A quick historical past of the Shetland Assault Pony
As an avid caver, Phil Underwood is dependent upon his tools for successfully mapping the slim passageways and sharp turns of the caves he explores, as even a comparatively minor quantity of inaccuracy can result in the ensuing maps being very incorrect.. Again within the Nineteen Nineties, he would deliver alongside a mechanical compass, clinometer (for measuring angles relative to the bottom), and reel of tape to get distances. Nonetheless, this was not a really perfect setup because of the cramped circumstances and the necessity for extra mild than his headlamp might present, so he determined to invent a digital machine to supply this performance.
After arising with the memorable identify of “Shetland Assault Pony” while in a pub, Underwood’s preliminary prototype consisted of a laser pointer, LED readout, and a user-facing button on the aspect. Shortly after, the following iteration contained an OLED module for displaying the present time, distance, and battery in addition to a visible-spectrum laser rangefinder that eradicated the necessity for a tape measure, though some performance was nonetheless missing.
Plans for enchancment
For Underwood’s most up-to-date iteration of the Shetland Assault Pony, he opted to combine as many sensors as he might so as to construct the final word cave surveying device. The hand-held machine would preserve its compact form, Bluetooth connectivity, and laser rangefinder, but in addition have a built-in magnetometer and IMU for locating angles deep under the floor.
The circuit design and PCB
The circuit is predicated round a Seeed Studio XIAO nRF52840 Sense owing to its very compact footprint, BLE radio, and 6-axis IMU that may discover the downwards course with the accelerometer. For the magnetometer, Underwood went with an RM3100 since it could measure magnetic fields in three separate axes and preserve accuracy as soon as calibrated. Energy is delivered by a LiPo battery which is regulated by a 3.3V LDO and could be shortly recharged with an exterior charging circuit. Lastly, communication pins are uncovered for each the UART-driven laser rangefinder and the I2C OLED module together with a small buzzer and buttons for interacting with the consumer.
Constructing a tool
After fabricating the PCB, Underwood assembled the electronics and battery right into a single unit earlier than inserting it inside the 3D printed enclosure. The entrance of the machine has a transparent window for the laser rangefinder to see by and the highest cutout has a further piece of clear acrylic for the display screen. Every part else was sealed with a layer of silicone grease to assist in waterproofing since caves are usually fairly damp and muddy.
Mapping caves
One spherical of calibrating later and Underwood was prepared to start out surveying. Due to the “SexyTopo” cellular app, he might simply join the Shetland Assault Pony to his telephone and start importing measurements for the gap, inclination, and heading. The group of factors might then be joined right into a single path and leveraged to construct a digital map of the cave’s inside options and dimensions. To see extra about how Underwood constructed this compact machine, you may watch his construct log video right here on the element14 Presents YouTube channel.
