LX2
plus / advanced and LX4 plus / advanced
B2270901
Content is subject to change without notice!
10
The microcontroller supervises voltages coming from the divider R34, R35 and serial re-
sistor R12 and smoothed by capacitors C1 and C10, respectively. L5 again is a RF
choke. Zener diode D11 limits the voltage to stay below the maximum allowable input
value of the microcontroller.
The measured voltage difference is used to calculate a charge account.
Transistor T13 is a current sink, activated during self-diagnostic or in order to discharge
the battery. Resistor R43 limits the current and inductor L4 is a RF choke. Transistor T13
is turned on via resistor R45 by means of “active high“.
3.3.3
Microcontroller
All the controlling tasks are done by the 8 bit controller circuit IS1. The clock is generat-
edby the internal oscillator. External components belonging to the oscillator are the ca-
pacitors C4 , C5 and crystal Q1. Transistor T3 with additional components R8, R9, R16
and C6 form the necessary reset circuit.
The UART, implemented in the controller, allows communication with the pager. The sig-
nals RxD and TxD are coupled to one wire using diode D10. Resistor R15 serves as a
„pull-up“ resistor connected to the communication wire which is used in both directions. By
placing additional components marked * and using a suitable software, the charger can be
upgraded to be able to work as a programmer.
3.3.4
Temperature Supervision
The Charging Unit supervises the ambient temperature during the charging procedure and
varies the charge current accordingly, i.e. accelerated charge is permitted within a speci-
fied temperature range, only. The voltage of the resistive devider R31/ R32 is measured.
R31 is a temperature-dependent resistor.
3.3.5
External Alert Devices
After reception of an alert, relay REL1 is activated by T6, R13 and R14. Resistor R30 lim-
its the current and D2 serves as a free-wheeling diode. The time the relay stays active ,
i.e.the time the working contacts REL1A are closed, can be programmed (pager pro-
gramming).
Furthermore a square signal of appr. 1.2 kHz is output via transistor T4 (base resistor R2).
This transistor can be made up with external components, e.g. loudspeaker.
As an option, a switching circuit (R41, R42 and T12) can be placed which can drive a
suitable Buzzer for additional loud alert.
The alert can be erased by pressing button TA1 on the charger. The switching signal is
filtered by resistor R47 and capacitor C11.
