Simple dusk detector for battery operated Christmas lights.

[@rickyspecs]

Having watched a ton of your other videos I have been impressed by the reverse engineering explanations you do. Sadly most of it goes straight over my head! This one though I understood, so now I’m on the lookout for more “my level” stuff that I can use to build things. I’m still going to enjoy being mystified and amazed and watching you blow things up and melt them! Great channel. Thanks

[@Bosse8808]

To get the build last longer on batterys you can change that LDR to a IR phototransistor, and put it where the 100K resistor is and put a 1M ohm resistor where the LDR are, and you will improve battery life, just a thought. Great video!

[@PunakiviAddikti]

I have one led string still lit up after a month on 3 AA batteries! It's pretty dim but still lights up the dark sightly, just enough for a decorative lamp. I'm not kidding. The batteries were slightly dead to start with so yeah, it's still going.

[@shaunsautorepairs5410]

As its wet n windy outside im tinkering in the garage. ive just made a set of these with my £1.50 set of lights from pound savers...3x AA batterys.. They come wired with a 20ohm resistor. So i changed that for a 39ohm i believe it was and a 150k for the other.. Seems to work ok. Had to use the 150k instead of the 100k because they didnt go out unless it was fairly bright. I can see lots more of these being made...thanks for sharing clive..

[@me_asme]

Brilliant little project guide... Cheers

[@bobhatcher5505]

A Christmas project. Great stuff Clive, thanks!

[@kyoudaiken]

Quite interesting. I try to figure out to remove the voltage divider on the base or gate of the transistor or FET. I wonder if it is possible to just add the LDR with a series resistor from positive 4,5V rail directly into the collector/base to prevent current flowing to the 0V rail. This will make the battery last much longer.... If it works. :D

[@webchimp]

Aha, so handy, just what I'm wanting to make at the moment.

[@paratroy]

Clive could you do another video like this for a solar panels style build? Could you just add a solar panel for charging? In Australia it's pretty sunny all the time too! Cheers Troy

[@BCbikerhippy]

Am I correct to suppose this would not work with a 2x AA cell (3v) string, having insufficient voltage for resistors?

[@meowzic]

I really wish you could remake this using the components because I have no fing idea what you're drawing

[@townbell2248]

Could you make a video you creating this project?

[@waldenhouse]

Enjoying all your series' on varying projects. Have you written a book and/or made a portfolio of "hints tips and ides" at all?

[@meowzic]

So is that a breadboard you have rhe components connected to?

[@edwardbaines5384]

Thank's for this I have used it on some old garden lights on which the circuit boards got corroded. I will also use it on Christmas lights too, I was wondering if could turn on a relay what do you think? I have learned a lot from you keep the good work up.

[@CuteRock1995]

Hi, will any mistakes on wiring can possibly destroy the copper LED lights? also, if i make 3 set of fairy lights, can the LDR handle it all?

[@rimmersbryggeri]

what about using a micro pot in series with the ldr?

[@veraxis9961]

Nice. Does this sort of layout result in the lights gradually coming on as it gets darker, or is it a fairly sharp turn-on? using a 10 ohm resistor (approximately 120mA max assuming a 0.3V min Vce?) might be on the high side for a 200mA-rated 2N3904, and a switching transistor like 2N2222 or 2N4401 might work better. A much more complex version of this would be to use a low power op-amp or comparator to drive the transistor, then use a 10-turn trimmer or something as a reference voltage to allow for fine tuning of the turn-on threshold for a specific location. One might even add in a feedback resistor to give it hysteresis on the turn on/off level, although then you would need to be extra careful to shield the LDR from the light from the LEDs to prevent the circuit from oscillating.

[@bigclivedotcom]

It does turn on gradually. The circuit is designed for absolute simplicity as opposed to using a schmitt trigger and accurate threshold detecting.

[@veraxis9961]

That makes sense. Absolutely nothing wrong with having a simple design, and a more complex circuit might have lower battery life, anyway.

