Digital Clock Circuit Using IC 555 and IC 4026
In this post we are going to build a 12 hour – 7 segment display digital clock without any microcontroller. We will be using only basic CMOS ICs and pure logic to build the circuit, yet this circuit can be easily replicated by beginners in electronics.
We will see:
- Main Circuit Diagram.
- Pulse Generator for Digital Clock.
- IC 4026 Pin Configuration.
- IC 4017 Pin Configuration.
- IC 7408 AND Gate Pin Configuration.
- How to Set Time.
- How to Wire the Circuit Easily.
Circuit Diagram for 7 Segment Display Digital Clock:
Download high resolution image of the above circuit diagram: click here
The above circuit consists of 4 seven segment display driver IC 4026 which can display 0 to 9 on common cathode 7 segment display, one IC controls one 7 segment display. There are three IC 4017 which are decade counters, it tracks the time and reset the IC 4026’s count to “00” when the minute digit reaches 60.
There is a logic two input AND gate IC 7408 in this circuit which is used for resetting the hour digits to “00” when hour reaches “12”. The AND gate’s output goes HIGH when its two inputs are HIGH. The input for AND gate is provided by two IC 4017s (IC6 and IC7), when the clock reads 12 the pin numbers 2 and 4 of IC6 and IC7 respectively becomes HIGH and rest the IC1 and IC2 (4026s) to count “00”.
NOTE: This clock circuit will show 12:00 as 00:00 at midnight and also at noon.
The circuit needs clock signal to increment the counts, this is provided by the below circuit which outputs 1 pulse every minute.
Pulse Generator for clock circuit:
This circuit will output a short burst of pulse for every one minute which will increment the count in the main circuit. This circuit consists of two IC 4017s one of them will divide the input 1 Hz signal by 10 and another IC 4017 will divide the 10 by 6 so at the end we will get 1 pulse every minute (60 pulses).
The IC 555 is configured as Astable multivibrator whose pulse can be controlled using given 100K pre-set resistor. You have to adjust the pre-set and bring the pulse of IC 555 to 1 Hz. There are two blinking LEDs which can be inserted in between the hour and minute digits. All the circuit is power at 5V.
NOTE: The accuracy of this digital clock depends on how accurate you bring the IC 555 pulse to 1 Hz.
IC 4026 to 7 segment display connection:
You need to connect the 220 ohm resistor to each segment as shown above. Now let’s see the pin diagram of IC 4026.
IC 4026 Pin Diagram:
- Pin #1 is clock input, when we apply clock signal, the IC increments the count.
- Pin #2 is Clock Enable, when it is connected to Vcc the clocks inputs are ignored, it has to be grounded during normal operation so that counts can be incremented.
- Pin #3 is Display Enable, when it is connected to Vcc the 7 segment display lights up, grounding this pin will turn off the display but the count will be incremented internally, this can be used for power saving.
- Pin #4 is not used here.
- Pin #5 is carry out, when the count reaches 10 this pins outputs HIGH signal, this output is used for cascading another IC 4026 for 10’s place digit.
- Pin numbers 6, 7, 9, 10, 11, 12, 13 are output for 7 segment display.
- Pin # 8 is ground and pin # 16 is +5V supply.
- Pin #15 is reset, when this pin is connected HIGH the count resets to zero. This pins has to be grounded while incrementing the count.
Pin Diagram of IC 4017:
The IC 4017 is a decade counter meaning it can count up to 10. There are 10 output pins each gets high sequentially with successive input pulses. For example, when the IC is powered ON the pin #3 (Q0) gets high initially; rest of the output pins goes to LOW state, when a pulse is applied the pin #3 goes LOW and pin #2 (Q1) gets HIGH and rest of the output pins stays LOW, similarly for Q2 to Q9.
- Pin numbers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11 are output pins.
- Pin #8 is GND and pin #16 is Vcc.
- Pin #15 is reset, when this pin connects to HIGH signal the count reset to zero.
- Pin #14 is clock input.
- Pin# 13 is clock enable; when this pin is connect to Vcc the pulse will be ignored, during normal operation this pin has to be grounded.
