Mod 5 counter

[digital_geek]

I am trying to build a mod-5 counter and need a schematic for it. Any help it would be appreciated. If possible a schematic using all gates not IC's.

 

[Parag0n]

ever get the feeling someone wants you to do their homework for them?

 

[upand_at_them]

Yup. All the time.

 

[_3iMaJ]

I'll tell you how to do it but I won't give you the schematic.

You need either a decade counter or a 4 bit counter, either will work. Just use some logic to set the clear flag when you the number 5 shows up on the counter.

You can probably do it with less than 5 gates, its very simple.

 

[_3iMaJ]

I just realized a mistake above, since its a mod 5 counter, you want it to clock the reset at 5, but it will technically count to "5" but only for a split second. Just one of the many problems of being in the real world.

Sorry about that.

 

[upand_at_them]

I'd do it with a small, cheap PIC. But the homework assignment won't allow that.

Mike

 

[_3iMaJ]

You could build one with a few FFs, but I guess it depends how complicated you want it to get.

 

[jbeng]

A 7490 is constructed from a divide-by-2 and a divide-by-5 counter. Download the datasheet and look for the internal logic diagram. It details how the gates are connected internally to achieve these functions. Also, the 74hc390 is similar, but it has two div-by-2 and div-by-5 systems inside.
JB