Electronics

jeffrey · Guest

I want to build a alarm clock that will start counting up when it is
triggered. (e.g., at 5AM, it will go off and start counting 1 second,
2 second.) I can't seem to be able to find clocks like these. (I know
there are timers that will start counting up, but not clocks)

A Radio Shack employee suggested that I buy two clock-timers and
connect them. The clock on one will trigger the stopwatch on the
other. How would I go about doing this?

I've looked online for alarm clock building plans, but I haven't been
too successful. I don't have much experience in this. Any help is
appreciated.

I need to be able make several of these count-up alarm clocks. The
cheaper, the better. The easier, the better.

Thanks.

Lord Garth · Guest

You can do this with many clock chips by using the alarm output of one
to enable the second. You need to find the data sheet on whatever chip
you decide upon. There are probably many Mostek and National Semiconductor
clock chips around.

ehsjr · Guest

You didn't specify analog or digital clock. I made the worlds
simplest mod ? to a small quartz analog travel clock to start
when triggered. I use it to time how long it takes to discharge
a battery to a specific voltage with a given load. The clock
runs from a 1.5 volt AA cell. I stuffed a small strip of double
sided pc board between the battery + and the contact in the
battery compartment. The pc board sticks out of the back of the
clock. A wire is soldered to each side of the PC board - when
the wires are connected (by whatever - relay, switch, scr etc)
the clock runs. By setting it at exactly 12:00:00 before starting,
you have essentially a second counter that will last for 12 hours.

Like this:

-------------- ||
| AA }||{ < contact in clock battery compartment
-------------- ||
|| < double sided pc bo0ard
+----||----+
| |
| +---- < wires to
+--------------- < switch/relay/etc

Electronic Goldmine has clocks like the one I used: item #G14709
http://www.goldmine-elec.com/default.htm

Ed

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