Intro: PicAxe LED Dark Detector
First, I saw an interesting Instructable titled "Light Sensing LED - PicAxe Version" by Bot1398. I tried to reproduce this project but just couldn't get it working. However, I used much of Bot1398's circuit to make my own circuit that was similar and also worked.
Notice that the schematic reveals TWO LEDs instead of just one. I decided that maybe the input would be higher and more distinct using two LEDs. I also used a separate output and LED for my "display." The resistor for this LED is 330 ohms while the "pull down" resistor for Leg 2 is 10k ohms. I tried more than a few times to make the PicAxe code match the electronics of the schematic and then downloaded this to the PicAxe 08M2 microcontroller.
With the battery connected with normal lighting, the separate yellow LED doesn't light at all but when I cover the two sensing LEDs with my hand (or shut off the overhead light), the yellow LED blinked about 5 times a second. This project was a success as far as additional learning for me but a regular photocell might work better for a serious project...