By Xiang-Yang Lu
As thescope of use of Raspberry Pi grows wider, the recent development of such technology shifts it focus onto desktop computers and industrial applications, and there have also been some breakthroughs in self-making.
Raspberry Pi bag.builds- into a backpack
Davide Marchetti initiated a project called bag.builds. He puts the RPi, battery, and accessories into a backpack, while separating and positioning them using wooden boards and plastic fasteners. After every piece is positioned, he connected them to the wires.
The parts that Marchetti puts in a backpack include a Raspberry Pi 4, a docking station, a WRT1900ACS Wi-Fi router by Linksys. The router adopts an OpenWrt embedded operating system with VPN feature. There was also an external mechanical hard drive and an external solid state drive, both with a USB interface.
In addition, there are NVMe storage access with Thunderbolt interface, wireless transmission module with Wi-Fi Dongle and HackRF, and an active antenna in the frequency range of 1 MHz ~ 3 GHz. There are also speakers, Wi-Fi Hotspot feature by GL.iNet, and a smart phone to connect to the Tor network. Lastly, a 250Wh power bank. Judging from the photos he shares, there are also small monitors, mice, and headphones.
Raspberry Pi in water
Another project is to use Raspberry Pi underwater. There is a transparent acrylic container in cylindrical shape as the hull of a submarine model. Raspberry Pi, more specifically a Raspberry Pi Zero 2 W, serves as the main control system. The project was launched by Brick Experiment Channel, or BEC in short.
The mechanical parts of the submarine built by BEC are made of LEGO bricks. The submarine can propel forward, roll, pitch and yaw, and remain stopped, while keeping a distance from the bottom of the floor to avoid collision.
In addition, BEC uses a syringe as the ballast tank of the submarine to dive or surface through controlling the amount and distribution of water, where BEC uses the most traditional PID controller.
Another key to designing the submarine is the pressure sensor. BEC tried two types; one is ABP2LANG004BG2A3XX and the other is SSCMANV030PA2A3, both by Honeywell. BEC ended up choosing the latter.
The laser sensor, WPSE337 by Whadda, includes STMicro’s VL53L0X module. The sensor is set at the bottom of the submarine to detect the distance between the hull and the seabed. Later on, the TFMini-S Micro by Sparkfun was used, instead.
For the remote control, BEC turned to a toy submarine by a Chinese brand Mliu. The toy comes with a 27MHz wireless remote control and receiver, which were modified a bit, and voila. For other parts, the submarine adopts a LEGO battery box with an output of about 8 V, and there were the 2123 Pololu and the 5V2 S7V8F5 voltage regulator to supply power to the Raspberry Pi. A 16 GB MicroSD memory card was used, with the official standardized Raspberry Pi OS as the operating system. Python was used as the program for control.
The developing process and testing by BEC was very strict, where there were detailed records of the development process and the developers’ feedback. For Makers trying to work on projects that are more practical, BEC is a great reference.