Service manual

DCB, DCFCB and DCFCTB Models
38
Theory of Operation
Example
Received DTMF report string
*
C 1 D D 2 05
*
*
Starting character
C
Unit type DCFCTB with 2001 siren
1
Currently running function 1
DD2
Siren site number (0000) (0000) (0010), which equals site number
002
0
Sensor status is (0000),
Bit 1 is 0, rotation occurred
Bit 2 is 0, cabinet door is open
Bit 3 is 0, not used, always 0
Bit 4 is 0, AC power is on
5
Sensor status is (0101),
Bit 1 is 1, battery voltage is low
Bit 2 is 0, AUX 1 is closed
Bit 3 is 1, activation current not detected
Bit 4 is 0, local activation occurred
Chopper Motor Current Sensor Theory of Operation
Overview
The adjustable current sensor 2001062B is a window comparator device that uses
a Hall Effect current sensor and an LM358 based window comparator. The active
high output is opto-coupled and the entire circuit is powered by an MC78L08AC
voltage regulator IC. The ground for the circuit is selected by way of jumper J2
between isolated or earth ground. The operation of the circuit is such that if the
current passing through the probe of the current sensor is larger than the lower
preset level and is less than the upper preset level, an active high output results
turning on the opto-coupled output, indicating that the sensed current is within the
acceptable range.
Circuit Description
The circuit is energized when 12 VDC (nominal) is applied to J1-3 and ground is
applied to J1-1. The 12 VDC at J1-3 is applied directly to the MC78L08AC
voltage regulator, IC1. The regulated 8 VDC output of IC1 is applied to the
LM358 dual op amp (IC2) at pin 8, to MC14001B quad NOR gate (IC3) at pin 14,
and also to the Hall-Effect current sensor (CS1) at its (+) input.
Current probe CS1 is designed to generate a reference voltage of 1/2 the supply
voltage on its (0) output pin. With 8.0 VDC at the (+) input of CS1 and ground
applied at the (-) input of CS1, CS1 outputs 4.0 VDC on the (0) output when the
current passing through the probe of CS1 is zero. This voltage is applied to R2,