This was quite a week. On Monday I packed my bags and headed out to the VIMS Eastern Shore Lab (ESL) in wachapreague Virginia. Once out there I spent the week working with the animals they had in captivity and helping out the marine scientists out there. They had a large tank of Sandbar Sharks that we were working with for the tag data. On Monday when I arrived they gave me and Ben a lot of data they had collected from a commercial accelerometer system on the animals so we got started on that. That evening they caught more sharks for research and I helped to tag them and put them into the tank. The next morning we pulled two sharks out of the tank and attached more of the commercial accelerometers to them. Then after that we fed the sharks, we haven’t looked closely at that data yet but hopefully we get something interesting from the feeding. The next day it was time to retrieve the accelerometers, we caught the sharks again and pulled the tags off. Unfortunately the waterproofing on one of the tags failed, it got waterlogged, and we were not able to recover any data from it. The silver lining is now I have a commercial accelerometer tag that I can disable and look at how it’s made. Also the other tag was okay and we were able to get the data from it.
Next it was time to start thinking out the tags I have made over the summer. We initially thought that the prototype tags were too big to attach to the animals. However it was decided that we could probably get away with attaching prototype 4 to one of the larger sharks for a little while. Before we could do this though we had to find a fast and nondestructive way to waterproof the tag. The PVC we came with was to bulky for the small animals we had there. We came to the conclusion that we could use large heat shrink tubing for the waterproofing by selling a few inches on each side together. To test this we filled some of the tubing with paper towels, sealed the ends with an iron and through the whole thing into the tank tied to a cinder block. When we pulled it back out the paper towels were dry so it was time to put the tag in. That evening we sealed configured the tag and sealed it up. We then caught the shark we were using (code name: scratch) and attached the tag.
The next morning we went back out to the tank, re-caught scratch and removed the tag. We then took it back to the lab, opened it up, and it was dry! we Popped the SD card into a computer and saw that we had good looking data and it appeared that everything had gone off without a hitch. We looked at the data for a while and then started to recharge the battery for the tag and prep it for another deployment. We picked out another one of the larger sharks to try the tag on, and once the tag was ready we sealed it in a new piece of heat shrink. When we pulled the shark out of the water to attach it and saw that its stitches from a surgery it had a few days early were coming undone. We restitched the shark and decided not attach the accelerometer to it so it could have more of a chance to heal. Since we did not have a shark to attach the tag to, but it was packaged for deployment we decided to attach it to a cinder block and through it in for a battery and waterproofing test. In hindsight it was a good idea that we did this stress test.
When we pulled the tag out of the water the next day it looked fine, but when we cut it open at the lab a bunch of water poured out onto the lab bench. The heat shrink had not sealed properly and the tag flooded. The tag was destroyed but we were able to recover a partially corrupted data file from the SD card. From this we learned that it took three hours in the water for the flooding to get bad enough to kill the arduino, and that we can recover some amount of data from a uSD card exposed to salt water.
After this setback we went about trying to determine a better procedure for sealing the heatshrink. Eventually we were able to develop a system that revolved around heating the iron to around 300c and then sitting it on the heatshrink unplugged for ten minutes. When we felt confident with this system we sealed up prototype 3 for deployment. This was pretty nerve racking as prototype 3 is our last functioning prototype with a gyroscope on it. We went out to the tank, attached it to scratch the shark, and then it was time for me to leave the eastern shore. Prototype 3 is still on the animal at time of writing, I will let you know if it survives when I find out.
When I got back to Williamsburg all the pieces to assemble the sharkduinov1 boards had arrived. I put together a layer 1 board that worked, and then took a layer 2 board and arduino with it to try to assemble a full sharkduino. This is still very much a work in progress but hopefully next week I’ll have a few to show you.
Finally the layer three boards came in. These boards have a pressure and temperature sensor on them and were designed to be exposed form water and physically separated from the other boards.
I will post some pictures of the sharks and the device on the sharks when I have time to go through those photos.