# I need a circuit board builders .02



## Acuta73 (Mar 17, 2008)

Ok, I need to build multiple SMT LEDs into a "chasing" flash array. I can figure out the simple bit of putting the resistor and the SMT onto a micro board, but how do I control them in order to make them "chase"? Without a good picture, in other words, to light one after the other in sequential order and repeat? Is it possible to mount multiple SMT with a single resistor? I know bloody little of electronics, but am an eager student.

Is it possible to even put this into layman's terms?

Eric


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## Acuta73 (Mar 17, 2008)

I think I found my answer! Can get them in strips, so I don't have to do all the soldering and such. Unfortunately I can't get them white/blue staggered. Oh-well, blue by itself would work.

Link here

Only caveat is, I still can't find a controller for it. There's one on that site, but not sure if it would work. I want either "chasing" or fading on and off.

Not cheap, by any means. But very cool.

Eric


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## magnethead (Mar 18, 2006)

hmm... I'm thinking a transistor IC with a capacitor/resistor combination. Similar to a points ignition system in a car. capacitor loads up, dumps through the transistor, drops flow volt, builds up, dumps through resitor, ect through a stepping set of transistors. Although i can't say 100% how to set it up fully wouthout thinking more about it.


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## magnethead (Mar 18, 2006)

magnethead said:


> hmm... I'm thinking a transistor IC with a capacitor/resistor combination. Similar to a points ignition system in a car. capacitor loads up, dumps through the transistor, drops flow volt, builds up, dumps through resitor, ect through a stepping set of transistors. Although i can't say 100% how to set it up fully wouthout thinking more about it.


wow, whatdya know. 

http://www.aaroncake.net/circuits/chaser.asp

http://wild-bohemian.com/chr-info.htm


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## Acuta73 (Mar 17, 2008)

Ya know? That's some cool stuff. Bummer it's all greek to me. lol

As I said, circuitry is not something I've ever done. But it has enough promise, I think I need to learn more. I actually understood most of the schematic on Aaroncake, but would have no clue how the heck to put that onto a board. And now clue if it would work with 50-100 SMD LED in a string. Looks like it would be cheap to build, though. Most of the SMD LED are 50 cents USD or less, and the components on that board probably don't add up to $10. I like the idea of using a simple pot to adjust chase rate, too. Can see one possible(?) issue, circuit shows a 9v input, not 12v. 

And those strips I linked are 2 wire. Could be an issue. Doubt I could use them, though they'd be the easiest answer.

Things to ponder. Glad I have time on this one.

Eric

P.S. Could someone explain what they mean when talking about Anode and Cathode in wiring LEDs??? = )


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## magnethead (Mar 18, 2006)

Ssrogg said:


> Ya know? That's some cool stuff. Bummer it's all greek to me. lol
> 
> As I said, circuitry is not something I've ever done. But it has enough promise, I think I need to learn more. I actually understood most of the schematic on Aaroncake, but would have no clue how the heck to put that onto a board. And now clue if it would work with 50-100 SMD LED in a string. Looks like it would be cheap to build, though. Most of the SMD LED are 50 cents USD or less, and the components on that board probably don't add up to $10. I like the idea of using a simple pot to adjust chase rate, too. Can see one possible(?) issue, circuit shows a 9v input, not 12v.
> 
> ...


I learned out of books, of all things. Very little hands on. 

LED (light Emitting Diodes)- Diodes are electronic check valves. Electricity will only flow through them one way. Therefor, you have to check which way you install them in a circuit. Another note for diodes, is for a non-lighting diode, there is a 0.6 volt drop. The Anode and Cathodes of an LED are just it's positive side and negative sides. Their location from the flat spot is how you identify them.

Transistor- A transistor is a flow gate. All basic transistors have the same design- electricity flows from one outer peg to the other. But the middle peg decides if it flows or not. If the middle lead does not have any voltage going to it, electriciy will not flow through the transistor, and vise versa. Although some do the opposite effect- will not flow with an active center.

Though the schematic shows a 9 volt input, a 12 could be used, but you'd have to check the ratings for the IC's and NAND gates (basically special transistors).


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## magnethead (Mar 18, 2006)

I would say, the easiest way to do what you want is use the schematic from aaroncake, which drives 10 LED's. Then use 2 of the assemblies for 20 LED's. Which would be enough for 2 per side on a decagonally shaped disc. I wouldn't suggest using a strip, you'd have to use a relay and have each strip act as an individual lamp in the schematic (so 10 strips). Unless you did two strips all the way around, one white and one blue, and only used a 2 position counter as upposed to 10.

However, you can eliminate the IC's just be using a series of flasher circuits..considering i have no clue where to buy IC's.










http://wild-bohemian.com/electronics/flasher.html

That's your better option. You can put blue on one side and white on the other. As typical, it'l run on 12 VDC is you get 12V components. You can use the 3.6 V LEDs radioshack has (or a 50 pack off ebay) and mirror what I did for hybrid- 3 blue and 3 white per 'layer', and as many layers as needed to light up the case, to the point that the 470 ohm resistors may be able to cut down to 100 ohms.