- Pin #12 is for carry out function.
Pin diagram of IC 7408:
The IC 7408 is two input logic AND gate, it has 4 gates; we are using just one of them.
- Pin #14 is +5V and pin #7 is GND.
- Pin #1 and 2 are input and pin #3 is output, similarly for rest of the gates.
The output gets HIGH only when its two inputs are HIGH; if any one or both the inputs are LOW the output goes LOW.
How to Set Time:
You can set time using the given two push buttons, one for hours and one for minutes. You have to push and release the button for incrementing one digit, long pressing will not increment the count.
How to Wire the circuit easily:
Wiring the circuit is the tedious part of this project and connecting a single wire incorrectly can mess the project. You can wire the circuit without any mistake by finishing a bunch of wires of with same colors as shown in the schematic.
The main circuit wiring is smartly indicated with colors: Red, black, green, pink, yellow, blue and cyan (clock input). Finish any one of the colors first and move on to next, this will ensure that all the connections are done properly.
Once the main circuit connections are done; now connect the all 4 seven segment displays to four IC 4026s. If it didn’t work at first attempt don’t give up.
24 Hour Clock Design:
Here we are going to discuss 24 hour digital clock design using IC 555 and IC 4026.
I would like to thank the guy with the username “kuma” for sharing his 24 hour clock design. He not only successfully replicated 12hrs clock project but also able to modify it to 24 clock and added some useful features.
We can see that he made this clock neat as possible. We can spot a 3V coin cell which will keep track of time even after disconnecting main power, once we reconnect the supply the display will turn ON with correct time.
24 hour Clock circuit:
Readers who are interested in making 24 hour clock instead of 12 hour may follow the changes in the circuit diagram. Kuma suggested to keep all other section of the circuit same and make the mentioned changes in the wiring of IC 7408 and two IC 4026.
If you have any questions regarding this project, feel free to express in the comment section, you will get a guaranteed reply from us.
I made it and it worked perfectly after like 2 attempts. (12 hour clock)David (Reader)
further i added hourly beep buzzer/a memory cell (cr2032)/second display using led/Kuma (Reader)
limits current and voltage to 60mA,dc5v. my 1hz accuracy is very high.(1.02hz)according
to my oscilloscope.
123 thoughts on “Digital Clock Circuit Using IC 555 and IC 4026”
Hi, nice project, I would like to ask, how the circuit has to be modified if we would like to have 24h clock? Besides, if I want to use bigger 7 segment displays (more leds in 1 segment), what needs higher voltage and current, how the power adapter should to be implemented in the circuit? I know it is more complex, voltage and current has to be divided/separated, etc., but if you could give some suggestions or send an example that would be great. Thank you in advance!
We will try to update an circuit with 24hrs clock soon or later.
Can you tell me the part number of the 7 segment display. Only then I can proceed. Many readers asked about the same, but no one is tell the number or the specifications of the bigger display you guys talking about.
The display would be a 4inch 1digit red 8 segment led display KYX-40101AS (Common Cathode). Thank you.
Thanks, i will take a look.
When you use that large SSDs (KYX-40101AS), did you increase the voltage? What is the current limiting resistor you use? I have those large SSDs and they won’t work with 5V. Minimum is 9V for them. I increased the voltage to 9V but still they don’t work.
what change should have make for 24 hours clock??can u please explain me
We have to design a new circuit for 24 hr clock, modifications don’t work here.
I will try to make one publish soon 🙂
i already modified this ckt for display 24hr.and its working.
That’s fantastic… Good job.
is there any way to sent my 4017 /24hr watch project to you,
plz let me know.
You can share your circuit here in the comments, by uploading your circuit, prototype etc to google drive and share your link.
We will take it from here and update it in post.
further i added hourly beep buzzer/a memory cell (cr2032)/second display using led/
limits current and voltage to 60mA,dc5v. my 1hz accuracy is very high.(1.02hz)according
to my oscilloscope.
That great! we are gland you have done this..
You have taken this project to the next level….
kudos to you!
link to 24hr modified ckt;-
my finish project and ckt;-
lets close look;-
Thanks kuma for sharing your work, this will motivate other electronics enthusiasts / beginners to make this project or something similar.
