2 Nov
2011
2 Nov
'11
2:45 p.m.
The only 4 pin DIPS I've seen have been
bridge rectifiers.
Total side note: I've seen some that are optoisolators. An wful lot of those clocks are not multiplexed
at all.
The one clock I've dug into in enough detail to say anything about this
is multiplexed by a factor of two, driven off mains power. Half the
segments are (potentially) driven during one half of mains power, the
other half of the segments during the other half of the power cycle.
This means it flickers at 60Hz, which was apparently considered
acceptable, and, actually, I'm not sure that's all that wrong a
decision for its target purpose.
I know that clock because I used it to make a _big_ clock to hang on
the wall: I opened up a commercial clock, cut the ribbon cable between
the main PCB and the display, probed the display to deduce its pinout,
and wired up a bunch of LEDs in an electrically similar configuration
forming digits about ten inches high. The original clock board fits,
with plenty of space to spare, in a corner of the result.
I am sure you're right. I am thinking back to something I did about 25
years ago. I built a magzien project to receive and decode the MSF
standard time broadcassts. This project had a BCD output to drive an
external display, and I obtaiend a Radio Shack large-display clock which
I extracrd the display from and interfaced it to this MSF receiver. I
remmebr this display as being 2-way multiplexed, come to think of it.
The IC in the Radi oSHcak clock had fewer than 40 pins I think, though. I
will still have it _somwwhere_, just don't expect me to find it.
-tony