Frequency counter 3 Seven segment displays

[Rhys Cooper]

Hello

Have to design and build a frequency counter for little project. Have a good grasp on the fundamentals but am so stuck on making this. I have made a multisim simulation of what I thought would work after much research, but it doesn't.



When I simulate it, the displays don't display anything. If anyone know where I have gone wrong would appreciate the feedback. Or if I am in the totally wrong ball park some guidance would be great!

Many thanks
Rhys

 

[Vbase]

The pic of your circuit is too small to be read.

 

[BradtheRad]

I open your image by dragging it to a graphics editor.

Have you tried operating each component by itself, to make sure it works the way you expect? (For instance, can you get any number to appear on one of the displays?)

The columns of IC's must get the correct sequence of gate signals, in the correct polarity. The counter, the latch, the decoder. Not necessarily in that order.

 

[chuckey]

If the display do not show anything, then they must be short of Vcc or connection to earth. If they were wired correctly then the drivers can't be wired correctly, else they would show a series of 0s.
Frank

 

[Audioguru]

The schematic that is covered with dots shows old TTL ICs that are not powered.

 

[Rhys Cooper]

Managed to work out why the displays were not working.

The 74LS47D needed pins 3, 4, 5 connected to vcc +5v.

However now the frequency meter is working with a display, the set frequency on IN A to measure is displayed on the display. But then after another cycle it adds the frequency value on top of the current value so its essentially counting up 450 each time.

Does anyone know how to wire it so that it just keeps the value of the frequency input and only changes if the frequency input changes and changes to the new value?

Many thanks
Rhys

 

[Rhys Cooper]

managed to get it work a little better by making R01 high, and R92 low. In a hope it would maybe latch and hold the frequency input and then refresh after a set interval which it has.
But I am only getting 99% of the actual number due to the duty cycle of the frequency input which I dont quite understand. So if anyone has any info on this it would be greatly received



Many thanks
Rhys

 

[KlausST]

Hi,

you have a gating with a 1Hz frequency and 1% duty cycle --> 99% of 1s is counting. Your measurement window is 990ms.

change frequency to 0.99Hz.
giving 1.0101s * 0.99 = 1.000s

Klaus

 

[Rhys Cooper]

Thanks, that has sorted that bit out. I was hoping that it work instantaneous, such as if the frequency changed at source the display would show it changed right away. But it takes about 20 seconds for it to then change at the display if I change the input frequency. Is this a wiring problem, or just software related issue?

Many thanks
Rhys

 

[KlausST]

HI,

you could start a timing analysis on this.

But most likely it is not "real time" so the delay is from software.

Klaus

 

[Rhys Cooper]

I think its the software as well so gonna go ahead and build it on a breadboard, and do some real tests on it. Hopefully it works, thanks for all the help everyone