# DIGITAL CLOCK

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#### Hasan Nahid

##### New Member
CAN ANYONE PROVIDE ME A FULL CIRCUIT DIAGRAM FOR MAKING A DIGITAL CLOCK USING 555 TIMER ? THANKS

#### Pommie

##### Well-Known Member
That is a really bad idea.

Mike.

#### Hasan Nahid

##### New Member
OKAY! I NEED TO SHOW HOUR MINUTE AND SECONDS . WHAT WILL BE THE EASIEST WAY TO DO THIS?

#### alec_t

##### Well-Known Member
Using all CAPITALS is regarded as shouting. Please don't do it.
Is this a school/college assignment?

#### JLNY

##### Active Member
To answer the question, there are several ways of doing it:

1. Gang together binary counter ICs and connect the outputs to 7-segment driver ICs to drive leds for the digits. You will need to set the counters to reset at the appropriate numbers (e.g. 60, 60, 12/24). driving this from a 555 timer would be problematic because 555 timers rely on a very simple RC timing circuit that is not very frequency accurate and won't be stable over time.

2. Use a crystal oscillator and divide it down to 1 Hz to drive the same arrangement as above. Typically, one would select a crystal with a frequency that is divisible by a power of 2, such as 32.768 kHz (2^15 = 32768 Hz), and use binary counters to divide the frequency down.

3. Use a microcontroller with a crystal for the clock reference and multiplex the outputs to drive the 7-segment displays. The frequency accuracy of this method will depend on the way in which the program is coded. There are probably a zillion tutorials on how to do this online, so I won't go into detail here.

4. Use a microcontroller with an external RTC IC to keep track of the time, and use the microcontroller to multiplex the data to the segment displays. Typically one can get RTC ICs that can communicate with the microcontroller via a serial protocol such as SPI or I2C. Using an external circuit to keep track of the time eliminates the need for precise timing in the code.

5. ebay

#### schmitt trigger

##### Well-Known Member
I've built several clocks using all the methods described above, and in times of money, effort and performance, I would suggest #4 for a DIY project.

There are also standalone ICs. National Semi used to offer them. They have been obsolete now for a while but may still be found online.

More modern and inexpensive table clocks utilize Chinese-designed ASICs. One only adds the display and some passive components.

But if you don't have the time or expertise to design a clock from scratch, then a simple kit from Ebay would do.

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#### Hasan Nahid

##### New Member
This is a project for my class. I need to build the circuit and demonstrate it showing hour , minutes and second and the date if possible .
If anyone can help me with required schematic diagram of this would be much appreciated.
using microcontroller is not allowed .

#### alec_t

##### Well-Known Member
Is it a condition of your assignment that you must use a 555?

no .

#### Nigel Goodwin

##### Super Moderator
Just search on google, there are numerous old circuits out there - 40 years ago such things were common projects, but not using a 555 as that would be a really poor clock.