Liquid Sky in Green




About: Woodsman and field tutor on a week day. Life long inventor, designer, engineer for the rest of the time. From items that make life easier to items with no reason to be....other than the idea popped into my h...

The liquid sky effect is simple but very effective with a little bit of smoke.

It produces a flat sheet of laser light, the smoke swirls around in ever moving patterns.

The specification for this one is as follows

Motor, 3" diameter, 12volt computer cooling fan.

Mirror, First surface mirror from a laser printer (more on this later).

Laser,  10mw ( can be any type/colour/power ) It would also be easier to use a module as you can connect the power by soldering wires onto the PCB,

Power supply, Dell laptop 12vDC power supply and a 12vDC to 3vDC adaptor.

Mounting board, MDF

Housing, Instrument case from Ebay

Step 1: The Basics

The most important part of this project is the mounting of the mirror on the motor.
I tried 6 mirrors, 4 mirrors, 2 mirrors and found I could not mount them accurately enough to get a single line of laser light, more than 1 line spoils the effect.

I ended up using a short piece of the scan mirror from a laser printer, this mirror is around 3/16" thick and due to the thickness is easy to mount, plenty of adhesive area.

Setting up the mirror takes time, to start with I stuck it to the fan with double sided tape and powered up the fan with just enogh volts to turn it (too fast and the mirror can fly off). The mirror must be centred to prevent vibration.

Shining a laser onto the mirror gave me 2 lines, one from the front, one from the back of the mirror, it also gave some scatter from the 2 ends so I painted the ends and the top with matt black paint.

To get a single line I just pushed the tip of a cocktail stick under the edge of the mirror to tilt it slightly and spun it up again, I repeated this a number of times until I had a single line. I then ran a bead of super glue around the joint to fix it in place.

Step 2: The Laser

The laser needs to be modified to be on when power is supplied, to do this I used a cable tie to hold down the button. I also needed to replace the batteries with a power supply connection
The drawing shows one solution, I cut the back of the laser off just behind the thread, found a plastic "top hat" insulator that would just fit into the laser barrel. The brass negative contact is the head of a brass wood screw with a hole drilled in it for the wire. The positive wire is soldered to the cut down battery holder. Take note that the voltage polarity is negative to the module and positive to the case, red and blu ray diodes are the other way round.

I clamped the laser to a piece of chipboard using copper "P" clips.

Step 3: Assembly

The fan and the laser were both screwed down onto a piece of MDF.

Wiring is simple, the output from the mains/12v supply goes to the fan and the input of the 12v to 3v adaptor, output of adaptor goes to the laser.

The plastic case has a front panel which I cut in half, I stuck half to the base, stuck the other half to the lid so that when the case was assembled there was a narrow slit where the beam emerges.

Regards rog8811

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    11 Discussions


    10 months ago

    Can I purchase this somewhere? Or can someone build it for me? I'll pay of course

    1 reply

    Reply 10 months ago

    If you are in the UK use rog8811@gmail....... (with the usual ending) make me an offer as I have not used it for some long time.


    2 years ago

    I did this a very long time ago but I seem to remember that the position of laser to mirror is not to critical, I did it by trial and error. I think the laser ended up just front of centre of the fan/mirror assembly.


    6 years ago on Step 2

    The diagram below pretty much covers it,  the dell power supply outputs 12 volts for the fan and the input to the variable supply (used to plug into the car cigar lighter) set to 3 volts for the laser.

    Remember polarity on green lasers is positive to case, negative to centre contact.

    Supplies liquid sky.jpg

    6 years ago on Step 2

    Can you give me specific details on how you wired the laser to the power supply? I tried last Halloween to wire mine to an ATX power supply from an old computer but the laser would always short it out for some reason. I'd like to not have to buy a specific laser pointer PS.


    8 years ago on Introduction

    Hate to be rude, well not really... But there is a much simpler method to obtain a laser line. If you shine the laser through the side of a cylindrical lens ( glass rod, like you use to stir stuff in chemistry), it will project a straight line, just like laser levels available at most hardware stores. Copy machines use to have a motorized octagonal mirror, and that assembly is fairly cheap surplus.

    4 replies

    Reply 8 years ago on Introduction

    We should do the maths I think.......

    Let us assume a scan angle of 100 degrees in both your design and mine, let us also assume the use of a 10mw laser in both cases.

    Your 10mw spread over 100 degrees = 0.1mw per degree.
    My 10mw scans the same area 100 or so times a second =10mw per degree.
    Which do you think will be brighter?

    Just try using a laser level line to light up smoke for a liquid sky, this is why good quality laser printers and photocopiers use a scanned line.


    Reply 8 years ago on Introduction

    Wrong !
    The instantaneous power at a point when the laser is at that position will be 10mW. But... It will only cover 1 degree for 1% of the time (over 100 degrees) so averaging a power of 0.1mW per degree.

    We should do the maths properly ;)

    So yeah, it will appear the same brightness using either method


    Reply 8 years ago on Introduction

    It won't look the same you know, I have tried it!

    I agree I over simplified my answer, you need to take into account persistance of vision and a number of other factors.

    The main one is that, using saphire, glass and quartz rod (I have experimented with all 3), there is a spread of intensity, bright straight ahead and a reduced intensity to both ends. The best width of line (angle of spread) is obtained by offsetting the laser from the centre of the rod, this still exhibits a high power spot straight ahead and using a green laser you can see the driver pulses along the line .

    By scanning you get an even spread of light and the pulses are hidden


    Reply 8 years ago on Introduction

    Yeah, I suppose with a glass rod it won't be an even distribution but you still only average 0.1mW/degree over 100 degrees.

    Either way it's a nice setup :)
    Do you have a video of it running?