You have done a good job of modifying 12 hrs to 24 hrs clock. You work will be published soon 🙂
Can you, please, also tell where did you connect cr2032?
Hello kuma, peace be open with you…can i have your WhatsApp no to ask your more detail about your project, I’m still study in electronic engineering and had this topic for my project, could you please be kind to guide me… I’m already stuck with this, and also not in understanding state with your circuit… please
Kuma has given enough info regarding his modification. If you guys don’t understand his schematic we will try redraw the full circuit soon.
if you have proteus project about this ,please send me
Sorry, we don’t have Proteus simulation.
hi solari, i modified this ckt for 24hr disply. if u send me ur E mail i can post the diagram to u.
Can you send me the full circuit for 24 hr clock my e mail please thanks.
this is the ckt of a 12hr watch.the full ckt. the negative lines are show in green. positive line are red. signal lines are in blue. i added display on /off switch if you guys interested in power saving. you can add push button for that part. when all 4026,3rd pin connects with positive 5v they become display on mode.and ignore the above red ic and red rectangular drawing. if you want to add 24hr part just see the ckt diagram i posted above, and modify only that particular part. if you want to add [cr2030] 3v memory cell. connect the negative side of the cell directly to ckt’s negative line. and connects cells positive side to ckt’s positive line through a IN4148 or similar one. (IN4148diode)
as forward bias the memory cell.( +side of memory cell —–|>|—– +side of the ckt) the link to full12hr ckt;-
Hi, I have a question regarding this mod, are the 3 shown ICs the same, only connection changed? Because I would get one extra IC if I compare to original design…
Trying to figure it out, thanks.
For 24 hrs clock, I think kuma did only connection changes.
Thanks. Actually those connections on the mod are add-ons, right?
I mean, on the mod, the reset line doesn’t appear to connect on the second 4026, plus the 7408-2 now connects to 7408-6 but does it still connect on 4017 (same for 7408-1 for connection to the 4017)? This part is unclear yet for me…
Yes, in the prototype some of the ICs are add-ons. The mod you are referring to kuma’s 24 hrs clock right?
Yes exactly, but I assume the 4026 are the same, as they drive the 7-segment display. For me this is alright, what is confusing is the way it alters the rest of the connections surrounding those 3 ICs… exept for Vcc and ground obviously, because taking this mod 100% takes away the connection to 4017-4 (second one, in the middle). Need to study datasheets better, eventually answering this terrible question… 😉
We will try to post full circuit diagram of 24hrs clock soon or later, this will clear everyone’s doubts.
What if we only replaced 2 connections (in blue) only:
For 4017 on the left, move connection from 2 to 4, and for the next one move connection from pin 4 to 10.
This would then become 2 high and 4 high at the 7408 input will give a high on the reset line, right?
Which circuit you are referring to? The original one?
Yes, original design with those relocated pins… seems the easiest way.
By the way, thanks for this great idea, I love those projects but don’t have knowledge for design.
There are many possible logical solutions to this digital clock, if you think your logic is feasible, just try it and let us know. 🙂 yeah, it going to be a messy wiring work.
Well I bet it can’t be as messy as the relay tester I made… 😉
Again thanks for your design, and for the challenge… for the rest my soldering iron became my mistress lately. I’ve made the display on separate pcb… will look like a (*word auto sensored*) …
i also want a 24hrs circuit diag
[Email link removed]
can u send the diagram thanks
There is a download link provided in the post.
Hi! Can this circuit be added with seconds on a seven segment display? Is it possible to switch from 12h to 24h?
Yes, seconds digits can be added with modifications. You cannot switch from 12hrs to 24hrs or vice-versa. Either you have to build 12hrs or 24hrs clock.
I made it and it worked perfectly after like 2 attempts
That’s fantastic David, good job!
Thanks for sharing your success, I will place your comment at the bottom of the post.
In which software, you drew this diagram?
We use a software called fritzing, which is free.
Will it does simulation or any other best software to simulate this project.
I tested this project practically, You can use any simulation software like Proteus or multisim etc.. I never tried to simulate this circuit in those simulators.
