# help with my project

#### Amr Samy

Joined Dec 19, 2019
3
I am required to design a digital timer that has 4 digit , two of them for seconds and the other is for minutes .When you reach 59, in the next clock cycle the minutes are augmented by one and the seconds resets to 0, and restarts counting.
you will need following components:
7447 BCD to seven segment decoder (with inverted outputs)
Common anode 7-segment display
350 Ω resistors
Male-Male Jumper wires
5V supply (or battery). You can use a 9V battery and a voltage divider
555 Timer IC
can some one explain what should i do step by step as i am beginner?

#### dl324

Joined Mar 30, 2015
10,003
Welcome to AAC and thank you for posting in the correct forum.
can some one explain what should i do step by step as i am beginner?
For school work, we can only offer guidance. You need to show your best effort so we can see where you're having problems and guide you to a solution.

The rate of progress will largely depend on you. When is this assignment due?

#### Amr Samy

Joined Dec 19, 2019
3
Welcome to AAC and thank you for posting in the correct forum.

For school work, we can only offer guidance. You need to show your best effort so we can see where you're having problems and guide you to a solution.

The rate of progress will largely depend on you. When is this assignment due?
i should finish this project by 25\1\2020. but the problem is that we didn't learn how to implement logic circuits in lectures. i definitely have no practical knowledge.

#### dl324

Joined Mar 30, 2015
10,003
but the problem is that we didn't learn how to implement logic circuits in lectures. i definitely have no practical knowledge.
Instructors rarely give assignments that they know students won't be able to complete. Design the counters using the material you've covered in class and we can go from there.

Start with the easy part. Design the 555 circuit that will give you your 1 second timebase.

Then design the seconds (S1) counter. When you have it working, work on the 10's of seconds (S10) counter.

If you don't have the parts on hand, we can do a paper design, but you might find it more useful to actually breadboard the circuits.

#### Dodgydave

Joined Jun 22, 2012
8,815
Here is a diagram from the internet for one segment, you need to add 3 more using the count out pin and reset the seconds counters on 59 /00..

#### dl324

Joined Mar 30, 2015
10,003
i definitely have no practical knowledge.
Have you been able to wire the least significant seconds digit with the huge hint you were given?

#### Amr Samy

Joined Dec 19, 2019
3
Have you been able to wire the least significant seconds digit with the huge hint you were given?
I have been able to design 1 digit timer , but i have questions:
do i need to use three more 555 timer ICs and change output frequency for each one?
how could i reset when it reach 59 ?

#### djsfantasi

Joined Apr 11, 2010
6,145
I have been able to design 1 digit timer , but i have questions:
do i need to use three more 555 timer ICs and change output frequency for each one?
how could i reset when it reach 59 ?
Why do you think you might need three more timer ICs? Can you think of any way where you may not need three more ICs?

What happens when the first digit reaches nine?

#### MrChips

Joined Oct 2, 2009
20,215
Suppose that you did design the project with three 555-timer circuits.
What would be the frequency of the first, second, and third 555-timer?
How would you ensure that the timer frequencies were kept at the exact ratios?
How would you ensure that the timers were running exactly in phase with each other?

#### dl324

Joined Mar 30, 2015
10,003
I have been able to design 1 digit timer
but i have questions:
do i need to use three more 555 timer ICs and change output frequency for each one?
That's one way, but I doubt that that's what your instructor had in mind. If you have doubts about what is required of you, ask your instructor for clarification.
how could i reset when it reach 59 ?
Read the datasheet to understand the capabilities the counter offers.

#### djsfantasi

Joined Apr 11, 2010
6,145
Read the datasheet to understand the capabilities the counter offers.
I can’t emphasize what @dl324 said in his post. Given a datasheet, almost any question you have is answered. Like how to connect multiple counters... how to stop counting... and others.