Electronic Circuit: Dark Activated LED light with photoresistor
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- เผยแพร่เมื่อ 31 ก.ค. 2015
- In this video we learn how to build an automatic night LED light using a NPN transistor and a photoresistor. We build a simple circuit and by it learn how transistors work.
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I searched a dozen places before I find this channel who actually explained it. A+
Thank you, it worked! I had a yard decoration running on AA batteries that had to be turned on and off. So i hooked this up for it to come on automatically when sun goes down.
thank you for explaining so clearly how the components work to achieve the desired result.
I am glad you find the video useful!
Your 4 min video is better then 2 hour of my campus lecturer, super clear explanation
Thanks a lot!!!! I had a lot of trouble with all the connections. But after watching this video, I could make the circuit and now my project is actually working. Thanks for your help! :)
Hi there, I’m building a bike light. I managed to flatten out the inductance spikes with a continuous light. In addition I was thinking of a much bigger capacitor of around .22-1F added to that the bike light should only consume energy in the eve. Do you think this setup would allow to store the energy in the capacitor? Do you think it would be wise to add a voltage drop lockout? My main concern is that the extra resistors would take the energy that would otherwise be going to the led.
I'm only just getting into this stuff and this video is very helpful! Thank you so much for taking the time to make it! :)
check out forrest mims mini- engineering note books .
Thank you, Learned so much
Great tutorial I had tried several other web based tutorials but your's seemed to be the one that worked for me, got the project up and running in no time. Can you please demonstrate how to add addition LEDs in either series or parallel?Thanks
+Danny Martin I am glad that my video was helpful!
Finally someone who can speak English clearly
Helpful and well explained- thank you.
Thanks Sir! You saved my day!
can i use more than 1 led and what resistor would i need if i use 9v battery?
I really Enjoyed your video my self ! Been looking for video's for My grand-son to watch on electronics circuits trying to get him interested thanks.
Thank you for the tutorial, it was very useful for me
Hi. Why did you place the load on the transistor's emitter? It is my understanding that when using a NPN transistor (per the diagram), the load should be placed at the collector. Thanks!
Thank you so much. Your explanation, Diagram and video is very accurate and working. Thank you.
I am always watching your nice vídeos, please keep making them... Have a good vacation!
CONGRATS finally I understand this circuit you taught a Brick something you are a very good Teacher Thx, Ed
Great Video! Keep posting more videos please.
How do you calculate the resistor values if I used say 3.3V input?
Thank you so much for this wonderful video. I understand the electronic circuit now so much better! :-) can you tell me which program you use to draw the circuit on the computer? Thanks in advance and good luck with everything.
Super helpful, thank you!
Could capacitors be used before the LED to exaggerate the dimming effect?
thank you, wonderful explanation
I like the way you explain how the electronic works .
Thanks. Did I miss why 100 ohm resistor was used ? Also if i put NPN by 180 degrees, will it work the opposite way i.e. led on only when it is day? something I will try
can the circuit be revised to turn on MOSFET when the light on the photoresistor is activated. Working at 12 volts
What do I need to add or change to make this work with two LEDs?
Thanks, it is great example, simple to understand, please keep creating new videos... :)
Danke die Skizze mit den Pfeilen erklären das super. Kein anderes Video bei TH-cam erklärt es besser.^^
sorry don't speak whatever language that is. My apologies.
What is the Power consumption when it's sunny/ Led off?
So, R1 & R2 are a voltage divider. I know Q1 will probably switch on at .7V, but I don't know what resistance level R2 must be at to cause Q1 to switch on & off. At which actual resistance amounts must the photoresistor be at to cause the transistor Q1 to switch on & to switch off?
Hi, great vid, I would like the LED to go on when the LDR goes from dark to lit. Is this as simple as reversing the LDR?, thanks
You won't need transitor for it ,you can just connect it in series with LED.🤗
Thank you!
That's loved this video got it straight away thanks
Great Lesson. Thans ! Like !
This was really helped me out
Only that worked so far thanks!
Can I do this with more than 1 leds?
WHat I should do, if I want to use it in my car. But I need it on 12V
Another great tutorial! Cheers
Eric William -MKme Tech Thanks Eric!
can i add buzzer to it?
Can we use a 9v battery instead of 4AA batteries?
These videos are really helpful and nice small projects to explore the world of electronics.
Thank you.
hi!
when i connect the component, the LED already turn on without/with me covering the LDR. So, any suggestions?
Try reducing the amount of power in your circuit... say 3.7V rather than 6V
Using different values of Resistors will help you.
I had the sampe problem
I use a different transistor and another LED, so i had to change the 2k resistor with a 10k resistor and then it worked
Thanks!
Awesome videos!!!
Excellent Tutorial. I finally successfully implement Thanks a lot. I search all the net but not work any implementation but your tutorial is finally worked. Thanks again. Now i have a question that how can i connect PIR sensor with this diagram. Because when dark come then pir sensor activate the light . So how can i do this.