[@kd8fki]

Can these be bought premade where you just hook a power source and whatever light in this voltage range? I have seen the ones for out door lighting and some the size or ardeuino but those seem a bit big looking for one that maybe found in a solar light maybe potted. Any suggestions,

[@ChrisFredriksson]

I really like these lights and I've watched I think most if not all of your string light videos as we've this year received these in stores pretty much everywhere. I haven't seen these in previous years, but might just be that I haven't been looking for them. Anyhow, great video by the way! =) But I got a couple of these now at home, runs off 4.5V / 3AA cells just like yours, they also feature a timer with 6h on and 18h off. Works more or less perfect! However, the batterylife comes down to around 6 or maybe 7 days. I'm thinking of sticking a 5V power adapter on it instead, I guess it shouldn't be a huge problem. But I'm not a huge fan of having these wall adapters plugged in 24/7.. So Have you thought of increasing the battery life on these in any way? Maybe solarpowered version? I watched your solarpowered meteor light video just a few minutes ago and I like it. However, I hate LiPo batteries ;) Any chance you would be interested in making a solarpowered version of these with some "safer" batterycell? I'm not completely sure, but it feels like rechargable AA are more "safe" than LiPo? Just a thought for a coming video, would be fun =)

[@bigclivedotcom]

+Chris Fredriksson If you stick a resistor in series with the LEDs it will extend the battery life at the expense of initial intensity. Try something in the range of 10 to 100 ohms.

[@ChrisFredriksson]

+bigclivedotcom Is it that simple? I know quite "a lot" of electronics, no way near what you know for sure! But I mean, I know a good amount I guess.. =D However, just thinking of such an easy thing, that doesnt work for me =( But thanks! I really appreciate it, gonna try this tomorrow! =D Really appreciate the reply! =D

[@falfas55bgas]

Clive, I'm trying to figure out how to power LED christmas lights with a Bosch 12V power tool battery. The AA battery style lights have too short a run time (180 hrs?) and the power tool batteries I have plenty of. I want to power them for at least a couple weeks. The strings made for AA batteries seem to be smaller lights on shorter strings. I'd like typical strings of at least 50 or 100 lights and be able to run at least two strings. It's been awhile since my circuits class but I understand more than the average lay person. I'm not sure of the LED's specs. What voltage it requires to determine the resistance needed. I also liked the daylight sensor circuit in this video. Can this be incorporated? If I know the specs on the parts, I have no problem building it. I have some pine trees on a hill in some horse trails and thought it would be neat to put red and white lights out there so when riders go through with the snow on the ground, it would be kind of magical.Cheers.

[@bigclivedotcom]

For simple parallel strings that run from a battery pack you can use a USB power bank to run them for a long time if you add a series resistor. I looked at that recently when I made a video showing how to add a chopped USB lead to a string of dollar store lights.

[@KDubSanDiego]

I wish I understood this as I really want to make this work for some battery powered LED lights in my little library. It seems like you need a LDR, a transistor, and a resistor, however, in your drawing there seems to be two transistors, one 10-100 ohms and the other 10k-100k? Is that ohms? It would really help to actually see the parts and how they are assembled instead of a drawing for people who are unfamiliar with circuit drawings.

[@theoneohmresistor]

Yes, there are two resistors, one for current limiting for the LEDs, and one for the transistor to turn on... The principle how the transistors work, is quite complicated, so let's just call the 100k resistor, the resistor for the transistor. Now about the lower value resistor, 10-100Ω (yes, ohm), the lower the resistance the brighter the LEDs will be. If you live in dark spots of the city (barely any street light), you will be ok with 100R (hundred ohm) resistor. Also depends on the number of LEDs... If you live in okay lighting, then 51/62Ω will be enough. You can always play around the resistance, and see what's working out for you.

[@paulmacgiollacaoine8619]

very cool

[@markae0]

I am going to change this , change the LDR for a temperature dependant resistor and put it in/on my fridge, to let me know my fridge is working properly.