IC 4026 and 4017 are not available in that software?
Not in Fritzing
Fritzing is not simulation software, it is only used for drawing circuit diagrams.
You have to label and set pin number for any IC you are dealing with.
In complete circuit diagram, (the clock input 1 pulse)wire is connected with red (Vcc) in middle.
and positive side of 1N 4007 is linked with other wire in 5th pin of 4017 IC.
Both are correct or not?
Can you please explain your question again in a better way, your question is confusing.
We can help you out…
our understanding from your question is: it is not same.
how much current does it use per hour (mah)?
can you provide a full circuit diagram?
We have already provide the full circuit diagram.
i took this experiment as my course project, but i can’t simulate in proteus ?is it possibleto implement without simulation?? what should i do? the ic’s used here can’t match with the proteus ic’s configuration… im feeling disappointed, can you help me please?? only 2 days remainin….. please help me, can i talk to you in WhatsAp?? my no [Removed by Admin].
This project is tested practically, this is the only way you can implement without simulation. We never tried using any simulation software.
If you have any further question you can ask here.
why you used only 3 4017IC’s in main circuit?? All the black coloured wires connected each other in circuit?? Can i know please? can i use any alternative way to generate pulse?
The functions of IC 4017 is described in the article. All black wires are to be connected to negative terminal of the supply.
Yes, you can use any pulse generator that can output one pulse per minute.
why u used resistors with 7 segment display? which type of battery i should use as power source ??
They are current limiting resistor, without them display will get damaged. You have to supply 5V to the circuit.
From your questions what I can interpret is that you are very beginner in electronics. These projects are too advanced for you, my request is that please learn fundamentals of electronics from resistor, capacitor and inductor practically, only then any circuit diagram make sense to you.
You can ask us any further questions here.
I can’t find 100k preset potentiomete, got only 10k preset in shop, what to do now??can u please help me
Go ahead with 10K, try to make 1 sec blink.
should i use two 5V power supply or a single 5V power supply is enough for whole experimen??
Obviously single 5v supply..
After completing the connections, here what happens when I put the power on (I use 2 CR2532 or whatever, makes 6V of supply, thought it was no big deal):
LEDs comes on one time for the lenght set by variable resistor then comes off, no display ever.
My question is, I’m using 5611BH as 7-segment display wich is common-anode… there is no difference in the pinout though between 5611BH and the scheme provided in your tutorial, but could it be a display problem, appart of that non-blinking LEDs?
You cannot use common anode display in this project, IC 4026 is common cathode display driver.
Thanks, my error then but I learned there was two polarities with the display. Meanwhile the two LEDs should still flash the seconds? Looks like pretty much independent circuit, pulses would still come out the 555 timer even if not displayed on the 7-segments, it is only flashing one time after power up. Do you have a clue? I triple-checked connections, maybe couple more times then…
The LEDs can blink independent of 7 segment display. It seems like fatal wiring errors in your circuit.
But don’t give up that easily, we faced similar issues too, while we were designing this circuit we couldn’t tell whether it was a design flaw or wiring error.
Yet we succeeded.
can you tell me the connections of 3v cell to the circuit and please give me the full schematics of 12 hours clock.
in my previous project i made a 24 hours adjustable digital rtc clock using arduino uno
you can send me the schematics here [email removed]
The main circuit shown here is 12hrs clock. We will try to update circuit with 3V back up cell soon or later.
note that IN4001 diode near the minute set switch. please change that diode anode and cathode to other direction. sorry my mistake.
Hi, I have made it almost functionnal at my second attempt (first time I used common anode displays and had to remove everything, quite a mess) and as mentionned in a previous comment, moved the wires for the reset line to pin 4 on the 4017 next to 7408 then to pin 10 for the other one. Outputs should read 24 then reset.
Mine doesn’t reset, it’s like a 100h timer, wich I don’t understand yet… another bug is this switch I’m using for display, passed the continuity test but when powered, it doesn’t matter whether switch is on or off. More than that, powering on with the switch off gives a weird display, some segments are not lit where they should and starting randomly and not at 00:00.
