The **ALM-11-R** is an electronic component primarily classified as an **RFID Antenna Loop Module**. These are typically low-frequency (LF) inductive components used in wireless identification and proximity sensing systems. --- ### 1. Key Technical Specifications The ALM-11-R is designed to interface with RFID reader ICs to facilitate the transmission and reception of data via magnetic fields. | Parameter | Typical Value / Description | | :--- | :--- | | **Component Type** | Inductive Loop Antenna | | **Operating Frequency** | 125 kHz (Standard LF RFID) | | **Inductance** | ~1.08 mH (millihenries) | | **DC Resistance (DCR)** | ~30 - 45 $\Omega$ | | **Mounting Type** | Through-hole (THT) or Lead-wire | | **Application** | RFID Readers, Access Control, NFC (LF) | --- ### 2. Functional Electronic Breakdown #### A. The Inductive Loop The core of the ALM-11-R is a copper wire coil wound to a specific number of turns. Its primary function is to create an **electromagnetic field** when an alternating current (AC) passes through it. In RFID terms, this is the "Exciter" coil. #### B. Resonance and Tuning To function efficiently, the ALM-11-R is usually paired with an external **tuning capacitor** ($C_{res}$). This creates an LC resonant circuit: $$f = \frac{1}{2\pi\sqrt{LC}}$$ For the ALM-11-R to operate at 125 kHz, the external circuitry must match the inductance ($L$) of the module with the correct capacitance ($C$). #### C. Power Transfer It utilizes **Inductive Coupling**. When an RFID tag (transponder) enters the field generated by the ALM-11-R: 1. The module transfers power to the tag via the magnetic field. 2. The tag modulates its own load to send data back. 3. The ALM-11-R detects these small changes in the field as data signals. --- ### 3. Implementation Circuit (General) ```cpp // General Logic for interfacing an ALM-11-R with a Driver IC [ Reader IC ] ----> [ Resistor/Capacitor Network ] ----> [ ALM-11-R Antenna ] ^ | |___________________[ Signal Return ]____________________| ``` --- ### 4. Common Use Cases * **Access Control:** Used in wall-mounted card readers for office security. * **Asset Tracking:** Integrated into handheld scanners to read passive tags on inventory. * **Immobilizers:** Found in automotive ignition systems to verify the key's ID chip.