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Subject: Re: 7 Segment LED Timer

Date: 03/06/00 at 11:45 AM
Posted by: Brian Snell
E-mail: bsnell@lara.on.ca
Message Posted:

In Reply to: 7 Segment LED Timer posted by Dan Gillies on 02/24/00 at 3:35 PM:

: Hello,
: I'm in need of help for making a 6 Digit, 7-Segment LED Countdown timer. I has to be capable of Hours, Minutes, and Seconds. Any information you can give me would be most appreciated, for I'm compliming some info on making one for a group and need as much of that info as possible.
: Thanks,
: Dan


Reply: Greetings. There are some IC chips available from Intersil-Harris but only 4 or 8 digit, It would be possible to use the 8 version and ignore the first 2 digit connections, or ignore the lasr 2 digits and utilise a x 100 timebase to allow the visual reading to be correct. Look up application notes in Intersil-Harris catalogue for the ICM and ICL series under "Counters"
If you have good electronic construction skills, you could assemble a 6 digits counter using circuit data available in Motorola Handbook covering the MC14553B chip. This uses 2 of the 14553B, 2 of type 14543B and 3 2N3906 multiplexed digit drivers plus, of course, 6 x 7 seg LED readouts. The circuit does not cover BCD pre-loading of the required countdown, nor interfacing to provide an output on "00 00 00" but this may still be accomplished dependent on how you see the external user operation. I have used variations of this circuit and found it reliable.Any 6 digit "clock" chips are unsuitable as they seldom have a "countdown" selection -- also they are very difficult to find in 6 digit.
Feel free to E-Mail me if I can be of any further help.

Lots of luck.

Brian Snell.


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