DO Supply is a global automation parts reseller focused on hard-to-find and obsolete industrial automation
products. Based out of Raleigh, NC, we service customers worldwide, providing excellent customer and sales
support, as well as offering our top-of-the-line warranty on all parts sold.
ControlLogix communication delays are often not the fault of a single component. In most field situations, the culprit is not a broken device but a design misalignment among the controller’s capacity, the choice of communication module, and the network built around it. A ControlLogix system is modular, and delays often trace back to a specific design decision: too many nodes on the I/O bus, the use of an antiquated bridge module, or a backplane routing configuration stretched beyond its performance envelope. Getting a strong grip on these mechanics and moving away from thinking of delay as just a generic “network problem” is what will distinguish a permanent fix from a temporary workaround. Every ControlLogix controller has an upper limit on the number of nodes and connections it can support, and exceeding that limit is one cause of communication lag. A node is any device added to the I/O configuration, and pushing a network beyond that count can cause delays that no amount of...
In PowerFlex variable-frequency drives (VFDs), the DC bus functions as the internal power bridge and electrical reservoir between the AC input rectifier and the output inverter stage. Once the incoming AC line voltage is rectified, the DC bus capacitors smooth and stabilize the resulting DC bus voltage by reducing voltage ripple, thereby delivering a steady DC supply to the inverter. They also temporarily absorb the regenerative energy produced during overhauling-load conditions or motor deceleration, reducing rapid voltage fluctuations and improving energy efficiency. This article provides a comprehensive overview of the fundamentals of DC bus voltage in Allen-Bradley PowerFlex drives. Knowledge of pre-charge drive operation, DC bus capacitors, shared DC bus configurations, DC bus regulation, regenerative energy management, and common DC bus-related faults enables engineers and maintenance personnel to maximize the reliability of PowerFlex drives, improve overall system performance...
Modern motor control relies heavily on variable frequency drives, yet the components that safeguard them are often the first to suffer budget cuts. Line reactors, also known as input reactors, are often seen as optional add-ons rather than necessary safety measures. The electrical mechanics underlying reactor protection, the failure types that reactors avoid, and the cost justification for implementing them on each drive installation are all discussed in this article. In simple terms, an input reactor is a three-phase inductor placed between a drive’s input terminals and the incoming AC power source. Its purpose is surprisingly straightforward: it increases the line’s impedance. In a drive environment, this impedance smooths out the abrupt current spikes that occur each time the drive’s rectifier bridge charges its DC bus capacitors, as it resists rapid current changes. Drives convert incoming AC to DC using an SCR bridge rectifier or diode. Because the current is drawn in brief...
Teams with short timeframes set up Rockwell’s PowerFlex drives every day, and most of that work only touches the handful of parameters needed to make a motor spin: voltage, frequency, and a start reference. Once the motor turns, the commissioning checklist gets signed off, and everyone moves on to the next job. But PowerFlex drives feature dozens of secondary parameters that regulate efficiency, thermal load, fault tolerance, and lifespan. When these are left at their defaults and never reviewed, the drive still runs, but often well below its capabilities. Factory settings on a PowerFlex drive exist for one reason: broad compatibility. They are built to work across a wide range of motors and applications, which means they are rarely ideal for any single fixed installation. A default acceleration ramp, carrier frequency, or stall timer is enough to get a drive running. Still, it won’t match the thermal properties of a specific motor, the inertia of a specific load, or the electrical...
It’s no secret that AC drives, particularly variable frequency drives, have been efficiency and productivity boosters for automation facilities. Manufacturers boast about how their drives can pay for themselves with the money you save with reduced energy costs, while also reducing mechanical wear throughout the system For those who want to stick to their guns and continue using their conventional motor controller until it breaks, there is a cost to waiting. AC drives are effective because they address many of the inherent inefficiencies and mechanical stresses associated with controlling motor speed using fixed-speed equipment. Without one, a facility may be paying a hidden tax through wasted energy, increased maintenance, reduced process control, and premature equipment wear. One of the biggest arguments against installing an AC drive is often the initial cost of the system. One may argue that an AC drive may be more difficult to install, and if done improperly, could lead to even...
