Honeywell DPCB21010002 / IRTP131 Printed Circuit Board
The Honeywell DPCB21010002, also identified as IRTP131, is a multilayer printed circuit board designed for use in Honeywell industrial automation and process control systems. It is believed to be part of a power regulation or I/O interface module for distributed control systems (DCS) such as the Honeywell TDC 3000 or Experion PKS platforms.
Board Architecture and Components
The board measures approximately 180 mm x 150 mm and is constructed from FR4 material with 4 layers (signal, ground, power, signal). Key components include a voltage regulator (LM2596 series), optically isolated inputs (HCPL-3700), relay drivers (ULN2003), and a microcontroller (Atmel ATmega128, 8-bit). A 16 MHz crystal oscillator provides timing. Edge connectors (64-pin DIN 41612) facilitate connection to a backplane. The board is coated with a clear conformal lacquer for humidity protection.
Power and Electrical Characteristics
Nominal supply voltage: 24 V DC (18-30 V). The onboard switching regulator produces 5 V (1 A) and 3.3 V (0.5 A) rails for logic circuits. Input current: 120 mA typical at 24 V. The board features 8 digital inputs (24 V DC, opto-isolated) and 6 relay outputs (2 A at 250 V AC). A watchdog circuit monitors the microcontroller; if a fault occurs, the outputs are disabled and a red LED indicates error. Reverse polarity and overvoltage protection (TVS diode) are present.
Communication and Diagnostics
An onboard RS-485 transceiver (MAX485) provides half-duplex serial communication at up to 115.2 kbps, using Modbus RTU protocol. Diagnostic LEDs include: Power (green), Run (yellow), Error (red), and eight individual input status LEDs. A 4-pin header allows in-circuit programming of the ATmega128 via ISP. The board also includes a temperature sensor (LM75) for overtemperature shutdown >85°C.
Environmental and Mounting
Operating temperature: 0°C to 60°C. Storage: -40°C to 85°C. Humidity: 10% to 90% non-condensing. The board is designed to be mounted in a closed industrial cabinet with IP20 minimum. Four mounting holes (M3) at corners are used for standoffs. Shock and vibration: designed to meet IEC 61131-2 specifications (10 g shock, 2 g vibration).
Typical Applications and Replacement Notes
This board is often found in legacy Honeywell controllers for burner management, chemical dosing, or water treatment systems. If replacing, ensure that the firmware version (stored in ATmega128 flash) matches the original application. The board contains no field-replaceable fuses; internal polyfuses auto-reset after overcurrent. Spare boards should be stored in anti-static bags away from strong electromagnetic fields.
