This is our schematic diagram that we are trying to do. It should count down from 5 to 0 and we ran it in proteus and it works. The only problem we have left is that the seven segment diode doesnt show the correct number of counting. We inserted LEDs for each output of the JK flip flops to know if the signal being sent to decoder is correct and it is correct. We dont know why it doesnt show correctly in the 7-segment.

We used arduino (5V) as the power source and also for the clock signal. When I try to measure the voltage that enters the decoder it is around 3V left, u think this is the problem? How can we solve this?

 

You have three input pins on your 7448 that are not connected in your diagram. How are they connected in your actual circuit?

If the answer is that they aren't, then that is very possibly your problem. Never leave inputs unconnected unless they are specifically specified as being suitable to leave floating.

Which family of parts are you using? 74HC, 74LS, 74somethingelse?

Are all of the parts from the same family?

 

You have three input pins on your 7448 that are not connected in your diagram. How are they connected in your actual circuit?

If the answer is that they aren't, then that is very possibly your problem. Never leave inputs unconnected unless they are specifically specified as being suitable to leave floating.

Which family of parts are you using? 74HC, 74LS, 74somethingelse?

Are all of the parts from the same family?

When we ran it in proteus it works just fine so we didnt think of using the three floating connection. Can I ask if you have an idea where we can connect it?

We are using 74LS

 

The three inputs are active LOW as indicated by the bubble in the diagram. Hence you need to connect them to logic HIGH to disable those functions.

 

When we ran it in proteus it works just fine so we didnt think of using the three floating connection. Can I ask if you have an idea where we can connect it?

We are using 74LS

Never rely on simulators to properly deal with floating inputs (again, unless the datasheet makes it clear that this is acceptable).

On CMOS parts (such as the 74HC family) leaving inputs unconnected can physically destroy the chip if they float to an intermediate level that results in both the pull-up and pull-down transistors being turned on (a condition known as "shoot-through").

On TTL families, including 74LS, unconnected inputs are generally pulled high as a consequence of the way the input circuits are designed. But this is a very weak pullup and shouldn't be counted on for proper operation.

A bigger problem for you might be your power supply for your 74LS parts. They are intended to operate from a 5 V (±5%) supply, so if you are powering them from 3 V. there is no way to predict how they will behave.

As for what you should tie those specific inputs to, instead of just telling you, I'm going to refer you to the datasheet for that part -- you need to get used to examining datasheets to find out how to interface to the chips you use, so this should be a pretty easy foray into that. Go look, and if you can't figure it out, come back and ask specific questions about what's not clear and we'll try to help you understand it and, more to the point, how to properly interpret the information provided in the data sheet.

 

Is the 7-segment display component common cathode as shown or did a common anode get slipped in?