feeling the whole time he talked to me that he was trying to sell me steak knives or life insurance. Ugh. But, he did say I was missing out for not using Twitter... so I tried tonight to "tweet" my play by play of making and posting the Mega Lithium Backpacks. Twitter seems like more of a pain than it's worth...
This is the new version of the Mega Lithium BackPack, a specially designed version of the Lithium BackPack Chris, Mike, and I built for the new Arduino Mega. Over the past few weeks, I got a lot of emails about folks who really badly wanted a backpack for the Mega, so I took a vacation day and built one. (ps thanks to pete, who helped proofread the schematic and suggested the new arrangement of power rails, and chris who looked over my shoulder the whole time).
The Mega Lithium BackPack is an Open Source Hardware battery shield for the Arduino Mega that snaps to the back of the board, and provides around 15-27 hours of battery power to circuits built with the Arduino Mega (depending on the circuit). It gives a 3.3 volt, 5 volt, ground, and battery capacity testing signal that can be plugged into the Analog input port to test how much battery power is left.
Here's a picture of the first official Mega BackPack ever built (I lost my other camera, so I had to take this picture with my iPhone, which is old generation, and I hate it because it gets more and more outdated every other month, and I wish I could just swap out the camera in it):
Just like the original Arduino's, the Arduino Mega has these neat little screw holes in strategically placed locations throughout the board, that make for great places to put small stand-offs, that allow the Backpack to hang on to the backside of the Arduino without moving around:
Here's a shot that I took on a piece of white foam board, showing how the Mega Backpack is the same size and shape as the Arduino MEGA, and showing it side by side with the original Arduino:
For some reason, the flash on Matt's camera that I borrow has been acting up, so I had to edit this picture manually to remove the gray in the background. That took a while... I wonder if there's a professional tool for picture cleanup? I still spend way too much time on this part:
One of the nice things about being small and making Open Source Hardware is that I've gotten to meet a lot of interesting guys like pete (thanks!) who have lots of engineering experience. Pete offered to proofread the entire schematic before I built he PCB's, and that resulted in the whole thing working in only 1 revision! Thanks! It was also Pete's idea to string together the power and ground lines to make them visibly clear that they all do the same thing. Incidentally, the top rail is the "status" wire, which can be tested with the Arduino's analog input to see how much charge the battery has left, and there's a 5 volt and 3.3 volt line, just like the original Lithium Backpack:
I just uploaded a bunch of the other pictures I took over at Flickr, and I listed some for sale by themselves, or in starter packs with Arduino mega's.
As long as I'm building them myself (and with Justin and Mike's help, and anyone else who might want to make the trip down to Connecticut, the Mega backpack's will be the same price as the original Lithium Backpack, until I get tired of soldering them myself - ha)