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A short historical past of the Shetland Assault Pony
As an avid caver, Phil Underwood is dependent upon his tools for successfully mapping the slender 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 carry alongside a mechanical compass, clinometer (for measuring angles relative to the bottom), and reel of tape to get distances. Nonetheless, this was not a perfect setup as a result of cramped situations and the necessity for extra gentle than his headlamp may present, so he determined to invent a digital gadget to offer 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 subsequent 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 may with a view to construct the last word cave surveying device. The hand held gadget would keep its compact form, Bluetooth connectivity, and laser rangefinder, but additionally have a built-in magnetometer and IMU for locating angles deep under the floor.
The circuit design and PCB
The circuit relies round a Seeed Studio XIAO nRF52840 Sense owing to its very compact footprint, BLE radio, and 6-axis IMU that may discover the downwards route with the accelerometer. For the magnetometer, Underwood went with an RM3100 since it could actually measure magnetic fields in three separate axes and keep accuracy as soon as calibrated. Energy is delivered by a LiPo battery which is regulated by a 3.3V LDO and will be rapidly 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 person.
Constructing a tool
After fabricating the PCB, Underwood assembled the electronics and battery right into a single unit earlier than putting it throughout the 3D printed enclosure. The entrance of the gadget has a transparent window for the laser rangefinder to see by and the highest cutout has an extra piece of clear acrylic for the display screen. Every little thing else was sealed with a layer of silicone grease to assist in waterproofing since caves are typically fairly damp and muddy.
Mapping caves
One spherical of calibrating later and Underwood was prepared to start out surveying. Due to the “SexyTopo” cell app, he may simply join the Shetland Assault Pony to his cellphone and start importing measurements for the space, inclination, and heading. The group of factors may 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 gadget, you possibly can watch his construct log video right here on the element14 Presents YouTube channel.
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