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I thought I'd take apart a set of new Xmas lights to see how they are evolving.
The answer is that I doubt they could evolve more without going to a blob chip.
The pinout of the chip is similar to a PIC12 microcontroller, but I'm not sure what it actually is.
The LED driving comes directly from two IO pins, so the chip has either got a built in H-bridge driver, two high current outputs, or they may just be abusing standard outputs and relying on the internal FET resistance to limit the current.
After the video I reassembled the module and tested it on a bench power supply. It drew 84mA while alternating and 64mA while static (alternating quickly) on a 4.5V supply.
I did a voltage/current test on an alternating mode, and the results were:-
4.5V 80mA
4V 60mA
3.5V 39mA
3V 15mA
2.7V 4mA
Below 2.7V the unit shut off, which is good for NiMh cells as it will reduce the risk of reverse charging of the first one to discharge completely. The intensity at 2.7V was pretty good for just 4mA.
The use of alternating polarity LEDs saves a lot of wire for a flashing effect, and may also reduce the risk of static DC corrosion of the wires when water inevitably wicks up the LED heat shrink. Unfortunately it makes it a bit harder to run the string directly from a simple USB power cable adaptor.
The 32.768kHz crystal frequency would need divided by 15 binary stages to get to 1Hz. A PIC microcontroller has the option of an RTCC (Real Time Clock Counter) which can be set to divide the clock frequency. It could be used to pre-divide and allow a more relaxed incrementing of the second stage counter for daily cycle timing in software while also maintaining the flashing patterns.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.

Like it or not, christmas is approaching, and since all the christmas lighting has started appearing on the shelves at places like jack stores and ramsey, i thought i'd buy some now. I think this is this year's stock. It could be left over from last year, but the isle of man loves its christmas lights because the general environment is pretty dark, so they look fantastic in the gardens, so they always sell out a christmas light. So i think this is new stock.

Let's take a look and you might think well, you've featured christmas lights before. Yes, i have, but i like to see how things evolve. I like to see how the colors and phosphors evolve and i like to see how the control systems evolve so restart you're. Getting a fairly nice little battery pack now i'm wondering they've got smaller sets.

I wonder if they contain the same battery packets, it's got a proper seal and it seems waterproof, um, okay, let's stick some batteries in and then we shall whip this cover off and see. If the circuitry is changed, if it's a still, what was it last year, microcontroller uh an h bridge driver right, i won't bother closing it. I will close it. I shall close it down and click it.

Okay, that probably made a really loud pop in the microphone. Click yeah, it's the usual polarity inverting one. I'm going to unravel these and see how they're wired it's just a parallel circuit. So this is the type that has alternate polarity leds and it swaps the polarity going out to the output.

So if you put it through to the two three five, six, seven, eight, oh new patterns, if you put it to the static setting, it's not actually static. I don't know. If it's going to show the camera, you can see a slight shimmer, it's actually alternating the polarity to the two channels to make them stay on. This is quite annoying because otherwise it'd be really nice.

Just to you know, use these with say a usb power supply, but if you do that only every second led will light that could be useful. It means you could choose a string, that's either just red and yellow or just green and blue. So, let's see what the circuitry is like, this also has the ubiquitous timer, that's in it so combination, which is all the facts in wave sequential, which is only two channels, so not that exciting, slow glow which is terrible, chasing flash. It's all right, it's very classic effect, slow fade.

Also a bit uh twinkle flash, that's the kind of new one and steady on right, let's open it, so i shall put the batteries out and we'll see. What's inside, i can remember the first ones these came out. They were terrible, they uh tried to use the existing higher voltage lights and used a little boost circuit and uh. It resulted in very short battery life and instability of circuitry.

I shall zoom down this actually i'll bring it up here and i shall zoom in it's way out of focus and then i shall focus on that. Boop uh. What am i seeing? Not a lot? I don't see i'm gon na guess this is a single-sided circuit board, this chip, capacitor, probably across supply rails, button, um and probably a crystal for the accurate timing right taiwan, i'm going to whip this circuit board out and we'll take a closer look at it. One moment please: okay, let's explore.

