555 timer countdown

[admeech29]

Is there anyways I can make a 555 timer countdown from a number that I choose than fire a switch after so long. Or is better just to use a pic?

Thank you,
Adam

 

[HarveyH42]

A microcontroller would be a much simpler/cheaper solution if you have the programmer and can write the program. With the 555, you'll need a presetable up/down counter, another chip to convert the count to your display, and something to drive the display. You would also need to decide how you want to set the inital count. There are likely several of these count down timers on the web, cheap ones at Walmart .

 

[justDIY]

to calm our nerves, please disclaim that you aren't building an IED

 

[admeech29]

I am not building and IED. I don't want to just buy a countdown. I can use PIC but I don't know how. Also I wouldn't mind using a 7 segment display. But where do I buy pic's. I want to also be able to program the time into whenever I want to.
Thank you,
Adam

 

[HarveyH42]

Yeah, I don't know how to use a PIC either... I use AVR microcontrollers. If you already know how to use a PIC, you must know how to program, so the only problem would be the display. Past couple of weeks we had a PIC clock thread going that dealt with multiplexing 7 segment displays. Should be just what you need. Believe they had the code and hardware, but don't remember which PIC or what language, as I don't use PIC, and only done assembly so far, but looking into BASIC.