Trouble Shooting - KEP MMI-1500 Installation & Operation Manual

4.0 Trouble Shooting

4.1 Power Problems
Problems on power up: Unit does not light or unit lights but does not display any windows.
1. Check wiring for proper polarity.
2. Check power Supply for proper Voltage and Current capacity.
3. Check fuse.
Problems during operation: Faulty unit operation may be due to problems with power quality. The HMI has been
designed to work in environments where electrical noise is present. However, extreme electrical noise still causes
problems. Make sure that the system is properly earth grounded.
4.2 Communications Problems
Sometimes communications fail. When communications fail, the unit automatically tries to establish the
communications link again. During the time the unit is establishing communications, the touchscreen of the unit does
not respond. Function key operations are interrupted. The implication is that the unit should not be used for
Emergency Stop applications. A loss of communications can happen at any time. Using the function keys on the unit
for critical operations can lead to a potential disaster. It is good programming practice to allow for safe operation in
case of interface failure.
There are various reasons why this happens;
Improper programming: If the MMI window is programmed to access data from an invalid register or bit address
for the PLC, the unit receives an error message from the PLC. The unit interprets this as a loss in communications.
Be sure that all data points being displayed are valid for the PLC that is connected.
Loose or incorrect cables: Make sure that all cables are secured and configured properly for the PLC.
Time outs: Make sure that the PLC is responding to requests from the HMI in a timely manner.
Power loss: Make sure the PLC has power and is running properly.
Electrical noise: Faulty unit operation may be due to problems with power quality. The HMI has been designed to
work in environments where electrical noise is present. However, extreme electrical noise still causes problems.
Make sure that the system is properly earth grounded.
The use of proper grounding techniques insures reliable communications. Make sure the controller and the HMI are
connected to good earth ground sites. This allows EMI (Electro-Magnetic Interference, commonly called electrical
noise) to be channeled to ground where it can no longer disrupt electrical operations. Be sure to route
communications cables in separate bundles and locations from AC power and control wiring. Do not run
communications cables near solenoid and relay coils or AC and DC drive controllers. Care should also be taken to
locate the HMI itself away from sources of EMI.
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