I would like to be able to leave AMOS outside soon to test it for long term logging of data in an outdoor environment. With all of the electronic devices that it currently uses, there is a substantial drain on the battery, especially at this time of the year when there are really only about 9 hours of sunlight per day. So AMOS needs to have some way of powering down its various power-hungry components while just leaving some minimal electronics running. As a first step towards this, I created a little circuit with some diodes, a pair of AA batteries, a 1 mF capacitor, and a relay controlled by the microprocessor on the serial wireless link to power down virtually everything (including the Raspberry Pi) whenever there is a gap (two minutes or longer) in the activity detected by the Raspberry Pi. The original intention of this was to work as a means of doing a hard-reset on the Pi if its program crashed or stopped unexpectedly. But the powering down could also be used according to a defined schedule (say for long periods of time at night) in order to maintain a good level of charge on the main battery.
Last week I had mentioned that the I2C on the Raspberry Pi had gone kaput thanks to a brief "touch" of the 5 V fuse with the +12 V battery terminal. Yesterday the replacement Pi arrived, and I was able to plug it in and confirm that its I2C bus worked fine. However, the I2C bus on the analog to digital converter (which was connected at the time of the touch) was not fine. It still did not work at all, and the voltage level on the SCLK line was hovering around 4.7 V, not something you would expect for a 0 to 3.3 V clock signal. So apparently the "absolute maximum" rating of 7 V for the power input to this A to D converter really does mean something. While hunting today for a replacement unit, I came across the ADS1115 from Texas Instruments. This is a similar sort of I2C analog to digital converter, but it is less expensive, offers the same 16-bit resolution on 4 single-ended channels, and also can sample at a whopping 860 samples per second! I think the device that I blew only had 16 samples per second.
I subscribe to a couple of different "Google Alerts" about robotics. In one of these today, I came across a Carnegie Melon University (CMU) web page that featured a number of different robotic projects that they are working on, including a robotic airboat: https://frc.ri.cmu.edu/robots/
They have a really strong robotics program at CMU, so it is sort of a nice validation to see that the idea of a robotic airboat has some merit.
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