dark sensor swith to turn ON arduino?

Hello, I have been building projects with discrete components. Drawing circuits, etching boards, drilling billions of tiny holes and a lot of soldering and wires. old school, and the project performs as intended. someone much smarter than I said I could do the same thing with a micro processor. Wouldn't that BE COOL.

I have a couple questions. I have found similar but not exactly what I need to know in reading through similar topics. This one being about LDR's and motion detectors turning on LED's. similar, but not quite.

What I would like to know is....is it possible to have a LDR circuit TURN ON the arduino. meaning during the day it sleeps and once it is dark it wakes up. performs its night time tasks and then goes back to sleep at dawn and is it possible to achieve hysteresis without having to use a comparator circuit. such as an lm339 and associated components?

the device I built operates on batteries so power consumption is a HUGE factor. I believe I can quickly learn to program the operational part. As I said I haven't found anyone yet, using a LDR to turn on the unit? does anyone know if this is even possible?

Thank YOU

What I would like to know is....is it possible to have a LDR circuit TURN ON the arduino.

Yes why not?

and is it possible to achieve hysteresis without having to use a comparator circuit. such as an lm339 and associated

It is electronics, you have to use components are you afraid of them or something? You can make the same function in a number of ways but how ever you do it you have to use parts. Or is it just LM399s that give you the willies?

As I said I haven't found anyone yet, using a LDR to turn on the unit?

It is exactly the same as turning it off only you put the LDR between the +ve and input with a pull down resistor instead of between the input and ground with a pull up resistor.

Hello, the answer is no ain't skeer'd of electronics. the item I build is completely hand made as stated. So...1st of all I know ABSOLUTELY NOTHING about arduinos. my objective IS TO. I read more forum posts on putting the arduino to sleep. there are 4, "I think" options, the LAST being the most power saving.

I don't want to build circuit boards by hand anymore, IF! there is a simple way to use a "SIMPLE" dark sensor switch to put to sleep and wake up the arduino and make it task its tasks. I would like to learn. and that requires someone to teach me.