IR LED (invisible VLL)
Status: ✅ device-confirmed — a full VLL frame over invisible IR programs the Micro Scout (an ESP32 onboard IR LED, decoded at 30–40 cm on direct aim, 2026-07-19). Better range than the visible-RGB path.
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). Drive it baseband (plain on/off digitalWrite, no carrier) — VLL has no carrier; a 38 kHz-modulated IR LED will not be decoded.
Confirmed build (2026-07-19)
An ESP32 onboard IR LED driven baseband with the standard VLL engine — a real Micro Scout decoded ping/beep/motor codes at 30–40 cm on direct aim. Earlier "onboard IR too weak" guesses were wrong — it was the drive method (a stray carrier), not brightness. Trade-off: VLL needs point-blank direct aim, so it suits a handheld host (screen + battery, aim by hand) rather than a USB-tethered board.
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