Checked wiring everything seems good, pretty much on a dead-end actually with this non-resetting line.
its heck of a work when you try new logic in the circuit, but keep on working.
To get a guaranteed result try the original circuit.
Since everything looks ok, I checked input voltage wich dropped down to 3.2V… this could trick the counts (at 24 the 1 and the 5 were high) in the undefined area? Though usually 2V to 5.5V would be considered a High signal, what do you think?
Voltage should not drop at any part of the circuit either it should be 5V as high or 0V as Low, except at 7 seg display after resistors.
If voltage drops something went wrong or current supplied not adequate.
Why did kuma in his 12hrs circuit connect the Vcc pin of 7408 to ground or is it for adding the 3v ?
And will using 1N4001 instead of 4007 improve the freq accuracy?
Changing the diode will not improve accuracy.
Can I have the full list of the required items?
We will try to update it soon..
Hi. My circuit is working properly on proteus but minute is changing after every (1 minute 26 second) real time..
how to fix this problem can you please elaborate..
i don’t understand (100K pre set adjust for 1 Hz part) so I use 100 k resistor instead of it.
I am gland that you made the circuit work using simulation.
You should not use 100K fixed resistor in the place of a variable resistor. 100K preset is provided here to adjust the frequency of IC 555 to bring pulse generator’s output to 1 Hz.
If you use a fixed 100K resistor, you cannot make pulse generator’s output to 1 Hz and you will get delayed increment of digits like you got now.
Can u please give the list of components, I want to build this circuit as my semester project
All components necessary are mentioned in the two circuit diagrams, the main one and the pulse generator. Take a printout of the both and give it to the shopkeeper.
If I write each and every component to make a list, I could miss some components.
Hi, is it possible for you to make a video tutorial building the circuit? I am completely new to this and have no idea how to start making it.
Sorry mike, we didn’t document a video while prototyping this project.
If you are a beginner in electronics, then this is not the project to start with, try simple and smaller circuits.
The change from 12h clock to 24h could be done much more simply by detecting “4” in IC7 and “2” in IC6.
1. Blue line from IC6.2 (Q1) to IC5.1 (1A)
2. Blue line from IC7.4 (Q2) to IC5.2 (1B)
1. Blue line from IC6.4 (Q2) to IC5.1 (1A)
2. Blue line from IC7.10 (Q4) to IC5.2 (1B)
I’d like to offer a minor improvement for the 1/60 divider, the one that outputs the 1 minute pulse.
I recommend connecting the output diode to Q1 (pin 2) of the leftmost 4017 instead of the blue line.
Take a look at the leftmost 4017 that does the 1/6 operation. The blue line gets the Q6 and feeds the reset pin. Note that reset is asynchronous so one the Q6 pulse is above some threshold (probably VCC/2) it resets the counter and resets all Qs (Including Q6) ASYNCHRONOUSLY. This means that the duration that Q6 is high is unpredictable and very short. Using this signal as input to the next stage is hazardous.
I understood your concern.
The 1 min pulse generator was purposefully made to give out a pulse from Q6 (left-most 4017) that connects to reset pin 15.
The pulse duration of “high” of Q6 is constant during every reset-cycle and it is predictable.
According to IC 4017 datasheet the reset pin or any input pin needs a minimum pulse width of 250 ns (at 5V Vcc). Now the Q6 is connected to reset pin, while resetting the IC the Q6 will stay high for a minimum of 250 ns only then the IC accepts it as a reset signal.
This 250 ns (typical) signal width is enough to trigger other digital ICs in the circuit too, these ICs are designed to operate at MHz frequency (maximum) so just imagine how short the pulses would be.
We did not choose a pin that has much wider pulse output like pin 2, which will stay high for 10 seconds (for every minute) because it interfered with time setting.
For every one minute, the buttons will not respond for 10 seconds because the input pulse pin is pulled high.
Is there a PCB drawing of this circuit from the computer? Thanks .
Sorry, we don’t have PCB drawing for this project.
Hi, I have tried to make the circuit The display is running perfectly and the push button succesfully increments the number. However the clock itself is not running and the display stays stationary. Can you provide a possible solution?
