Introduction: Dark Sensor ( Light Sensor / Automatic Street Light )

Here is my new simple Electronics project about  Automatic Street Light Control System or Dark Sensor.

it is a simple and powerful concept , which uses transistor ( BC 547 NPN) as a switch to switch ON and OFF the street light system automatically .
It automatically switches ON lights when the sunlight goes below the visible region of our eyes. ( e.g in evening after Sunset ).

it automatically switches OFF lights when Sunlight fall on it ( e.g in morning ) , by using a sensor called LDR (Light Dependent Resistor) which senses the light just like our eyes.

Needs no manual operation for switching ON and OFF...

Step 1: Things You Need...

Parts:-

* 1    BC547 transistor
* 1   220 k resistor
* 1   330 ohms resistor
* 1   LED (any colour )
* 1   9v battery
* 1   battery clip
* 1   LDR ( light dependent resistor  )

Step 2: AND...

*  Connecting wires
*  soldering rod and wire
*  wire stripper
*   Cutter

Step 3: Circuit Diagram

solder the transistor on the 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 ohmsresistor .






Step 4: Finsih... Uuuhuuuu... :p

The simple circuit is ready for testing now . Connect 9v battery terminals to the circuit as show in fig and see the output . As you block light falling on Light dependent resistor (LDR), the LED glows .


Comments

author
JC143 (author)2017-08-16

Is it ok to use 6 volts

author
JC143 (author)2017-08-15

is that okey if i will use 6v insted of 9volts

author
dnfh1949 (author)2016-11-17

Could the circuit be modified to work the other way round, so that it switches ON in sunlight and OFF in dark? I suspect its v. simple, but so am I!

author
SulaimaanC1 (author)dnfh19492017-01-19

Yeah just dont use the transistor

author
Er_tanmay_joshi (author)2016-12-28

Which type of resistors I need to use

author
Er_tanmay_joshi (author)2016-12-28

I want to connect 10 white LEDs with 9 volt.. suggestion please guys

author
danieljohn7291 (author)2016-12-21

Hey can someone help me plz?

can someone tell me what the 2 resistors specifically

author
anilk194 (author)2016-11-01

How may bulbs can be connected in this circuit. Can you explain me ways to connect about 6 bulbs (total Approx 9 volts- 1.5 Volt Each). Also upto how much volt led i can connect in this circuit

author
EastsidePrep (author)2013-12-27

How do you make sure that when the light turns itself on, it doesn't then sense the light and turn itself back off?

author
MohamedS372 (author)EastsidePrep2016-10-02

you can add a capacitor of 100uf at the base of the transistor to delay the time of biase raise time, so if a 5 second of light accidentally hit the LDR it will not effect imediatly, rathar it will take about 8 seconds.

author

yeah , it is true..
in this case should keep some distance in between LED and LDR .

author
BurgersBytes (author)2014-01-12

The circuit can run 2 LED's for over a month with just 2 AA batteries. I use a similar one to light up my wall clock with 2 bright warm white flat top LED's.

author
AndrewP14 (author)BurgersBytes2015-05-25

Hi please help me with this? - im a total newbie trying to learn how to dabble in the "dark arts" :-) Cant get my circuit to work and dont know whats wrong. Here are the various parts i have used.

Transistors

Bc547; Tip127; 2n3904 - could this be the problem? The tip127 is the only PNP Transistor i can see according to the data sheet...

3x Different types of Leds. Red:1.2vF White :3.2vF,

3x differnet types of light detectors

- Photo Transistor 940nm

-Photo Sensor 940nm

- LDR

Battery i am using is a 1.0ah 4.1v battery (4.1v is actual tested voltage)

2x POTS, 1x 1k, and another 10k pot.

Doing above on a breadboard

The problem is, The both LEDS stay on when connected, they just get brighter with more light, it seems my circuit is more of a light detector that switches LEDS on when it detects light rather than the opposite way around?

Ive tried switching the transistors, switching the leds, switching the POTS, and some other resistors i had (not sure of spec right now) but still cant get it right?

what other info can i add for you to assist?

Thanks, Andrew.

author
MohamedS372 (author)AndrewP142016-10-02

what exactly is your goal here, !!,, draw it for me and give me all details , and i may help you.

author
dhiruandroid (author)2016-01-29

Is This use for ac street light on electric board.

author
MohamedS372 (author)dhiruandroid2016-10-02

in the current situation, only low voltage control, but with a SPDT relay ( 220v AC - 30 amp- 24v DC )you can put its coil in the collector way, then you can control a bigger and high voltage lights

author
krishna Hariharan (author)2016-07-24

charge from the battery flows from negative to positive right ? then what is the use in having that 220 kohm on the right of the base of transistor ? it should be on the left right so that it will restrict the flow to base ri8 ?

