January 2001
5C - 16
Functions - Dosing System
Service Manual Cafitesse 500
C.4
Electrical Diagrams
C.4.1 Circuit - Concentrate Coil
Fig.1
concentrate
coil
service panel
On/Off
switched mode
power supply
delivery
button
voltage regulator 19.75V
+10.5V
switching
transistor
measurement
resistor
24V
DC
●
The 24 V dc of the switched mode power
supply is controlled by a voltage regulator
which supplies the right and left concentrate
coil with 19.75 V dc. The LEDs on the
control unit indicate whether the power
supply of the concentrate coils is
guaranteed:
Yellow LED - supply of the left concentrate
coil 24 V
Green LED - supply of the right concentrate
coil 24 V
●
Pulses are transferred to the coil when the
delivery button has been actuated. Each
pulse releases the delivery of 0.105 cc.
●
The MP controls the pulse duration and the
intervals.
a)
Pulse current and pulse duration:
●
Pulses are generated when the
microprocessor selects the concentrate coil
via two transistors and switches it off at a
coil current of 5.2 A. The current is
measured by a voltage measurement at a
measurement resistor.
voltage [V]
------------------- = 5.2 A
resistance [Ω]
●
In standard function, the pulse duration is
6.7 msec. If the pulse duration is not
between 6.5 and 6.9 msec., the error
message 'B2 Error' is indicated, which can
only be read out by means of the service
device.
The MP switches the transistors off
after a max. pulse duration of 10 msec.
even if the peak current value is not
achieved. When the circuit is not
interrupted, dosing is still possible, but
it is not exact.
