CMUip-2212 Cabinet Monitor Unit
Operations Manual
Eberle Design Inc.
Page 15
Section 3
INPUT SIGNALS
3.1
LEDGUARD
®
FIELD SIGNAL SENSING
The CMUip-2212 uses a technique called
LEDguard
®
that is designed to better monitor the
characteristics of LED based signal loads. Each field signal input is measured and
compared to both a high threshold and a low threshold value to determine On / Off status.
This differs from conventional standard NEMA operation where the active threshold is
picked according to the color of the field signal. Once the high and low On / Off thresholds
(Section 5.1) have been determined using the input RMS voltage, the individual fault
monitor functions use the appropriate threshold to determine if a fault condition exists.
LEDguard
®
Green/Walk
Yellow
Red/Dont Walk
Conflict
Low
Low
---
Red Fail
High
High
High
Dual Indication
Low
Low
Low
Clearance
Low
Low
High
3.2 LOAD SWITCH CURRENT
Load current is sensed by the HDSP based on total load current to all colors of a channel.
Total load current is an indication that a signal load is present. Lack of adequate load
current indicates no active load (i.e. burned out lamps) or an open field wire condition. Load
current monitoring is used by the Lack of Signal monitoring function (see 2.5) to detect the
loss of signal load while the load switch is in the On state.
A channel will be sensed active when the load current exceeds the programmed Channel
LOS Current Sense Threshold programmed for that channel in the Datakey. A channel will
not be sensed active when the load current is less than the Channel LOS Current Sense
Threshold programmed for that channel in the Datakey. A hysterisis value of +/- 2 mA is
used for load currents less than 120 mA. A hysterisis value of +/- 16 mA is used for load
currents greater than 120 mA.
The Channel Current Sense Threshold should be programmed for each monitored channel
based on the minimum signal load under all worst case conditions.
3.3 PDA CONTROL SIGNAL INPUTS
3.3.1 LOCAL FLASH STATUS
The cabinet should be wired such that operation of the cabinet in AUTO mode will place an
active voltage on the LF STATUS pin (see Section 5.1). Operation of the cabinet in FLASH
mode should be open circuit on this input. The CMUip-2212 will report the state of this input
in the Type 209 (195) frame. See section 2.9.
3.3.2 MAIN CONTACTOR (MC) COIL STATUS
The cabinet should be wired such that the MC COIL STATUS input is connected to the
control side of the main contactor signal bus relay coil. An active signal (see Section 5.1)
on this input indicates the Signal Bus should be powering the load switches. The CMUip-
2212 will report the state of this input in the Type 209 (195) frame.
3.3.3 MAIN CONTACTOR (MC) SECONDARY STATUS
The cabinet should be wired such that the MC SECONDARY STATUS input will be
connected to the output side of the main contactor signal bus relay. An active signal (see
