This board is a modification for HTC Vive Base Stations ("lighthouses") that increases their tracking range.
HTC base stations work by producing alternating global synchronization flashes using an IR LED array followed by laser curtain sweeps for 3D localization. Because we use tiny photodiodes on our headstages (with about 1/10 the effective area compared to those in the HTC headset), they are only capable of working at ~3 meters from an unmodified base station. This issue is entirely caused by the power of the global synchronization pulse. The synchronization pulse must simultaneously blanket the entire room in IR light and therefore its irradiance goes down as the square of distance from the base station. Therefore, a very powerful LED array must be used. Conversely, because the laser curtains are 2D sheets, their irradiance goes down linearly with distance so they are easily received by the headstage at large distances without modification.
This board is a drop in replacement for the standard LED array inside the HTC Vive base station. It replaces the standard 9-LED array with an array of 120 LEDs. Each set of 15 is controlled by a fast, low-side transistor switch. The board draws about 700 mA DC at 12V. The pulse current (~60 us long, 2 MHz-modulated pulses operating at ~1% duty-cycle) is approximately 200A, with 5A for each LED. During a pulse, the LED array is decoupled from the input power using a high-side load-switch. This means that all pulse energy is taken from local capacitance such that the rails the driving motors inside the base station are not transiently loaded.
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Copyright Jonathan P. Newman 2017.
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