NT 0928 Rev.A0
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2.2.1.2.2. Watch-dog
The WATCHDOG circuit comprises the following elements: U10, U11, C12, D2, D1, R4, C11.
When powered up the capacitor C12 is charged by the U10 circuit, via diode D1.
The charge is maintained at a threshold of over 1.5 V during operation.
The software writes, every 1 ms.This writing generates a 5V/1µs impulse on the U7.10 output, which re-
charges the capacitor C12 via a high pass peak detector circuit made up C8, D3, D2. The C12 capacitor
discharges in resistor R4.
When the software stops, the capacitor C12 completely discharges. The U11 RESTIN* line falls to 0 and
the RESET signals are activated, stopping all syringe-pump control operations in the inactive state.
Fault signals, the blinking FAIL diode and the continuous BUZZER are stuck in an active state.
WATCH-DOG trigger time is less than 400 ms.
2.2.1.3. Keyboard/display interfacing
2.2.1.3.1. Display registers
The display system is made of LED’s and of a 2 lines of 20 characters LCD graphic screen.The U7 cir-
cuit allows to address the matrix of the LED’s, the U8 circuit allows the writing and reading in the display
controller.
The LED’s matrix are DIG0 to DIG7 and SEG0 to SEG7.
The FAIL LED shows the device is failed, the command is inverted to be active by default at RESET. It
is active at 1 on the display board. The FAIL diode is out of the matrix to be able to light on when the
micropossor does not work.
2.2.1.3.2. Buzzer
The BUZZER command is inverted and controls the transistor, T3, which is mounted as a common
transmitter. Working in parallel, the transistor collector drives the BUZZER on the display board and the
nurse call relay on the motor control power supply board. After starting the pump, the BUZZER is acti-
vated for added safety.
BUZZ signal: J5 pin 6 and J3 pin 24 50 mA 6.75 Volts maximum.
2.2.1.3.3. Keyboard register
The keyboard is based on a 6 x 3 matrix, with 2 separate keys - TON and TOFF - with 1 common
point (GND). They turn power ON and OFF respectively and are connected to the display board. TON
and TOFF signals only transits via the CPU board.
The columns of the keyboard are driven by the same signals as the columns in the display matrix, thus
facilitating simultaneous keyboard and display monitoring. Register U15 reads the status of the three
keyboard lines, LIG1, LIG2 and LIG3 in order to check whether a key has been activated.
2.2.1.3.4. Motor control register
The U12 motor control register generates 4 motor phase signals, A,B,C and D, the I current control sig-
nal, the motor rotation opto control CDOPT1 signal and the BOOST BOOSTER control signal.
2.2.1.3.5. Sensor status register
The U16 sensor status register reads the microswitch digital sensors and the syringe pump opto switch.
Summary of Contents for INJECTOMAT 2000 Anasthesie
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