Photoresistive Element: Power Rating 100-200 mW

Component Specifications

Definition

A photoresistive element, also known as a photoresistor or light-dependent resistor (LDR), is a passive semiconductor device whose electrical resistance decreases with increasing incident light intensity. It operates on the principle of photoconductivity, where photons with sufficient energy excite electrons from the valence band to the conduction band, increasing the number of charge carriers and thereby reducing resistance. In industrial photocell sensors, it serves as the primary sensing component for detecting presence, position, or light levels in automated systems.

Working Principle

The working principle is based on photoconductivity. When photons strike the semiconductor material (typically cadmium sulfide or cadmium selenide), they provide enough energy to excite electrons from the valence band to the conduction band, creating electron-hole pairs. This increases the number of free charge carriers, which lowers the electrical resistance of the material proportionally to the light intensity. In darkness, the resistance is high (typically megaohms), while under illumination, it drops significantly (to kiloohms or less). This resistance change is measured by a circuit to produce an output signal.

Materials

Cadmium sulfide (CdS) or cadmium selenide (CdSe) semiconductor deposited on a ceramic substrate, with metal electrodes (often silver or gold) in a comb pattern to maximize surface area. Encapsulated in epoxy or glass for protection against environmental factors.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Power Rating	100-200 mW
Response Time	10-100 ms
Voltage Rating	100-300 V DC
Dark Resistance	1-10 MΩ
Light Resistance	100-1000 Ω
Spectral Response	400-700 nm (visible light)
Operating Temperature	-30°C to +70°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 9001, IEC 60747-5-2

Parent Products

This component is used in the following industrial products

Photocell Sensor

A light-sensitive electronic component that detects ambient light levels and triggers electrical responses.

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Engineering Analysis

Risks & Mitigation

Sensitivity degradation over time
Slow response time compared to photodiodes
Non-linear resistance-light relationship
Cadmium content requiring RoHS compliance handling

FMEA Triads

Trigger: Prolonged exposure to high-intensity light
Failure: Permanent reduction in sensitivity or increased dark resistance
Mitigation: Use within specified light intensity ranges; incorporate optical filters or duty cycling in circuits

Trigger: Moisture ingress or contamination
Failure: Unstable resistance readings or short circuits
Mitigation: Proper encapsulation; use in controlled environments; regular maintenance checks

Industrial Ecosystem

Compatible With

Photocell sensors, light meters, automatic lighting controls, industrial safety curtains

Typical Suppliers & Equivalents

Vishay, Hamamatsu, Excelitas, generic LDR components from electronic suppliers

Compliance & Inspection

Tolerance

±20% resistance variation under standard test conditions (e.g., 10 lux, 25°C)

Test Method

IEC 60747-5-2 for photoelectric devices; resistance measured with a multimeter under controlled light exposure using calibrated light sources

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Photoresistive Element

Manufacturer profiles associated with Photoresistive Element.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the typical lifespan of a photoresistive element in industrial use?

Typically 50,000 to 100,000 hours under normal operating conditions, but it can degrade faster with high light intensity or temperature extremes due to material fatigue.

How does temperature affect a photoresistive element's performance?

Temperature increases can reduce dark resistance and alter response characteristics; most industrial-grade elements include compensation circuits or are specified for stable operation within -30°C to +70°C.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Photoresistive Element