. . . . . Alerton TX-653P PLC Programmable Logic Controller for HVAC - The Alerton® TX-653P™ is a high-performance programmable logic controller designed for HVAC and industrial equipment. Common applications include rooftop units, unit ventilators, central plant equipment, air handling units, and clean room equipment. It operates either as a stand-alone controller or as part of a site-wide, integrated DDC system. All TX-653P control logic is programmed using Alerton's easy to learn DDC programming language. This self documenting software includes a complete library of control functions, enabling totally flexible control strategies. A single TX-653P can contain multiple control loops for various parts or multiple pieces of equipment. The TX-653P communicates with the Alerton global controller over a two-conductor communication trunk at 9600, 4800, or 1200 baud. A portable computer running Alerton TDS software can also connect directly to the TX-653P with an optional portable computer cable. The TX-653P is designed for high-speed data processing, with an internal DDC loop cycle time of 100 msec. Programmable timers have a resolution of 100 msec. Inputs are universal and support thermistor, dry contact, 0-5 VDC, or 4-20 mA signals. A 24 VDC power supply is built-in to provide up to 150 mA of power to external field transducers. The TX-653P supports the Alerton Microset™, a wall mount temperature sensor that contains a digital display and simple pushbutton controls. All input and output values can be viewed at the Microset. CMOS circuitry, a four layer circuit board with separate ground plane, hardware and software input filtering, and power supply noise filters ensure reliable and stable operation. The communication trunk is optically isolated to prevent ground loop problems. The CMOS processor incorporates an internal watchdog monitor, and the power supply voltage is monitored to provide automatic shutdown and data backup. All program data is stored in nonvolatile EEPROM.. Alerton. Honeywell. TX-653P.