For years, hanging pendant controls were the only game in town for the economical control of overhead handling systems, especially cranes. Still the dominant installed overhead control technology today, pendants are a tried, true and affordable solution. However, wireless radio remote controls are catching on quickly and dominating new installations as well as retrofits.

Safety is an important reason behind this shift. "A pendant control doesn't allow the operator to be in the most convenient place to operate the equipment," says Brian Landries, materials handling products manager, Control Chief (814-362-6811). "Put a radio receiver on the crane, and you allow the operator to walk around the equipment and be more productive."

Ergonomics also comes into play. "You're seeing a different operator today, including women operators," says Perry Pabich, vice president sales and marketing, Magnetek (262-783-2500). "As a result, controls are getting smaller and also easier to engage."

Finally, the price of wireless systems is decreasing. "It's getting to the point where the cost of radio can be justified except in systems where the overhead equipment just isn't used very much," says Bill May, spokesperson, Cattron-Theimeg, Inc. (724-962-3571).

When you look at the number of systems already installed, pendant controls are still the most prevalent overhead handling control technology.

"Pendant wired control is the most traditional and the most reliable technology for overhead materials handling because it's hard wired right into a motor or PLC [programmable logic controller]," says Magnetek's Pabich.

The basic overhead crane might have three directional motions—backward and forward, sideways, and up and down—as well as two speeds. But it's not uncommon to see pendants that control seven motions. They also perform auxiliary functions such as controlling and synchronizing the operation of two hoists. A range of three to five speeds or even infinitely variable speed are also common.

Users are also adding more functionality to their controls, such as the ability to control additional devices, like an underhook or even peripheral devices. Control systems, for instance, might be wired to start a conveyor or open a bulk storage device that interfaces with the crane.

Despite the reliability of pendant control systems, more sophisticated applications are opening the door for radio remote controls. "The traditional way to control multiple devices is 'festooning' wires from motor to motor," says Landries of Control Chief. "The cost of doing that is prohibitive and the wiring can get caught on the load that's being moved."

Festooning isn't a problem with radio remote controls. And the price of putting multiple radio receivers on motors to receive instructions from a controlling device has dropped significantly in recent years. That's making radio remote controls the system of choice for most new installations as well as retrofits.

"The price gap between a hard-wired pendant and radio control has been closed in many applications," says May of Cattron-Theimeg. "And in many cases, you can do more with a remote control than a pendant. A common transmitter, or controller, can provide a signal to multiple receivers on a crane and a peripheral device."

Price aside, pendant controls often made sense in the past because remote control devices were bulky and heavy. But just as consumer electronics have gotten less expensive and smaller, so have industrialized devices. "In the past a radio controller could weigh over 15 pounds," says Pabich. "Now you have transmitters that are under a pound and even smaller, depending on the level of functionality."

A radio remote control system consists of a few basic components. A receiver is mounted on the machinery and wired into PLCs or motors that are going to be turned on and off by the system.

The control comes from the hand-held transmitter, which sends a controlling signal to the receiver. That signal tells the receiver which device to activate and what to do.

Transmitters are available in a variety of configurations and sizes. The control may come from buttons, paddles, joy switches, rotating controls or a combination.

As with other materials handling systems, providers of overhead control systems are building flexibility into their products. And it's not just a choice between joy sticks and buttons on a hand-held controlling device.

At the low end of the market, a wide variety of economical, off-the-shelf systems is available. "You get a transmitter with basic functionality and receivers to operate the machines at an affordable price," says May.

Off-the-shelf systems are often equipped with an I-key, an electronic key that contains the frequency and other programming information for specific receivers on specific machines. The transmitter doesn't have to be programmed for a specific piece of equipment. Instead, an operator can pick up any hand-held transmitter and then install the I-key that will operate only the equipment needed for that job. That reduces the number of transmitters needed in a facility.

In higher-end applications, users are asking for features like anti-collision sensors as an extra layer of safety, and controls that can synchronize the travel and lifting speeds of dual trolleys or dual hoists that might be needed to move large or bulky products.

New software packages are providing better system monitoring and diagnostics. "A maintenance group can wirelessly do diagnostics and status checks of their cranes from up to 1,500 feet away," says Pabich.

An additional important development is that radio remote controls developed for overhead materials handling operations are finding other uses in the factory and warehouse.

"This year, we've seen several out-of-the-box applications for wireless remote controls," says Landries. "It's for users who know they need to do something, and they don't want to run wires to do that."

Radio remote controls used for overhead systems, for instance, are being adapted to allow operators or maintenance personnel on the ground to quickly stop an assembly line when a problem develops. "We've seen manufacturers provide a radio link that can be worn on a belt to their operators," says Pabich. "If something happens on the line, the operator can stop the line from that link rather than leave their post."

Another example is putting radio remote controls on a lift truck. "We can open up to 999 dock doors in a facility with just one remote control," Landries says. "That's good for any food processing or distribution center where they have lots of doors and don't want their lift truck drivers jumping off the machines. It's both a safety and productivity issue."

Other applications include using the technology to position overhead conveyors or to open and close doors in hazardous environments, like a steel mill furnace area, nuclear facility or in the mining industry.

Those systems may not have cranes, but they all have a motor that needs to be stopped and started. "If it has a PLC for control, that can be done wirelessly," says Landries.