Table of Contents
Advertisement
Theory of Operation-DM
505
and Q1405. The segment information at the cathode of
each LED is displayed as its anode is strobed high. The
display is strobed in the following order: digit
1,3,2,
and 4.
Digit f is the least significant and digit 4 is the most
significant (1 or 0 ) . The digit strobes are also routed
through sections of
the range switches
t o providedecimal
point information t o
the display. Transistor
Q1507 con-
trols the most signifFcant digit, U1001.
The sign is enabled
by
switches S2K and S2B, which
connect thesign anodes (t11001 pins 1 , 6 , a n d 7 ) to+12 V.
T h e cathode of the negative segment of
the
sign (pin 4) is
hard-wired low through R1601. The sign of the input from
U1303, pin
5, is
buffered through U1302Etothe cathodes
of the positive
segments
of the sign (U1001, pins 3 and 5 ) .
If the sign has been enabled by S2K or S2B, a positive sign
will be displayed when pins 3 and 5 are low.
Advertisement
Table of Contents
