Manual Operator Control

Every machine action performed in Manual Mode requires a deliberate operator command. Nothing moves or otherwise performs work unless the operator has requested the action.

An operator command requests a machine action; it does not directly authorize or carry out that action. The control program determines whether the requested action is permitted and how it is carried out.

In a PLC Pro installation, every actuator and every device capable of performing work is provided with the controls required to operate it in Manual Mode. The operator must be able to request the individual actions or limited sequences needed for setup, recovery, adjustment, maintenance support, and troubleshooting.

A deliberate operator command is an intentional request for a specific machine action or defined limited sequence. The request results from an operator action taken for that purpose. A permissive becoming true, an interlock clearing, or another installation condition changing is not an operator command.

The operator issues the request by deliberately using the control provided for the intended action. Depending on the installation, that control may be a pushbutton, selector switch, foot switch, lever, pendant control, HMI screen control, or other operator-interface device.

Foot switches, levers, pendant controls, and other application-specific devices may be used when their physical form improves deliberate operator control. A foot switch may allow the operator to keep both hands available for positioning material or tooling. A lever or joystick may provide intuitive direction or proportional control, while a pendant may place jog and equipment controls near the area being observed. These devices must be located, guarded, and arranged to reduce the possibility of unintended operation.

A pushbutton is well suited to a clear, discrete request such as starting or stopping a motor, opening or closing a valve, or initiating a limited sequence. Separate pushbuttons may be provided for the two actions, or one pushbutton may request paired operations. For example, a pushbutton labeled “CYLINDER EXTEND/RETRACT” may request retraction when the cylinder is extended and extension when it is retracted. A momentary pushbutton may also provide a jog request for as long as the operator holds it.

Selector switches should be used sparingly by the PLC Pro. They are well suited for choosing among options that should remain visibly selected, such as configuring a workstation for “PART A” or “PART B,” establishing “FORWARD” or “REVERSE” direction when using a jog button, or selecting a setting for the station. Because they retain their position through Emergency Stops and power failures, they should not be used for a function that must remain cancelled after safety-system reset or power restoration. Selector switches are generally not recommended for direct paired actions such as extending or retracting a cylinder or clamping or releasing a device.

A command may be momentary or maintained. A maintained command is handled so that an existing switch position cannot unexpectedly initiate an action when Manual Mode becomes active, after safety-system reset, or after power restoration. The switch-arming method used for maintained commands after an Emergency Stop is described in Emergency Stop Mode Recovery.

HMI screen controls are commonly used for individual device commands, jog controls, and limited-sequence requests in Manual Mode. They allow many operator controls to be provided without requiring a separate hardwired device for each command.

Operator controls for individual device commands, jog controls, and limited-sequence requests should be grouped by machine element. Each group should identify the machine element with a label (ex: “EXIT CONVEYOR”). The controls within that group should use functional labels, including “REV/FWD,” “RAISE/LOWER,” or “CLAMP/RELEASE,” to indicate the actions requested when the controls are used.

Analog and variable-value controls may be used when the operator must select a speed, position, pressure, temperature, timing value, or another adjustable setting. Depending on the application, the control may be a potentiometer, rotary encoder, slider, joystick, thumbwheel, or HMI numeric or slider control. The selected value should be clearly indicated, and the available range should be limited to values the installation is designed to use.

For screen-based numeric adjustments, the PLC Pro may use a “LESS/MORE” control pair. The labels may instead be “LOWER/HIGHER,” “SLOWER/FASTER,” or another pair appropriate to the adjustment. The operator does not need to understand the underlying numeric value; she or he needs only to determine whether less or more of the controlled effect is required. Each button applies a defined increment or decrement to the current setting. If the resulting value exceeds an established limit, the corresponding limit is applied; otherwise, the adjusted value is applied to the device setting.

A deliberate operator command may request one machine action or initiate a defined limited sequence. When the operator requests a limited sequence, the individual actions within that sequence do not each require a separate operator command; they are carried out as parts of the complete operation the operator deliberately requested.

For example, a positioner may use one cylinder to raise and lower and another to move between its home and working positions. Pressing the “HOME” button may request a limited sequence that raises the positioner and, after the fully raised condition is detected, returns it home. When the positioner is already home, only the raise action may be required. When it is already home and fully raised, no action is required.

A limited sequence remains confined to its defined operation. It does not place the installation in Auto Mode, authorize unrelated machine actions, or authorize another operation after the requested sequence is complete.

The PLC Pro provides Manual Mode controls for every actuator and every device capable of performing work. No machine element is omitted, and every individual action or limited sequence required to operate it manually is provided.

Complete Manual Mode coverage includes every available action of each machine element. A cylinder must be extendable and retractable, a reversible mechanism must be operable in both directions, and each device must be startable, stoppable, positioned, engaged, released, or otherwise operated as its design permits.

Complete Manual Mode coverage is not limited to actions normally used during automatic operation. It also includes the individual actions and limited sequences needed for setup, recovery from interrupted operations, adjustment, maintenance support, and troubleshooting.

Supporting devices are included in this coverage. A pump, brake, lubrication system, vacuum generator, positioning device, or other machine element is not omitted merely because the control program normally operates it as part of another action or automatic sequence.

For example, a workstation may include an indexing conveyor, retractable part stop, lift table, clamp, and vacuum generator. Its Manual Mode controls allow the operator to jog the conveyor in either direction, extend and retract the stop, raise and lower the lift, clamp and release the fixture, and start and stop the vacuum generator. A defined “HOME” command may also initiate the limited sequence required to return the complete workstation to its home condition.

• Every Manual Mode action results from a deliberate operator request.
• A limited sequence remains confined to the operation deliberately requested by the operator.
• Every actuator and work-performing device is operable in Manual Mode.