Hacking a Christmas Tree for Less Blinkyness

Hacking a Christmas Tree to Blink Slower

What good is a fiber optic self-lighting Christmas tree if it flashes so fast it will put you into an epileptic attack? The answer is “Not very good”, if you ask [Mads Nielsen] a.k.a [EcProjects]. So [EcProjects ] started a little project to slow the Christmas tree’s blinkyness down to a more reasonable rate. The task didn’t seem too difficult at first but turned into a quality tutorial building a variable frequency H-bridge motor control.

After opening the base of the tree [EcProjects] found a 12 volt AC geared synchronous motor turning a multi colored translucent plastic disk. A bright spotlight was shining upwards through the turning disk into the ends of hundreds of small fiber optics. This mechanism dumps loads of multi colored light out the ends of the fibers at the tips of the Christmas tree branches as the disk turns.

His goal was to slow down the motor; however, the rotation was based on the 50 Hz mains signal. In order to continue using this motor a lower frequency AC power source was needed. What follows in the video is an excellent lesson on how an AC synchronous motor works plus how to build a variable frequency control and H-bridge using some transistors, resistors and CMOS 4069 inverter chip.

In the end the frequency drive could only be lowered to about 30 Hz before the synchronous motor would stall and reverse using his design. [EcProjects] was bold enough to include several fails which always provides more opportunity for learning and is greatly appreciated.

If you believe you have a better solution please share your idea in the comments. I’m sure the first proposal will include an Arduino and servo modified for continuous rotation, but any solutions would be fascinating including modifications to his design. You can join us after the break to watch the video.

41 thoughts on “Hacking a Christmas Tree for Less Blinkyness

    1. Gear reduction would’ve been my first choice too. But since you already said that, how about changing the pattern generating mechanism all together?
      Take a smal TFT, should be the size of the fibre strand. Take away the backlight (basically do the conversion as you would for making a DIY video projector) and put it inbetween the lamp and the fibres (actually you might want to replace that lamp with something that runs cooler, like a high power LED, to safe the TFT from heat death) and then use a microcontroller (use a Parallax Propeller, to keep the “Spin” in there) to generate any kind of interesting pattern at any desireable rate of change.

  1. Why not put in a 555 running a few colored LED’s directly, ditch the disk and the motor. No need for a micro controller or anything fancy.

    It looked like the light source was pointed at a bundle of plastic fiber, you could easily place a few large LED’s in that space, heat might be more of an issue but it would also use less power.

  2. No electronics at all, gear reduction will do this easier as vonskippy mentioned.
    Simply move the motor over and add a simple 4-1 reduction gearing. can probably do it with lego gears.

  3. Gear reduction was my first thought but making gear cages isn’t always trivial, and gears can be noisy too. Who wants a noisy Christmas decoration running? A pulley reduction system would be simpler, and quieter than gears.

    Perhaps just change the colored plastic disk to a coarser pattern that does not change so quickly?

    1. Changing the disc was my first thought, print a slowly changing rainbow vortex pattern on a transparency sheet, cut it into a circle and and use that for the new colour changing disc, 10 minutes, tops and throw the phenytoin away!

          1. How well I know this, having spent several years taking that crap. I’m glad to be rid of it and onto meds with slightly fewer side effects.

            I will say this for it, though: it does what it is supposed to do.

          2. I have been taking phenytoin for over 19 years. Until test show it affecting my liver I’m sure I’ll be taking it until I die, because for me it’s effective. For myself side effects haven’t manifested themselves.

    2. The pulley system might be good. I’d look at Fischertechnik, a design toy designed by Germans! It’s very functional, gets used in robots quite a bit, and in University courses in control logic, making miniature elevators to control and the like. It’s not cheap, but you might be able to order just a couple of pulleys and some mounting bits.

    1. Markers are actually pretty bad for colouring things you shine light through, they’re not dense enough, or saturated enough. Not sure what you’d use instead, even coloured plastic would have to be quite thick. Maybe stained glass paint would do it, but it’s a lot of outlay for a single use. Might be the disc is the hardest bit to replace.

  4. Given that the load is so minor and there will be a flywheel effect to some extent from the gearcase, I’d think a simple duty-cycle PWM would achieve the same result. 555 timer to generate the interruptor pulse and then SSR or relay to the motor lines. Put in a potentiometer if adjustability is desired.

    1. Relays can’t really do PWM, they’d wear out really quickly, and there’s a possibility of EM noise. If it were a DC motor your idea might work. Being an AC synchronous motor, chopping the AC would probably just make it vibrate. Then overheat! It’s actually looking quite a tricky thing to solve, probably the H-bridge solution he used is the simplest way that would actually work.

      1. Hint: Each of the 4 transistors would only steer the current in one direction, so you could have a reverse bias diode connected to each transistor in parallel. (4 in a full-bridge)

  5. The two transistors get warmer than the other two because one driver is a class B style emitter follower (which dissipates more heat because the output is limited to your base voltage [!!!] minus base-emitter voltage) and the other is a push pull inverter. You should have replaced the emitter follower with another push pull inverter and use another inverter to drive it.

  6. I have the same tree and I have modified it, but the purpose of my modification was to reduce the power consumption. So I replaced the halogen bulb with en 5 watt led and the ac motor with a very small stepper motor, witch is also being ran at a reduced voltage since no torque is required to spin the disk. The stepper motor is one of those 5 wires types that can be controller simply with 4 transistors and a small micro-controller. I chose this solution because I had the parts already at hand, otherwise I would probably have gone with at small gear-reduced motor.

    1. Why? The reflector on the stock lamp pretty much insures that each fiber will get pretty close to identical illumination. Give the seasonal use and relatively little run time during the season power consumption shouldn’t be a killer

  7. i have a similar tree, but it was made much different at the base, in a few weeks the mechanical parts wore down. i ended up hacking a standard bulb base into it and using one of those color changing led spot lights in it, though now i dont get the rotating colors any more. and i have to finish it off a little better still.

  8. For my own fibre optic tree I was thinking about swapping in an RGB LED with a suitable diffuser. Less intense light output and control over the colours, at the expense of different colours showing across the tree simultaneously.

  9. Loved the video and the little fails! It really looked like a very complex solution, I’d also have replaced the motor or put some sort of belt gear reduction… but at least he got it done :) Still looks quite fast and seizure-inducing, though.

  10. I have the same problem and I went to IKEA and I got the new LED lights disk multicolor with auto control for 12 dollars I took the whole bottom part and just put this new LED and it does the trick with the xmas Tree amazing results even better and direct connection no transformer required

  11. Hello. Sorry for the question outside the subject. Maybe you can tell me what type of halogen lamp you are using. Parents faulty lamp threw and did not even look what voltage and watts.

    1. old question, but just for future reference: A co-worker asked me for help to fix one of these for his mom. It has a wonky 12V AC transformer, and as the Halogen lamp is 24 Watts it needs over two Amps for the lamp and motor. You do not find many over 2A 24VAC “wall warts” sitting around, and they are more expensive than others just because they are rarely used. They should be quite heavy as well, if they are any good. In fact, I suspect the transformer was not really quite big enough in the first place (along with low-end construction), as that is what burned up on the one I looked at. Not wanting to buy such a large 12VAC transformer that is junk anyway, and not wanting to mess with an enclosure etc. for an good, over 2A, industrial transformer I have around, I am replacing the guts with LEDs and a microcontroller.

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