I mainly worked on two things this week. The first was finding some academic articles relating to my research. I had to do this for the class part of honors research. I actually found two in particular that are pretty cool.
The first is about the effects of attaching tags to small sharks on the sharks behavior. The researchers attached GCDC tags to lemon sharks in a tank, and compared how sharks with and without a tag behave. They concluded that they have to look at more than just the mass of the tag to determine if it will change the animals behavior.
The second is about using magnetometers to look at animal movement, as opposed to just using them to help with dead reckoning. They are sort of using a magnetometer with an accelerometer to try to answer some of the same questions we are trying to answer with the gyroscope.
Another charging test
I also spent a lot of time working on the battery charging. This time I used a sketch to put the Arduino into a low power state, then plugged it directly into a battery charger and a battery. This sketch brought the current draw of the Arduino down to 0.3mA. It turns out that this is low enough that the battery can charge normally while the Arduino is attached! This means that I will probably not need to make a load sharing circuit. I have a few tests using off the shelf components and sharkduinos and everything seems to be working well. The next step is to create my own board for the charging circuitry. That way it can test that it works well on it’s own.
I spent almost all my time this week introducing new people to the project. It looks like we are getting three new members of the team, and it’s very exciting!
I may introduce the new members on this blog later if they want, but right now everyone is focusing on getting them up to speed so they can start doing great work.
On the more technical side I kept working on the MOSET polarity protection circuity. I attached it to the breadboard Sharkduino and checked everything out it. It looks good and feel ready to incorporate the MOSFET onto a Sharkduino board.
Finally I kept working on finding a way to charge the LiPo while it was connected to the Sharkduino. This time I used one of Ben’s sketches to put the Sharkduino into a low power. Hopefully it draws so little current that the battery won’t notice the load, and charge normally. An Arduino running a blank sketch draws 3.70ma, this code gets it down to drawing 0.36mA. This might be low enough that the charging will work, but I’m not sure yet.
I took the summer off from the project for an internship, but the fall semester has started up so I’m back on Sharkduino!
This week I spent mostly getting things ready for the semester. I moved to a new room, and organized my supplies.
I did get a little bit of real work done too, I realized that our new batteries were wired backwards from our previous ones (ground is on the right of the connector for the old ones, but on the left for the new ones). Luckily we didn’t plug any of these backwards batteries into a Sharkduino, but I did destroy a charger before I realized what was happening. Fixing this problem was easy, but tedious. I just undid the connectors and reversed the wires going into them.
To keep this from happening in the future we are going to be more careful about inspecting new batteries before plugging them in. We are also looking at added reverse polarity protection circuitry to the Sharkduino. At our power level I think this circuitry can just be a P-MOSFET. A picture of my test circuit for that can be seen below.
Blowing up chargers wasn’t the only battery work I did. I am also conducting tests to see if we need to separate the LiPo from the sharkduino system while charging it, or if it will still charge normally while the Arduino is pulling a little current. These experiments are ongoing so I’ll talk more about them when I have results.