Changing a speed stored as a fixed value in Click PLC logic requires editing and downloading the PLC program; changing a value held in PLC data memory does not. For the planned stepper and GS1 VFD, an EA1 C-more Micro can give an operator a way to select or enter values, while the Click program still decides how to apply them to each device.
Keep the laptop for commissioning, not routine speed selection
Do not design around editing an instruction and downloading the PLC every time an operator needs another speed. That approach works for a fixed program value, but it turns an ordinary production adjustment into a PLC programming task. It also makes the operator dependent on a computer and someone authorized to change the program.
Do not assume an HMI recipe is required. The requirement is that the operator make a selection and that the PLC use the selection when it executes the motion or drive logic. A few permanently fixed choices may need only discrete inputs and simple selection logic. The HMI adds value when the machine needs more choices, editable setpoints, or operating information on a screen.
Do not expect the panel to replace PLC control logic. The panel supplies operator selections or values; the PLC must read them, decide when they apply, and issue the appropriate commands. An HMI selection that is not connected to the PLC logic will not change motor behavior.
Separate fixed program values from editable setpoints
A speed embedded directly in a motion instruction is part of the PLC program. To change that fixed value, edit the logic on the PC and download the revised program. That is the answer when the speed exists only as an instruction constant.
A different design stores the speed in a PLC data-memory location and has the instruction use that location. The PLC program then remains unchanged when the stored value changes. The evidence for this Click application identifies DS, DD, DH, and DF memory locations as possible places for a motor-speed value; choose a location and data representation that the specific instruction and PLC support.
A PC can also change a stored value through the programming software's Dataview, without downloading a new program. That is useful for commissioning or maintenance, but it is not the same as providing a production operator with an on-machine interface. Decide who may change each value and how the value is protected from accidental or unauthorized changes.
Use selector switches when the speed list will stay small
For a permanently limited number of known speeds, wire selector-switch inputs to the PLC and program the PLC to select the corresponding setpoint. The same basic pattern applies to a VFD that accepts preset-speed selections through digital inputs: the PLC or input wiring chooses among the configured options. Confirm the drive's control method and input configuration in its documentation before assigning the machine wiring.
An analog-capable Click PLC and a speed potentiometer are another option when the application needs an adjustable speed rather than a short list of discrete choices. Confirm that the selected PLC hardware provides the required analog interface and that the receiving device accepts the signal type before designing around this method.
These alternatives keep the interface simple when requirements are stable. If the number of choices grows—for example, from three options to ten—or operators need displayed status, a C-more Micro may provide a more flexible operator interface. Compare the complete panel, wiring, configuration, and maintenance cost with the switches and other components the panel replaces; do not decide from panel purchase price alone.
Configure the C-more to pass operator choices into PLC logic
For the proposed architecture, the operator selects a function such as A, B, or C on the EA1 C-more Micro. Configure the panel to communicate the selection or setpoint to the Click PLC. In the PLC program, read that value and use logic to select the intended stepper speed or VFD command at the point where each device is controlled.
- Choose whether operators select named, fixed options or enter numeric setpoints. Use discrete selection logic for a small, fixed list; use a numeric value or a stored selection for a broader range.
- Assign PLC data locations for the operator selection and any setpoints. Confirm the supported data type, range, and scaling for the relevant PLC instruction and for the way the drive or stepper command is expressed. Do not assume the stepper and VFD use identical units or value ranges.
- Build PLC logic that validates the selection, maps it to the correct stepper command or VFD setting, and defines when a change takes effect. Decide what the machine does at startup, on an invalid selection, or if the panel value is unavailable; use the machine's operating requirements to establish those behaviors.
- Configure the C-more screen to display and modify the intended PLC values. If using recipes, verify how the chosen panel configuration transfers values and confirm that the PLC logic consumes those values. A recipe is one possible interface function, not a substitute for the PLC mapping logic.
- Check communication settings and hardware compatibility for the proposed port arrangement: panel on port 1, stepper drive on port 2, and GS1 VFD on port 3. Confirm the exact PLC, panel, and device manuals for supported protocols, port roles, cabling, and whether the devices can communicate as intended at the same time.
