newbie logic

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jon_jon_phenomenon said:
hi i am designing a logic circuit and i want to make an output go from 0 to 1 to 0 at the press of a button

any ideas?

thanks
Click to expand...

You mean you want to generate a short positive pulse in response to a button press?. There are a number of ways to do this, but essentially it's called a monostable circuit - a 555 can do it, as can various configurations of logic gates.
 
Debounce circuits were discussed in this forum some weeks ago. I suggest you search on "debounce" or search for my posts as I made a contribution.

Len
 
555 monostable

thanks for the replies

ok, a 555 monostable is getting closer,but i really want the input to change from 0 to 1 , so that it can only be activated once, instead of a push switch

any way of modifying the circuit in the attachment?

my apologies if i was a bit vague earlier
 

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  • 555.jpg
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Re: 555 monostable


It's still just as vague :lol:

You said originally that you wanted 0-1-0, now you say 0-1.

Which is it?.
 
Re: logic

jon_jon_phenomenon said:
oops

i want the input to go from 0 to 1 (im using an SR latch for this)

the output from 0 to 1 to 0

hope its clearer now
Click to expand...

No, I'm afraid not :lol:

At a guess, I'd presume you want a single button press to generate a short positive pulse, but only once - after been pressed once it won't work again (until reset in some way).

How about telling us exactly what you are trying to do?.
 
logic

ok

in the pic here , each time a button is pressed a led comes on.
the 1st press is green, 2nd - red , 3rd - green again, pressing them in any order should follow this pattern

however pressing a button more than once, causes the counter at the top to count another step, which could cause the 'other' led to turn on.. (both undesired)

so i need something to stop each button having any further effect after being pushed once
 

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  • count3a.jpg
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logic

ive tried this way using an SR latch, (just on the 1st switch) and some gates

because when 1 led comes on , then the NOT Q outputs at B and C must be different

but theres a problem with the counter - after the button press , the logic at D stays at 1. thats why i wanted '0 to 1 to 0' to go in at D

any better?
 

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  • count9a.jpg
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Re: logic


Yes, it makes sense now - but it didn't on it's own :lol:

As usual, I'm going to suggest a PIC to do it - a PIC 16F628, the switches, LED's and series resistors are all that's required. It would drastically reduce your component count and enable you to do anything you wanted with the buttons.
 
A PIC is a wonderful device :lol:

It's basically a complete computer on a single chip, you program it to do what you want - essentially becoming a custom chip for your design.

Have a look at the tutorials in my signature, they will give you some idea of what you can do with them.
 
have a look at state machines.

the best pace to start on a design like this is to draw a flow chart. and have a good look at wha tyou need and what parts of the circuit will be repeated.
 
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