How to manage logic gates with pulses?

[daipapagaya]

For example, using a momentary push button (normally off), 3 led and the logic gates needed, how can i do this?.

- 1st pulse. If all leds are off, turn on the first.
- 2nd pulse. If led 1 is on, turn on 2 and 3.
- 3rd push. If all leds are on, turn off all.

Of course, logic gates must be maintained in position between pulses.

I know how to do this using static switches, so there is always tension, but with momentary the logic of the circuit dissapears after the first pulse .... Any ideas?.

thanks

 

[carbonzit]

At least two ways to do this:

1. 3 flip-flops
2. Binary counter that resets after 3rd bit set (0--> 1--> 2--> 0--> 1--> 2--> ...)

 

[crutschow]

Since you have three states you could do it with two flip-flops.

 

[carbonzit]

How can you get three states out of two flip-flops? There are only two outputs (unless you count the Q-bar ones, which are only the inverse of the Q outputs).

Either this won't work or I'm missing something obvious here ...

 

[BrownOut]

How can you get three states out of two flip-flops?

You can get up to 4 states from two flip-flops.

1 - 00
2 - 01
3 - 10
4 - 11

 

[carbonzit]

Four sequential states? How?

 

[crutschow]

Four sequential states? How?

Look at BrownOut's sequence. It's a binary sequence of the two FF outputs. Two bits give you four states. You hook the two FFs up as a 2-bit counter to get the four states.

Edit: For the op's requirement you would configure the FFs to count states 1, 2, and 4, skipping state 3. (See attached)

 

[carbonzit]

Look at BrownOut's sequence. It's a binary sequence of the two FF outputs. Two bits give you four states. You hook the two FFs up as a 2-bit counter to get the four states.

Edit: For the op's requirement you would configure the FFs to count states 1, 2, and 4, skipping state 3. (See attached)
**broken link removed**

So you'd need an AND gate to generate state 4, correct?
And how do you get the FFs to skip state 3?

Just saw your attachment and am studying it. I see you're using J-K FFs.

 

[crutschow]

Yes, I just added the attachment. J-K FFs are easier then D FFs for this type of circuit since they require less (no) external gating.

Edit: No, you don't need any external gates for 4 states either. See the attached for a 2-bit, 4-state counter configuration of the two FFs