UniOP ePAD03/04 Human Computer Interface

UniOP ePAD03 and ePAD04 Compact Human Machine Interface: From Technical Features to Field Operations

In industrial automation projects, the cost of human-machine interface (HMI) is often directly proportional to its functional complexity. However, a large number of simple control tasks (such as small packaging machines, temperature control boxes, and simple tooling tables) do not require high-resolution color touch screens, but rather value the reliability of physical buttons, wide compatibility of communication protocols, and extremely low economic barriers. The ePAD03 and ePAD04 launched by UniOP are products targeting this niche market. They offer a much higher functional density than products in the same price range at an entry-level price, and are clearly positioned as an ideal alternative to the successful MD00 series models. In addition, some models support an extended operating temperature range (suffix -00B6 and -00B7) and can operate stably in extreme environments such as -20 ℃ to 60 ℃. This article will comprehensively analyze ePAD03 and ePAD04 from multiple dimensions such as hardware architecture, communication capability, software functionality, installation size, and common troubleshooting, and provide engineering recommendations for smooth migration from the MD00 series.

Product positioning and model differentiation

EPAD03 and ePAD04 are the smallest and lowest cost graphical human-machine interfaces in the UniOP family. Both use monochrome graphic LCDs, equipped with 4 user programmable function keys and 7 system keys, and support access to fieldbus (Profibus DP, CANopen, DeviceNet, Interbus) and Ethernet through optional modules. The core differences are mainly reflected in the display resolution and real-time clock (RTC) configuration:

EPAD03: Equipped with a 120 × 32 pixel monochrome LCD, active display area of 70 × 21 mm, supports hardware RTC (battery backup, CR2430 lithium battery), user memory 512KB Flash, recipe memory 16KB, 256 event lists, and 1024 alarms.

EPAD04: The hardware platform is essentially the same as ePAD03, but does not include a hardware real-time clock (RTC). The event list and recipe memory functions are marked as "-" in the original table, indicating that there may be limitations at the software level. Its display resolution is 4 lines x 20 characters in text mode (based on a 120 x 32 pixel dot matrix of the same size).

In short, ePAD03 is a fully functional version (with timestamp recording capability), while ePAD04 is the ultimate cost cutting version for pure display/input tasks that do not require time tracing. Both models have three sub model suffixes:

-0046: Standard operating temperature 0~50 ℃

-00B6: Extended working temperature 0~60 ℃

-00B7: Expand the working temperature range to a wider range (storage temperature -20~60 ℃, working temperature may be as low as -20 ℃? The original text is not clear, but the suffix is different)

When engineers choose, if they need to record the precise time of alarm and event occurrence (such as for ISO or GMP traceability), they must use the ePAD03 series; If only used for real-time data display and parameter settings, ePAD04 can further save costs.

Detailed explanation of hardware architecture and interfaces

2.1 Display and Interaction

EPAD03/ePAD04 adopts a 120 × 32 pixel monochrome LCD, which can display text of 4 lines × 20 characters. It can also display bar charts, numerical values, and simple icons through scalable fonts and dynamic graphic objects. Although the resolution is low, it is sufficient for most parameter monitoring and setting tasks. The screen is LED backlit, and the contrast is adjusted through software.

The physical buttons include:

4 user programmable function keys: support slide in legends, users can print paper labels and insert them next to the keys for easy function definition (such as start, stop, menu).

7 system keys: usually including directional keys, confirm keys, exit keys, etc., used for navigation menus and numerical input.

5 user programmable LED indicator lights: can be mapped to the bit status in the PLC, used to display motor operation, faults, etc.

4 system LEDs: display basic status such as power and communication.

This fully physical button design makes the ePAD series more reliable than touchscreens in glove operated, oily environments, or situations with strong vibrations.

2.2 Power Supply and Electrical Parameters

Supply voltage: 18~30 VDC (nominal 24V DC)

Current consumption: 0.25 A @ 24 VDC (typical power consumption 6W)

Fuse: Automatic recovery type (self recovering fuse)

Protection level: IP65 front panel (dustproof and water-resistant)

Weight: Approximately 1 kg

2.3 Mechanical dimensions and installation openings

According to technical data:

Panel size (width x height): 149 x 109 mm (5.86 "x 4.29")

Hole size (width x height): 136 x 96 mm (5.35 "x 3.78")

Installation depth: 53 mm (2.08 ")

This compact size allows it to easily replace the MD00 series (which typically uses similar openings) and is also suitable for installation on control cabinet doors or operation boxes with limited space.

