5.1.4 Seize Detector Circuit
The size detector is made up to three slits for detecting
30 cm records, three slits for detecting 17 cm records, and
two LEDs and two photo transitors. It detects the record
size by detecting the existence of LED light passing through
the slits.
• When there is no Record
Light from LED 0301 (for 30 cm) goes through the
slits in the turntable and rubber sheet and strikes photo
transistor 082. 082 goes ON and OFF according to the
revolutions of the turntable. In the same way, the light
from 0302 (for 17 cm) strikes 081, and 081 ON and OFF.
When 082 (081) turns on, 09 (08) also turns on and
that output goes to the 01 pin 24 which is the 30 cm rec
ord size pin (pin 25 is the 17 cm record size pin). 01 deter
mines that there is no record.
• When there is a 17 cm Record
When the 17 cm record size slits are covered by a record,
081 turns off, and 080 remains off. Due to this, "H"
is input into 01 pin 25. When the 30 cm record size slits
are not covered, it's the same as no record, and 082 and 09
go ON and OFF according to the revolutions of the turn
table. The waveforms show in figure are then input into
01 pin 24. 01 then determines that there is a 17 cm record
because of this.
• When there is a 30 cm Record
Since the 17 and 30 cm record size slits are both cover
ed, 081, 08, 082, and 09 all turn off. 01 pins 24 and 25
both receive "H" input, and because of this 01 determines
that there is a 30 cm record.
• When there is no Record
• When there is a 70 cm Record
• When there is a 30 cm Record
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