I need to trigger a buzzer every minute or ten minutes depending on a situation. I am not sure where to start really. I was considering a 555 timer, but can I set that up to be variable with time?
You will find it very difficult and expensive to get 10 minutes with 2% accuracy directly with a 555 timer. So as Dab suggests you could run the timer faster and use some additional logic to count down 555 pulses. A processor is not over the top - it will be cheaper and better. Don't use a PIC or Atmel (unless you are already using them and have the tools). The cheap PICs have horrible timers and very poor on chip resources. Look at the NXP LPC1111 (1 off £1.44 Farnell 1786280) -nice ARM processor - so small you can use the free Keil toolset (Keil is part of ARM) and you can programme with a serial link to a PC which you can do with a variety of cheapo tools. The ARM (unlike the tiny PICs) has real 32 bit counters, brown out detection, proper power on reset, accurate internal clock, decent ADC, a fair bit of IO, enough RAM and flash to use C etc.
If you are going to make zillions of something it may be worth wrestling with a PIC to save a little on the processor but it doesn't pay if you will only build a few hundred, let alone one. Don't be put off by the LPC1111 package - its easy to home solder - if you want to go that way post again and I'll tell you how.