2.4 Environmental adaptability

Standard model (-0046) operates at a temperature of 0~50 ℃ and has a storage temperature of 5~85% RH (without condensation)

Extended Temperature Model (-00B6) Operating Temperature 0~60 ℃; -00B7 can support a wider range (storage -20~60 ℃, working temperature may be as low as -20 ℃ not specified but commonly seen in this type of suffix)

Compliant with electromagnetic compatibility standards for industrial environments: EN 61000-6-4 (radiated interference) and EN 61000-6-2 (immunity)

Communication and network functions

3.1 Dual Drive Communication Capability

EPAD03 supports Dual driver communication, which means it can communicate with devices of two different protocols simultaneously (such as connecting a Modbus RTU inverter and a Mitsubishi FX PLC). EPAD04 shows "Dual driver capability" as "No" in the technical table, which means it only supports single driver. This is another important difference between the two at the software level.

More than 130 communication drivers are supported, covering mainstream PLC, instrument, and driver brands. The physical interfaces include:

PLC ports: RS-232, RS-485, RS-422 (multiple protocols share the same physical interface, configured through software)

Aux Port: can be expanded to fieldbus or Ethernet through optional modules

3.2 Optional Bus and Ethernet Modules

Although ePAD03/ePAD04 does not integrate industrial Ethernet, the following optional modules can be inserted through the Aux port:

Fieldbus modules: Profibus DP, CANopen, DeviceNet, Interbus

Ethernet module: Supports TCP/IP and can be used for:

Connect PLCs with Ethernet interfaces (such as Siemens S7-1200, Rockwell CompactLogix)

Download/upload projects from UniOP Designer via Ethernet

Transfer alarm, event, and recipe data to the upper computer (PC or server)

Build UniNet network (UniOP HMI data sharing network based on Ethernet, supporting OPC Server)

For applications that require remote monitoring or centralized data management, Ethernet modules are almost an essential option.

3.3 UniNet Network

EPAD03 supports both Client and Server modes for UniNet networks. This means that it can act as a client to read data from other UniOP HMIs, or as a server to provide its internal variables and alarm information to other devices in the network. For example, on a production line with 5 operation stations, only one ePAD03 needs to be connected to the PLC, and the remaining four can obtain data from the first one through UniNet, thereby reducing the communication burden on the PLC.

Deep analysis of software functions

EPAD03/ePAD04 uses UniOP Designer 6 software for engineering configuration. Although the hardware cost is low, the software features are very rich.

4.1 Alarm and Event List

Number of alarms: 1024 (both ePAD03 and ePAD04 support)

Event List: ePAD03 supports 256 historical events (with timestamps, dependent on RTC); EPAD04 does not support event lists (or has a capacity of 0)

Alarm information can be associated with bit addresses, priority and confirmation methods can be defined, and can be output to the upper computer through print ports or Ethernet.

4.2 Formula Data Storage

EPAD03 provides 16KB of recipe storage, which can be divided into multiple recipe tables, each used to store a set of process parameters. Formula data can be transmitted to the upper computer via Ethernet for backup or analysis. For ePAD04 without hardware RTC, the recipe memory is marked as "-" (which may not be supported or have very small capacity). Therefore, ePAD03 should be selected for projects that require formula functionality.

4.3 Multilingual and Unicode Support

Applications can have multiple built-in languages and switch between them at runtime through system bits or buttons. All text information can be exported in Unicode format, making it easy for translators to localize using standard tools. Scalable fonts enable different language fonts (such as Chinese and Cyrillic letters) to be displayed clearly within a limited pixel area of 120 × 32.

4.4 Macro Editor

The powerful macro editor allows users to write scripts for key events, screen switches, or timers. Macro instructions include mathematical operations, logical judgments, bit operations, serial port sending, etc. For example, a simple PID parameter self-tuning logic can be implemented locally without the need for PLC intervention.

4.5 Password Protection

Eight level password protection can restrict different users' access to screens, function keys, and system menus, effectively preventing accidental operations.

4.6 Data Display Format

Supports multiple display modes such as numerical values, text, bar charts, and dynamic graphic objects. There is no limit to the number of variables that can be displayed per page (limited only by screen size and refresh rate).

Replacing MD00 Series: Engineering Points and Precautions

EPAD03/ePAD04 is officially defined as an ideal replacement product for the MD00 series. MD00 is an early text display of UniOP, which also features physical buttons and a small monochrome screen. During the replacement process, the following points should be noted:

Physical compatibility: The opening sizes of the two are similar (MD00 is usually 136 × 96 mm or similar), and the ePAD series can be directly installed on the original cabinet door opening without the need for sheet metal modification.

Communication driver: ePAD supports over 130 types of drivers, covering almost all protocols supported by MD00. But there is one exception: when the MD00 uses a 20 mA current loop interface, the ePAD series cannot directly replace it (the original text states "except when the 20 mA current loop interface is needed"). At this point, it is necessary to install a current loop to RS-232 converter or choose another model (such as the BKDR-46 series supporting current loops).

Engineering migration: MD00 uses outdated programming software (possibly MDTool or early UniOP Workshop), and engineering files need to be manually rebuilt or converted through export/import mechanisms. It is recommended to reconfigure in Designer 6 based on the original screen layout and variable definitions, which usually takes 2-3 days.

