I am trying to design a circuit that has two LEDs (red and green) at the output plus a buzzer and two push button switches (one for each LED). Normally the green LED should stay on. When i press the red push button switch the green LED should go off and red the LED should light up. If the red LED stays on for more than 45s, the buzzer should beep. To silent the buzzer i should use the red push button, pressing which should not turn off the red LED. The buzzer should beep again after 45s if the red LED is on. when green push button is pressed, the green LED should light up and red LED should turn OFF and the buzzer should get deactivated.....

need help, pls

 

Do a search for "Brozids", he is a user I helped develop pretty much exactly what you are looking for.

There is a new version going on, where it can be programmed between 1 to 16 minutes with 4 switches.

When I have more time I will get back with you. Until then, here is the project it is based on...

555 Monostable

 

This sounds a lot like something Dr. Pavlov would devise...

Details? (just curious, it's like a Simon game but with 2 colors)

 

Actually I misread the OPs post, it is a fairly unique but doable project. Before I put pixel to screen I'll need to see him come back, as opposed to hit and run.

 

It would be a heck of a lot easier to do this with a microcontroller like a PIC. Unless you really need to use 555s for some reason.

This sounds like a homework assignment.

 

We both suffer from the "If all you have is a hammer, then everything starts looking like a nail" syndrome, but on different sides of the fence! It is only easier for PIC if you know how to how to use them to begin with, otherwise it is a mountain of a learning curve.

I'm waiting for the OP to return myself.

 

We both suffer from the "If all you have is a hammer, then everything starts looking like a nail" syndrome, but on different sides of the fence! It is only easier for PIC if you know how to how to use them to begin with, otherwise it is a mountain of a learning curve.

I'm waiting for the OP to return myself.

But nothing like the present to learn!

Yep I could do this project in about an hour with a PIC. But a 555 timer and logic I might be spending a few days to figure it out


Moot though. Looks like another hit and run as suspected.

 

i am a beginner for PIC as well. which PIC should i use for this project? is PIC16F84 is OK? how can i choose the right PIC?

 

U can chose PIC by counting ur IO's.

Means how many inputs and how many outputs you want.
that is one point to note when choosing a pic.

By the way...where are u from?

 

i am a beginner for PIC as well. which PIC should i use for this project? is PIC16F84 is OK? how can i choose the right PIC?

16F628A more than fulfills your needs at $1.71 each. There are tons of demo programs out there for that PIC due to how common it is, and with the features it offers. Find some source code for a timer with button inputs and strip it down to what you want, or start from scratch. For people new to programming, it's often easier to get a known working program similar to what they are trying to do, then cut out parts they aren't using instead of writing one from scratch.

Build it on perf board, use the ICSP (In Circuit Serial Programming) diagram in the datasheet to connect the programmer to headers, it's just 3 wires to the IC + power and ground.

You would need to get a PICKit 2 programmer/debugger to program it, one time fee of $35.

MPLAB - Free from Microchip for assembly language programming, which is about as fun and easy as moving over broken glass using only your eyelids to pull you along. Purists will say assembly is easy and the best way, that's just because they've already made it across the glass, and like watching others suffer in the same way.
C compiler - Free. I use sourceboost C, others here use MikroC Both offer free versions that are very generous with lack of limitations other than code size. HiTech is free demo, but limiting as well. Most of the code

 

i am a beginner for PIC as well. which PIC should i use for this project? is PIC16F84 is OK? how can i choose the right PIC?

You are back! Great!

The PIC that you want is one that I have on hand. So I can help you easily.

But seriously, pretty much anything will do as long as it has enough inputs. I use the 18F series because they are optimized for C and make coding just a bit easier.

Get your programmer, a simple sample program and then post back in the Embedded Forum with more questions.