Digital Clock using LS7490 decade counters

Status
Not open for further replies.
Z

Zordon

New Member
So i have a school project where i have to build a digital clock using 7490's i have already built the seconds and minutes part but i am kind of confused on how to handle the 24 hour counter. current the circuit below will count to 29 and reset to zero. i want it to reach 23 and reset.

LEFT seven segment display Most significant digit

**broken link removed**
 
Schema attached of two times 7490 IC's to decode 00 to 23 and reset to 00 again for a 24 hour clock.

Hope it helps you with your clock

Regards, Raymond
 

Attachments

  • DSC01829.JPG
    118.9 KB · Views: 3,407
Or use two times 7490 IC's and a 7400 to divide the 24.

You have an option available to drive a date counter if you wish.
 

Attachments

  • DSC01830.JPG
    123.1 KB · Views: 2,022
Last edited:
RODALCO said:
Or use two times 7490 IC's and a 7400 to divide the 24.

You have an option available to drive a date counter if you wish.
Click to expand...

The design with the NAND gates seems a bit pointless, compared to the design without. The 7490 has an AND gate on the reset line, so it seems sensible to use it when it helps, like in the first design you posted.
 
Answer

Hey, I have to build one of those too!!!
Can you put up yours so I can see what you have wrong, mine, was little different we did not have to all the way to 24 but do it 12 and say either pm or am
 
here is what i did, i also made a 555 timer to provide a clock pulse
 

Attachments

  • Clock.jpg
    69.5 KB · Views: 4,962
I made the same circuit, but there is some problem while simulation. The seconds are not displayed properly. I am posting my circuit file(in multisim format), please help me out with the circuit.
Thanks.
Link-
**broken link removed**
 
don't worry about getting it to work in multisim. It's a waste of time, if you have a large circuit it usually won't work.
 
what is the logic behind hours circuitary of digital clock

plz clear me the logic behind the hours circuitary of the digital clock
 
Here is an attachment i googled of the net.
uses 7490 no gates.
 

Attachments

  • digitalclk.pdf
    395.1 KB · Views: 4,926
need help

Can any one help me how i can generate clock pulse from crytal oscillator.

Also send me some tutorials for AVR Microcontroller
 
this type of clock consume more power so AC/DC converted power needed.
on the other hand, it clear all data if black out of power, in the case it's better if it continue counting in itself without displaying by backup battery.
so any chip that can--
1. continue counting during black out.
2. display hh:mm:ss
 
which chips drives on low supply voltage

which type (TTL/CMOS/others) of chip can work on low supply voltage(5V dc)
 
Last edited:
Status
Not open for further replies.

Similar threads

O
  • Question
Reading Digital + Analog Data from Sensors / Bus
2
Replies
26
Views
3K
Tony Stewart
D
Transparent OLED Clock
Replies
5
Views
2K
dotmatrix24
D
C
  • Question
Using Handheld PC as universal remote
Replies
4
Views
966
Lightium
L
  • Question
Multiple Voltage inputs for Digital Input pins
Replies
6
Views
1K
schmitt trigger
S
  • Question
Project help request: Striking a bell manually, alarm clock.
Replies
12
Views
3K
stevef22
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…