1 Nov
2011
1 Nov
'11
6:44 p.m.
On Nov 1, 2011, at 4:29 PM, Tony Duell wrote:
Yeah, I corrected that later. Silly mistake. :-)
For example,
most cheap clock radios have one 4-pin DIP running the
Iasusme htat's '40 pin DIP'. The only 4 pin DIPS I've seen have been
bridge rectifiers. An wful lot of those clocks are not multiplexed at
all. Think about it.
THey are genuine 7 segment displays (no decimal points0, and the most
significant digit is either blank, 1 or 2 (or maybe blank and 1 if you
have 12 hour clock). There's easily enough pins on a 40 pin chip to
direclty drive those, along with a few other outputs (flashing colon,
alarm, turn-on-radio, etc) and inputs (setting swtiches, etc).
May be true; the few cheap clock radios I've disassembled to try to fix (because their
alarm noises were particularly effective and they were no longer made, not because I was
too cheap to pay $9 for a new one) certainly all had the same chip (or generic functional
equivalents) driving them. They were all multiplexed drivers, and the datasheets went
into great detail about how to wire up 7-segment displays properly.
Admittedly, it's a statistically invalid sample (about 3, if memory serves). Perhaps
I'm misremembering the size of the DIP; it could have been a 28-pin. Those clocks are
long-dead (they turned out to have dead ICs of one type or another, and since they were
all long out of production, replacements were unavailable), so I can't look them up
again.
- Dave