SB040182025 – PHOTODETECTOR CELL SCHEMATIC BLOCK

This schematic block features the NSL‑19M51, a cadmium sulfide (CdS) photoconductive cell used as a light-dependent resistor. Its resistance changes in response to ambient light: lower resistance under bright light, and higher resistance in darkness. The sensor is encapsulated in a moisture-resistant TO‑18 ceramic package, ensuring durability in various environmental conditions.

Designed for straightforward integration, this breakout module exposes its two leads so you can easily form a voltage divider or connect it directly to an ADC. Its passive behavior makes it simple to use in light-sensing, control, or feedback circuits.

Key Features:

• CdS photoconductive (resistive) output
• Light resistance: ~20 kΩ to 100 kΩ (at ~10 lux)
• Dark resistance: ≥ 20 MΩ (after light removal)
• Peak spectral response at ~550 nm (visible light)
• Resistance “gamma” (responsivity non-linearity): ~0.7 in 1–10 lux and 10–100 lux ranges
• Maximum voltage rating: 100 V (peak, AC or DC)
• Power dissipation: 50 mW at 25°C
• Operating temperature: –60 °C to +75 °C

Typical Applications:

• Ambient light sensing (e.g., for displays or lighting control)
• Light-based trigger or comparator circuits
• Photo‑metering or automatic brightness adjustment
• Educational or prototyping projects
• Night‑lights or daylight detectors
• Passive light-based feedback sensors

By integrating this Quickboards schematic block, engineers can quickly implement reliable light-level sensing with linear passive behavior, avoid the need for active components, and take advantage of a well-characterized, durable LDR design.