I am looking at creating a light that is triggered by an existing light source. I don't want to touch the other light source wiring at all so I am looking at a photocell. The function I had in mind is when the device is powered up (on/off button) it measures the ambient light, it updates this ambient light levels in intervals and only triggers when there is a sudden change, when the existing light source turns on, turns on high or turns off. So the existing light source has three modes, off, medium and high brightness.
I am planning on using two or three 10w LEDs, I guess I need some sort of microcontroller, batteries for power, a photocell and from what I have been reading, a logic level MOSFET? I am looking to make this as small as possible but in the same time at a reasonable price and avoid excessive heat (I understand heat is unavoidable). I have been looking at this Mini Photocell. I haven't really looked at any LEDs yet since I don't fully understand the other components I need.
I am asking for some guidance in what kind of components I need to make this, I have been searching but got a bit overwhelmed about all the available components. Any ideas of a small microcontroller to use and what type of MOSFET? I guess I only need one analog input and one pwm output, right?
Thanks for reading!