Honeywell HA71, Technical Manual

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HA71 Digital Gas Controller
Revision 3 (04/08)
HA71 Technical Manual 3-2
3.0 Main I/O Interface PCB
The most basic HA71 Controller requires only the I/O PCB shown in
Figure 3-1 for interfacing to field wiring. The HA71 primary power supply
is applied to terminals 9 and 11 of TB2. This may be from 10 – 30 VDC.
WARNING
HIGH VOLTAGES SUCH AS 115 VAC APPLIED TO THESE TERMINALS
MAY CAUSE SEVERE DAMAGE! DC output terminals 10 and 12 on TB2
provide up to 500mA of output power for powering remote devices
such as lamps, transmitters etc.
This PCB includes both master (COMM 1) and slave (COMM 2)
RS-485 Modbus
®
ports, 5 amp form C relays for each common
alarm event (A1, A2, FAULT/A3 and HORN), and power supply I/O
terminals. JP1 allows the RS-485 ports to be configured for 2 or 4
wire operation. A 26 pin ribbon cable connects the I/O PCB to the
HA71 CPU and Display nest assembly. Two I
2 C bus connectors allow
addition of optional functions such as analog I/O and discrete alarm
relays for each channel.
Horizontal jumpers installed in JP1 connect the RS-485 port’s RX
and TX lines, simplifying 2 wire daisy chains by providing additional
terminals for incoming and outgoing cables. For example, installing the
2 COM 1 jumpers connects screw terminals 1 and 5 and terminals 3
and 7. Socketed RS-485 terminating resistors R6 (COMM 1) and R12
(COMM 2) are located on the MAIN I/O board. These resistors should
be removed if communication wire lengths are very short (less than
25 feet), or, if the port is not a the end of the communication line.
An optional Auxiliary Relays piggyback PCB (part # 10-0144) may be
added to the I/O PCB via ribbon cable J4. These add another form C
contact set to the common A1, A2 and HORN alarms. Auxiliary Relay
contacts are available at the TB1 (AUX) terminals shown in Figure 3-1.
J1 is 26 pin ribbon to
main controller
Spare shorting strips
Ribbon connector to
optional Auxiliary
Common Relay PCB
Optional Aux. Relay
piggyback Board
(#10-0144) shown in
dotted lines
COMM1=Master; COMM2=Slave
J2 and J3 connect to
I
2
C oprional I/O
Fuses DC OUT power
to option boards that
require 24 VDC
RS-485 terminating resistors
(remove for short wire paths and
when HA71 is not end of path)
Apply only nominal 24 VDC
(min 10 VDC, max 30 VDC) power
to terminals 9 and 11 of TB2
TB2 terminals 10 and 12 provide
fused 24 VDC power to HA71
option boards requiring such power
TB1 AUX. RELAYS (OPTION #10-0144)
Figure 3-1. Main I/O Board with Common Relays