Function improvement: Compared with MD00, ePAD series has added functions such as graphic display, scalable fonts, recipe storage, Ethernet options, etc., which can increase data traceability for devices while replacing them.

Common troubleshooting and on-site maintenance

Based on the hardware features and on-site usage experience of ePAD03/ePAD04, the following six types of faults and their handling methods are summarized. Before performing any internal operations, be sure to disconnect the 24V power supply.

Fault 1: After power on, the screen does not display and the LED does not light up

Possible reasons:

The power supply voltage is too low or the polarity is reversed.

Internal self recovery fuse action (such as after output short circuit).

The power module is damaged.

Troubleshooting steps:

Measure the terminal voltage with a multimeter, which should be between 18-30V.

Disconnect all external devices (PLC wires, modules), keep only the power supply, and power on again. If restored, the external short circuit will cause the fuse to operate, and it will automatically recover after cooling.

If there is still no power, replace the power supply or repair it.

Fault 2: No response or delayed response to buttons

Possible reasons:

The button is mechanically stuck (sliding into the label paper and lifting up).

The keyboard membrane is aging or has entered liquid.

The system has entered a password lock state.

Troubleshooting steps:

Check if the physical feel of the four function keys and seven system keys is normal.

Enter the system diagnostic mode (press and hold a combination key while powering on, refer to the user manual for details) to test the keyboard matrix.

Clean the stains on the edges of the button film.

Confirm if there is a password lock, try entering the default password or contact the system administrator.

Fault 3: Communication interruption or data error

Possible reasons:

RS-232/485/422 wiring error or cable too long.

The communication parameters (baud rate, data format) do not match the PLC side.

The optional module used is not installed correctly or the driver is not enabled.

Troubleshooting steps:

Open the current project in Designer and verify the PLC port settings.

Use short distance (<15 meters) direct connection testing to eliminate cable and interference issues.

If using an Ethernet module, check the IP address, subnet mask, and port number.

Use serial port monitoring tools to capture messages sent by HMI and confirm if there are request frames.

Fault 4: Inaccurate real-time clock timing or power failure reset

Applicable model: ePAD03 only (ePAD04 without RTC)

Possible reasons:

The internal CR2430 lithium battery has run out of power (usually with a lifespan of 3-5 years).

Replacement steps:

Disconnect the 24V power supply and open the back cover (pay attention to electrostatic protection).

Find the CR2430 battery holder and remove the old battery.

Install the same model CR2430 lithium battery (with the positive electrode facing upwards) to ensure compatibility with the operating temperature range (industrial grade batteries are required for extended temperature models).

Power on again and enter the system menu to calibrate the date and time.

Fault 5: The screen display contrast is too low or too high

Possible reasons:

The contrast software settings are not appropriate, or the ambient temperature causes LCD characteristics to drift.

Adjustment method:

Find the contrast adjustment slider in the system menu or user interface (via software settings).

If there is no open adjustment option, it can be achieved by adding contrast adjustment variables or key macros in Designer.

If the adjustment is ineffective, it may be due to LCD aging or driver circuit failure, and the display screen needs to be replaced.

Fault 6: Unable to program or transmit data through Ethernet module

Possible reasons:

The Ethernet module did not obtain a valid IP (DHCP is not enabled and static IP is not set).

The firmware versions of Designer and HMI do not match.

The switch or firewall is blocking the required port (default 1024 or custom).

Troubleshooting steps:

View the status and IP address of the Ethernet module on the system information page of the HMI.

Use the ping command to test connectivity.

Specify the correct IP address and timeout time in the transport settings of Designer.

Upgrade HMI firmware to the latest version.

Upgrade Path and Selection Suggestions

When ePAD03/ePAD04 cannot meet the requirements of a new project or needs to be migrated from this series to a higher performance platform, the following paths can be considered:

Path 1: Keep the ePAD platform and add extension modules

If the current project requires access to Profibus DP or Ethernet, simply purchase the corresponding optional module and insert it into the Aux port without replacing the HMI body. This is the lowest cost upgrade method.

Path 2: Upgrade to eTOP series

If you need color display, larger screens (5.7 inches or more), touch functionality, or faster processors, you can choose the UniOP eTOP series (such as eTOP 05, eTOP 10). These models also use Designer 6 software, and the engineering files can be partially reused, but the layout of the screen needs to be redesigned (due to significant differences in resolution).

Path 3: Completely replace with third-party low-cost text screens

When ePAD04 also exceeds the budget, a large number of domestically produced text displays on the market (such as Xinjie OP320 and Weikong LEVI series) can be used as alternatives. However, it should be noted that:

The communication driver of domestic screens usually only supports a few PLCs (such as Mitsubishi, Siemens, Delta), and may not be directly connected to non mainstream PLCs.

The programming software for domestic screens is completely different from Designer, and the project must be completely rebuilt.

The number and functions of physical keys are often fewer than the ePAD series (usually only 4-6 function keys).