Monday, July 16, 2012

ROV-Suite: Bottomside 1.1.0 Released

Great news!  I just uploaded the first revision of ROV-Suite's bottomside code to the repo and to the downloads page.  This new version supports a depth sensor, a voltage sensor and a digital compass.  Please note that while the libraries have been used (my robotics team used those very libraries to get 3rd place in the MATE ROV competition) and tested, the entire setup has not been tested yet.  Since it is late here tonight, I'll do some bench top testing tomorrow.  

Here's the setup:
Compass (HMC6352) hooked up to the Arduino's A4 and A5 (I2C) pins.
Voltage sensor (Phidgets P1135) hooked up to the Arduino's A1 analog input pin
Depth sensor* (Phidgets P1115) hooked up to the Arduino's A2 analog input pin

Now the depth sensor's setup is a little tricky at first, but it is really robust in practice.  In fact, in our testing, we found that the library was accurate to within a centimeter!  Since the P1115 is really just an air pressure sensor, you must use the water to compress a volume of air that must then compress the pressure sensor.

The flexible diaphragm is pushed inwards (towards the P1115) as the water pressure increases.  That causes the volume of air inside the sealed container to decrease, and since the container is sealed, the pressure then increases.  From there, the P1115 reads the absolute air pressure inside the sealed container and converts that to a depth reading.  I will admit, this is not my design.  A mentor on the team, Jay Isaacs, came up with it.  The only downfall of this setup is the maximum depth of the pressure sensor (as it can only have 36 PSI atmospheric on it, only 21.3 PSI of water pressure can be applied before it exceeds it's maximum pressure rating).  According to some calculations with the help of Engineering Tool Box, it's maximum depth is 49.2 feet of water.

I hope to test out this code more fully soon so that I can catch any bugs it's hiding.

Thanks for stopping by!

Chris Konstad

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