Building Challenge: Make that fireplace glow and flicker

[PerryMakes]

Dear fellow Friends of the Brick -

I've got a problem that's been kicking around in the back of my head for few weeks now. I believe you'll find it interesting, relevant, and useful for your own creations as well - making this worthy of your precious time (which we could all use a little more of!)

Background

4738 Hagrid's Hut comes with a light brick for simulating a fireplace / wood-burning stove. I noticed during the build that if I held the LED in the on position and periodically let it flicker off for just fractions of a second, I could get a much more realistic look for the fireplace.

Goal

Produce a pseudo-realistic looking fireplace by utilizing LEGO light sources (54930c01, 54930c02, 61930c01, etc) and a control mechanism responsible for generating the flicker effect. This will be just one element in a medium-sized Christmas display involving animated trains, buses, buildings, etc...

Problem

I see there being two very different ways of making this happen: 1) mechanically using the yellow and red light bricks 2) electronically using a mindstorms brick + IR sensor + PF lights. As a software developer going on 20 years, #2 would be simple to implement if it weren't for the fact that I'd like to keep the brick free for other functions elsewhere in the display. That means I'm stuck with a mechanical solution whether I like it or not! One thing that I do like about this option is the lighting. The power function lights would require a colored filter of some sort... the yellow and red light bricks have that already taken care of. I've still been experimenting with placing them behind transparent "filters" but that's more for generating reflections/refractions.

My big stumbling block is the mechanical method for creating the flicker effect by holding down the button on the light brick - periodically releasing it - wash - rinse - repeat. Because the mechanical action is going to be much much slower than an electronic one would be, I'd anticipate needing to use a handful of the light bricks, allowing for some pseudo-randomness in the total brightness / dimness / flicker.

Ideas

This is where I beg for your support! Or at least tell me its silly and probably not going to happen. Then at least I can go back to watching Starbuck frack some people up in Battlestar Galactica and enjoy the rest of the evening

Cheers ~ Perry

[Sariel]

I don't know what pieces or how much space you have at your disposal, but the simplest and most reliable way I can think of is like this:

On assumption that the white brick with a light bulb is your source of light and it can shine through a pin hole in the wedge belt wheel, where a semi-transparent round plate is inserted. Then you can rotate the wheel by driving its axle or by putting a rubber band over it to achieve the flickering effect. You can adjust the speed of rotation as desired, and you can use several combinations of round plates in the wheel, including the opaque ones if you want the "fire" to flicker with more irregularity. Hope it helps.

Edited September 21, 2011 by Sariel

[Lucas]

Hi Perry,

the question is if you want to use pure Lego elements.

Because it is quite simple and cheap to build LED diod flashing circuit. You can make 4 pieces with different capacitors to achieve different frequencies. This should quite well simulate a fire.

[Illuwatar]

Hi Perry,

the question is if you want to use pure Lego elements.

Because it is quite simple and cheap to build LED diod flashing circuit. You can make 4 pieces with different capacitors to achieve different frequencies. This should quite well simulate a fire.

Had the same thought when I saw this. Must it be built with 100% Lego parts? If you are into microcontrollers, then it is easy. A small PIC or AVR MCU can do this with ease. And if you are skilled with the soldering iron, it is even possible to house that inside a modified brick of suitable size...

[Lucas]

Had the same thought when I saw this. Must it be built with 100% Lego parts? If you are into microcontrollers, then it is easy. A small PIC or AVR MCU can do this with ease. And if you are skilled with the soldering iron, it is even possible to house that inside a modified brick of suitable size...

Microcontroller is great but complicated for beginers because it requires programming. IMHO using a few transistors and capacitors is easer. There is example of circuit. You can use tough paper instead of circuit board.

[PerryMakes]

Thank you guys for the ideas. I knew that my thinking had been confined to a box - I just didn't know it was this bad!!

I don't know what pieces or how much space you have at your disposal

This is going in a front bay window with quite a bit of space (.75 x 3 meters). And my answer to any questions regarding what / how many pieces is always the same: never enough

but the simplest and most reliable way I can think of is like this:

[image removed]

On assumption that the white brick with a light bulb is your source of light and it can shine through a pin hole in the wedge belt wheel, where a semi-transparent round plate is inserted. Then you can rotate the wheel by driving its axle or by putting a rubber band over it to achieve the flickering effect. You can adjust the speed of rotation as desired, and you can use several combinations of round plates in the wheel, including the opaque ones if you want the "fire" to flicker with more irregularity. Hope it helps.

It helps massively. I developed one idea for doing this and it became almost impossible for me to think of any alternatives. Many thanks for offering this method.

the question is if you want to use pure Lego elements.

It's not required, but it is preferred. I can use other methods if they 1) are absolutely necessary or 2) result in a much better solution - there is no pressure to keep this LEGO-only. At the same time, making the attempt to keep it pure is good practice for situations where deviating from LEGO parts is not an option.

If you are into microcontrollers, then it is easy. A small PIC or AVR MCU can do this with ease.

Been looking for a small project to get my hands dirty with an Arduino kit. Could be a perfect opportunity.

And if you are skilled with the soldering iron, it is even possible to house that inside a modified brick of suitable size...

Have a rather new digital soldering station that hasn't seen much action... and my pops surprised me with a workstation for my Dremel over the summer - sounds like a great way to break them both in!

Microcontroller is great but complicated for beginers because it requires programming. IMHO using a few transistors and capacitors is easer. There is example of circuit. You can use tough paper instead of circuit board.

Looks like a great way to do it as well, maybe with a few modifications to allow for variable/random resistance and therefore dynamic blink timing.

[Illuwatar]

There you have it - a good time to use that Arduino kit... Making things appear random is much easier in code than in hardware (either mechanical or with discrete electronics). The Arduino might be too large to house inside a regular brick, but you certainly find a space to hide it inside the MOC. And hooking it up to the other PF-parts could be easily performed by modifying some PF extensions wires.

[FelixTheCat]

Too easy. Technic Control Centre - circa 1990.

Set a 2 minute program with random flickering to your liking and then run the program on repeat. PF Led lights should even work on the 9V terminals dont they? You should get a fair run time out of the 6 C-cell batteries using Led lights. You could even have one channel run a motorised track which would make a minifig "walk" to the firplace and stoke the fire and then return to where he was every couple of minutes.

[le60head]

That's a great idea!

Cant think of a better one really :)

I'd also say go with the technic control center !

[Lasse D]

Go with Technic Control Center II as it can run on both power adaptor and batteries.

[le60head]

Go with Technic Control Center II as it can run on both power adaptor and batteries.

Does it have a build in transformator plug? Didn't know that, thanks!

[DLuders]

@ le60head: This Bricklink inventory of the 8485 Control Center II set shows two different transformers; pick the one to match your country:

70931 "Black Electric, Train Speed Regulator 9V Power Adaptor 120V 60Hz":

70928b "Electric, Train Speed Regulator 9V Power Adaptor 240V (UK)":

[Blakbird]

@ le60head: This Bricklink inventory of the 8485 Control Center II set shows two different transformers; pick the one to match your country:

70931 "Black Electric, Train Speed Regulator 9V Power Adaptor 120V 60Hz":

70928b "Electric, Train Speed Regulator 9V Power Adaptor 240V (UK)":

Don't feel constrained to those transformers. You can use any 9-12V transformer with your Control Center II. I have tested dozens of different models. For maximum current through 3 motors, choose one with at least 1000mA. Picking a larger one doesn't hurt anything. The Control Center will only pull as much current as it can use.