University Project using 74xx ic's and timers.

[appleseed]

Hello i would like some help on finding a project that fits the title's description.
Some examples are: countdown timer, frequency meter (sychnometer) etc. The thing is that projects that have been done in the past are not acceptable. I spent two days trying to find something on google but i cant say i did. Anyway, usage of 8-10 74xx chips is suggested.
Any ideas at all...?

 

[appleseed]

**broken link removed**

this is the circuit i'm thinking of "designing". i just dont get 1-2 things about it so i need your help.

This circuit will divide the frequency of a TTL compatible square wave signal

says the description, but i dont get how can one make a TTL compatible square signal? do i have to use a decoder on the generator input? or something like that?
Another thing i dont get is why the division ratio in this example is 569. Oh and one last thing is, if u look at the schematic, you'll see that in all three 7490's there are two pins that are not connected.(For example look at IC3, what happens to pins 11 and 9?


thanks in advance..

 

[hjames]

says the description, but i dont get how can one make a TTL compatible square signal? do i have to use a decoder on the generator input? or something like that?

Read up on TTL thresholds and voltage ranges.

Another thing i dont get is why the division ratio in this example is 569. Oh and one last thing is, if u look at the schematic, you'll see that in all three 7490's there are two pins that are not connected.(For example look at IC3, what happens to pins 11 and 9?
thanks in advance..

Do you know how to read binary? What "values" of the connected pins?

 

[appleseed]

yeah sorry i get it. but why do i need to use counters?

 

[JimB]

For a project which is a bit different, try this:

https://www.electro-tech-online.com/threads/countdown-circuit-with-warning-beeps.22955/

JimB

 

[appleseed]

can someone please explain to me how the division works using this circuit? i mean, why is the number divided by connecting the exits that form the number 569 to a NAND gate? what happens to the actual measurement?
anyone..

 

[Hero999]

Looks like someone hasn't been paying attention in class.

 

[appleseed]

really helpful, man.
i appreciate it.

 

[Hero999]

I don't mean to be rude but this sounds like coursework to me and we're not doing it for you.

You ask about devision, in what respect, frequency? numerical? The former is easy but the later is quite complex, I wouldn't recommend doing it with simple logic gates.

 

[appleseed]

**broken link removed**


the kind of division shown above. and the thing is that my time is running out and i need some help. i dont need you to do it for me, i just need some help

 

[Hero999]

That link doesn't work.

I take it you're talking about a counter, there are ICs that will easilly do this, some will even allow you to set the number it counts up to before resetting. I don't mind helping you if you show us that you know where to start, but (as I've said I won't do all the work for you). Do you have a basic plan or action, what frequency is your input and what do you want to dirve?