Can I use a 555 timer for this project?

Thread Starter


Joined Feb 18, 2007
I need a timer that will begin counting when a button is pushed (the countdown must be uninteruptable even if the button is pushed again during the countdown), I need it to be programmable or have a switch that will preset the countdown to one of three different times, I need a display that will show the countdown, and when the countdown reaches zero, I need it to light a small light. Once the light is lighted, I need the button to restart the sequence again.
All of this will be battery operated.

Any info would be appreciated.


Joined Jan 28, 2005
The 555, together with several logic devices can handle many of the requirements that you have outlined however, the displaying of the countdown would seem to make this project less likely to be doable with a 555 timer and more likely to involve a microcontroller such as a PIC or an AVR. The countdown could be handled with the appropriate number 7-segment numeric displays or an LCD module.

How much circuit design experience do you have? How much have you budgeted for this project? How much time have you got to complete the project?



Joined Feb 20, 2007
Pic is the way to go imo. Picbasic makes them too easy to program and get running. Especially for somthing like this. However You will need a programer. Which cost $ or time how ever you spill the beans.