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Design & Build 2 Digit, 7-segment display

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I need to build a 555 timer in astable mode that produces a pulse onece each second. These pulses are counted (decimal) and displayed on a 2-digit, 7-segment when the display show 99, it should start over at 00.
Thank you for your time.
:)
 

jacobs_ladder

New Member
Best bet is to rig two counter chips or one dual counter to seven segment decoders. Then connect the seven seg decoder to the appropriate pins on the display. If you need to generate the clock signal, use an op amp resonator square wave. You can adjust the frequecny changing the RC values of the resonator.

Good luck.
 

Electric Rain

New Member
I should be able to help you, but I need a little time to do the research and draw up the schematics ok? :wink: I know most of the stuff, but I need to know just a bit more. :lol: Shouldn't take longer then... a week at the very most. Now I can't say that I WILL get it, but there's about an 80% chance. I'll start the research now. :wink: Wish me luck!

Edit: Correction, I SHOULD have it by tomorrow. :wink:
 

Electric Rain

New Member
Alright, this is what I’ve come up with. They’re not schematics, but I think it will work real well. :wink: First, go here: http://www.electronics-lab.com/projects/misc/012/ Then, follow the notes to build two of these. Now download the 555 timer calculator located here: http://www.andy-clarkson.me.uk/555/program.html (You may have to download the VB 4 files at the bottom of the page also.) to figure the values of Ra, Rb and C. You probably won’t be able to get 1 second exactly, but I think I found the closest you can get: Ra = 486K, Rb = 85K, C = 2.2uF. Then just connect pin 3 of the 555 timer to pin 14 (“Count in”) of the 74LS90 and you should be set! Please let me know if there’s a problem or if… anything. And anyone else, same thing.
 
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