User's Manual

MODEL 2130 MARKER BEACON
2-20 Rev. A April, 2005
This document contains proprietary information and such information may not be disclosed to others for any
purposes without written permission from SELEX Sistemi Integrati Inc.
2.3.4.3 Marker Beacon BCPS CCA Detailed Circuit Theory
Refer to Figure 11-13. AC line, neutral, and earth enter via TB1-1, 2, and 3. The AC line is fused by F5 and routed to the
external AC outlet on TB1-4. The AC neutral for the outlet is routed directly to TB1-5. AC earth for the outlet and both
external power supplies PS1 and PS2 are connected directly to TB1-6, 10, and 13.
Transformer T1 scales AC current detected for both System1 and System2 to its secondary where it is loaded by burden
resistor R3 and transient protected by CR15 before routing to DB25 connector J1.
The FFM / Marker Beacon pairs are designated as System1 and System2 and are identical in operation. System1 consists
of FFM1 and Marker Beacon1 while System2 is the FFM2 /Marker Beacon2 pair. Only System1 shall be discussed further.
The AC line after the transformer T1 primary is fused by F1 and switched by one side of DPDT switch S1. The output of
S1 connects to the primary of voltage-sensing transformer T2, whose secondary scales the voltage before full-wave
rectification by diodes CR3-6. This rectified voltage is transient protected by diode CR1 and filtered by capacitors C1 / C3
before routing to both connector J1 and diode CR54. Diode CR54 performs a diode-OR with the TESTAC1 voltage (more
information later) before entering current-limiter U1. Current-limiter U1 and resistor R1 insure consistent brightness of LED
CR13 regardless of AC voltage or TESTAC1 voltage levels.
The AC neutral, after transformer T2 primary, is switched by the remaining side of the DPDT switch S1 before routing to
TB1-9. An external AC-DC power supply connects to TB1-8, 9, and 10. The external AC-DC power supply converts AC
voltage to +15VDC and connects back to TB2-9 and 6. The positive side of this DC supply (TB2-9 and labeled +15VIN1) is
fused by F3 and routed to the Battery1 Charger / Changeover circuitry (more information later). The negative side of this
DC supply (TB2-6) is routed through current-monitoring resistor R6. The Kelvin-type output connections of resistor R6
are transient-protected by CR19 before routing to connector J1.
Battery1 connects to TB2-1 and 4 where it is reverse-voltage protected by diode CR12. The positive side of this +12 VDC
battery (TB2-1 and labeled BATT1+) is switched by Batt1 Disconnect switch S3 before routing to the Battery1 Charger /
Changeover circuitry (more information later). The negative side (TB2-4) flows through current-sensing resistor R4. The
Kelvin-type output connections of resistor R4 are transient-protected by CR17 before routing to connector J1.
Oscillator circuitry U8:A, C14, and R24 establish an 8192 Hz heartbeat for the battery fault testing of both Battery1 and
Battery2. Inverters U8:C and U8:B buffer and invert the clock signals so that counter U7 and flip/flop U6:A change on the
same edge. Counter U7 sets an overall time period of two seconds while AND gate U9 / U8:D presents a logic high to the
U6:A-5 input for 32 milliseconds of the 2 second time period. The logic high is clocked through U6:A to both the gate of
transistor Q4, shutting down charger U3, and to the gate of transistor Q11, placing a load of R30 and R31 on Battery1. If a
battery is not connected, the load will cause a logic low to be clocked through R81 / U6:B-9, turning on transistor Q5 and
Batt1_Fault indicator CR27.
In summary, once every 2 seconds for 32 milliseconds, a load is placed on the battery to check for its presence.
Charger U3 is a constant voltage / constant current integrated circuit whose final battery voltage is set by resistors R10,
R11, R12, and R13. Charger U3 switches the +15VIN1 through transistors Q1:A, Q2, Q3, diode CR11, inductor L2, and
resistor R8 to Battery1 in a switch-mode manner. Inductor L2 and resistor R8 establish the charger current through
feedback resistors R16 and R17. The switch-mode frequency of charger U3 is set by resistor R18 and capacitor C11. More
information on the charger U3 integrated circuit is available at the manufacturer’s web site.
Charger U3 also routes +15VIN1 through transistors Q1:A and Q1:B to VSUM1 while +15VIN1 is present. If +15VIN1 is no
longer present, Battery1 is switched though transistors Q10:A and Q10:B to this same point labeled VSUM1. VSUM1 is
filtered by capacitors C32, C34, C42, and inductor L4 before routing to switches S5 and S6. If switches S5 and S6 are
closed, VSUM1 is routed to connector J1-11 and 13 and lights MRKR1_DC and FFM1_DC indicators CR21 and CR22.
+15VIN1 also routes to voltage divider R44 and R45 which sets the “on battery” trip point of comparator U5:B, U5:C, and