egg timer circuit

Thread Starter


Joined Apr 8, 2009
Hi, my name is thamil, and i need to hand in a paper on an egg timer circuit by next week. I'm kinda stuck here. I need to design a test circuit that will illuminate an LED for 180 seconds (3minutes) after a switch has been asserted. This circuit as given in the question should incorporate 74LS163 counters plus any other logic/flip-flops that may be required with a clock supplied at 1 Hz using a 555 timer.

I already have the 555 timer circuit that supplys a 1 Hz frequency but the problem is i'm unable to design the circuit with 74LS163-s and flip-flops. Can anybody help me please! I'm really desperate. I can't find the design of this circuit and also the explanation part.

Pls help me. Site links to this circuit diagrams or diagrams of the circuit itself will be much appreciated. Thank you.

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Joined Aug 7, 2008
Did you pull-up a data sheet on 74 LS163? yes; good then you know it has 4 stages counting in binary up to 16, so you'll need 2 chips up to 256.Simplest decoding is a big NAND gate. 180- 128=52-32=20-16=4. so'll need a 6 input NAND, 128,not 64,32,16,not8,4. Draw this up and we'll add a FF or two, and maybe a gate or so and you'll have it.


Joined Aug 7, 2008
Well I have a version so might as well post it. EN P lost its +; LED based on red 2.5V. The fun will come when converting to pre loads and no bid NAND.



Joined Sep 21, 2008
Hi Thamil, did you see the past year solution from NTU? 1 counter mod 10, the other 6 and the last 3. that gives 10*6*3 =180