In a VFD-dominated industrial world, soft starters still have their place in motor control. They are a reliable way to protect your motors, the loads they move, and the systems they’re attached to. On top of that, they fit nicely into a budget-conscious build when a facility doesn’t need the extra features or programming that VFDs offer. Not every soft starter is built for the same job. Some are basic starters designed for simple start-and-stop control. Others are more advanced units with stronger protection features, better diagnostics, communication options, and more control over how the motor starts and stops. Each type has its own advantages, limitations, and best-fit applications. A variable frequency drive, or VFD, is the more common component to pair with a motor for industrial control. VFDs can control motor speed, improve efficiency in variable-speed applications, support advanced diagnostics, and, in higher-end models, offer features such as regenerative operation and...
General-purpose automation just cannot meet the demands placed on a control system by high-speed production. A vision-guided robotic cell that makes accept/reject decisions in less than two milliseconds, a packaging line that produces 1,200 units per minute, or a multi-axis servo system that coordinates ten simultaneous motion profiles are all unable to withstand the scan time variability, communication latency, or processing constraints that are acceptable on a typical discrete manufacturing line. A system that operates at line speed or one that becomes a bottleneck depends on the choice of processor generation, motion architecture, task structure, and communication topology within Rockwell Automation’s ControlLogix platform, which is specifically designed for this environment. This article discusses each of those selection decisions in the context of high-speed manufacturing requirements. Controllers that offer complex automation, integrated safety, motion control, and scalable...
There was a time when PLC memory planning mainly consisted of counting I/O points, estimating the number of instructions, and making sure that the program would fit inside the controller’s memory. This approach worked when a PLC’s primary responsibility was reading switches, controlling outputs, and keeping a machine moving through a relatively simple sequence. Fast forward to modern facilities, and you will see that PLCs are asked to do a lot more. In addition to running the core program, modern PLCs may coordinate motion, communicate with dozens of devices, and retain maintenance data. Every function that a controller is told to do requires memory, even when it doesn’t add many visible rungs to the program. Because of this, sizing a PLC for its memory can be an easy oversight. While it may seem to have enough processing power and I/O capacity for an application, it can fall short on program memory, data memory, retentive storage, or even communication resources. PLC memory is...
Modern industrial automation relies heavily on Programmable Logic Controllers (PLCs). PLCs are ruggedized, microprocessor-based industrial computers used to govern critical industrial processes across chemical processing plants, oil & gas systems, food packaging systems, water & wastewater treatment plants, manufacturing, and other industrial complexes. While control engineers and system integrators invest substantial effort into optimizing PLC control code, network configurations, and field input/output devices, a stable PLC power supply is equally vital for reliable system performance. Although PLCs are inherently designed to withstand harsh environmental conditions, such as vibration, extreme temperatures, and dirt, they do require a highly consistent power supply to function properly. An uninterrupted power supply prevents data corruption, logic errors, and catastrophic downtime in any PLC-controlled automation system. A stable PLC power supply readily converts variable line...
Reliability of control architecture is essential for large material handling systems. ControlLogix, part of the Rockwell Automation Logix family, has become a backbone for high-speed conveyor networks in distribution centers, parcel hubs, and manufacturing systems worldwide, owing to its reliability and adaptability. However, designing a ControlLogix conveyor system goes beyond the controller itself. A conveyor network running numerous divert mechanisms, hundreds of conveyor zones, and thousands of I/O points depends heavily on how the ControlLogix platform sits alongside distributed I/O, drives, industrial Ethernet, safety circuits, and PC-level systems. Below is a breakdown of the architecture that makes ControlLogix suitable for large conveyor networks, and the technologies engineers must account for. The ControlLogix platform, with its established 5580 family and the newer 5590 controllers from Rockwell Automation, is built for large conveyor solutions that need the performance...
Modern mobile machinery and modular skid systems rely on Human Machine Interface (HMI) devices for real-time visibility, reliability, and durability in rugged operating environments. Rockwell Automation PanelView operator interfaces are designed for machine-level monitoring, control, diagnostics, and visualization. When properly mounted and protected, PanelView terminals can be used on portable industrial equipment, mobile skids, and machine-mounted control stations where operators need local visibility into machine status, alarms, diagnostics, and process conditions. This allows operators to quickly understand machine status and respond to faults and process changes. PanelView Plus 7 Standard terminals are designed for easy programming and integrate with Rockwell Automation architectures. These interfaces dynamically visualize operating information, making them suitable for systems that require quick operation and troubleshooting. The PanelView Plus 7 Standard series is intended for...
