Introduction: How to Make a Dark Sensor

Picture of 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

Picture of 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

Picture of 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

Picture of 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 (author)2017-10-18

For how much time will it glow in total?

Aabhishek Sharma (author)2017-10-02

Making a simple touch sensor also having a finger pad. Check out this awesome Instructable.
https://www.instructables.com/id/Making-a-Simple-Touch-Sensor-Having-a-Touchpad

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

Pranavthegreat (author)savdd2014-04-29

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

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

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!!!!!!!!!!

AnindyaG1 (author)2015-05-14

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

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

its not working the way you said

its glowing without closing with hand any alternative for this.

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

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

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

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

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

just instead of the led replace the buzzer nothing else

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

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

Pranavthegreat (author)aaamir22014-04-02

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

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.

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

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.

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

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. ;/

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.

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?

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

ToXiCATOM (author)2013-06-07

Can i use H SC945P transistor?

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

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

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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