Manifested Problem Conditions:
Several customers have reported communication failure problems. The problem is manifested by a “No
communication” alarm, usually followed 35 seconds later with “Communication restored”. The system
experiences a reset. However, after the restart there may also be Motor Speed, Offset and/or Gain alarms
while the system restabilizes. It is possible that the system would not restart at all.
This condition has been traced to the voltage setting on the switching power supply. The supply is
supposed to come to Ircon from the supplier’s factory preset to 5 volts. However, several ScanIR II units
have been found with settings of 4.8 volts. Contact corrosion and temperature drift can cause the supply
voltage to drop even lower during operation.
Lower power supply voltage settings may cause more frequent “No Communications” alarms, possibly even shutting down the system and not restarting at all.
The combination of low power supply voltage levels and spikes of up to 200 millivolts from digital logic can
cause the voltage to dip below the threshold of the automatic system reset circuit.
Readjusting the power supply to 5.15 volts will make the ScanIR II system more tolerant of these environmental conditions and ought to eliminate false communication and reset problems.
See attached document for full description.