4 Bit Synchronous Counter to use as 4 Bit ADC

[andy1962]

Hello
Im really struggling with this question I've been given:
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Construct a four bit synchronous counter, then use as a guide to crate a four bit ADC which will:
When output 0 to 3 light should immuminate for low
When output 4 to 13 light should illuminate for ok
When output 14 to 15 light should illuminate for high

Then write boolean expression and create karnaugh map

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Ok so here's where i am so far with it, i have created the 4 bit synchronous counter on multisim:
http://imageshack.us/photo/my-images/855/counterg.png/

and i also produced my boolean expression:
http://imageshack.us/photo/my-images/687/booleank.png/

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I have no idea how to carry out the ADC stage of the counter and also i seem to be really struggling trying to simplify the boolean expression and with the karnaugh map. Not my strongest module I am afraid...

Any help would be very much appreciated Thank you

 

[LightHero]

. To create an ADC (Analog to Digital Converter) you need a comparator that will compare the input voltage to a set of reference voltages. The output of the comparator will be used as the input of your counter. You can use a 3-input OR gate to compare the output of your counter with the different reference voltages and activate the corresponding LED. For example, if the output of your counter is 0, then the OR gate will compare it with 0, 4, 8 and 12 and since none of them is equal to 0, the output will be 0 and the LED for low will be activated. If the output of your counter is 14, then the OR gate will compare it with 0, 4, 8 and 12 and since 14 is greater than all of them, the output of the OR gate will be 1 and the LED for high will be activated. For the boolean expression you can simplify it by using the rules of Boolean algebra. For example, you can rewrite the expression A'BC + ABC' + A'BC' as A'B(C + C') + ABC'. This will help you to simplify the expression further. For the Karnaugh map, you can draw a 4x4 grid and enter the output values of your boolean expression in the corresponding cells. Then apply the rules of Boolean algebra to simplify the expression. Hope this helps!