Today I made a watch (sort of) out of a 555 timer and a couple of components. For about each second, it flashes a green LED. When the signal is off, it flashes a yellow LED for around a second. There is only one problem with it, and that problem is that it's inaccurate. Over time, the components may break down and start malfunctioning, or some other problems. In case that happens, I put in a reset button to start it over. I have it running on 5V. I'm going to replace this circuit with an Arduino as a time keeper and have a seven segment display showing the time in 24 hour format.