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Hi guys,
it's been a long time when i posted a instructables so i am making this simple but great dark detector for you.

I made this also for my younger sister who need some light in her room while going to sleep.

Step 1: List of Parts

Parts Required are :-

1x Ldr [Light Dependent Resistor]
1x Bc547 Transistor
1x 220K Ohms Resistor
1x 100 Ohms Resistor [ Read Next Step for Other Colors of Led]
1x 10mm White Led
1x Battery Clip
1x 9v Battery

That's All.

Step 2: Schematic

How it Works :- An Led is Illuminated when it will detect no light. An LDR (Photoresistor) is used in this circuit for sensing the light and dark conditions, and transistor bc547 is working as a switch. When the LDR will detect no light it will open the transistor bc547 due to which the LED will light up. And The 100 ohms resistor is used to protect led from direct contact to 9v Supply.

Step 3: Assemble the Components

Assemble the Components according to Schematic and Remember the pinouts of bc 547.
Solder the Components Firmly :)

Step 4: Finishing Touches....

Now Solder the Battery Clip to the Wires as shown in schematic and Hot Glue whole Board to the battery.

Connect the Battery Clip to Battery.
And Test it.

Please Vote This Instructable in Contests.
Hope i could get something for my little sister's Birthday.
<p>i've tried to make an smaller one here it is i used a BC547,100K ohm resistor and a 4mm LDR </p><br>
<p>Nice Idea!!</p>
<p>nice project! :)</p>
<p>please send a photo from bottom </p>
<p>Soory bro i must have give this to my cousin and they live far away from my home so i cannot click a single photo.</p>
<p>please send a photo from bottom </p>
Would this work with a5mm led? I love this project!!!!
Yes it will work with a 5mm led too.And Thanks for Such a nice Comment!
It's amazingly awesome
It's amazing!
Nice project! Did it cause any self interference by having the sensor so close to the LED? In the dark it will illuminate but when it does it's no longer dark, and should try to turn itself off again (Same principle behind putting a mirrored shroud around the top of a street lamp).<br><br>Does the rest of the circuitry provide a safeguard against rapid changes in light intensity, or is the sensor just angled away enough that the additional light from the LED is far enough below the sensor's threshold that it still considers it dark?
<p>Yes, i have angled the sensor a little away from the led and the Led is not diffused too. therefore the angle of light will be above only.Also, Sensor is little away from it so it does not recognize the light coming from led side.</p><p>Thanks for the Comment!</p>
<p>Cool project!</p>
<p>This is really simple and cool! Good job :)</p>
Thanks :)
Thanks for such a nice Comment!
<p>Oh I love this! It's so compact and I always love those huge LEDS :)</p>

About This Instructable

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Bio: Just a Small Tinkerer ;)
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