I would like to make a circuit which turns a small fan on for about five minutes every half hour. I thought about maybe doing it with an Arduino Mini but maybe using a couple of CMOS 555 chips would save a bit more power for the fan (not sure that matters since the fan will probably use like 200-300 mA when it's on; it's going to be powered by a couple of 18650 cells). If I use 555 timers, how do I arrange them? Thanks.