How to Make a Dark Sensor

Hey guys ,
In this project I am going to show you how to make a dark sensor using a single transistor and some few resistors in just 3 simple steps .
here is my video this is my old dark sensor

Step 1: Things You Need

Parts:-
1) 1x BC547 transistor 
2) 1x 220 k resistor
3) 1x 330 ohms resistor
4) 1- small perf board
5) 1x led (any colour )
6) wires
7) 9v battery 
8) battery clip
9)ldr(light dependent resistor )
Tools:-
1) soldering rod and wire 
2) wire stripper 

Step 2: Getting Started

solder the transistor on the perf board and solder one wire of the ldr to the emitter and other to the base  , solder the negative wire of the led to the base of the transistor with a 330 ohms resistor and also solder 220k resistor with the one side of the 330 ohms resistor

Step 3: Finishing Touches

I have also used a SPDT switch it is optional I have used to pin headers as the connectors for the power .

Comments

[PrathamK5]

For how much time will it glow in total?

[savdd]

hey is there a way to make it so that when i hover my hand over it, it will stay on then when i hover over it again, it will turn off. thx

[Pranavthegreat]

I don't think so you can with just a transitor , you might need a microcontroller and PIR sensor

[Ingenerare]

A microcontroler with in combination with aLDR will do the job also

[dharmik pater]

When I supply current to the terminal the led starts glowing when there is light in the room and it still glowing after I put my hand on ldr hey please help me please!!!!!!!!!!

[AnindyaG1]

Nice project.. But led is blinking fast. How can i slow it.?

[prashanth.kumar.140]

its not working the way you said

its glowing without closing with hand any alternative for this.

[sunny.saraswat.3154]

if i use 200k resistor inthe place of 220 k resistor

and i use 300 ohms resistor in the place of 330 ohms resistor'

thanks

[sunny.saraswat.3154]

if i use 200k resistor inthe place of 220 k resistor

and i use 300 ohms resistor in the place of 330 ohms resistor'

thanks

[sunny.saraswat.3154]

if i use 200k resistor inthe place of 220 k resistor

and i use 300 ohms resistor in the place of 330 ohms resistor'

thanks

[sunny.saraswat.3154]

if i use 200k resistor inthe place of 220 k resistor

and i use 300 ohms resistor in the place of 330 ohms resistor'

thanks

[ankit.mehta.1401933]

Very nice project

but i want to use a buzzer in the place of led what should i do

Thxx in advance

[Pranavthegreat]

just instead of the led replace the buzzer nothing else

[ankit.mehta.1401933]

Very nice project

but i want to use a buzzer in the place of led what should i do

Thxx in advance

[aaamir2]

i have a problem.
i have followed the steps
but instead of Dark its working as a Light Detector any idea why Thanks

[Pranavthegreat]

just change reverse the transistor because using this circuit you can make both light as well as dark sensor

[lukeD]

hello, nice ible!
is there a way to control how much light there is needed to light up the led? i think it would be possible with other resistors, wich one would that be?
I want it to light up when it is only half dark.

[Pranavthegreat]

Replace any other resistor instead of 100 k or use a 100k pot so that u can change sensivity of the sensor

[muhammad-zka]

am i able to use it on 12v dc for a smd LED ??? IF SO TEll me about the things needed.

[Pranavthegreat]

I think so u cant as the the transistor will nt be able to bear that much current