This document explains how the legacy Apple iSight’s internal shutter sensing assembly works, based on direct probing and measurement. Original documentation for this sub‑assembly appears to be unavailable publicly, so this is a practical guide for repurposing it.
If you want to view my original notes they're available as raw_isight_notes.txt
The original iSight has a physical privacy shutter. Inside the cylindrical enclosure there is an IR (infrared) emitter + phototransistor pair that detects whether the shutter is open (camera exposed) or closed (blocked).
Observed connections (after removing / probing the iSight main board section):
| Pad | Function (Repurposed Meaning) | Notes |
|---|---|---|
| Shared | Internal +3.3 V distribution node | Feeds both IR LED and phototransistor collector |
| Left | IR LED side (through ~150 Ω resistor to GND) | Provides LED current path |
| Right | Phototransistor output node (through ~5.6k Ω resistor to GND) | HIGH ≈ 3 V = shutter CLOSED; LOW ≈0 V = shutter OPEN |
Two on‑board resistors:
- R2 ≈ 150 Ω (current limit for the IR LED path)
- R1 ≈ 5.7–5.9 kΩ
Measured resistances (summarized):
- Between
Rightand GND: ~5.8 kΩ (R1) - Between
Leftand GND: ~150 Ω (R2)
Two operating states:
| State (Physical) | Right (to GND) | Interpretation |
|---|---|---|
| Shutter OPEN | ~0.0 V | Active LOW |
| Shutter CLOSED | ~2.9–3.0 V | Pulled HIGH |
Therefore:
RIGHT == HIGH ⇒ Privacy engaged (shutter closed).
RIGHT == LOW ⇒ Camera exposed (shutter open).
+3.3V (Power / Shared)
├───────────────────────────────┐
│ │
│ (Phototransistor Collector)
(IR LED Anode) │
│ │
│ │
│ (Phototransistor Emitter/Right)
(IR LED Cathode / Left) ├───────────────── -> OUTPUT
│ │
R2 ~150 Ω R1 ~5.8 kΩ
│ │
GND GND
loop:
state = read_gpio()
if state == HIGH and stream_active:
pause_stream() # shutter closed
elif state == LOW and stream_paused:
resume_stream() # shutter open
sleep(small_interval)
Use debounce of 10-20ms to ensure clean transition if you observe any jittering.
“Apple” and “iSight” are trademarks of Apple Inc.; this project is unaffiliated.