Monday, April 18, 2022

AMOS Wireless HAT Module

 A lot has happened in the last few months, both in the greater world and in my own life. The war in Ukraine has unfortunately occupied much of my attention. I'm hopeful that the Russian invaders will be repelled from that country, but the present situation there is terrible, and I fear for the worst, both for Ukraine and the world as a whole. In my own life, I started officially working full-time at Measurand in March, although I had been unofficially working there full-time since November of last year. This means a bit less time for AMOS and In Nature Robotics, but the job itself is interesting, involving embedded product development and firmware. Plus having a full-time salary is helpful, given the way costs seem to be going higher and higher lately. 

In my own experience using AMOS, and in some of the feedback I've gotten from customers, one recurring issue has been the tangle of wires within the AMOS CPU box that connect the Raspberry Pi to the rest of the equipment (wireless module, AtoD, sensors, etc.). Sometimes one or more of these wires become disconnected, and it can be a challenge to find the disconnected wire and attach it to the correct location. 

Enter the new AMOS Wireless HAT (HAT stands for Hardware Attached on Top). 

It has a 40-pin header that plugs directly into the Raspberry Pi board, and uses printed circuit board traces rather than wires to connect the AMOS wireless equipment, AtoD board, and temperature and humidity sensors. It also allows direct soldering in of wires from the battery box module (for the propeller and rudder control). 

I have already noticed a few things that should be changed on the board, but the order for the first 5 prototypes is already in production, so I'll populate one to see how it goes, and then make some changes after that. 

The weather here is warming up; I'll need to get the demo AMOS up and running again to do some weekend testing again soon!

Sunday, January 23, 2022

Winter QA Testing

 Generally it's not a great idea to do AMOS testing in the winter-time. The local rivers and lakes are frozen, so an hour's drive is required to find the nearest available liquid water in the Bay of Fundy. And careful planning is required to ensure that tides, wind, waves, and the cold are all manageable. 

Two recent AMOS robot sales however required that the testing be done, so the van was loaded up in early January for a test down to McLaren Beach, just outside of St. John.

Both AMOS robots were equipped with underwater camera modules. Unfortunately, these proved to be problematic for the air temperatures of -7 deg C and water temperatures of 5 deg C. The plastic tubing, normally quite flexible at room temperature, became as stiff as steel in the cold. In shallow water, this meant that AMOS would get stuck (if it was moving slowly) or might snap off the top connector of the tubing if it struck the bottom at a high speed. So I packed everything up and headed back to make a couple of plugs for the camera holes; the underwater testing component would have to happen indoors. Fortunately the final destinations for these robots are considerably warmer than Canada in the wintertime, so freezing camera tubing won't be an issue. 

A return trip was then made to the Irving Nature Park a few days later, as McLaren Beach was inaccessible due to a recent snowstorm. The waves were stronger here, as it was less sheltered, but the first AMOS went through its sampling course flawlessly. The second one had trouble even starting however. It started up fine prior to leaving, and started up fine inside the van, but within a few minutes of having it outside on the beach (again about -7 deg C) it abruptly lost power and the LED light on the  power switch went out. My guess at this point was that the switch was faulty and didn't perform well in the cold, so after driving back I replaced it. 

A third trip was then made a few days later to Lorneville, as there was a strong wind out of the south that day, and the selected spot offered a bit of shelter from the strong open-water waves. Once again however, the AMOS robot lost power in the cold, usually shortly after the propeller was driven at high speed. This time I thought to carefully check the solar charge controller, and realized that its short-circuit protection circuit was engaging. This was a newer version of a controller which I've been using for the last 3 years; previous versions allowed you to disable the short-circuit protection feature, but this version did not. So back to Fredericton, to replace the solar charge controller with an older model. 

On the fourth trip back (to McLaren Beach), the 2nd AMOS robot also worked flawlessly:

So now both units have been shipped out and are due to arrive early this week. I'm looking forward to seeing how they will be used over the next few months. Hopefully around the middle of this year I will be able to provide an update blog with some details!

In support of these systems, the support page has been updated, and a number of YouTube instructional videos for assembly and testing have been created. These are a bit rough at present, but they should be effective I think. 

Saturday, November 13, 2021


Here are some pictures of the latest AMOS version (perhaps to be called "Mini AMOS"). It uses the same electronics boxes as the regular AMOS, except it only uses a 4 foot long bodyboard, doesn't have a solar panel, and uses a water propeller instead of the air propeller on the standard robot. The board shown below doesn't have a survey-grade GPS antenna (just uses a GPS / USB stick), but that could be added later if desired. As it stands right now, its weight is only 4.5 kg. 

There will need to be some minor software modifications to drive and control the water propeller, but these should be relatively minor. It will be interesting to see how fast it can go, and / or what kind of performance it has in wind, waves, currents, etc. 

Thursday, October 7, 2021

Flexible Underwater Ribbon Cable Guide

 The previous rigid 3-D printed shell that was used to join the underwater WeatherBox to the main electronics box on the AMOS surfboard needed to be replaced with something flexible that could flex and swing out of the way whenever underwater obstacles were encountered. 

Some inexpensive plastic tubing was purchased at Home Depot, and 3-D printed adapter parts were constructed for either end of the tubing, to join it to the WeatherBox at the bottom end and the main electronics enclosure at the top end. 

This made a nice, water-tight conduit for the camera cable to follow, but it proved to be difficult to design the top piece to be strong enough to withstand large bending moments that were produced whenever AMOS passed over a shallow, rocky area. Three different top-piece designs were fractured in separate field tests before switching to a slightly different design using a large cable gland at the top. Instead of fitting the top end of the tube over a 3-D printed male plastic piece, the top end of the tube was fitted inside the cable gland. A small amount of heat treatment with a heat gun was applied at the top end of the tube to allow it to compress slightly and ensure a snug fit. 