author
Nandynandy (author)2016-07-21

I need some detail from this circuit... What's the output power of this circuit

author
leseagle (author)2016-06-21

Love the simpleness of your work. However, for a practical guy like me, I need to know where and how to tie it to let's say an array of LEDs on a pole in the air... or street light. Would I just insert the circuit to the LED on either side of it? Or where in the circuit could I use it to practically switch something off... and on... it seems to be in a closed loop with no connection to another say 12V device feeding a bank of LEDs such as a street light. So is there more to the puzzle and what does that entail? Thanks, for the insights.

author
ShireenT3 (author)2016-04-15

where is its discription?

author
kanankutty (author)2016-04-15

hey brother,i have a 12v supply and a 12 v led strip,i need to implement this circuit with this what are the changes in components i need to incorporate??

author
SabiH1 (author)2016-03-16

how can i add 10 leds

author
DkPro (author)2015-12-11

How can i attach multiple LEDS in this circuit? Does it requires any alteration in the values of the resistors?

author
harshalpatil199529 (author)DkPro2016-02-26

tat depends on how many leds u plan to attach .. if u want to attach just 2-3 more leds then this circuit will work just fine just attach the leds in parallel.

author
GabrielK5 (author)2015-06-09

I don't understand something when current flows from the battery it gets to the node. Then it splits up to the 330 ohm resistor and 220 kOhm resostor. Since the first resistor has a smaller value the current must be higher there so the diode should glow at any time. Why is it turned off when the light is up?

author

that is because the base current to the transistor is negligible and therefore the transistor acts like a open switch and hence does not provide the grounding needed for the led to light up.

author
Dylan91 (author)2015-07-30

Hy i'm not an expert so maybe i made a mistake. I made the circuit you did there, but it's working in the opposite way. The LED is on in the light and off in the dark. Can Someone help what did i wrong?

author

just switch the position of 220k resistor and the ldr( light dependent resistor) and u will be fine.

author
khd1999 (author)2015-11-16

hi,

i have tried it and it works!!

but i have noticed that if i only use 330 ohms resistor the led is dim. when i only use 220k ohms resistor the led is bright and the led is bright even when both resistors are connected. can someone help me.. whats the use of 330ohms resistor here. in my case??

author
WinellenF (author)khd19992015-12-15

current limiter (to prevent LED burn) that is what i can think of

author
kkingsbury made it! (author)2015-04-04

Followed this for a project I was working on, worked great, thanks!

DSC_0430.jpg
author

Good

author
Syed Zainulabdin13 made it! (author)2015-12-04

I have made it and it works ..!

1449247170448314984771.jpg
author
JithinD2 (author)2015-10-13

it is for my school expo

author
SyedZ6 (author)2015-08-24

Can I use transistor BC548
instead of TNC547 PLS reply fast

author
Prashanth.AN (author)2015-08-22

author
Prashanth.AN (author)2015-08-22

author
Prashanth.AN (author)2015-08-22

author
HarisC (author)2015-08-21

I made exactly same but does nt work helpppppppp

14401690790821790813979.jpg
author
Muhaamad Nafis (author)2015-08-12

Excuse me if I use more than one LED should I add a resistor or a transistor and can or not if use resistor 100K for R2

author
AndrewP14 (author)2015-05-25

Hi - Very detailed Instructable - im a total newbie trying to learn how to dabble in the "dark arts" :-) Cant get my circuit to work and dont know whats wrong. Here are the various parts i have used.

Transistors

Bc547; Tip127; 2n3904 - could this be the problem? The tip127 is the only PNP Transistor i can see according to the data sheet...

3x Different types of Leds. Red:1.2vF White :3.2vF,

3x differnet types of light detectors

- Photo Transistor 940nm

-Photo Sensor 940nm

- LDR

Battery i am using is a 1.0ah 4.1v battery (4.1v is actual tested voltage)

2x POTS, 1x 1k, and another 10k pot.

Doing above on a breadboard

The problem is, The both LEDS stay on when connected, they just get brighter with more light, it seems my circuit is more of a light detector that switches LEDS on when it detects light rather than the opposite way around?

Ive tried switching the transistors, switching the leds, switching the POTS, and some other resistors i had (not sure of spec right now) but still cant get it right?

what other info can i add for you to assist?

Thanks, Andrew.

author
sudheerbabu (author)2015-03-11

i want the values of R1,R2,R3,.......C1,C2,C3,C4.

aslc.gifaslc1.png
author
sudheerbabu (author)2015-03-11

author
Hamow (author)2015-03-06

please i want a simple explanation for work of this circuit

author
SaeedH1 (author)2015-01-26

I have written a good article on automatic street light using 555 timer with ppt and report
http://techmess.page.tl/Automatic-Street-Light-using-555-Timer.htm

36db46c58cf72369a72169bf620a8651.jpg
author
sushaw.starry (author)2014-11-18

What procedure has been followed to choose the above specified values of the resistors and transistor?

author
key2world (author)2014-09-21

what should i do to replace the led with a cfl?

author
British Badger (author)2014-07-15

Ive made something light this (use more components) in a small robot I made (as seen in the profile picture) And I was going to update it to this smaller version but I wanted to check if copying you design was okay

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