Overview
The Allen-Bradley 1771-OGD is a discrete TTL (Transistor-Transistor Logic) output module designed for the PLC-5 Series B control systems. Unlike the 8-point 1771-OG variant, the 1771-OGD delivers 16 independent outputs, making it ideal for applications requiring multiple TTL signal interfaces. The module integrates directly into Allen-Bradley 1771 I/O chassis (1771-A1B, A2B, A3B, A4B) and provides logic-switching capability between High = True and Low = True configurations.
Key Features
- 16 TTL outputs — control up to 16 independent TTL devices from a single module slot
- Output diode protection — guards against overvoltage (>6.0V DC), reverse DC, and AC voltage faults; 0.5A @ 250V fuse-protected
- Configurable logic — switch-selectable positive or negative logic operation
- Low output delay — less than 1ms signal transition time for responsive control
- Dual power sourcing — draws from both chassis backplane (250mA @ 5VDC) and external customer supply (310mA max @ 5VDC)
Technical Specifications
Output voltage ranges from 2.7–5.25V DC (high) and 0–0.5V DC (low) with source current of 1mA and sink current of 20mA per output. The module requires 5VDC ±0.25V external power supply with maximum 50mV peak-to-peak ripple. Power dissipation reaches 2.8 watts maximum (9.5 BTU/hr). Operating temperature spans 0–60°C in non-condensing environments (5–95% humidity). The module carries CSA, CE, and UL certifications and is keyed to I/O chassis backplane positions 16–18 and 26–28.
Typical Applications
- TTL device control in discrete manufacturing and assembly automation
- Digital output interfaces for sensor-to-PLC signal conditioning
- Motion control systems requiring multiple TTL trigger signals
- Legacy PLC-5 system expansions and module replacements
- Batch process control with synchronized output sequencing
Compatibility & Replacements
The 1771-OGD is designed for single-slot installation in the PLC-5 Series B architecture. It pairs with complementary 8-bit or 16-bit input modules (1771-IG, 1771-IGD) in the same I/O chassis. When using two-slot addressing mode, the 16-bit 1771-OGD must occupy odd-numbered slots. The 1771-OG (8-point variant) is not a direct replacement due to reduced output count and absence of fuse protection. Verify backplane connector keying and available +5VDC supply capacity before installation. This used module performs to original specifications and is field-tested for integration into existing PLC-5 systems.
