IR LED (invisible VLL)

Status: ⚠️ sensor sees IR (confirmed); full VLL frame over IR not yet demoed

Program the Micro Scout with invisible infrared — no visible flashing — by driving an IR LED with the VLL timing.

Why it works

The Micro Scout's light sensor is silicon → sensitive to near-IR (700–1100 nm), and it has no IR-cut filter — confirmed on-device (a ~940 nm IR remote triggers it). (LEGO's own tower programmed the Micro Scout over VLL on a visible-red LED, not IR — its ~940 nm IR is the RCX serial channel.) See Micro Scout.

Wavelength

• 850 nm ⭐ — strong silicon response, only a faint dark-red glow (near-invisible). Most reliable.
• 940 nm — fully invisible (like a TV remote), weaker response → brighter/closer.

How

Same as Arduino · ESP32 + LED but with an IR LED (lower Vf → ~100–150 Ω). The phone torch can't do this (visible only).

1-minute test (no soldering)

Run a light-reactive program (Seek/Light Control) and blast the sensor with a TV remote (940 nm). If the Scout reacts, IR passes → invisible VLL is viable (850 nm will be even better).

Links

• Adafruit — Bluetooth remote for the LEGO Droid — BLE → LED VLL build