URGENT ... bicolor LED help

[noname06]

hi, i need to do a project about sequential circuit but i don't have any idea how to do. The question is when i turn on the switch, all 3 bicolor LED willl turn red. After a few seconds it will turn off one by one. When all the lights are off the 3 LED will turn green and a buzzer will ring. Any suggestion?

 

[Boncuk]

You might use a timer circuit (NE555) wired as astable oscillator to feed into a decimal counter (CD4017)

Connect the red anodes of the bicolor LEDs via a diode network to the counter output.

With each clock cycle turn off one LED after the other.

When count reaches 10 only the green anodes should connect to the diode network and count should be inhibited (pin13 of the counter to Q10).

Also connect your "self contained" buzzer to that output.

Boncuk

 

[noname06]

how do i turn off one LED at a time..i'm stuck at this part...is there anyway if i do not wan2 use ic..can anyone help me with the circuit diagram?

 

[Boncuk]

I'm afraid you have to develop an IC that does the required job.

As far as I'm concerned it takes three ICs to achieve the goal.

Boncuk

 

[noname06]

if i use an ic how should i connect the whole circuit? i'm new in electronic and dun really know much bout it

 

[blueroomelectronics]

I suggest you start with something simple. Flashing an LED with a 555 might be a good place to start.

 

[noname06]

i wish to but this is my assignment...i need to get that output using 3 bicolor LED

 

[Boncuk]

If it's your assignment then you should not request to be served on a silver platter for you.

Looking into microprocessors the hardware should not be difficult and your project would get along with one IC and a few transistors.

 

[ronsimpson]

NoName, Start off by getting a clear picture of what you need to do.
I think you need 5 states.
1). RED, RED, RED,
2). RED, RED
3). RED
4). no led on
5). GREEN*3+BUZZER (hold in this state)
Is this what you want?

Look at the IC CD4017.

 

[noname06]

yes that is wat i wan...i just do not know how to draw the circuit...

 

[blueroomelectronics]

What sort of school would assign you this without the basics first?

 

[ronsimpson]

You need a time base. A clock.
Find the data sheet for a LM555. Pick an example circuit. Change the R and C so you get a clock rate of 0.5hz.
If you can do that with little help then we can move on to the next step.

 

[Boncuk]

Hi noname,

here is my circuit design.

It uses a total of three ICs and five transistors. You might skip the LED driver transistors, resulting in very dim LEDs and no buzzer operation.

The buzzer must be self contained, meaning it must have its own oscillator circuit built in.

Circuit description: IC3 (CD4017) is reset during power up, thus activating Q0 to have the red LEDs D7 through D9 lit.

When pressing the momentary switch S1 the monostable oscillator is activated for 5 seconds resetting IC via T1 at pin4, resulting in no clock pulses to be fed into IC3 (pin14)

After IC1 has timed out IC2 generates pulses (adjustable from 5 to 10Hz using P1) keeping the red LEDs lit for four clock cycles. The fourth clock cycle disables D7, the sixth clock cycle disables D8 and the 6th clock cycle disables D9. The 8th clock cycle finally disables all red LEDs and switches on D7 through D9 green LEDs and simultaneously powers the buzzer.

This condition will hold until S1 is pressed again or S2 (RESET) is pressed. If S2 is pressed the count down will restart, omitting 5 seconds delay to turn off the red LEDs.

The board is purely single sided and measures 99.35X72.35mm (3.91X2.85").

If you want to obtain the Eagle files please PM me your full name and email address.

Boncuk

P.S. Increasing C3 from 1 to 10µF the clock frequency can be varied between 0.449 and 1.192Hz.