Basic dark activated circuit with LDR help.

I'm trying to turn on an LED with a dark activated circuit, and I've got a basic circuit working with an LDR, but the LED is barely lighting up. I'm only getting about 3V out in complete darkness.

I have a resistor and the LDR forming a voltage divider on the base of a transistor. I assume my problem is because my voltage divider is too far out of balance; but I'm not totally certain. I do know I'm getting similar results with a 2N2222, a 2N3904, and a TIP120. Right now I have a 100K resistor in with the LDR, and I've tried other values but none seem to really help this problem. I can get the circuit to switch on in more and less light, but it always seems to only put out about 3V.

Anyone else have experience with circuits like this?

 

It is literally just a simple voltage divider on the base of a transistor like the one on this page: http://www.buildcircuit.com/darklight-sensor-using-transistor/

I am using a 9V supply, a 100K resistor as the top value in the voltage divider, and a TIP120 transistor.

 

I tinkered with it some more today and got it. It was the fixed resistor in the voltage divider. I could have swore I played around with this in the past and settled on 100K as the perfect value for the sensitivity I wanted; but I guess not.

I added a parallel 100K to drop the resistance to 50K and now it works perfectly. I've got it soldered together and in a box.

What it is now that its completed is a control box I'm going to use with an LED lamp I'm making. I've got it wired through a two position switch so that I can turn it to "auto mode" or constant mode. Its running off a battery now, but I'm going to add a wall transformer to it. I've got one, but I'm using it as my bench supply right now. lol

Thanks for trying to help though! I guess I just should have tinkered more before asking for help.

 

Well I'm not a junior engineer, just a lowly tech, but I noticed that there isn't a fixed resistor between the positive supply rail and the base. At least 1K is the universal choice there right? Though I have to be honest I can't say I haven't been guilty of doing something similar when just toying with a setup on a breadboard. I did get quite the burn from a TO-92 package 2N2222 because of it once though; I hooked it up just to see if my circuit would work, got distracted by something, and by the time I got back and touched the package it was hot enough to leave a little mark on my finger. It didn't burn as bad as a shorted voltage regulator I grabbed at work one day though... that one actually left the imprint of the nut that holds it to the heatsink in my finger. lol

I did not know. Learn something knew every day.

 

Well that voltage regulator was a tricky one, it wasn't a dead short so it appeared to be working just fine. It wasn't even drawing a huge current load. I programmed the unit, ran through some functions, and thought everything was fine... then I grabbed it by the heatsink to pull the test cables free and yowza! Turned out to be a very tiny solder bridge only visible under a scope.