I shall zoom up a little bit uh, not an awful lot to see the back of the circuit board. Where is the circuit board? It's so small. I've lost it. It's just a plain circuit board with the crystal in the back.

Probably 32.768 kilohertz um there is a chip now, while this is a standard, microcontroller and they're abusing two of the output pins, because when an output pin is high, it was positive and when it's load was negative, it's possible. They could be abusing that, but uh to actually drive the leds directly, but i think this chip probably has a buffered output in those pins. I'm not sure it is. It has a very standard sort of power pin out here, but we have the negative communion and it goes to capacitor.

Positive crayon goes to a capacitor and they go to the supply rails of the chip. There is a button that pulls a one-pin to ground and there is that crystal in the back 32.768 kilohertz and then there's the two outputs to the leds and that's it, and they have added the provision here for a resistor to go into series to limit the Current through the leds, but they've just bridged that out with copper at the back of that, it's just a sort of design option that they've blocked out right. So the schematic it's not going to be very complicated. The schematic is going to look like this there's the plus fire 4.5 volt rail of the batteries which will drop gradually as the discharge here are the batteries three batteries in series double a's.

We have the little capacitor the de-covering capacitor, which goes straight across supply rails. Just to provide stability to the microcontroller, and then we have the microcontroller mysterious microcontroller no number could it be a paduk and it has a connection to the positive rail. It goes up a connect connection to the negative rail and then the outputs to the leds. Leds.

Keep your mind that some of them are in this polarity and some of them are in that polarity, so they can alternate as the uh it switches. Apart to the output, the leds alternate or for static it just uh alternates very quickly between them. So it gives that persistence of vision. It looks like they'll look continually.

There is the button which uh is going from the chip to the zero vote. Rail. That means internally. The chip, technically speaking, has a little pull-up resistor inside going to the positive rail and when you push that button, it pulls it to zero volts and that changes the logic state to zero on that input.

And then it knows that something has happened. And finally, it has the crystal which looks a bit like this in a schematic um, that is it it's one of the most simplest designs. I've come across yet now. Let me uh get the kink calculator and show you is this going to work hold on on? Let's try this 32 768, which is the frequency of the crystal divided by two equals sixteen thousand three or ninety four eight thousand one hundred ninety two: this is binary.

Four thousand. Ninety six, two thousand forty, eight one thousand twenty four five hundred twelve 256. 128. 64.

32, 16, 8, 4, 2 and 1, so that 32 768 actually divides down nicely in binary uh to a one hertz time base and uh in this circuitry. They will be uh dividing that again by 60 c, to get a one minute time base, then by 60. Again, to get a one hour time base and then they'll be dividing it by six to get that six hour cycle six hours on 18 hours off and then they'll, probably just counting a two-bit binary counter, because that will be when it's at zero. That will be the six hours on and then the all the other states will be off it's very.

It's almost boring. Quite frankly, it's just so simple they've, stripped it to the bare minimum, but that is how it is so. Uh yeah the leds, because they've got them all in parallel to match the intensities they have used the well. I can actually power this up.

This is where i blow all the leds up. I shall try not to blow the leds up with the power supply, so i shall find the two led connections there. They are, oh, that was a residual charging capacitor that made them flash and i shall gradually crank the voltage up, but they have used phosphor coated, leds, they're, all blue chips, the only ones that are raw blue chips are the blue leds. The green is phosphor and the red and the yellow is phosphor, so at three volts is that roughly than tends to they were before that's about 200 milliamps, maybe that's close to what they were before about 100 milliamps.

So i'm guessing the current will be limited by the output of that chip. And when i swap the polarity here, the green and blue are lighting one polarity and when i swap over to other priority, the red and yellows will light and there they are at the other side, which makes these lights just that little bit harder to try. I'm going to have to i'm going to have to resolve a little circuit that just simply does basically, i have h bridge drive with self feedback, so you can actually drive string of these without having their dedicated controller, because it's annoying when it's got this built-in features. But there we go, that is the current state of play with the christmas lights, i have to say i'm getting a slight deja vu.

