Sufficient Air Power

Because AMOS is somewhat susceptible to getting stuck in stringy seaweed, I bought an inexpensive plastic air propeller (for use with remote control airplanes), and an electronic speed controller from Amazon. This past weekend some scrap wood was added to the back end of AMOS to mount it, and some simple test software was created to calibrate and use the speed controller. I really wasn't too sure how it was going to go, i.e. whether or not this little plastic propeller would produce enough thrust to move AMOS anywhere or not.

Here is a picture of  Checkers with AMOS and the new air propeller:

And a video of the propeller in action in our green pool:

https://www.youtube.com/watch?v=NDXu83YbiPo

It was extremely windy when the above video was shot, which likely accounted for some of the rotation that AMOS experienced. At present there are no rudders for directional control, I just wanted to see whether or not the propeller could produce enough thrust to move the boat. For the video, the thrust level was at about 70% of maximum output. This corresponded to a current draw of about 20 A at 12 V, comparable to the maximum amount of power that I used with the water propellers. The battery inside AMOS is rated for a maximum continuous output of 20 A, so I probably wouldn't want to drive it beyond that for any length of time. As expected, there is not as much propulsive thrust exerted by the air propeller, compared to the combined efforts of the two water propellers. However, now that the water propellers are removed, there is less drag in the water. I'm also wondering if a more hydrodynamic hull (perhaps catamaran style?) might also help to reduce drag.

The ribbon extension cable for the camera arrived last week, so that was hooked up and tested to confirm that it worked correctly. I also spent an hour or two searching around the Linux geek forums to figure out how to setup the Pi to automatically connect to any of a number of potential wireless access points. This sounds like it should be easy, I mean PCs have been doing that for years right? But there was actually a lot of conflicting information on the Internet about how to do it on a Raspberry Pi properly. I had tried and failed a few months earlier, and have always been manually editing the /etc/network/interfaces file and rebooting every time I wanted to switch access points. But this time I managed to get the wpa_supplicant.conf file setup properly, so now AMOS can connect to any of 3 potential access points, without the need for editing the configuration file every time.

The next step is going to be to design an air propeller cage (so I don't cut my fingers off) and a motor / rudder system mounted to the cage, behind the propeller for steering. I've been looking at lots of pictures of airboats online, and have some idea of how to do it, but I'm sure there will be some challenges. I also recently purchased a pair of wireless transceivers: https://www.robotshop.com/ca/en/24g-transceiver-rf220su-module.html that claim to have a line of sight range of up to 3 miles, and contain an Atmel AVR 8-bit microcontroller (the same one used in Arduino boards). One of the transceivers will be used on a small mast on AMOS, and besides maintaining a communications link, will be used to continuously monitor the "health" of the main Raspberry Pi board. If the Pi board becomes unresponsive for a set period of time, the smaller 8-bit micro can control a relay that will "hard-reboot" the Pi. The small micro also has pulse width modulated (PWM) outputs, analog to digital inputs, and digital inputs / outputs, but I haven't decided what (if anything) to do with them yet.