The **99D-R2** is a widely used control board (PCB) primarily found in **automatic sliding door systems** (such as those manufactured by Caesar or other industrial automation brands). It acts as the "brain" of the door, managing motor output, safety sensors, and operational logic. --- ## 1. Core Electronic Components The board consists of several subsystems that handle power conversion, logic processing, and mechanical actuation. | Component Group | Key Function | Typical Hardware | |:---|:---|:---| | **Microcontroller (MCU)** | The CPU of the board; processes sensor signals and controls door logic. | 8-bit or 32-bit Integrated Chip | | **Motor Drive Circuit** | Controls the DC Brushless motor speed and direction. | Power MOSFETs or IGBTs | | **Power Supply Section** | Converts AC mains (110V/220V) to low voltage DC (24V/12V). | Step-down transformer or SMPS circuit | | **Input Terminals** | Receives signals from external devices. | Microwave sensors, photocells, keypads | | **Potentiometers** | Manual adjustment knobs for physical tuning. | Speed, Braking, and Hold-open time dials | --- ## 2. Key Interface Terminals The 99D-R2 board features a strip of terminal blocks. Understanding these is essential for installation and troubleshooting: ### Power & Motor * **AC Input:** Connection for the main power source. * **Motor Output:** Provides pulses to the DC motor to move the door leaves. ### Logic & Safety Inputs 1. **Sensor Input:** For motion detectors (microwave/infrared) to trigger opening. 2. **Safety Beam (Photocell):** Prevents the door from closing if an object or person is in the path. 3. **Back-up Battery:** Port for a 24V battery to ensure operation during power outages. --- ## 3. Programmable Adjustments The electronic design allows for "Trimmer" adjustments, which are small rotating screws on the board: | Feature | Description | |:---|:---| | **Opening Speed** | Adjusts how fast the door slides open. | | **Closing Speed** | Adjusts the speed for safety during the closing cycle. | | **Hold-Open Time** | Sets the delay (0–30 seconds) before the door starts closing. | | **Braking Force** | Determines how aggressively the motor slows down at the end of the track. | --- ## 4. Troubleshooting Indicators The 99D-R2 usually includes **Status LEDs** to help diagnose electronic failures: * **Power LED:** Should be solid green/red when the board is energized. * **Signal LED:** Flashes when a sensor is triggered. * **Error LED:** Indicates a motor stall, short circuit, or sensor obstruction. ---