Raspberry Pi Tank: Adding Range & Bearing Sensors for Precise Navigation

Step 1: Select Sensors

For the Raspberry Pi‑controlled tank, we selected an SRF02 ultrasonic rangefinder and a CMPS10 3‑axis digital compass, both sourced from robot‑electronics.co.uk. Their I2C interfaces keep wiring simple, and their low cost makes them ideal for prototyping while still delivering the accuracy needed for obstacle detection and heading awareness.

Step 2: Create a GPIO Break‑out

During earlier development, a basic connector pulled GPIO 7 and Ground to the motor‑control board. To keep the layout tidy, we now add connections for 5V, SDA and SCL, sharing pins across the rangefinder and compass. A small, hand‑crafted break‑out board consolidates these wires, preventing a tangled mess of jumper cables.

Step 3: Validate the Setup

Robot‑electronics provides ready‑to‑run sample code that reads both sensors on a Raspberry Pi. Running these scripts as root grants access to the virtual I2C bus. After compiling and executing the programs, the results were encouraging.

The compass returned a “forward” bearing that aligns with the header edge: if that edge points north, the module reports roughly 0° – a 10‑degree offset compared with a calibrated iPhone. While not perfect, this level of precision is sufficient for the tank’s basic navigation tasks.

For a deeper dive, see Tank Day 23: Range and Bearing.

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