It makes me wonder if i've taken a very similar one apart, but um that's what this one is and to be honest at that cost, it's actually worth getting just for things like the case, because that's a fairly good little waterproof case. Of course i've not actually tested it, but it looks pretty robust. It really snugs that seal down you click it shut, but there we go uh. This year's batch of lights, kind of which brand that was which brand is it.

Does it say no, it's got tons of text on it, self-import agencies, but the box looks like this and they do various multiples of these uh sets. They could do the sort of higher number sets, which i think above a certain level they switch to using the plug-in power supply, but below that 96. I think it's 48 or something like that. They do the battery operated ones.

But it's neat enough: it's a nice enough! Little set of lights!.

13 thoughts on “Very minimalist xmas lights control pcb”
  1. Avataaar/Circle Created with python_avatars TheWGBbroz says:

    I was working on an esp-powered "smart" egg incubator last winter with my dad, and one of the cheapo 5v/12v PSUs we bought from banggood died without any visual trace of a failing component. Would you be interested in receiving it for an autopsy, or would it be just another dead PSU on your pile of mail?

  2. Avataaar/Circle Created with python_avatars gertjan van der meij says:

    Hello Clive ! I like these, but I want them ( at least ) 8 hours on – 16 hours off , or 10 hours on – 14 hours off ! Maybe just 50/50, if the other timings aren't possible.
    Do you know an easy "hack" to do this ? Edit : I could just solder an adapter on it, and use a regular 230v clock switch, but I rather keep the battery power supply.

  3. Avataaar/Circle Created with python_avatars Markus Preckl says:

    When Clive said, "So I shall put ze' batteries out", it reminded me of Rainman Ray's Repairs (A guy on YT who works in a motor vehicle maintenance shop) when he says, "Poppin' zee hood" as he pulls that lever.
    "No, brain, there is no refrigerant charge for Clive to recover in that thing." Although i can imagine that, in a parallel universe, BigClive is doing car repairs for and with us as well! ๐Ÿ˜„

  4. Avataaar/Circle Created with python_avatars trone32 says:

    Hi Clive I wish you would do a circuit to run these lights and keep them static. I have just ordered some memory chips to mod the controller after watching your previous video to stop the annoying flash flash when I switch them on. I was thinking of using H bridge and a timer chip myself .

  5. Avataaar/Circle Created with python_avatars Samuel Ruiz says:

    I was wondering my solar lights battery died(18650) because it didn't have a under or over discharge protection so most of the batteries were discharged till no power was left. Was wondering if I could install a lipo battery with battery protection would it solve my issue and also I think my other set has protection would it be bad to have to have both protections one on the battery and one on the pcb

  6. Avataaar/Circle Created with python_avatars Geoff Press says:

    Interesting, I've been toying with using a microcontroller to drive multiple strings of LEDs for something a little bit different. If I used all the IO pins and a suitable driver circuit it should control 6 strings of LEDs, plus some pins for mode switching, plus a xtal for timing.
    Of course, this wouldn't fit in the original battery box, but it may not be a problem, since I'd end up with a couple of these boxes anyway.

  7. Avataaar/Circle Created with python_avatars Sewan & Sawen Creations says:

    Christmas is an unholy satanic holiday, just like Halloween…maybe a little but worse. Don't celebrate Christmas ya'll. It'll spoil the true spirit of God within. Just eat organic and don't present anybody with presents…it's of the lucifernt

  8. Avataaar/Circle Created with python_avatars Hamilton Mechanical says:

    Clive, i was thinking about you while hanging my lights the other day. I am pondering making a 4ft bubble light as a yard decoration LOL ๐Ÿ™‚ I'm always amazed how few people know about them! And of course looking for videos on bubble lights led me to your videos years ago. I got some sets this year branded as Lightshow Colormotion. I had to return one set for being defective, so if any fail by the end of the season i will have to send you a set LOL. They go through various color flashing modes, but the defective strand some bulbs got out of sync and it got worse and worse until the whole strand just gave up. upon repower they would work again for a while, and same end result.

