Instructables
Picture of Dark Activated Film Canister Night Light
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A light that turns on in the dark! Not as hard as it looks. We are beginners and if we could do it you could too.

We liked the mini-mood lighting and the flashlights we made but wanted to try something else. Cool Cat has several film canister flashlights in his room and a mini mood light but he forgets to turn them off. So we came up with an improved night light for him that will go on in the dark and off during the day.

This is different then the mini mood light as it does not have a switch, light sits lower in canister (providing a nicer effect), and the light turns on in the dark and off in light.

The pictures do not do this light justice. They look amazing in the dark.

http://www.instructables.com/id/Dark-Activated-Night-Light/ is what we saw on instructables. Please check it out.
http://www.instructables.com/id/Light-Sensitive-Night-Light/ was mentioned in the comments of the instructable above.
 
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Step 1: Material

Picture of Material
3V Coin Battery
100 Ohm Resistor
10K or 20K Resistor
Film Canister - Translucent
LED
LDR
Soldering Iron
Tranistor NPN
Wires - 2 About 2 Inches Long
Wire Cutters


Prototype Paper (Circuit Board) for Option 2 Shown with 20K Resistor

Step 3: Understand Transistors

Picture of Understand Transistors
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E is the emitter, B is the base, and C is the collector.

Illustrations taken from http://sunburst.usd.edu/~schieber/psyc770/transistors101.html
kiwinewt11 months ago
Have you thought of the magnet/etc attached to the lid? This way you would be shining it down into the canister, it could also be turned over for a smooth top. It would make getting the battery out to change it as well :)

Good work though. I might just have to do this myself!
Cats Science Club (author)  kiwinewt8 months ago
Take a look at http://www.instructables.com/id/Easy-LED-Color-Changing-Light/
Cats Science Club (author)  kiwinewt11 months ago
Great idea. We will see if that works (give us a day or two).
AndyGadget11 months ago
 
Great Instructable - Keep up the good work.

How about getting to grips with one of the free schematic capture packages for drawing circuits. This would improve the clarity of your circuit diagrams; essential once you start to draw more complex ones.  Many also feed into a PCB layout package which you'd need if you want to get into making your own boards. There's many around but beware as some tie you into their board manufacturer. I use the free version of DIPTrace.

The reason your LED sometimes flashes is that it's reacting to the additional light from the LED as above the 'turn OFF' threshold, then reacting to the dark again so turning ON . . .    Maybe angling the sensor towards the front of the container would sort this.

BTW - LRD should read LDR - Light Dependent Resistor.
Cats Science Club (author)  AndyGadget11 months ago
Thanks for the tips and suggestions!

Apologies about the LDR. That had to be annoying to read. Thanks for reading even with the glaring mistake :-)