driving a 7 segment display, making my own readout driver

[boc2100]

ok for a project i was told to make a voltmeter, i know how to do everything else but here is my problem
we have a a/d converter -ADC08 (its discontinued but managed to find datasheet for it) and 3 1/2 7 segment displays.
the only other stuff we are alowed to use are logic gates (and not or xor nor, etc all of them) so basically i need to make a display driver decoder on my own. most of the datasheets and things dont say how they are made just that for example pin a goes to A of display. not much help there. i am fairly good at understanding this area but i need a jump start of how to begin.
i already know this is gonna be a big mass of wires on a breadboard so dont say to give up.
thanks

 

[boc2100]

the displays are common cathode and they will be having around a 200hz voltage so that they arent damaged, i assume that they will have to be multiplexed, so i dont know how i will connect it to the ADC08.

 

[ljcox]

I assume the ADC08 is an 8 bit A/D.

So you will need to firstly convert the 8 bits into two 4 bit BCD words. I posted ideas on this topic some time ago, do a search of my posts.

Then you will have to convert the BCD into the 7 segment format. This can be done by drawing Karnaugh maps, one for each segment.

I don't know why you want to multiplex.

There are several reasons for multiplexing, here are some examples.

If you want a PIC to drive say 4 displays, multiplexing is necessary since the PIC does not have enough i/o lines to dirve them directly.

If you need to minimise the wiring, eg. the displays may be remote from the main PC board.

Computer keyboards use multiplexing in order to minimise the hardware and wiring.

Len

 

[kentken]

Take a look at a mc4511, they work great for displaying on a 7-seg.

 

[boc2100]

well hey for kentken i cant seem to find that chip or whatnot but i cant use a chip to do it i can only use a standard logic, and i have all the chips for the logic already.

and hey ljcox do you have a time range for me too look, you post alot and it will take awhile to find it myself.

thanks

 

[ljcox]

and hey ljcox do you have a time range for me too look, you post alot and it will take awhile to find it myself.

thanks

Have a look at "Binary to BCD conversion, Mar 26, 2004 and Converting BCD to Binary using combinational logic, Mar 9, 2004.

The second one is the reverse of what you want, but it may give you some ideas.

Len