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.
Minimum parts needed
Mounting board or housing
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, Deal extreme 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, when I built this green laser modules were rare and expensive.
Power supply, Dell laptop 12vDC power supply and a 12vDC to 3vDC adaptor.
Mounting board, MDF
Housing, Instrument case from Ebay
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.
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.
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.
There are other ways to do this, some laser printers have multisided mirrors already mounted on a motor, you just need to work out how to power it.
More useful info may be found here:
Laser modules may be purchased here
Other parts can be found on Ebay