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Build Your Own Fire Effect


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I do some work for a small museum and recently they asked me to light a display, part of which was a blacksmith's shop, and they wanted a fire effect. As all their lighting is now low energy I decided to use LEDs.


I originally thought of using LED MR16s but then I remembered I had some of bigclive's PCBs in stock. So, I ordered some LEDs, an Arduino and a MOSFET driver board.


Clive's PCBs are laid out for R, G and B LEDs. I decided for my desired effect to populate the board as 2 sets of red and 1 set of yellow. One set of red stays on permanently, the other two sets are driven individually from the MOSFET driver board. I used the 5mm Superflux LEDs in Red and Yellow.


Here's the LED PCBS...




...I've built two as I'm not sure if one will be bright enough.


And here are the other bits...




The MOSFET driver board sits on top of the Arduino...




I've never used an Arduino before and for simple projects like this I'm quite impressed. What's particularly nice is the huge range of add-on boards aka shields. The software is about 10 lines of code and uses random numbers to set the brightness of the attached LEDs via PWM and a random delay between changes.



If anyone is thinking 'that looks useful' I'd say 'give it a go'. If you can solder you can build this; there's nothing difficult at all.



The finished PCBs will be fitted into a standard £5 halogen flood fitting and will be powered from an LED transformer.



Bits bought from...


PCBs from bigclive

LEDs from Phenoptix

MOSFET board from eBay

Arduino from eBay



The MOSFET board is overkill really. Each channel can do 5A; I'm currently running them at 150mA so they don't even get above room temperature.



My code is still being tweaked but currently looks like this...


// LED Fire Effect

//set the pin numbers. Not all IOs can do PWM
int yellow_led = 5;
int red_led = 6;

void setup()
 //set the IO pins to output
 pinMode(yellow_led, OUTPUT);
 pinMode(red_led, OUTPUT);

void loop() {
 analogWrite(yellow_led, random(255));
 analogWrite(red_led, random(255));

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Brian that is brilliant, I was just thinking of replacing the flicker circuit I put in our old real fire at home with something more efficient the other day. Bring on Payday and may have a go at that
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I made a pretty impressive flame effect around a cauldron for Wizard of Oz, using 8x 50W GU10s, some chicken wire mesh to hold random shapes of appropriate coloured gels above the GU10s, four 120mm mains fans and some Habotai silk (the thinnest, lightest silk available)


It took a bit of messing about to get the air flow right, and learnt some things about air flow and aerodynamics in the process! (eg; two fans arranged in a "double-push" configuration give less air-flow than one fan on its own!....


Use white Habotai silk, positioned in the middle of the air stream (which might not necessarily be the middle of the aperture), uplit with some GU10s, with randomly shaped pieces of red, yellow, orange and blue gel in a mesh sandwich above.


The cauldron I made with my bro-in-law (professional handyman - plus a bit of help from my sister's cats!) had to accommodate a child actor climbing in and out twice per show, so an old wooden desk top was put inside, with steps to get out, and a hollow back. The entrance through the back of the cauldron was cut out once it was built, to aid rigidity during the build.


http://www.lancs-it.co.uk/images/cauldronframe_t.jpg http://www.lancs-it.co.uk/images/cauldronframe2_t.jpg http://www.lancs-it.co.uk/images/flameset_t.jpg



http://www.lancs-it.co.uk/images/cauldronnews_t.jpg http://www.lancs-it.co.uk/images/cauldron_t.jpg

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The large superflux panels have been quite popular for various applications other than RGB mixing. I've also used them myself with single colours inside props.


The RGB controller kit I have on my website does various flicker effects that look good with red and yellow LEDs. For subtle effects the flame modes dim each channel up and down randomly. For more vivid effects the colour burst modes switch the channels suddenly between random intensities.


With reference to the silk flames, the fans need a baffle above them to take the "twist" out of the airflow that tries to roll up the silk. I did tons of experiments with silk flames and LED lighting a long time ago and there's a quite a science to producing a good reliable effect.


Silk is best. Synthetics just don't work as well.

Asian fashion shops stock silk. Choose white and colour it with light.

12V fans are quieter and have a stronger airflow than mains fans due to their smaller motor.

A baffle to create a straight air flow in line with the silk gives a more reliable effect.

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I would love to have a go at building something with these kits, I can solder, but how easy is the rest of it to build?


Just started playing with Arduino last couple of months myself, plug together both code and physically is how easy it gets.


Software is written in `sketches` and programs via USB directly to target board and `shields` plug on top of the target board.

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I would love to have a go at building something with these kits, I can solder, but how easy is the rest of it to build?

Both the Arduino board I used and the MOSFET driver came ready made. Clive's LED boards are easy to solder up; I reckon if you can manage D-type or DIN connectors you can manage those. I had to add three wire links onto the MOSFET board to select the drive signals. The other connections are screw terminals.

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Without wanting to sound like I'm advertising my wares too much, I designed the kits to be as easy to build as possible. Most are on single sided boards with thick tracks and large pads to make them easy to build and mod.


I've got myself an Arduino to play with too. Not tried it out yet though. The original RGB kits are based on PIC12 processors programmed in machine code (assembler) for speed and designed to be completely stand-alone.

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