The question of whether to replace the row of pushbuttons and selector switches on the HMI eventually arises on practically every classic machine or control panel. One touchscreen rather than twenty separate devices seems like a straightforward surface-level alternative. The engineering response is far more complex. The way the operator interface is wired, how PLC logic processes inputs, how data is logged, and how alerts are displayed are some of the key changes. Everything else that comes into contact with the hardwired safety circuit must remain unchanged. The difference between a clean migration and one that results in unexplained PLC logic rewrites, or safety compliance problems mid-commissioning, is to formally distinguish between these two groups before the project begins. Before discussing what changes, it helps to be precise about what a pushbutton panel is doing at the wire level. Each pushbutton, start, stop, jog, and mode select wires a physical contact directly to a PLC...
Choosing the right PanelView HMI is no easy task; it’s not just about the screen size or the communication protocol. A major choice is whether a PanelView terminal will be equipped with a keypad, a touchscreen, or both. PanelView models with a keypad enable a variety of functions under harsh operating conditions that touchscreen interfaces cannot. By understanding the true costs and benefits of these input methods, engineers, operators, and maintenance personnel can select the most appropriate PanelView solution for their application. Modern PanelView families vary widely in the input options available. PanelView 5310 and 5510 terminals use touchscreen input, while PanelView 800 and legacy PanelView Plus 6 models include keypad, touchscreen, or keypad/touchscreen options depending on the model. PanelView Plus 7 Standard terminals are primarily touchscreen-based. The choice of interface affects the operator’s efficiency, navigation speed, maintenance requirements, system reliability...
Variable frequency drives and programmable controllers have evolved from loosely connected hardware communicating via hardwired I/O to tightly integrated systems that share tag-based data, diagnostic information, and motion commands over a single industrial Ethernet network. The main point of this architecture in Rockwell Automation environments is the ControlLogix platform, and its integration with the PowerFlex drive family defines how modern Allen-Bradley-based control systems handle motor control from simple pump speed regulation to coordinated multi-axis positioning. This article covers the full integration architecture across hardware, communication protocols, Auto-Device Replacement, CIP Motion, and diagnostic practices. Order PowerFlex 755 Drives Here The PowerFlex drive portfolio spans several product lines, each with distinct integration characteristics when paired with ControlLogix. The PowerFlex 525 (catalog 25B series) is a compact drive rated from 0.5 to 30 HP and...
Industrial automation systems depend on PLCs exchanging data reliably and on time. When communication delays enter that chain, whether between PLCs and an HMI, between controllers on a network, or between PLCs and field devices, the consequences extend well beyond a sluggish screen update. In process-critical environments, even a few milliseconds of unexpected latency can cascade into equipment damage, unsafe states, or production loss. Delays in PLCs communication originate from multiple layers of the system. At the physical layer, cable quality, termination integrity, and media type set the baseline. At the network layer, excessive node counts, improper topology, and bandwidth saturation introduce queuing delays. At the application layer, message scheduling, packet fragmentation, and polling intervals determine how frequently data is actually refreshed. Order CompactLogix PLCs Today In EtherNet/IP-based systems, the dominant protocol on Allen-Bradley ControlLogix and CompactLogix...
If you have spent any time reading about automation equipment and how they work, you would come across phrases such as: “Real-time control”, “real-time monitoring”, “operates in real-time”, or “real-time deterministic behavior”. It becomes one of those things that you might be afraid to ask about because it’s thrown around so much that it seems like it’s common knowledge. Alas, we at DO Supply don’t judge and encourage learning opportunities, so let’s get you up to speed on what ‘real-time’ actually means. In the world of industrial control, “real-time” is a more precise engineering term. It means predictable, rather than “fast”. A real-time system isn’t defined by how quickly it responds, but by whether it responds within a guaranteed, bounded window of time, every single time. That guarantee is what engineers call determinism, and it’s the whole reason the phrase gets used so often around PLCs, drives, and industrial networks. To put it in perspective, say a video game you’re...
