Douwe Egberts Cafitesse 700, Back Office Manual

Page: 188 / 265

July 2004
5C - 12
Functions - dosing system
User-Interface
on - off
Modul A + C
+ 19,75V
+24V
Transistor
B2 Coil
Power supply
• The 24 V direct voltage from the switched
mode power supply unit is controlled by a
switching controller providing the concen-
trate coils with a direct voltage supply of
19.75 volts.
• Pulses are transmitted onto the coil when-
ever the delivery button is pressed. Each
pulse results in an output of 0.105 cc.
• The micro processor controls the pulse
duration and the intervals.
a) Pulse current and pulse duration:
• Pulses are generated when the concentrate
coil is selected by the micro processor via
two transistors and switched off again at a
coil current of 5.2 A. The electric current is
measured by measuring the voltage on a
measuring resistor.
• Regular functioning has a standard pulse
duration of 6.7 msec. If the pulse duration
is not between 6.5 and 6.9 msec, the error
message "B2 error" is then indicated.
The micro processor switches off the
transistors following a maximum pulse
duration of 10 msec. even if the peak
current value has not yet been
reached. If the electric circuit has not
been interrupted, the dosing operation
is still possible but inaccurate.
C.4 Electric circuit diagrams
C.4.1 Electric circuit – concentrate coil
Fig.1
Module B+C
+19.75V
Cafitesse 700 - Functions - Dosing system