This design worked perfectly: it had enough "flex" to be able to swing up out of the way of obstacles, without putting too much stress at the top cable gland connection. Here is a video of AMOS crashing into an underwater rock. The WeatherBox and its cable guide swung out of the way and were undamaged:

I enjoy combing through the videos from these tests, looking for fish. Here were a couple that were briefly captured in the most recent test yesterday (October 6):

My favorite clip came at the end of the test when AMOS was just floating near a partially submerged tree. I really like how the light from the sun is shining on the tree in this video, it looks kind of magical:

Friday, September 24, 2021

AMOS Captures Some Fish

 Things have been busy lately, and there hasn't really been much occasion for taking AMOS out in the field. Over the last week though, I was able to develop some software for saving 30 fps 1920 x 1080 video files on AMOS, while still continuing to do all of its regular navigation and data saving stuff. Testing and debugging was done in the pool, and everything seemed to be working well. 

This morning I took AMOS out to Kelly's Creek to test how the navigation, sensor data saving, and video recording all worked together. I was worried that the addition of the video recording in a real environment would slow down the other functions, possibly resulting in sluggish handling or missed data samples. Everything seemed to work pretty well though, although when I had plotted the course the night before, I had not realized how low the water level actually was. The waterline was about 10 m in from where it appeared to be on the ArcGIS map that was used to setup the course. Unfortunately, the WeatherBox  that housed the camera underneath AMOS struck a rock at full speed, and the 3-D printed extension piece that connected it to the main electronics enclosure snapped under the strain. The WeatherBox was quickly flooded, but I was following close behind in the kayak and was able to turn off AMOS's power switch a few seconds later. Clearly a more flexible extension piece will be required here. Perhaps something like a short rubber hose could work?

Despite this accident, the rest of the test was a success. Depth, temperature, and conductivity data were all recorded normally, AMOS navigated itself normally, and 9 video files were recorded, mostly of air bubbles and river vegetation, but at 1:10 of the video below, you can see 3 small fish swimming by for a few seconds:

The end of the above video is where the WeatherBox struck the rock and the camera module was flooded. Unlike the last camera flooding which occurred in salt water, this one was in fresh water, and after storing the camera module in a bag of desiccant for 12 hours, it was confirmed to be unharmed. 

Wednesday, September 1, 2021

AMOS Looks Underwater

 Last month's assumption that the o-ring seal on the WeatherBox required improvement proved to be correct. The printed part had tiny imperfections underneath the o-ring that allowed water to slowly leak through. A WeatherBox customer who was using it to observe a muskrat underwater came up with a brilliant solution: he found that using some marine goop (ex. in the channel holding the o-ring worked to fill in the small imperfections in the plastic and create a watertight seal. I've built a few WeatherBox enclosures since then with the channel filled with Marine Goop and they have all worked quite well.

To take pictures and video underwater with the 6 foot AMOS surfboard, an extension piece was required to get the WeatherBox below the waterline. The bow of the surfboard where the camera is located is pitched upward at about a 20 degree angle, so this requires a curved extension piece. The creation of this extension piece required a couple of weeks. At first, rendering the model in OpenSCAD took days for my laptop to finish, although later iterations of the model used some 2-D optimizations with extrusions that shortened the rendering time to about 24 hours. The first two model attempts also had small gaps on the side with the largest radius of curvature, which led to leaking. Eventually a working model of the curved extension piece was created:

The extension piece was fitted on AMOS and used to capture this underwater backyard pool video:

Apologies to viewers for the acting talent used in the above video. In Nature Robotics operates on a tight budget. 😉

Coming up next week is the final round of  the 2021 edition of the Ocean Startup Challenge ( In Nature Robotics is in the mix again this year, and will be pitching on Thursday, September 9. 

Wednesday, July 28, 2021

Drip, Drip, Drip, How to Make a Watertight Window?

 Some work has been done over the last couple of weeks on trying to adapt the WeatherBox to function as an underwater camera enclosure. This work has been educational but not entirely profitable. Some underwater tests had been done in the pool, and at the time appeared to be successful, but they were too short (less than 5 minutes) to really prove out the leak-worthiness of the enclosure.

A longer test in a real-world environment confirmed that the enclosure leaks too quickly to be of any use for underwater pictures or video. A slightly modified version of the enclosure with a longer stem was attached to the underside of AMOS and used to record a video frame every second, for a 1 hour test along the shoreline in Cap Brule, New Brunswick. The stem was not really long enough to keep the camera underwater all of the time, and the mounting pins inside this particular enclosure had snapped off, so the camera board was not properly centered. The camera software uses an auto-brightness adjustment, which I think was confused by the alternating views above and below the water. 

The camera ceased to function after about 20 minutes of operation. When the boat was taken out of the water about an hour later, it was half-full of sea water. The camera board was immediately rinsed and dried off, to no avail. A subsequent test confirmed that it no longer functioned at all. 

Some decent depth, temperature, and conductivity data was collected for the test, showing a nice correlation between the 3 parameters: the shallower water was warmer and had a higher measured conductivity.




Here is a video created from stringing the individual 1 Hz video frames together and increasing the playback speed by 5x. Not much to see really, just a lot of bouncing up and down and the occasional piece of seaweed:

I'm going to test out some changes to the camera enclosure cap this week; at this point it looks like the weak point is the O-ring seal with the enclosure window.