100 K resistors : http://www.radioshack.com/product/i...t&kw=100k+resistor+1/4+watt&parentPage=search : .99

470 resistors : http://www.radioshack.com/product/i...tt&kw=470+resistor+1/4+watt&parentPage=search : .99

10 uf control capacitors : http://www.radioshack.com/product/index.jsp?productId=2062393&cp : 1.59

2N3904 switching transistor : http://www.radioshack.com/product/index.jsp?productId=2062609&cp : .79


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## magnethead (Mar 18, 2006)

On hybrid, I did 3 LED's per layer with a 220 ohm resistor in front of them. Which would replace the 470 ohm and LED on the schematic. 

You could cascade this circuit into itself to make a chaser. take the whole circuit, and put it in place of each 470/LED sequence. So that you'll have 4 LED's flashing chasingly/randomly. So that not all the blues and not all the whites are together- it'll be half the blues, half the whites, the other half blues, other half whites. Or at least that's what i can theory up. 

There's a very Minute possibility that I could put it all together for you then UPS it to you if you think you're too incompetent to do it. For a fee, of course :tongue:


Here's an expanded schematic as a cascaded circuit. Also on there is how the layer of LED's would be wired in. I found that 220 ohm resistors were fine for a 3 LED set off 12 volts.


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## magnethead (Mar 18, 2006)

Also, something that flew my mind, for that to work properly, the core 100K resistors (in the bottom parent circuit) would have to be bumped to 10M resistors, if not higher, and the 100K's in the child (top) circuits dropped to 50K if not 10K. That would probably give you something like what you want. It'll almost be like a random LED lighter- exactly what you'd want for a UFO lighting system.

If you leave the parent at 100K and make the child resistors in the 10K to 50K range, it may look closer to a chaser. the child resistors would set the interval between blue and white alterations (smaller = faster pace), while the parents set the interval between the left and right circuits. But if all 6 are the same, then iy'll only light one half or the other because the child circuits wont have time to switch colors before the power to them is switched to the opposite side of the parent circuit.


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## magnethead (Mar 18, 2006)

I'm reading my electronics handbook, RS# 62-5004, pages 50 and 113.

the flasher in the book is very similar to the one i've posted, except it uses PNP transistors on the positive end, upposed to the NPN shown on the negative end of the circuit.

in a schematic, the line side of an LED is the cathode (connect to ground) side and triangle is Anode (positive) side. On the transistor, the arrow points the direction of flow (Collector to Emitter for NPN; Emitter to Collector on PNP).










In the circuit shown, the positive charge goes from the source to the anode side of both LEDs, through the resistors, to the collector of the transistors. 

Also, it goes though the high resistance resistors, down to the base of the transistors.

Meanwhile, it also goes into the storage capacitors

Now, the logic part (i'm gonna go left to right)- 

As the electricity goes through the (left) LED's and resistors, the power has to go into the (left) capacitor because the transistor is closed. Since the (right) resistor is high, the power takes the easiest path- being stored in the capacitor. But since there has to be a complete circuit, while the capacitor is building voltage, there is a slight energy amount going into the base of the (right) transistor, allowing it to be powered on. This allows the electricity to flow through the (right) LED and resistor, through the transistor, and won to ground, making that side light up. 

Yes, it's confusing, even to me. But it works. What makes it switch sides is that while one LED is on, the capacitor for the opposite side is charging. The power source never actually goes directly to the LED, the capacitors power them.


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## Acuta73 (Mar 17, 2008)

My God, Magnet. You did a ton of work! Hats off, my friend. Now I just need to get my addled brain together enough to figure all your work out! lol

The random circuit would be perfect for the interior "stars". Still want contiguous chasing OR fading for the exterior. The 10 LED strips would be too short unless I could somehow synchronize them?

Wasn't ignoring your help, by the way. We started new delivery routes this week so work has been chaos and I haven't gotten online all week. Haven't gotten to drawing out Stardust, either. Need to get off my hind end and start, but I came home to a list of honey-do's. Hopefully I can get away for a while tomorrow and do some of my own "work".

Still need to case-up my Sony into Prowler sometime this weekend, too. /sigh

I hate it when life interfears with my fun!

Eric


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## magnethead (Mar 18, 2006)

the strips would only light all of them at once, not chase. All the LED's in the strip are more than likely in parrallel. You're gonna have to build your own LED set or pay out the .... for a chase arrangement.


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## Viking1234 (May 21, 2008)

I'm going up to visit my Electronics teacher tomorrow and I have quite a bit of hands-on experience with this type of thing. 

I wish I had a camera, I could show you step by step how to build it.


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