A Fully Functional LEGO Submarine ROV

This is Hackster, so I know that I am preaching to the choir here, but LEGO is pretty amazing. Young children can snap together LEGO bricks to create simple structures, of course. But even older kids and adults can take advantage of LEGO's wide range of products to build quite complex machines. The LEGO Technic series in particular contains many parts that make powered mechanisms possible. If you want proof, take a look at this fully functional LEGO remote submarine built by the proprietor of the Brick Experiment Channel on YouTube.

This submarine isn't just a toy. It has all of the features one would expect to see on a real submersible ROV (remotely operated vehicle). In can dive to precise depths using a water ballast with both a pressure sensor and laser rangefinder. It has forward/reverse propulsion and the ability to rotate clockwise and counterclockwise. It can record its underwater surroundings with a camera, complete with depth and water temperature readouts. And the pilot can operate it with a remote control. It even has an onboard LEGO minifig captain.

Almost all of this sub's mechanisms are made of LEGO Technic parts. The water ballast, which is a syringe that pulls water in or pushes it out to adjust buoyancy, actuates via Technic motors and rack and pinion gears. Technic motors also spin the two propellers that provide forward thrust and rotational thrust. Those motors are magnetically coupled to the propellers, which helps maintain a watertight hull. That hull is a cylinder of plexiglass, with custom plexiglass caps sealed with O-rings.

Controls commands transmit to the sub via a scavenged RC transmitter and receiver combo. A Raspberry Pi Zero computer interprets those commands and controls the motors accordingly. It also monitors the pressure sensor and laser rangefinder. Using an algorithm based on PID (Proportional-Integral-Derivative) tuning, the sub can quickly dive to a specific depth without overshooting it.

The sub's first tests were in a pool and it performed very well. From there, it set out on a 200 meter voyage up a stream. It navigated that shallow stream without issue and recorded the entire journey.

If you want to build your own LEGO Technic submarine, the full build details and the Python code that runs on the Raspberry Pi are available on the Brick Experiment Channel website.