im doing a rather large project for my school tech area and to complete the project, i need to build some sort of a counter, preferably 7 seg display, that can count both up and down, and reseting to either 0 or 20 would be amazing. If anyone has any ideas or could help it would be most appreciated.

 

There are several presettable up/down decade counters that could work (7419X, etc.). Take a look at the Texas Instruments and On Semiconductor sites. There are some dual decade counters but I've not seen one that is presettable up/down. You'd need a BCD to 7-segment decoder like a 7447 to interface to the display.

 

You can also consider the 4000 series CMOS logic IC's. These operate over a much wider voltage range (3v-16v) than the 74xx TTL series (~3v-~6v depending on exact type)

The 4510 is a decade up/down counter with preset and reset. The preset can be handy if you wish to start the count at a certain number.

The 4511 is a 7-segment LED display driver for CC (common cathode) displays; it can source up to 25mA current per segment.

There is a brief intro to some 4000-series CMOS ICs on this page:
http://www.kpsec.freeuk.com/components/cmos.htm

Here is a link to Texas Instruments' CD4510B IC: (same as 4510)
http://focus.ti.com/lit/ds/schs071b/schs071b.pdf
Product page: http://focus.ti.com/docs/prod/folders/print/cd4510b.html

Here is a link to Texas Instruments' CD4511B IC: (same as 4511)
http://focus.ti.com/lit/ds/symlink/cd4511b.pdf
Product page: http://focus.ti.com/docs/prod/folders/print/cd4511b.html

 

Hi TheBlindman,

I recently did a similar project which I was able to complete thanks to the help of many people on this forum. Check out: http://forum.allaboutcircuits.com/showthread.php?t=55545&page=2 or check out pages 78-80 in the August 2011 edition of Nuts & Volts.

This is a two digit, 7-segment circuit that will:
1) Count up or down (one digit at a time or continuously if you hold the up or down buttons)
2) Reset to zero
3) Flash at a selectable rate
4) Be controlled wirelessly if you choose
5) Allow you to choose how big you want your segments (alternately, you could just use standard 7-segment displays if you don't need it large and forego the ULN2982s)

The parts and design were selected to be low cost. You can reduce the design and cost quite a bit if you don't need the remote, continuous counting, or flashing.

Let me know if you have any questions or need to know how to modify something. I've still got this on a breadboard working.

 

You may find this site useful as well.

http://www.edutek.ltd.uk/Tutorials.html

regards

Fenris