Fresenius Medical Care 4008 E Technical Manual page 404

Stepper motor control ( circuit diagram 7/9)
Initial control:
After a reset at IC 24, pin 28, the level at IC 24, pin 8, is checked. H level corresponds to
bicarbonate operation; with L level, only the concentrate pump is activated.
The first trigger pulse at IC 24, pin 7, is used to initialize the pumps.
Operation:
The concentrate or bicarbonate pump respectively is activated by a trigger pulse at IC 24, pin 7.
The step-number memory ICs (latch IC 2 or IC 1) are energized and read in via the control line IC
24, pin 6.
L level applied to pin 6 = concentrate pump step number
H level applied to pin 6 = bicarbonate pump step number
The direction of rotation is reversed at pin 5 of IC 37 or at pin 5 of IC 26 respectively.
The optical sensor signals (bic pos/conc pos) are shaped via the Schmitt trigger circuit IC 16 and
read in at IC 24, pin 19, and IC 24, pin 18.
Between the individual strokes, the motor current must be reduced (L level at IC 37, pin 10, and
IC 26, pin 10).
Valve control (circuit diagram 8/9)
The data residing at latch IC 7 and IC 10 are directed to the driver modules of type 2068 and
activate the individual factors.
Dialysate valve control:
Only by H level via the V24-en/V24b-en release line of CPU 2 can valves 24 and 24b be activated
via IC 51 and IC 40.
Water inlet control:
Via IC 51, the H level of IC 7, pin 12, releases the float switch signal and controls valve 41 via IC
18, pin 3 and pin 2. Valve 41 can also be directly controlled via IC 7, pin 13, and IC 31, pin 12.
8-107
Fresenius Medical Care 4008 4/09.03 (TM)