Electronic Toggle switch

T

thecritic

Member

• Dec 14, 2009

• #1

I have a push button and two LEDs (red and blue).
I want them to be assembelled such that
1. When I press the push button, one of the LED is turned on and glows. It stops after I release the button.
2. When I press the push button again, another LED is turned on. It also stops after I release the button.
3. Repeat 2.

Here is a pic for help.

I think I need to use things such as Flip-flop, But I don't know how to use them. Any help will be greatly appriciated.

 

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T

thecritic

Member

• Dec 15, 2009

• #2

I think, my question was too much confusing.
What I am basically asking is --> how to make a single push button turn on two different LEDs turn by turn?

 

K

KMoffett

Well-Known Member

• Dec 15, 2009

• #3

Toggle Flip-Flop Tutorial & Circuits - Flip Flop Tutorials - Electronic Hobby Projects Just a D-Flip Flop with the /Q fed back to the D input. You will need to denounce the clock input or the FF will toggle with each bounce as the switch closes.

Ken

 

T

thecritic

Member

• Dec 16, 2009

• #4

After spending much time on learning about flip-flops, one question has stilled remained an answered to me-->
How do I create a clock signal??? Does pressing a momentary switch simulate the clock signal?

 

K

KMoffett

Well-Known Member

• Dec 16, 2009

• #5

The "clock" is just a switch closure in your case. It either pulls the clock input high then low, oo low and then high, depending on the particular flip flop logic or chip. Mechanical switches actually bounce open and closed several times, very quickly as they close. To prevent this from toggling you FF several times you add a "debounce" circuit to your switch: How to debounce a switch

Ken

 

T

thecritic

Member

• Dec 16, 2009

• #6

I set J=k=1 (i.e. Applied Vcc to both J and K pins) and I used a momentary switch to send a + signal (Vcc) to clock (Cp) pin for a short time.
But the problem is that the Q and Q' pin never toggled state. It was always Q=0 and Q' = 1. Where am I getting wrong?

 

K

KMoffett

Well-Known Member

• Dec 16, 2009

• #7

Sounds like it should work. what chip are you using?

Ken

 

T

thecritic

Member

• Dec 16, 2009

• #8

I am using 74HC73.

 

T

thecritic

Member

• Dec 16, 2009

• #9

The chip's datasheet says its negative edge triggered.

 

K

KMoffett

Well-Known Member

• Dec 16, 2009

• #10

It should have toggle when you lifted you finger off the button.

Can you provide a schematic of how you hooked it up? Unused inputs need to tied appropriately to +5 or ground.

Ken

 

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T

thecritic

Member

• Dec 16, 2009

• #11

I had been using almost the same cicuit you provided but leaving the unused pin vaccant. I also didn't use the Capacitor and Resistor.

(see some modification)

 

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T

thecritic

Member

• Dec 16, 2009

• #12

KMoffett, I tried what you told and it worked!!! Thanks a lot.

(At first I was quite lazy to tie unused pin of the unused FF2 to +5 Volts. But it didn't work. So, finally I gave a last try by connecting all of the unused pins to +5 volts or GND (except outputs). And my last try paid me off.)

 

K

KMoffett

Well-Known Member

• Dec 16, 2009

• #13

Leaving inputs floating on CMOS ICs can cause all kinds of unexpected results. Pullup or pulldown resistors assure the inputs maintain their

 

T

thecritic

Member

• Dec 17, 2009

• #14

The circuit you provided is triggered on push. How can I modify it to be triggered on release???

 

K

KMoffett

Well-Known Member

• Dec 17, 2009

• #15

I think that this will work. Note that the switch is a "normally-closed" pushbutton, where the original was a "normally-open".

Ken

 

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T

thecritic

Member

• Dec 17, 2009

• #16

I am sorry but I needed to use push to make switch. (Actually, I will be using a +5 Volt pulse that comes from another circuit. I want this circuit to be triggered on the end of the pulse)

 

K

KMoffett

Well-Known Member

• Dec 17, 2009

• #17

thecritic said:

I am sorry but I needed to use push to make switch. (Actually, I will be using a +5 Volt pulse that comes from another circuit. I want this circuit to be triggered on the end of the pulse)

Click to expand...

You need to spell out out all your specifications when you request a circuit.

Ken

 

Boncuk

New Member

• Dec 19, 2009

• #18

thecritic said:

I am sorry but I needed to use push to make switch. (Actually, I will be using a +5 Volt pulse that comes from another circuit. I want this circuit to be triggered on the end of the pulse)

Click to expand...

Tell the forum when you have made up your mind.

You have more than three possibities:

1. Push to make on positive edge
2. Release to make on positive edge
3. Push to make on negative edge
4. Release to make on negative edge
5. Make your wife jump on the switch (result uncertain)
6. Forget it.

That's what I mean torturing forum members with unborn solution findings.

This is no place for quizzes or riddles!

Just keep in mind what it would cost you ordering an electronic designer with your nebulous and/or/perhaps on monday logic!

Boncuk

 

T

thecritic

Member

• Dec 19, 2009

• #19

I am extremely sorry for appearing so ignorant.
No more questions, no more torture.
Sorry and Bye.