Why is the LED not bright when using this circuit? If using a 1k trimpot with LED, LED is super bright, but with your circuit even with 100 ohm resistor from transistor to led its weak. Help please.
I totally agree with the rest of the commenters. a simple but yet very good tutorial explaining the concept of transistors and current flow. Good job!! oh, and have a great vacation! :-)
Dog Rox Thank you!
hello, can i use 9v of battery?
how if input input voltage is 24vdc?
Worked good for making fake night vision cameras thanks!
Sir plz tell how many led's i can use in this project
What changes do I need to make in ratings of the components if I want to use a 10W LED???
mosfet?
Um Bro you can also use a Relay in place of led to turn On Off and an LED Bulb.
Or a High power Transitor TIP Series
hey! what should i use to light up 10 leds using ldr?
Increase Decrease the Resistance at Collector Value or use Larger Mah Battery.
hi
i want to make LED flash using a 20 or a 30 watt w LED.... i wish to have to trigger the LED ON/OFF using a phototransistor as a trigger....can u suggest a circuit.... (am trying to build a simple LED FLASH for cheap diy photography)
+santosh shetty I have to think about it and I will make a video on that. It is a good idea.
+educ8s.tv thanks
If I use different npn transistor then will the setup of registances change?
Yes, you have to check the datasheet of your transistor in order to choose the appropriate resistor values.
Amazing
nice project! with best explain...
how can we make same project but with 12v battery? we use mosfet or just n transistor?
+Kamal Aziz A single transistor can do!
+educ8s.tv thanks ! i want to use it with a car battery !! is there an effect of high curent or any one can work ?
in series or parallel
Thank you! Your video is the only one I found that explains HOW the circuit works and the path that the current follows. I finally made it. I used a 12v LED bought from a store and a power bank with 8 AA batteries, with no resistor after the LED.
Glad it helped!
The center leg on transistor is ran to both resistors. But why do each resistor go to different sources? (photo to ground and resistor to pos).
R1 comes from power, through Photo to ground. It makes a circuit.
Thanks 👍
so what if I want to do the opposite? what if I want the led to be on when it is light or what I really want to do is power a solenoid with a laser pointer.
Then don't put the Photoresistor, and while your at it take off the 100Ω resistor.
Is it necessary to use the resistors and the transistor
Yes. Without the Resistors the LED will heat up and become defected. same with the transistor, it is crucial!
Adding a diode really makes this circuit work.
your enlish is verry charm and beautiful ...btw can i use 9v batery ?
dan laesu Yes you can. You will have to use more resistance in order to have the LED not blow out
i will do so :-) thx m8
BTW it's 'English' and 'Very' not "enlish" or "verry"
So , in Day time Current draining through LDR ? due to low Resistance ........PLZ ANS if anyone can explain it
Hello! I was wondering if i need a resistor 1/2 w, 1/4w 1 w, or if that didn’t matter. Thanks
I am very late, but in this case, the wattage won't matter as you aren't pulling that much through.
how does i control the sensitivity?
Change R1 to an trimpot.
how could you add a pot to make the led dimmable
In a potentiometer, there are 2 inputs and 1 output. To use a pot, plug the resistor from the base of the transistor into one of the side inputs on the potentiometer. Then take a wire from the middle and plug into the positive.
nicely explained - thanks.
My led stays on and only shuts off with a flashlight directly on the photoresistor? Can someone help?
Is there a way to make this work with 1 AA battery?
Led requires at least 2 batteries
Sloud it work with bc547?
+Vincent Wiedermann yes!
no
Yup
Is there a reason why this does the exact opposite of what it's supposed to do? Do I have the wrong kind of photoresistor?
I had the same issue, my transistor was installed backwards.
What would be needed to create a 120V system? and how would that circuit look?
Please if you are new to electronics, don't even try it, it is very dangerous.
My led turns on when there is light present and turns off when no light is present.. what is the problem?
in transistor
It works
can I use 9V battery??
kinda the same question i ask
Yes. I've used a 9V battery in my circuit too!
You can use any voltage as long as by the time it gets to the bulb it's the required voltage to run it. Make sure all the components can handle the voltage as well. If voltage is too high it can overheat and burn out. I think 9v might be too much power for the led. You can try connecting it directly to the battery to see what happens.
Not working :(
Write a program for the above circuit
Nice
A switch? That black thing?
A transistor surely.
I guess im stupid because my LED just powers straight on despite the photoresistor and I have no idea why
oreo binteo!
Thank you!
Fun
It's wrong to put the load on the emitter rail of a transistor. Put it on the collector rail.
Why?
not working waste
yeah, i know, so I kind of messed around with the circuit and finally made it work.
It is not working
Don't waste your time. This circuit does NOT work.
It works
Yeah i tried to make the circuit but it didn't work. I found out that he's been messing around with the current by switching the positive current on the negative terminal and vice versa. I messed around with my circuit and i have successfully created it! My problem was that the circuit worked oppositely for me because the photoresistor was not working so I placed it on the same row as my LED and it worked!