  9. Avataaar/Circle Created with python_avatars mike jones says:

    Cool, i got almost the same set from the dollar store here (Canadian dollhairs) 4 plus tax, a set of 80 and only the white colour but everything looks nearly identical, including the functions. I tried for fun to put a 12 to 5v voltage regulator to try and reuse a 9v 500mah power supply, lately ive bene converting dollar store lights to USB powered and wondered if i could use a wall power adapter instead. And it worked, sort of… 5v came out the other end, but when fed into that PCB with the micro controller, i got really glitchy settings. Only 1 usable setting with only half the lights working. I left it on for a while and eventually i turned normal with all lights working then went back to being glitched. Anyway I supposed I need a smoothing capacitor with the voltage regulator? I remember hearing microcontrollers can be sensitive to voltage changes, so for a simple usb charger you can use those voltage regulators without smoothing capacitors but not a good idea if your using it to powerr microcontrollers. I thought it was lack of amps at first and tried a higher power supply with the same results. I did salvage a capacitor im gong to try and see if it works, if not just ill just go with a usb power.
    Im an eletronics newbie so its cool to see this set of lights on here, I really like them even on battery the last pretty good long while like 3 days maybe more withouth noticable brightness change, the other lights with no microcontrollers start to dim after a day, which is why the cycle feature is really cool and a pleasant suprise when the lights automatically came on today when the sun went down, so i have to agree bigclive here, they're nice lights. I was hoping you could program them, like each light individually could go on and you could make like snakes type effects , but like bigclive says they are really stripped down and only so much pattern (programs) you can do the way they're wired up.
    I guess the next step is making your own microcontroller? hah Dave from Dave garage, retired microsoft programmer does lots of LED work with adrunio micro controllers, he seems to have that figured out even though he says he's not a hardware guy, he did write a library to control led strips so you can program them to whater patterns you like using an adrunio microcontroller, he was going to sell it but made it open source. So i dont know about diy microcontroller, that would still be a cool thing.

  10. Avataaar/Circle Created with python_avatars Graham Rule says:

    At work we have some folk who can't stand flashing lights. All the strings of lights we have for the tree are like these: they turn off after a few hours and when they come on they are in a flashing mode of some sort even if they'd been put in the steady on mode earlier. My boss (correcly) has pointed out that I'm not a qualified electrician so won't let me mess with them as they plug into the mains. I'm thinking of 'accidentally' breaking them and seeing if I can 'mend' them by using a usb power supply with no flashing or timer anywhere. A usb power supply is like a computer thing so my boss might let me do that.

  11. Avataaar/Circle Created with python_avatars CRAFTCAKE SAM says:

    Hi Clive, given the rise in the self bought power brick and cable market, I would greatly appreciate if you could do a video on this topic, and perhaps give your purchasing recommendations. There are a lot of generic brands springing up across all price points. Are these a scam? Should I trust a company I've never heard of to sell me a Gallium Nitride charger, or any mains adapter capable of some of the wattages claimed? Would greatly appreciate your input and I hope it would be a topic that's up your boulevard.

    Thanks for the great videos.

  12. Avataaar/Circle Created with python_avatars Pelle Reinke says:

    I find it interresting they grind off the markings of the chips in these sort of things.
    Is it to prevent others from copying their circuit easily? (would be kinda ironic considering where these things come from)
    Or to disguise that this circuit is in itself a copy of something else? (which makes little sense so basic it is)
    Or because the chips are refurbished from other stuff?
    Or perhaps the chip is a clone of a namebrand one?

  13. Avataaar/Circle Created with python_avatars Palmit says:

    Good morning BC sir ๐Ÿ™‚ As always the video is very enjoyable. Thank you! May i ask a question? Looking at the photography, It appears that the chip has all 4 pins shorted together with solder on both sides. Is that an optical illusion? Or some kind of electronic wizardry? or am i wrong?

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