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led flash and fade. how? Answered

Video of Ravelight

Picture of Ravelight

Im interested in building a product that utilises coloured LED lights with multiple flashing and fading patterns.

I have pulled apart a few LED products and examined the PCB's and the components and have a general idea of what is going on, however it is all new to me, and im unsure of the possibilities that exist. For example, i didn't know you could get pcb's so small...

Basically i need the power source to be the small button cell batteries (up to 6 if necessary, though 3 or 4 would be preferable). With at least 4 LEDs of different colours (RGB etc). A similar design to what I want to make is a flashing LED light stick like people use at raves that I found. It has a button that seems to simply complete a circuit momentarily, and pressing it down again and again, scrolls through its 9 different flashing patterns.

I have seen various different LED toys that vary on this, but are basically the same idea.

The thing that I don't understand (on top of a lot of other small things) is what is under the black blob on the PCB? Is this something like a 555 timer? an IC? And how are these programmed to give all the different patterns? is it a microchip?

This thing cost me $3 from a shop. three dollars!! cheap as....this is what I want for my product. can anyone help me out to understand?

I can post a picture up in the next couple of days if people can't understand what i'm talking about.

Thanks

17 Replies

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Goodhart (author)2009-05-04

a transistor, a few caps, and a few dual decade counters (or a quad) would work.... I have one I am building without the decade counters...but that could easily be incorporated in to my simple design.

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Goodhart (author)Goodhart2009-05-11

I haven't finished it yet....but this can be done with just a few capacitors and a transistor.....I will have 1/2 of such a circuit published by the end of this week.....if I can find time to get back to making it look better.

PS: by 1/2 of the circuit, I mean that the switch turns the LED on, and it fades out......adjustable time with a potentiometer

It shouldn't be hard to create the fade in from this circuit too.

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noi noi (author)2007-10-16

I have added a link through to a picture and video of it. Under the blob is smaller than a button cell. I spose, im wondering if I should just track down the company that makes these and see what it would cost for a modified version to suit my specs? or if I should suss it out more and learn the basic to see what possible. On an aside. Do you reckon its possible to add an infrared receiver on the board to act as the momentary swith? and still have it remain as small as it is (i.e. no bigger diameter than a buton cell)

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gmoon (author)noi noi2007-10-16

That's such a simple device, the smallest micro-controllers, like a ATtiny11 could drive it. In fact, it's so simple it's probably some sort of programmable gate array (the ASICs mentioned before.) They'd be even cheaper. Could you explain why you'd want an infrared interface? Definitely higher cost, and it bumps up the processing requirements (dozens or hundreds of these working 'in sync' would be amazing...but line-of-sight operation would make 'em finicky.)

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gmoon (author)gmoon2007-10-16

Ah, but if you had a large infrared driver hooked to the sound system.... ;-D

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noi noi (author)gmoon2007-10-16

well, i want the PCB to be fully enclosed in acrylic. to cycle through all the flash options would mean opening it up and changing it, then putting it back together. i thought maybe i could use infrared to turn it on and off so i didn't have to open it up. to me, infrared is really convoluted and im sure there is a better option. but im not sure of the possibilities. magnets? i dunno i've seen others that work by physical shock, but this is not suitable. and i've got another led thing that wont turn on unless its dark. this uses, i think, a light variable resistor. but this is no good either. and we are talking somewhere between hobby and mass produced. maybe a run of like 200-500 or something if it all turned out well and good.

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gmoon (author)noi noi2007-10-16

Why not include an on/off switch? You can't really seal the device, unless it's a one-shot disposable--ya gotta change batteries...You might as well be using glow-sticks.

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noi noi (author)gmoon2007-10-16

well, without going into too many details. it does come apart for battery changes. but not very quickly. it is fully enclosed when using it.

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noi noi (author)2007-10-15

cheers. i'll look into it. btw, the part im referring to under the black blob would be no bigger than 5mm across. we still talking about micro controllers. all the stuff in the pictures looks bigger. plus, there just aren't many circuits coming out of it...when i get home tonight (about 10 hours time) i'll post up a pic.

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gmoon (author)noi noi2007-10-15

5mm is plenty big for a micro controller. I know some custom ASIC chips that have 160 lines bonded out that are less than 4mm square (in fact, you might have an ASIC on that board, could be cheaper than a uC.)

Here's a nice link from Bunnie's Blog that shows how small the actual chip is in a DIP.

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Goodhart (author)gmoon2007-10-15

I have seen 555 timers at 1.6x0.8mm...barely bigger then

.

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gmoon (author)Goodhart2007-10-16

Nice way of illustrating.... @ T3h_Muffinator: I think noi noi is planning mass production...

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Goodhart (author)gmoon2007-10-16

Yeah, I did that because I am still struggling with measurements concepts like mm, um, etc. After 50 years of being immersed in "inches and feet" conversion comes slowly :-)

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gmoon (author)2007-10-12

Micro controllers--that's what you seek.

PIC or AVR -- your choice. There are others, of course, but these are the cheapest and most 'hobby friendly.' Instrucables has some great resources for you-- Charlieplexing, or getting the max from you're output lines (there are limitations); Programming and AVR with a cheapo parallel port cable, etc. (search for LED, AVR, PIC for more.)

Microcontrollers normally use PWM (pulse width modulation) for fading fx. The POV fx is cool, here's one by Ladyada.

You'll never reach the $3 price point without huge quantities (and manuf in china.)

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gmoon (author)gmoon2007-10-12

Should have pointed you to ladyada's personal website, not just the store. It has the info you need to build your own from scratch.

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T3h_Muffinator (author)gmoon2007-10-15

He can get pretty close, though! He should be able to get sample AVRs from Atmel, and then most of the rest of the components he already has (i think?) All he needs now is a parallel plug, some wire, and a computer with a parallel port (You know, for easy programming).

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Goodhart (author)2007-10-12

I believe I understand what you are talking about. I have a "scavenged" board from a game, that has a bunch of LEDs on it, and depending on which button it pressed, or how many times A button is pressed, different things happen (scrolling, flashing, sequential flashing, etc. I remember it used a single IC to control all that (I don't have the thing here with me, but it was a CMOS logic gate/flip flop, if I remember correctly).

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