WiFi buoy for OpenROV 2.8 testing

control-systems
electronics

#1

Before I purchased my OpenROV, I had built a DIY ROV a few years back which used a buoy for control and video via an RC receiver with PPM output, and an analog video transmitter with baluns and cat6 cable. That ROV was scrapped, but I still had the buoy and recently decided to re-purpose it for my new OpenROV 2.8.

The buoy is a watertight food storage container with a 3D printer filament spool screwed into the bottom. Holes were sealed with an epoxy designed for plastic. On top is a 3d printed part meant for holding a flag. The tether length is set and secured by wrapping it several times through a carabiner which is hooked through the spool.


Inside, an ASUS RT-N12 router is secured along with the homeplug topside adapter using double sided tape. The router accepts 12V DC and is powered by a 2200mah lipo battery. A 5V UBEC provides power to the topside adapter. This battery should last very long, but another could easily be added in parallel if it doesn’t.


The buoy floats nicely, and is dragged around by the ROV without much effort. I’m using small 3D printed floats to make the tether neutrally buoyant (source:http://www.thingiverse.com/thing:1557029). Using tons of these would make spooling the tether a nightmare, and I’m not sure how they’ll handle pressure, but for the short length of tether needed for testing the buoy in this shallow lake, they work nicely.


I first tested the range on land with my laptop’s wifi adapter. It didn’t work very well, so I opted for this long range WiFi adapter: https://www.amazon.com/gp/product/B003ILWRLI/ mounted on a tri-pod. Using this setup, I was able to motor my rov out to a fountain in the lake which I measured using google maps to be a little over 200ft away. At this point, the latency in the video was substantially greater than normal, so I chose to return. My range with my laptop’s stock WiFi adapter was only about 50ft on land before it reached the same level of latency.


I was also testing a 3D printed manipulator which used a car door lock actuator. I was more focused on the WiFi buoy, so the only thing I managed to catch was my own tether!


Those are bubbles on the outside of the acrylic, not water droplets.


The range isn’t very impressive, but this was a quick and dirty test with the router’s antennas at extreme angles so they would fit inside the container. I have a 3W WiFi booster: https://www.amazon.com/gp/product/B00BX9YZI0/ that I’ll be trying out, and I will mount its antenna straight up through the lid. This should result in dramatically greater range.

Also, I have this camera on order: https://www.amazon.com/gp/product/B00VDSBH9G/ which supports h.264 output. I’d like to experiment and see if the reduced latency and bit-rate of h.264 streaming compared to MJPEG would improve my WiFi experience.


#2

@tgfeminella,
Have you considered using this 5GHz Base Station with one at each end. No need for a WiFi router if your laptop has a Ethernet connection.
Regards,
TCIII AVD


#3

The range people get with these are pretty impressive, but I’d need a bigger buoy to accommodate one of these stations, and I’m trying to keep my setup fairly portable. I’ve installed the router’s booster and if that gets me 300-400ft of range, I’ll be satisfied. If not, I’ll probably explore other options.

So far, I really like the buoy because it cuts down on the frequency of tether tangles and snags. The downside is that if it does get stuck 200ft out in a lake, I’m going to have to swim for it :grin: