The **ALR-142-R/Q** is a specific series of high-performance photo-sensors (photocontrols) manufactured by **TE Connectivity (formerly Tyco Electronics/ALR)**. These components are primarily used for street lighting and commercial outdoor lighting control. The "R/Q" designation usually refers to the **Response Type** (Instant or Delayed) and the **Quality/Testing** standards. --- ### 1. Key Electronic Components The internal architecture of these units consists of several critical electronic parts that work together to automate lighting based on ambient light levels. | Component | Function | Description | | :--- | :--- | :--- | | **Cadmium Sulfide (CdS) Cell** | Light Sensing | A photo-resistor that changes its resistance based on light intensity. It is the "eye" of the unit. | | **Bimetal Switch** | Actuation | A thermal-mechanical switch that bends when heated by a resistor, physically opening or closing the electrical contacts. | | **Heating Resistor** | Control Trigger | A small resistor wired in series with the CdS cell. When it's dark, current flows through the resistor, heating the bimetal to flip the switch. | | **MOV (Metal Oxide Varistor)** | Protection | A surge protection component (usually rated around 160+ Joules) that protects the unit and the lamp from voltage spikes/lightning. | | **Polypropylene Cover** | Environmental | A UV-stabilized housing that protects the internal electronics from moisture and sun degradation. | --- ### 2. Technical Specifications The electronics are designed to handle high-voltage AC loads typical of municipal infrastructure. * **Operating Voltage:** 105–305 VAC (covers 120V, 208V, 240V, and 277V systems). * **Load Rating:** Typically 1000 Watts Tungsten or 1800 VA Ballast. * **Turn-on Level:** 1.5 Foot-candles (Standard). * **Turn-off/Turn-on Ratio:** 4:1 (Provides a "deadband" to prevent flickering during sunset). * **Connection Type:** 3-prong NEMA twist-lock plug. --- ### 3. Electronic Behavior: "R" vs. "Q" While the base model is the ALR-142, the suffixes denote specific electronic calibrations: 1. **Delayed Response:** The electronics include a thermal delay (usually 30–60 seconds). This prevents the light from turning off due to temporary flashes like car headlights or lightning. 2. **Fail-On Mode:** These units are electronically designed so that if the sensor or heating element fails, the circuit remains closed. This ensures the street light stays **ON** (safe) rather than **OFF** (dangerous) if the part breaks. --- ### 4. Circuit Diagram Logic The electronic flow follows this logic: 1. **Daylight:** High light = Low resistance in CdS cell = Current bypasses heater = Bimetal remains cool = **Contacts Open (Light Off).** 2. **Nighttime:** Low light = High resistance in CdS cell = Current flows through heater = Bimetal warps = **Contacts Close (Light On).**