Instructables

12 Hour TTL clock

Picture of 12 Hour TTL clock
http://youtu.be/hGamMP2yvWo
This was the final project for my Digital 2 class it was so well received that I thought I would share it. To begin the project I created the circuit virtually. By starting this way I was able to work a lot of the kinks out of my design while also making sure to use only the parts that I had in my kit.

 
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Step 1: Gather your parts

Picture of gather your parts
Parts List:
1. 555
2. 7408 AND gate
3. 7447 BCD to decimal decoder
4. 74LS90 Decade counter
5. 74LS93 Counter
6. 74LS76 JK flip flop
7. 331 resistor chip
8. 104 capacitor, 1µf cap, and a 10µf cap
9. (2) 503 potentiometers
10. 10K potentiometer
11. (6)or (3 dual) seven segment displays (common anode)
 

Step 2: Minutes and seconds

Picture of Minutes and seconds
final project 003.JPG
final project 004.JPG
 I began with a 555 timer set up with three potentiometers, two are for the actual timing of the circuit and the third is in parallel with the 503 to allow the time to be set. The seconds and the minute’s portion of the circuit are identical so wiring these were straight forward. The 1’s of seconds receives the clock signal at the 74LS90 (Decade counter) it counts 0-9 then clocks a 74LS93 for the 10’s of seconds. The 93 is set to count 0-5 by running two of the outputs B and C through a 7408 AND gate which resets the IC on the sixth clock pulse and triggers the 74LS90 in the minute’s section of the circuit.

Step 3: Hours

Picture of Hours
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The hours portion of the circuit while using the same components as both the seconds and the minutes is a little more challenging (Logically anyway). The first hours digit needs to count 1-9 then 0-2. This can be accomplished by tying pins 3, 6, and 7 to the output of the AND gate. By doing this it allows for a normal count 1-9 but when the second hours digit is a 1 these two high signals along with the B output on the 90 trigger the reset and clock starts over at 1:00.

please send me a copy of your circuit diagram !!

help me !!

yahoomail :: vincentgonzales372@yahoo.com

jnimes5 months ago

the list of materials is not complete...

what diode did you use?

what value of resistor if I can't buy anywhere the 331 resistor chip?

what is 503 and 205 in the picture? is 503 really a potentiometer but it looks like a ceramic resistor?

also, in the schematic you provided there is the 3 input and gate which is 74ls11 if i'm not mistaken but you didn't include it in the list...

the schem you provided is blurred, can't read the labels of each component clearly....

i hope you would reply immediately ^^ i have read other comments saying it is working and I want to make it to but there are some missing information in your post. Thanks in advance :D

rezacumi7 months ago
does it can set the clock time?
imsajid1 year ago
Sir please send me the clear circuit. I have to submit my project report ..... please Sir My Email id is: Almurshid5@gmail.com
ughani21 year ago
plz send me circuit diagram for 12 Hour TTL clock
my email
usmanghani915@gmail.com
darthneo2 years ago
Wow this is very impressive!

Can i ask how accurate your clock is with the 555 timer?
josgrg (author)  darthneo1 year ago
It is not as accurate as a real clock it loses appox. .68 sec a day which doesn't sound like much but over a large period of time say a week or a month the lose is significant.
waddaphak2 years ago
good day sir! can i have a copy of your pdf without having PRO ACCOUNT please.. ill be using it as a references in our on going project.. thanks
josgrg (author)  waddaphak1 year ago
I no longer have a copy of it. But if you do a internet search for a diagram you should find one easily.Sorry
Orion16151 year ago

Hi!
I was wondering if you could use these parts to make a simple 30 second counter that would activate something or bleep when it comes to 0, with one button to reset it while its counting...

Its for a tiny little project so the simpler the circuit, the better, and this seems like a whole lot more advanced circuit... Any ideas?

Thanks!
josgrg (author)  Orion16151 year ago
Yes, it is possible but it is not very efficient or accurate. Because the 555 is used for a 1 Hz square wave the "timing " is not as stable as it needs to be for an actual timer.I would use a RTC ( real time clock) IC for the circuit you want it would make eveything much simpler.
trialex2 years ago
Wow excellent work!

I've been mucking around with a design using TTL chips like the very useful 4026 which combines a decade counter and 7-seg decoder into one chip. Of course nothing is simple, and I think I need a transistor driver between the 4026 and the LEDs, thereby negating the "all-in-one" advantage of the 4026.

How much current does your clock draw?
chochinooo2 years ago
this was awesome..thanks much but what was the led for??..
josgrg (author)  chochinooo2 years ago
The LED indicates A.M. or P.M.
duggerpato2 years ago
I did a counter on a giant breadboard similar to this in a digital electronics class too. Fun fun.