ELCOM Euro-50, Service Manual

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Euro-50 Service manual
48
Elcom s. r. o.
Table 5.26. Signals for interfaces COM2 RS232 - XC13
XC13 Signal Description
1 nc unused
2 GND-XC13 Relative potential
3 RXD1-232-1 COM2 RXD
4 TXD1-232-1 COM2 TXD
5.12. Interface for an FM connection
The hardware supports FM with I2C communication. The I2C1 interface of the microcontroller is used as the FM interface.
Table 5.27. Signals for interfaces for connecting FM - XC1
XC1 Signal Description
1 VDDQ Supply voltage for FM circuits
2 GND Relative potential
3 VBAT Voltage for production of burning voltages for OTP EPROM
4 GND Relative potential
5 FMDATA-1 I2C DATA
6 FMCLK-1 I2C CLK
5.13. Buzzer
The sound signal of the cash register is handled by the piezoelectric converter OBO 13240ST. The buzzer is controlled
by the signal BUZZER - 4kHz.
5.14. Power supply board
The cash register is designed to operate with an internal accumulator. This means that without a connected Li-ion ac-
cumulator, the cash register will not start. The power supply board houses individual supply voltages, an accumulator
charger and connectors.
5.14.1. Input filter
The cash register is powered by 12V DC voltage. The current drawn with this voltage does not exceed 800 mA. The
reversible FU1 circuit breaker protects the cash register circuits from overloading with excessive current in case of
faults in circuit NL1 (BQ 24123), or another component in the circuit supply voltage 12V.C5, C6 and C7 are filtering
condenser suppressing vf signals, and together with L4 they create a filter. VZ2 serves for dampening voltage peaks
with high energy, which could be dangerous for the cash register circuits. The diode VD4 limits reversing of polarity
of the supply voltage.
5.14.2. Charging the accumulator
Charging the Li-ion accumulator and supplying the cash register circuits is handled by the circuit NL1 (BQ24123). The
charge current is set by the resistors R5 and R11 to a value of 800 mA. The number of serial charged articles on the
Li-ion is set to 2 by the R4 resistor; that is the nominal voltage of the articles is 7.4V. The pre-charging current is set by
resistor r10 to a value of 80 mA. A accumulator which was deeply discharged and whose voltage fell below 6V thus
begins to charge with this current. If the voltage of the accumulator surpasses 6V, charging begins with a constant
current until the voltage of the accumulator (VBAT) does not exceed a value of 8.4V. Afterwards, the NL1 circuit swit-
ches into the charging mode with constant voltage and the charging current is lowered. When it falls beneath a value
of 80 mA, charging is stopped.
Capacitors C8 and C9 block the supply voltage for circuit NL1, which works in switching mode at a frequency above
1 MHz. Condenser C12 determines the period that passes before continuous charging is forcibly ended. The period