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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  )

<p>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!</p>
<p>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 </p>
How do you make sure that when the light turns itself on, it doesn't then sense the light and turn itself back off?
<p>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. </p>
yeah , it is true.. <br>in this case should keep some distance in between LED and LDR .
<p>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. </p>
<p>Hi please help me with this? - im a total newbie trying to learn how to dabble in the &quot;dark arts&quot; :-) Cant get my circuit to work and dont know whats wrong. Here are the various parts i have used.</p><p>Transistors</p><p>Bc547; Tip127; 2n3904 - could this be the problem? The tip127 is the only PNP Transistor i can see according to the data sheet...</p><p>3x Different types of Leds. Red:1.2vF White :3.2vF,</p><p>3x differnet types of light detectors</p><p>- Photo Transistor 940nm</p><p>-Photo Sensor 940nm</p><p>- LDR</p><p>Battery i am using is a 1.0ah 4.1v battery (4.1v is actual tested voltage)</p><p>2x POTS, 1x 1k, and another 10k pot.</p><p>Doing above on a breadboard</p><p>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?</p><p>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?</p><p>what other info can i add for you to assist?</p><p>Thanks, Andrew.</p>
<p>what exactly is your goal here, !!,, draw it for me and give me all details , and i may help you.</p>
Is This use for ac street light on electric board.
<p>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</p>
<p>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 ?</p>
I need some detail from this circuit... What's the output power of this circuit
<p>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.</p>
<p>where is its discription?</p>
<p>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??</p>
<p>how can i add 10 leds </p>
<p>How can i attach multiple LEDS in this circuit? Does it requires any alteration in the values of the resistors?</p>
<p>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.</p>
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?
<p>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. </p>
<p>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?</p>
<p>just switch the position of 220k resistor and the ldr( light dependent resistor) and u will be fine.</p>
<p>hi,</p><p>i have tried it and it works!!</p><p>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??</p>
<p>current limiter (to prevent LED burn) that is what i can think of</p>
<p>Followed this for a project I was working on, worked great, thanks!</p>
Good
I have made it and it works ..!
<p>it is for my school expo</p>
Can I use transistor BC548<br>instead of TNC547 PLS reply fast
I made exactly same but does nt work helpppppppp
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
<p>Hi - Very detailed Instructable - im a total newbie trying to learn how to dabble in the &quot;dark arts&quot; :-) Cant get my circuit to work and dont know whats wrong. Here are the various parts i have used. </p><p>Transistors</p><p>Bc547; Tip127; 2n3904 - could this be the problem? The tip127 is the only PNP Transistor i can see according to the data sheet...</p><p>3x Different types of Leds. Red:1.2vF White :3.2vF, </p><p>3x differnet types of light detectors</p><p>- Photo Transistor 940nm</p><p>-Photo Sensor 940nm</p><p>- LDR</p><p>Battery i am using is a 1.0ah 4.1v battery (4.1v is actual tested voltage)</p><p>2x POTS, 1x 1k, and another 10k pot. </p><p>Doing above on a breadboard</p><p>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?</p><p>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? </p><p>what other info can i add for you to assist?</p><p>Thanks, Andrew.</p>
<p>i want the values of R1,R2,R3,.......C1,C2,C3,C4.</p>
<p>please i want a simple explanation for work of this circuit</p>
I have written a good article on automatic street light using 555 timer with ppt and report<br>http://techmess.page.tl/Automatic-Street-Light-using-555-Timer.htm
<p>What procedure has been followed to choose the above specified values of the resistors and transistor?</p>
<p>what should i do to replace the led with a cfl?</p>
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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