Plzzzz help me its urgent... i need to design this circuit on multisim. See the attachment

 

There are marks on each question so I guess this should belong to the homework section.

What have you done so far? Have you chosen the chips to be used like counters and 7 segment decoders. Are you 7 segment LED common anode or cathode?

BTW, I dont use multisim. I only use proteus. Is that OK?

Allen

 

I don't know where to start.Our lecturer has asked us to use these specifications:
Set-down transformer+full bridge rectifier
2 key space(reset+pause)
4N38(used to stimulate LDR)
one 555 timer
one 74LS157D
one74LS48N
one 74LS139N
four LED Display.
he didn't precise about the LED...
Proteus is ok. I will do it again on multisim

 

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Mod note: Duplicate question

 

A good place to start is to make your best effort then post a schematic. If you search the AAC forums, you will find many threads using these parts in similar applications. If you google the part numbers, lots of circuits pop up. Another good approach is to consult the datasheets for your parts and look at sample circuits.

Note that all of these approaches are to give you ideas on how to proceed. Don't expect to find a complete circuit that satisfies all of your particular requirements or expect someone here (or anywhere) to design your project for you. That's up to you.
Good luck and welcome aboard.

Mod note: @Yoshinee2708 and @Hans Chamroo are teammates working on the same project.

 

74LS157D is 2-1 mux in SMD.
74LS139N is 2-4 decoder.
74LS48N is 7 segment LED decoder.

But you are not given any counters to do your timer design and I think that's odd. Well then, I'll just start with the 74LS48 and one LED display and make that working first. Then I'll make the 1 Hz pulse using the 555 timer chip.



Allen

[PS] I dont put resistors to limit the LED current in the SIM, but you have to add resistors 330 Ω in real Hardware.

 

Here's a basic 555 timer circuit that will give you a pot-adjustable output that you can process with a counter to produce the display that you are after:
https://www.systemvision.com/design/one-second-555-timer

 

Thank you Allen. I will Try to reproduce and find those components in ,multisim.

Darrel, thank you.

I got a question for both of you.
The 555 timer timer should operate at what frequency, and how will the timer stop at 59m59s?

I have made some research work on it, but i still did not understand it!

From Hans and Yoshinee.

 

I got a question for both of you.
The 555 timer timer should operate at what frequency, and how will the timer stop at 59m59s?

The frequency of the 555 is mentioned in post #6.

How to stop the timer when it reaches 59M59S is easy. Just use a NAND or AND gate like the attached...

Allen

 

Thank you allen.

I have been working on it for long and finally i was able to realise it.
Instead of a multiplexer, i have use a decade counter and it work well.

For now it am working on the transformer, full wave bridge rectifier with capacitor filter.
It is not an easy task to power the circuit, the display blinks with the voltage drop when lighting the cuicuit.

 

What size is your transformer? What about your capacitor?

Here's a circuit that has roughly the right sizes to convert from 230V AC to 9V DC:
https://www.systemvision.com/design/bridge-rectifier-230-v-ac

 

For now it is working on the transformer, full wave bridge rectifier with capacitor filter.
It is not an easy task to power the circuit, the display blinks with the voltage drop when lighting the cuicuit.

Is the circuit working on 5V?
What is the output voltage of the transformer after the rectifiers?
Could it be your transformer is under-capacity (too small for the job)?

Allen