[@bigclivedotcom]

A fridge thermometer is very useful for temperature monitoring.

[@darrylbuckingham7440]

I'm wanting to install red LEDs on a elderly lady's gate tied into her solar powered gate opener with a 12v backup battery. I only want the lights to come on at night to make sure the battery doesn't die, will this work connecting to the 12v marine battery???

[@bigclivedotcom]

You can get 12V dusk sensor modules.

[@rogerbeck3018]

now watching again 2019. WouldClive comment upon waterproofness (or otherwise) of the led array?

[@bigclivedotcom]

The copper wire LED strings with resin Bob LEDs are very weather resilient.

[@rogerbeck3018]

@@bigclivedotcom excellent, thanks. [now you should sleep].

[@bm8292]

Can the circuit be used with a 12v DC power supply

[@bigclivedotcom]

It should, but you can also get 12V dusk sensors.

[@richardsandwell2285]

Currently trying to build a similar circuit, I was trying to keep things simple, I like Mosfets, low resistance channels, and less power wastage, no moving parts to go wrong, however, I need to switch around 3-15 watts 12 volts from my 12-volt off-grid supply bank. I do not do lots of electronics, so I am not super clever with it. My test circuit uses a P-channel Mosfet an IRF9540N because I need to switch on the positive, high side of the circuit, however, I want it to function more like a proper dusk to dawn sensor, I am getting feedback issues with the circuit and also threshold point issues when it is not quite dark enough to fully trigger the Mosfet. What I really need is an Hysterisis adding, but I am not sure how to simply achieve this with resorting to more complex electronics. Any ideas anyone?

[@retrogamerjapanVids]

I built this circuit with a 2N3904 but had to use a 640K resistor with the LDR. The 100K resistor resulted in LEDs being always on. The 640K solution worked, but I was only getting about 2.6v to the LEDs. Is my LDR defective? thanks for the cool video.

[@bigclivedotcom]

It might just be a less sensitive LDR, but you could always try a different one.

[@johnturner9561]

Great video BigC, will this circuit work on a 12 volt setup. I am wanting to mod a 10 watt rechargable work light with a 3 watt green led and install a six cell 18650 protected pack and charge it with a solar panel. Keep taking sh#t to bits, love it.

[@darrylbuckingham7440]

I am installing red LEDs on a gate at someone's house on a dead end road, people keep running over the gate so I want to put self sufficient solar powered with a 12 volt backup battery powering the gate opener but I want the LEDs to only come on at night. To save battery life, will this work being powered from the 12 volt battery???

[@joshnicoll6761]

technicaly they dont absorb water they adsorb it which means the moisture sticks to the surface of the silica

[@-yeme-]

i misread the title as duck detector and now Im disappointed :/

[@stewartcaldwell5299]

Was this before the purple pen ?

[@bigclivedotcom]

Same type of pen, but to colour of the barrel indicates the ink colour. I actually get the purple ones because I like the case colour, and then empty them and refill with black printer ink.

[@SICDavid]

I’m a non electrical DIYer and I really like your video. I too live in a remote area and cars are parked outside with mice and wood rats seeking shelter. They heed light so your solution is great and would keep criders out from under my hood. Can I just buy a photocell and connect to the string of led lights?

[@markhodgson2348]

Or a 2N3055 transistor haha great cuicuit Clive

[@JerryEricsson]

I have done a LOT of your projects, and usually get all screwed up trying to convert from the BC547 to the 2N3904. Must be dislepsic or something but I came on a simple solution! It is now easier to just order the BC547's bulk off EBAY, they come just as quickly as the 3904's and there is no longer that pin out confusion for us old farts who's brains are no longer firing on all 8 cylinders (US Motorcars you know!) So now when a quick project comes up like these, I can just use the British version and all is once again right with the world, well until it comes to the damn 240v vs 120v again confusion reigns and i simply skip the project.