Hello, i'm looking for any tips on building a generic countdown timer to work with a 7-segment display. I have a really decent knowledge of electronics and and Integrated Circuits, but I don't currently know of which IC might be best for this project. I've built a countUP timer with a 4026 and it was pretty simple and I know how to manipulate all of the connections for the most part. (there's no way to have the 4026 count down, right?)

Anyway, I don't want to use any type of Microcontroller and/or PIC or anything like that (that's something I'm currently just starting to read into); I want to do this soley with IC's. I heard that the 4029 might be what i'm looking for, but I also heard that I'd need a 7-segment decoder IC (a 4511?) to use in conjunction with the 4029 and a 7-segment display. Does anyone know of any IC's (what are they called? dividers in this instance, i'll assume. is that a proper assumption??) that will basically work in an opposite manner than the 4026 and have outputs made to work with a 7-segment display??? Thanks. -Joe

PS: let me know if you need any clarifications as to my intent if these brief paragraphs were unclear

 

You could use a 74HC192 (http://focus.ti.com/docs/prod/folders/print/cd74hc192.html) to do the timing (it supports counting up AND down), which gives the output in BCD. You'll still need a BCD -> 7-seg encoder as you mentioned. To my knowledge and from a quick Google search, I couldn't find anything that outputs it in 7-seg code.

 

a 4510 BCD Up/Down counter IC is what you need, you can check this out here to see how to hook it up to 4 7 segment displays.... http://www.doctronics.co.uk/4510.htm

B. Morse

 

You could use a 74HC192 (http://focus.ti.com/docs/prod/folders/print/cd74hc192.html) to do the timing (it supports counting up AND down), which gives the output in BCD. You'll still need a BCD -> 7-seg encoder as you mentioned. To my knowledge and from a quick Google search, I couldn't find anything that outputs it in 7-seg code.

what's the encoder for then , if it outputs in BCD?? Is it so the lights of the display aren't more dim when the digit reads "8' opposed to "1" (because of the extra segments on)??? Or is BCD something different?? Thanks

BMorse: thanks man, i'll check that out

-Joe

 

what's the encoder for then , if it outputs in BCD?? Is it so the lights of the display aren't more dim when the digit reads "8' opposed to "1" (because of the extra segments on)??? Or is BCD something different?? Thanks

BMorse: thanks man, i'll check that out

-Joe

BCD and 7-seg code are something different.

 

BCD and 7-seg code are something different.

aaaahhhh...that makes sense now. What exactly is BCD?? -Joe

 

Hello,

On this page you will find links on BCD decoders:
http://www.educypedia.be/electronics/digitalcodes.htm

There are other pages like that on other digital topics too:

Digital electronics:
Arithmetic circuits D/A-A/D converters Number systems Codes and decoders Flip flops Technology Counters and registers General overview Technology-CMOS Digital logic Memories Technology-TTL Timers and oscillators

Bertus

 

What exactly is BCD

Binary Coded Decimal - http://en.wikipedia.org/wiki/Binary-coded_decimal

 

thanks guys! -Joe