Because the planned port allocation and the decision to control the VFD through communications or preset/digital inputs were still design choices, settle those details before ordering parts. A panel can provide the operator interface, but it cannot resolve an unsupported port/protocol combination or make two devices share a communication resource that the hardware does not support.
Diagnose a speed selection that does not take effect
| What you see | Check first | Likely design or setup issue |
|---|---|---|
| A speed change requires a program download. | Inspect whether the speed is a literal in the PLC instruction or a value read from data memory. | The program uses a fixed instruction value instead of an editable data location. |
| The screen selection changes, but the stepper or VFD does not. | Monitor the PLC selection value, then trace the logic that reads it and issues the device command. | The panel is not writing the intended PLC value, or the PLC logic does not use that value in the active command path. |
| The displayed option and motor response do not match. | Compare the selection-to-speed mapping in PLC logic with the device command configuration. | The mapping, units, scaling, or selected drive control method does not match the intended choice. |
| One device responds while another does not. | Check each device's configured control method, wiring, communication status, and port allocation. | The stepper and VFD have different command paths, or the planned communication arrangement is not configured as intended. |
Use PLC monitoring to isolate the path in order: verify that the panel changes the intended memory value, verify that the PLC reads the current selection, then confirm that the corresponding command reaches the intended device. This separates a screen/data-link problem from a PLC mapping problem and from a device-side control or wiring problem.
Restore production with a controlled fallback, then make the design permanent
If the HMI path is not ready, a temporary fallback can be a tested selector-switch input for a small, known set of speeds, or a maintenance PC changing a data-memory value through Dataview when qualified personnel can safely perform that task. Do not treat either fallback as a permanent solution if operators need many options or frequent setpoint changes. Record the active value and selection method so the next shift does not mistake a temporary arrangement for the intended production interface.
For the permanent repair, update the design drawings and PLC/HMI configuration so the source of each setpoint is explicit. Document how operator choices map to the stepper and VFD, what values are valid, and how changes take effect. Keep machine stopping and emergency-stop functions in an appropriate independent safety design; an operator screen is not a substitute for hardwired or safety-rated stopping functions.
Verify the operator-to-device path before release
- With the machine in a safe test condition, select each configured option and confirm that the expected PLC selection or setpoint value changes.
- Monitor the PLC logic and confirm each selection maps to the intended stepper instruction value or VFD command. Test each configured option rather than only the default.
- Confirm the stepper and VFD each respond through their intended control method. Check actual commanded and displayed values against the approved machine settings; use the drive and stepper documentation for acceptable ranges.
- Test startup and invalid or unavailable selections according to the behavior defined in the machine design. Confirm that loss of panel communication does not create an unintended motion or speed command.
- Power-cycle and repeat the checks if settings are expected to persist. Verify persistence from the configured PLC/HMI behavior rather than assuming a displayed value is retained.
Release the machine only after the operator selection, PLC value, command mapping, and device response agree. If any link is unclear, return to monitoring the data path before changing program logic or replacing hardware.
Frequently asked questions
What happens if I change a speed stored directly in a Click PLC instruction?
You must edit the PLC program and download it to change a fixed instruction value. If the instruction reads a speed from a PLC data-memory location instead, changing that value can avoid a program download.
What happens if I add a C-more Micro to select stepper and VFD speeds?
The panel can present operator choices and pass them to the Click PLC, and the PLC logic can map those choices to the stepper and VFD commands. Configure and verify the communication path, PLC data mapping, and each device's control method.
What happens if I only need three fixed speed options?
PLC inputs and selector switches can select among a small, known set of programmed values. Consider an HMI when the list may grow, operators need editable values, or displayed machine information justifies the added configuration.
Stop and escalate to AutomationDirect's official support channel if the manuals do not resolve port compatibility, data mapping, or device command configuration. Do not release the machine while a selection produces an uncertain command or an unsafe response.