Introduction: 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

author
savdd (author)2014-04-27

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

author
Pranavthegreat (author)savdd2014-04-29

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

author

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

author
dharmik pater (author)2015-07-11

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!!!!!!!!!!

author
AnindyaG1 (author)2015-05-14

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

author
prashanth.kumar.140 (author)2014-12-18

its not working the way you said

its glowing without closing with hand any alternative for this.

author
sunny.saraswat.3154 (author)2014-11-21

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

author
sunny.saraswat.3154 (author)2014-11-21

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

author
sunny.saraswat.3154 (author)2014-11-21

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

author
sunny.saraswat.3154 (author)2014-11-21

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

author
ankit.mehta.1401933 (author)2014-11-13

Very nice project

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

Thxx in advance

author

just instead of the led replace the buzzer nothing else

author
ankit.mehta.1401933 (author)2014-11-13

Very nice project

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

Thxx in advance

author
aaamir2 (author)2014-04-02

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

author
Pranavthegreat (author)aaamir22014-04-02

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

author
lukeD (author)2013-09-08

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.

author
Pranavthegreat (author)lukeD2013-09-20

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

author
muhammad-zka (author)2013-07-20

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

author

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

author
ππατσάκης (author)2013-06-21

I have a question because i am kinda dummie.i cant understand how this circle works, imean the led should light when there is light in the room and not the opposite.i have followed yous instructions and it really worked but i need an explanation i think. ;/

author

actually using the same circuit u can make a light sensor too you just have to change the place of the resistors , instead of the 220k ohms resistor use LDR and replace LDR with 220k ohms resistor and then you can light up the led when there is light , if still dont understand just try the project on the breadboard.

author
ππατσάκης (author)2013-06-20

if i use 3 leds (1.5v each) and 4.5v power . do i need any resistors?or the resistors have a different purpose?

author

There is no need of any other resistor as you are already using 330ohms resistor which is for the led , I hope this will help you

author
ToXiCATOM (author)2013-06-07

Can i use H SC945P transistor?

author
Pranavthegreat (author)ToXiCATOM2013-06-07

you can try using it but i prefer you should use BC547 as it is suitable for this circuit you can also use BC546, BC548, BC549, BC550

author
Rohit.panwar001 (author)2013-05-13

hi thanks for sharing.
but i want to know that how can i control my room light with a dark sensor

author

hey rohit thank you for your comment and I am also trying to control my room lights with a dark sensor and I have searched a lot ,you can use a relay to control the 220W bulb or simply google it

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