Darren Harris wrote:
What's a "split"?

Apparently not just plain multiple displays, each with its own
"latch" button, all started and clocked together.

Cheers!
Rich


Splits = individual lap times.

I'll settle for a single LCD display if I have to.

Since this appears to be too complicated, perhaps I can start off with
something simple. Does anyone know how to build a simple timer with an
LCD screen that shows hours, minutes, and seconds?


Unfortunately, driving an LCD screen isn't a simple thing; they are
really designed to be driven using software. There may be front-end
chips which simplify them, but LED 7-Segment displays are much easier to
drive from discrete logic.

Building a 'simple' timer with discrete, digital logic isn't as easy as
it seems. You need

1) a timer source, like an oscillator circuit
2) a counter (or more like a set of counter chips)
3) logic to sample these counter outputs, and display the results on an
the LED segments.

At the least, this will require

1) a crystal oscillator/divider, like the philips hef4521b combination
oscillator/divider chip. Using a crystal, you can generate accurate one
second clock pulses

2) a set of bcd counters, one per decade of timing accuracy.
3) a set of LED 7-segment display drivers, one per digit.
4) some 7 segment displays
5) power supply
6) enclosure

You can get fancy and multiplex the LED displays, thus cutting down on
the number of chips required, but this increases the complexity a bit,
requiring more logic.

Note that a microcontroller costing less than a buck can replace 1-3
with a simple program of about 100 lines of assembler. Also, there are
designs for discrete timer circuits out on the web, if you want to look
and see what you are getting yourself into before starting.

If you decide to try to show speeds, you'll need division as well, which
is fairly easy in a microcontroller, and much harder with digital logic.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.