P20K2E7 7.5
7.3 Speed Control Unit (Command Unit)
As a general rule, this unit is attached to the lefthand side of the control box by means of two screws
and is mechanically connected by means of a pitman rod with the treadle located on the sewing
machine stand.
Electrical connection is made by inserting the cable with 7-contact plug into the correspondingly marked
female connector (X7) located on the lefthand front face of the control box.
The speed control unit is a mecano-electric converter, dividing the treadle stroke into 16 different digital
values comprising 4 bits each.
To achieve this, the speed control unit is equipped with 4 signal tracks (A, B, C, D).
The 16 digital values are listed below together with the treadle stroke (treadle position) and with the
uppertaining command.
Coding Chart of the Speed Control Unit:
Position: Outputs:
ABCD
-2 0110Treadle heeled fully (seam end, SN)
-1 0111Treadle heeled slightly (PF lift)
0 1111Treadle zero position
+1 1110Treadle toed slightly (PF down)
+2 1100Speed step 1
+3 1101Speed step 2
+4 1001Speed step 3
+5 1000Speed step 4
+6 1010Speed step 5
+7 1011Speed step 6
+8 0011Speed step 7
+9 0010Speed step 8
+10 0000Speed step 9
+11 0001Speed step 10
+12 0101Speed step 11
+13 0100Speed step 12 (n-max treadle toed fully)
7.4 Synchronizer (Position Control Unit)
This unit is mechanically attached to the machine handwheel and is connected with the righthand front
face of the control box by inserting a cable with a 6-contact plug into the female connector (X9) marked
with the synchronizer symbol.
The synchronizer is a mechano-electric transducer (angular position transmitter) comprising a
transmitter disk equipped with a signal track and a synchronization track. Signal generation is
performed by photoelectric means via light barriers.
The signal track furnishes 480 pulses per revolution on two channels (FA, FB). The two pulse
sequences are electrically phase-shifted by 90 degrees and thus permit recognition of the direction of
rotation. The synchronization track furnishes one pulse per revolution having a width of 240 pulses
furnished by the signal track.
The synchronizer is a precision instrument. To prevent malfunction, please do not open the
unit!
Synchronization of the drive system and the machine is made with the synchronizer by a teach-in
process within user programming (zero adjustment of the machine).
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