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16  Using Arduino / LEDs and Multiplexing / Help me chose the right LED? 4 x 4 square grid with acrylic top on: September 10, 2012, 12:05:36 pm
Guys, please, I'm building a 4 x 4 LED square grid. So, I will build a 25 cm x 25 cm box with 3 separations horz. e 3 vertically. So, in total, we will have a 4 x 4 square grid. (16 squares)

Each square will have a red led. On top, a white-frost acrylic, so now I need to figure out which led will be best. So I get good illumination and also a good view angle, so it just don't show a red dot, but an uniform red square.

Here are some leds from eBay, if you find better ones (only eBay) please let me know, ok?

http://www.ebay.com/itm/100-pcs-5mm-straw-hat-Red-LED-Wide-Angle-20000MCD-/120496125516?pt=LH_DefaultDomain_0&hash=item1c0e20f64c

http://www.ebay.com/itm/100-pcs-Red-5mm-straw-hat-LED-Wide-Angle-Light-Lamp-Free-Shipping-/170842661548?pt=LH_DefaultDomain_0&hash=item27c70422ac

http://www.ebay.com/itm/100Pcs-5mm-Flat-Top-RED-LED-Wide-Angle-Light-LED-/260520802647?pt=LH_DefaultDomain_0&hash=item3ca83ff957

This leds I already have here, but the V.angle are terrible.
http://www.ebay.com/itm/100-pcs-5mm-Red-LED-Lamp-Ultra-Bright-Free-Resistor-EMS-/160557816658?pt=LH_DefaultDomain_0&hash=item2561fddb52

Thank you for any advice.

Best Regards, WilliamK
17  Using Arduino / Project Guidance / Re: 16 Touch Sensors - its working [code] but I wonder ... on: September 08, 2012, 06:04:11 pm
Well, I will be building the prototype soon, it will handle 16 ultra bright LEDs, so one sensor per LED. I will check some nice screws this week, to see something I like. ;-) Once I have something nicer to show, I will post pictures.
18  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 06, 2012, 12:21:21 pm
I'm using the CapSense Library and a 16ch Analog Multiplexer. I had to mess with the code around a bit, in order to get only true positive touches.

http://arduino.cc/forum/index.php/topic,121508.0.html

As soon as I have the first prototype ready, I will post about it.  smiley-mr-green
19  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 06, 2012, 12:04:29 pm
Ok, here's the final deal, a friend also helped me out with the math.  smiley-mr-green

I will drive 2 x 74HC595 in series, so I can get 16 outputs.
Them I will drive those 16 outputs directly to 2 x ULN2803A

On each output of the ULN2803A, I will put a 100 ohm resistor + UB LED. (2.3Vf 20ma)

In my tests it works perfectly. And if I want a second LED to make it more bright, I just put another 100 ohm resistor and add in parallel.

Now I need to get some White-Frost Plexy to test how this will look like.

Here's something some guys did that are similar to my idea. But I plan on using RED-Only LEDs (Ultra Bright) and a 4 x 4 pattern instead.

http://e2e.ti.com/group/microcontrollerprojects/m/msp430microcontrollerprojects/447779.aspx

The difference is that in my project, each square will be touch-sensitive. ;-)
20  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 03:39:21 pm
Maybe I'm not explaining things right or I just got lost.  smiley-red smiley-eek-blue

Anyway, as I asked, can't I just use 2 x ULN2803 chips and 8 pins from the Arduino?
21  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 03:28:12 pm
It doesn't matter, I can do both, just wondering on what I could do with the stuff I already have that will get my ultra brightness.  smiley-mr-green
22  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 03:18:31 pm
Can't I just use 2 x ULN2803 chips and 8 pins on the Arduino? (I don't need many free pins, only 4 for a multiplexer, and 2 for UART)
23  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 03:11:36 pm
Sounds interesting, but how can I do that? Do you mind teaching me, pretty please? ;-) ;-)
24  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 03:01:41 pm
:-p

Too bad I don't have those. But I will see if the local shop carries it... (doubt it)
25  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 02:51:50 pm
I need it to be as bright as possible, since a plexy will go on top of the LEDs. ;-)
26  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 11:39:02 am
But I guess using a 4x4 matrix will present less light brightness compared to the other solution, right?
27  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 11:34:22 am
Oh, thanxs!

I got some ULN2803A here, would those work too?
28  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 11:16:30 am
One thing I'm wondering is to just do a matrix of leds instead of using the shift c595 ic. Any ideas on that?

For 16 leds using the C595, I would need two x C595, a resistor + transistor + resistor for each led.

Now, for a 4 x 4 Led Matrix (total of 16 leds) connecting directly to each pin on the arduino, I would have 4 pins for the row and 4 pins for the column. Now, wouldn't I use less ICs? I know that I will need to use a timer to handle the leds, just like SparkFun did on the 4x4 Button SPI product.

Anyway, just brainstorming out loud ... ;-)
29  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 10:09:53 am
Oops, actually they were called "5mm Red Ultra Bright" (I copied this from the purchase I made)

So they are like this:

http://www.ebay.com/itm/100pcs-OF-RED-5mm-ROUND-HEAD-ULTRA-BRIGHT-8000-mcd-/271047071506?pt=LH_DefaultDomain_0&hash=item3f1baa1712

FORWARD VOLTAGE: 2.3 VOLT
FORWARD CURRENT: 20 MA
30  Using Arduino / LEDs and Multiplexing / Re: Super Bright Red Led - BC547B Transistor, but which Resistors? on: September 05, 2012, 10:08:47 am
Perfect! I'm learning, thanks!  smiley-cool

One thing, how can I know the details of a LED? I bought in bulk, all I know is that they are super bright red leds. (I think they are 5mm, I could measure)

They look just like this one:

http://www.ebay.com/itm/100-Pcs-5mm-Red-Superbright-diffused-LED-Light-lamp-2-Pins-5000-6000-Mcd-/180967282597?pt=LH_DefaultDomain_0&hash=item2a227d97a5
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