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Topic: Buddys LED project (Read 1 time) previous topic - next topic

ubotbuddy

I mentioned this in a previous section here but I wanted to acknowledge that whatever I learn for my own project I gained MORE useful information from this thread http://arduino.cc/forum/index.php/topic,114901.0.html than from all of the video I have researched and watched on YouTube.  So kudos to Pedro for sharing his process and Crossroads for his considerable level of help.  Obviously, there were others in there so don't think I left you out   ;)

http://mystarbright.com

When I saw that site above I knew I wanted to recreate it.  I know I could buy it but where is the fun in that.

Believe it or not that window decoration is a 8x8 LED setup and I believe they are using Super Bright LEDs.  Most of the animations are 20 frames in length so it is VERY doable with Arduino.

I am almost at the build stage for the 8x8 but I am waiting for my shipment of components including a 74HC165 and a 74HC595.  I ordered both not knowing which one would be best but I am sure that will be an easy task.

While my parts are shipping I will ask this of anyone.  I know there is some fabric that might be good for mounting of the 8x8 LEDs but as far as I saw it was pretty much a small size.  At the commercial site they are using a plastic backing for the LEDs but I know zero about how that could be created...maybe it is an outsourced kind of thing.

For now...I will mount on some kind of stiff cheap board unless someone has an idea.  I am completely open here.

Now for a design question.

What is the Darlington ULN2803 component used for in Pedro's project?  In some other LED matrix designs that I have studied it does not appear.

Yes, I will be posting pictures and code as I progress so stay tuned until I get my parts.  lol

Thanks!

Buddy

Lavan

Instead of using transistors to drive LED's,  ULN2803 is used.  Its easy and no complexity compared to using the transistors.

CrossRoads

In Pedro's thread, reply #15, the ULN2803 sinks the current from all the cathodes.
If all 8 LEDs in a column were, that would be up to 160mA. A 74HC595 alone cannot do that.  I think it has a limit of 70mA for the whole chip.
Another choice for the 2 chips would be to use a TPIC6B595, which is a shift register with high current sink capacity - so pretty much a combined HC595/ULN2803 in one package. But I think Pedro wrote that he had the '595s already.

Whether a high current buffer is used depends on the multiplexing scheme.
If you want to light a whole column at once, a buffer is needed.
If you want to parse out the anode bits one at a time, then you can get by without.  Refresh rate is 1/8 or less of what you can achieve writing a byte a time.
I come from high speed hardware design world, no way I'm doing 1 bit a time.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Riva

Quote
Believe it or not that window decoration is a 8x8 LED setup and I believe they are using Super Bright LEDs.  Most of the animations are 20 frames in length so it is VERY doable with Arduino.

Sounds like a job for the MAX7219/MAX7221. Simple to use with arduino library support. Low component count 1x MAX7219, 1x Resistor & 2x Capacitors per 64 LED's (http://arduino.cc/playground/Main/MAX72XXHardware) Chip can be cascaded. LedLibrary supports 8 chips so 512 LED's

ubotbuddy

Thanks guys for the info!

As soon as I get my 74HC165 from the slow boat I will be starting (Arg! I hate the wait).

I don't have the other chips (MAX7219 or ULN2803) but I will order those as well just so I can see the differences between them and the effects they create.

I figure I don't need them since the example I saw on the Arduino.cc playground area did not have them.  If I have to wait much longer I may do a raid at a local mom n pop electronic store.

CrossRoads

Next time order locally. www.dipmicro.com has lots of stuff, www.taydaelectronics.com, and often digikey.com and mouser.com are less expensive than  e-bay too.

You can start coding now, you have access to all the data sheets.

For instance,
http://www.ti.com/product/sn74hc165
is a parallel load -serial output shift register, I can't envision how you will be using this with an LED display.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

ubotbuddy

DipMicro is who I am waiting on.  I got the express shipping so it should be here any day...I hope.  ;)

After I put my order in with the Chinese it clicked with me that it might take a few months to get over here so I placed a quicker order with DipMicro.

I just need to be a bit more patient.  The lack of it has been a curse for me.  lol

CrossRoads

Dipmicro stuff comes quick.  I just got a box with power adapters, couple of LCDs, motor shield. Ordered the 21st, late at night of course, was here the 24th or 25th.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

ubotbuddy

Hallelujah!  My shift registers (74HC595) finally arrived.  Now for a trip to Radio Shack to find some wire wrappers.

More to come


Pedro147

I love it when the slow boat finally arrives... happy wiring Buddy  8)
http://www.pedroduino.com

ubotbuddy

Need a bit of help.  I have started but I am going slow to ensure I setup stuff correctly.

If you look at this tutorial http://arduino.cc/en/Tutorial/ShiftOut

You will see this http://screencast.com/t/Vd5Ddepq

What is that component?

I am trying to do this as a step 1 so I do not want to blow up my Arduino board.  ;)

Here is the circuit  http://screencast.com/t/CEmjFdZz3

thanks!!!

AWOL

#11
Sep 04, 2012, 09:21 pm Last Edit: Sep 04, 2012, 09:25 pm by AWOL Reason: 1
It looks like it is meant to be a disk ceramic capacitor, but really, from the Fritzing, that's just a guess.

I hate Fritzing.

The text describes it as
Quote
Notice the 0.1"f capacitor on the latchPin

I guess the double-quote is meant to be a Greek mu, but that's a guess.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

ubotbuddy

Thanks.  Maybe one day I will recognize these things.  LOL

Hang on while I wipe the NOOB off my face.

Back to my project.  I will be posting images so stay tuned.

Thanks again AWOL

Pedro147

Hi Buddy,
I looked around a lot for info on shift registers and these are the best three sites that came across  IMHO as they say these daze   8) Pedro.


http://tronixstuff.wordpress.com/2010/04/30/getting-started-with-arduino-chapter-four/

http://www.gammon.com.au/forum/?id=11518

http://bildr.org/2011/02/74hc595/

http://www.pedroduino.com

ubotbuddy

Thanks Pedro!  You da Man!

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