Why Engineers Choose the 1734-APB for PROFIBUS Integration
When a PROFIBUS DP network needs to interface with POINT I/O modules, the adapter module you select determines how smoothly that connection performs. The Allen-Bradley 1734-APB from Rockwell Automation solves this challenge directly. It is a PROFIBUS DP Network Adapter in the Bulletin 1734 POINT I/O series that simultaneously resides on the POINT I/O backplane and the PROFIBUS network. This dual position allows it to act as the communication bridge between your I/O modules and the PROFIBUS master.
As a consulting engineer, I recommend evaluating this adapter when you need a proven interface that handles up to 63 POINT I/O modules on the PointBus side. The 1734-APB functions as a master unit on the PointBus and as a slave unit on PROFIBUS, exchanging I/O data with the PROFIBUS master. This architecture simplifies system design because one adapter manages the entire backplane while presenting a single slave node to the network.
Technical Specifications That Matter
Understanding the key parameters helps you plan power budgets and wiring correctly. The adapter accepts a nominal input voltage of 24 Volts DC with an operating range of 10 to 28.8 Volts DC. Field side power is rated at 400 milliamps, and the inrush current reaches 6 amps maximum for 10 milliseconds. The POINTBus current is 1000 milliamps, which supports the logic power needs of connected modules.
Power consumption is 8 Watts, and power dissipation is 2.8 Watts at 28.8 Volts. The adapter includes reverse polarity protection for input overvoltage. During input interruptions or dropouts, the output voltage stays within specifications for 10 milliseconds at 10V with maximum load. It converts applied 12 to 24 Volts DC field power to PointBus 5 Volts power, supplying 5 Volts logic power to the POINT I/O modules. The PointBus output current is 1 Amp maximum at 5 Volts DC ±5% (4.75 to 5.25).
Power Budget Planning
The 1000 milliamps POINTBus current and 400 milliamps field side power give you headroom for expansion. You can power up to 14 I/O modules with a maximum of 10 Amps of field power, with 75mA current draw. Plan your module count and field power distribution against these limits before installation.
Protection and Stability
Reverse polarity protection prevents damage from accidental wiring errors. The 10 millisecond hold-up during input dropouts keeps your I/O stable through brief power disturbances, which reduces nuisance faults on the network.
Where the 1734-APB Fits in Your System
This adapter suits applications where a PROFIBUS DP master must control distributed POINT I/O. In a manufacturing cell, the 1734-APB can interface up to 63 POINT I/O modules with the plant PROFIBUS network, letting you consolidate discrete and analog signals into one slave node. In a process skid, the adapter converts 12 to 24 Volts DC field power to PointBus 5 Volts power, simplifying power distribution across the backplane. For retrofit projects, the adapter’s SELV, NE Class 2, or PELV power supply compatibility helps you meet CE Low Voltage Directives without redesigning your power architecture.
Installation and Setup Guidance
Install the 1734-APB at the left side of a 1734 system. This position is required because the adapter manages the PointBus and provides logic power to all downstream modules. Verify that your input voltage stays within the 10 to 28.8 Volts DC range before applying power. Confirm that your field power supply meets SELV, NE Class 2, or PELV requirements for CE Low Voltage Directives compliance. When wiring, observe the reverse polarity protection feature, but do not rely on it as a substitute for correct polarity. After installation, verify that the adapter communicates with the PROFIBUS master and that all connected POINT I/O modules receive logic power.
Compatibility and Integration
The 1734-APB operates on two networks simultaneously. On the POINTBus, it communicates with up to 63 POINT I/O modules. On PROFIBUS, it exchanges I/O data with the PROFIBUS master as a slave unit. This dual-network capability means you can integrate POINT I/O into an existing PROFIBUS DP infrastructure without replacing your master controller. The adapter’s ability to power up to 14 I/O modules with a maximum of 10 Amps of field power gives you flexibility in module selection and layout.
Maintenance and Reliability
Inspect the adapter periodically for secure mounting and proper ventilation. Check that input voltage remains within the 10 to 28.8 Volts DC range during operation. Monitor power dissipation at 2.8 Watts at 28.8 Volts to ensure the enclosure temperature stays within acceptable limits. Because the adapter has no moving parts, wear is minimal. The primary reliability considerations are stable input power and clean PROFIBUS cabling. Address input power quality issues promptly, since the 10 millisecond hold-up at 10V with maximum load protects against brief interruptions but not sustained outages.
Selection Checklist Before You Buy
Before ordering the 1734-APB, confirm your PROFIBUS DP network requirements and the number of POINT I/O modules you plan to connect, up to 63 maximum. Verify that your field power supply meets SELV, NE Class 2, or PELV requirements. Check that your input voltage source provides 24 Volts DC nominal within the 10 to 28.8 Volts DC range. Calculate your POINTBus current demand against the 1000 milliamps limit and your field power demand against the 400 milliamps field side power rating. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
How many POINT I/O modules can the 1734-APB support?
The adapter communicates with up to 63 POINT I/O modules on the PointBus. It can power up to 14 I/O modules with a maximum of 10 Amps of field power.
What input voltage does the 1734-APB require?
It accepts 24 Volts DC nominal input with an operating range of 10 to 28.8 Volts DC.
Does the 1734-APB provide reverse polarity protection?
Yes, it features reverse polarity protection for input overvoltage.
What happens during an input power interruption?
The output voltage stays within specifications for 10 milliseconds at 10V with maximum load.
What power supply types are compatible with the 1734-APB?
To comply with CE Low Voltage Directives, use a Safety Extra Low Voltage (SELV), NE Class 2, or Protected Extra Low Voltage (PELV) power supply.
