The Current State of CdS Photoresistors

Photoresistors still thrive in low-cost, low-precision scenarios like:

Toy light-activated switches

Basic ambient light sensors in DIY electronics

Industrial photocontrols with slow response needs

Their analog output and simplicity keep them viable for hobbyist projects and legacy systems.

Why Replacement is Accelerating?

Performance Limitations

Slow response time (milliseconds vs. nanoseconds in photodiodes)

Temperature instability and aging effects

Rise of Superior Alternatives

Photodiodes/Phototransistors: Dominate in LiDAR, optical comms, and high-speed detection.

Integrated Ambient Light Sensors (ALS): Found in smartphones, combining IR filtering and I²C output.

Photovoltaic + ADC Solutions: Enable self-powered sensing for IoT devices.

Industry 4.0 Demands

Smart factories prefer digital sensors with programmable sensitivity and no calibration drift.

Survival Niches

Photoresistors persist where cost beats performance:

Educational kits (e.g., Arduino light meters)

Disposable electronics (e.g., sunrise alarms under $5)

The Verdict

While not obsolete, photoresistors are becoming a "legacy component" outside ultra-low-cost segments. Silicon photonics and MEMS-based sensors will likely push them further toward obsolescence by 2030.