Page 284 - Making PIC Microcontroller Instruments and Controllers

2A4 BUILOII{G A SIIPLE EIGHI-BUIIOII TOUCH PAiIEL

;mi!ffil$i H€aders added to the LAB-XI board for extension ot pin signals
to the Danel.

pulls all of PORIB up with the internal pullups (OPTION REG.7=0) ard then
conducts. Conductjon takes place when
grounds each line when the phototransistor
the transistor is illuminated with IR. The circuitrv for a one line Dair is shown in
Figure 20.7.
5 VOLTS

lhe lB LED is ON and

THIS IS THE
CONDITIONWEWANI

FkUfSI$l$ Single lB transmitter-ptrototransistor pair
wiring. (Signallolhe PORTB pin is on or high when beam is noi