Faux Fire From Water.... With Lasers! :)

The idea was to have childrens story time around a glowing fire, there was no way we could have a fire in the classroom as there was no chimney, no problem I knew I had an old fire basket in the bushes at home, I also had a bag of old coals from a real flame gas fire, I would make a faux fire!

Old gas fire coals

Led marker lights

5mw red lasers

24v ultrasonic fogger

Arduino and other circuit parts

small 12v fan

1.5mm red plastic sheet

4mm clear acrylic sheet

40mm plastic tube

screws glues

I started by breadboarding an Arduino nano with 3 transistor outputs for the leds and wrote flicker01

I connected it up to 12v and 3 LED marker lights, happy with the result I rebuilt the circuit on veroboard and added a 24v to 12v regulator, this was needed as another part of the build requires 24v.

I built a chip board frame to fit the cast iron grate

The frame was made deeper with 3mm MDF and a base with a 60mm diameter reccess in the middle was made to drop inside it.

The assembly was placed on my vacuum former and a sheet on 1.5mm red plastic sheet was heated and sucked into the frame, the reccess in the middle is for an ultrasonic fogger, I was going to fill the form with water deep enough for the fogger to work.... not a good idea it turned out, too much water needed making it too heavy and great danger of spillage. .... at this point I also decided the cast iron grate was far too heavy so it went back into the bushes from whence it came. I decided to build a wooden version of the grate that weighs much less.

I now adapted the same chipboard frame to take the ceramic coals I had saved from a real flame gas fire.

I ran a piece of 20mm MDF down the centre to leave a gap in the coals for my flame effect, once all the coals were in place I loaded the frame into my vacuum former with another sheet of 1.5mm red plastic, heated it up and gave it a suck. This formed the shape for the coals to be mounted, this plastic sheet was finished off by cutting a 20mm slot down the middle to let the smoke and flames out.

The sketch shows the basic construction of the fire. As well as the chipboard frame, fire base and fire bed already described I also needed a 25mm high spacer made of clear acrylic and what I have called the "chimney plate" to which will be mounted the LED flickering lights the lasers and a small fan, which I will describe next.

A piece of 4mm acrylic sheet was cut to the same size as the chipboard frame.

The fire base was dropped into the frame, the chimney plate was placed on top and a number of screwholes were drilled, thread inserts were then installed in the frame.

A couple of sheets of chipboard were cut, and stuck together, with a 60mm hole to surround and support the fogger pocket. A 24v fogger was inserted in the pocket held in place with silicon putty. After drilling a couple of holes in the chimney plate water was added and everything assembled to test the smoke effect.

I made up a frame from 20mm clear acrylic which will go between the chimney plate and the fire bed.

The plate was drilled for LED marker lights that are inside the chimney which is a rectangular tube made from 4 pieces of 4mm clear acrylic that is tall enough to reach the slot in the firebed.

When I ran this with the fogger going and discovered that it did not look "flame like", it was just yellow smoke.

A rethink was needed.... I decided that lasers were the answer....

A couple of things I know about lasers, beam can be seen in fog and if they are unfocused they have a rectangular fan shaped light. to this end I removed the lenses from 3 laser modules.

I drilled a piece of 4mm acrylic to mount the lasers taking care to get the beams all in line, this was mounted in the chimney and the lasers wired up to 5v, once lit I fired up the fogger and taped up the gaps between the flames with masking tape. I cut another piece of acrylic to fit the top of the chimney, laid it on and marked out where the tapes were placed and cut slots to let the fog out, this was stuck to the top of the chimney.

As the fog is heavier than air it would just tumble out of the chimney to give the smoke and flames height a fan was added to the chimney plate. Additional flickering LED's were added to add to the effects.

The fire bed was too red so I spatter sprayed it with grey primer and white rattle can paints for an ash effect, the coals were then stuck in place with thick superglue.

The fire basket was constructed from scrap pieces of 18mm plywood shaped in a similar way to the discarded cast iron one, this was all glued and screwed around the assembled fire. A back piece was cut from a sheet of 6mm MDF, decorated with a laser cut tree shape and the whole thing was painted matt black.

The back piece was spatter painted with grey primer and white for an ash effect.

As stated earlier I realised that the original design required too much water so a piece of plastic drain pipe was silicon sealed around the fogger unit but then I needed a way to fill it with water and in fact empty the water. This was easily solved with a length of plastic tube and a syringe.

Filling is a bit of a faf as it takes 15 syringe fulls to get the right amount of water (yes I could get a bigger syringe)

Emptying is easy, hold the tube low down and pull the piston out of the syringe and the water will syphon out.

The wiring and the syphon tube were brought out of the back panel and the circuit board was mounted and a cover added.

This was the end of the project for me, I just knocked up a cardboard fireplace to give an idea of the finished item and then covid stopped everything,,,, we have yet to do story time :(