It seems like there could be an issue with your 1 min pulse generator, please go ahead and debug this circuit.
Sir I have replied you about my resetting issue in the pulse generator circuit but you don’t reply.
According to your ckt the resetting is not happening.
I have replied to your previous query, didn’t reach you? Can can ask again.
Hello, is it possible to ask for an IEEE Report for this particular project? I am asked to make one for my final project. Thank you before.
Sorry, you cannot find IEEE project report for this clock project because it is proprietary of this website.
Hello, my circuit only increments the minutes up to 4 after that it stops increasing. Also the minute doesn’t reset at 59 and goes to 60+. Same goes for the hour. Please help.
That’s a strong sign of bad wiring.
Use your multimeter to check continuity of connections patiently, it could take time. Make sure your connections are firm. Loose connections could miss clock pulses.
Pls can i get the complete circuit diagram for the 24 hrs clock, i really don’t understand the diagrams as they’re all segregated from each other (not together). Will be glad if i can get it all in one piece
We will try to make a article for 24hrs clock, it could take us some time.
Sir, I have made this clock on Proteus and working fine. Now I will design this circuit on PCB. But I have to change 100k preset into 2M ohm to adjust the correct time. But I will try first 100k preset.
Sir, is it possible to add another segment for seconds. If yes, please reply with the changes that I will have to do.
Thanks in advance!
If possible could you please share your simulation file with us? (google drive link). We’ll showcase it here with your name and it will help digital clock enthusiasts, only if you wish to share.
Practically, we have tested it with 100K preset and 2M may not work as expected. Is it possible to add another segment for seconds? Very much possible, but we need to re-design the clock from the core again. If possible we’ll try to post a schematic soon or later.
did anyone made this clock on proteus or any other software please share
Some readers made did made proteus simulation, but they did not share the file with us.
Hallo sir can you please tell me how to connect alarm circuit and provide me the schematic of alarm ckt.
Currently it is not possible for us to do, may be in future……
Thanks for sharing this. I keep reading on other sites that the 555 is too unstable to use for a clock and usually they recommend a crystal oscillator instead..not true?
Crystal oscillator is the best when it comes to accuracy, but if you use IC 555 as the clock source you may need to set the correct time once in a while.
Thanks for this project, i have gone through it again and after a few adjustments, now im able to simulate it on proteus. I will upload what i did soon but presently I’m having a slight issue, Is it possible for me to add a buzzer to the circuit for hourly time beep, if yes then where do i i connect the leads of the buzzer (i know one has to go to the ground, but where will the second pin go). I tried several times but it was disturbing the clock pulse. The minutes were just incrementing without control. Any solution to the buzzer issue?
The hourly buzzer is possible, we will try to do in our next update.
In short, you need a mono-stable multivibrator connected to a buzzer and you need find a correct trigger point i.e. a point in the circuit where a pulse will be generated every hour. The time period of the mono-stable multivibrator determine how long the buzzer will beep.
If possible please, share a link (in comments) of google drive of your simulation, I will update it on the article, this will help other readers and your name will be published too.
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Does this work like a clock? If you start or connect it to a source it automatically counts from 00:00 – 11:59?
Can someone send me its schematic diagram?
hello, can I put am and pm led indicators for the 12 hours
Hi, we will try to implement AM/PM indicator in near future.
i have tried to make 1 pulse/min generator circuit for 12 hrs clock circuit multiple times but every time when i am checking the output of it by adding a multimeter or led with the pin no. 5 of first ic 4017 i can’t get any voltage . So i can’t add it with the main circuit.
I think there may have a problem with the connection between the 5 no pin of the first ic 4017(1 pulse/min output pin )and it’s RST pin.
please give me a genuine circuit or reply me where i have done any mistakes.
Hi, sorry for the delayed reply.
You cannot see the pulse because the signal lasts only few nano seconds, you can capture it on a oscilloscope.
To confirm your if your circuit works, test it with the main circuit. Additionally you can check if any pulse is going to pin 14, if there is pulse then everything is working fine.
If I connect big display by this circuit so power will be increase