Pages: 1 [2]   Go Down
Author Topic: LED matrix  (Read 4214 times)
0 Members and 1 Guest are viewing this topic.
berlin
Offline Offline
Sr. Member
****
Karma: 0
Posts: 293
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I am trying to get my led matrix to run off the 7219, but wierd crap is happening.  I copied the code for the diagonal, uploaded it, and then all the leds come on.  They are all way to bright, and are not in a diagonal.  I can get them to flash messing with the hex numbers in the loop, but they only go from really bright to a slightly less really bright.  WTF IS GOING ON!!!  i cant get them to turn off at all unless i remove the clock wire on the arduino, removing the 5v going to the 7219 pin 19 makes them dimmer but doesnt turn them off.  Any help would be great, if no one can help I will post a picture of my breadboard later.

try swapping the polarity of your LEDs. this might solve your problem.


Logged

Daniel
Guest
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I am trying to get my led matrix to run off the 7219, but wierd crap is happening.  

a few ideas:

- make sure you have a ground return connection  between the Arduino and the 7219
- this is a high-current load, so is you power supply big enough? The Arduino's on-board regulator may not be adequate.
- high-current loads require good power supply bypassing: .1UF and 330UF capacitors between +5 and GND, located near the 7219 will do it.

D
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 1
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I am also having trouble controlling my leds.  I took a picture of the board.  I used the code posted in this forum, which is similar to the sample code in the arduino program.  I'm thinking that my wiring is wrong.  It seems right in theory, but am I missing something?  What is wrong with my project?

Logged

0
Offline Offline
Full Member
***
Karma: 0
Posts: 183
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

i don't have a matrix but I read the datasheet and to my surprise the connections are not in numeric order. So it is not 0-7 from the first to last leg. Check the links in previous messags in this thread. Direct link to a datasheet: http://www.lc-led.com/products/lc2088tw1c.html

If possible try to use more than one colour for the wires. It is so easy to make a mistake and you won't notice it. You can also try to switch on 1 row, use Massimo's code with something like this:
max7219_put(0x01, 0xff) Here 0x01 is row1. So, try row1 to row8 and see what led's switch on. Rewire row for row until it works.

I made a circular matrix with the driver, wiring the whole thing was a challenge but using different coloured wires certainly helped. Figuring out to which rows the wires were connected to was time consuming but worth the effort. I haven't put it in the playground yet because making a circular matrix is apparently easier than writing in the playground.  :o
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 1
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi all,

I'm afraid I'm having the exact same problem as michie -- an led array wired to a max7219 that's wired to an arduino in the default configuration.  I built the array myself with sockets, so I can verify the polarity of the leds, swap them out, and so on.  

I'm getting the same odd behaviour -- all leds go on, removing the connection between pin 19 on the 7219 and 5V dims the leds slightly but doesn't turn them off.  swapping the polarity of a row of Leds doesn't alter the outcome at all.

Your suggestions are as follows:

- make sure you have a ground return connection  between the Arduino and the 7219

--- by this I take it that the grounded pins from the 7219 are attached to the gnd pins on the arduino. Check.
 
- this is a high-current load, so is you power supply big enough? The Arduino's on-board regulator may not be adequate.  

-- I've used a larger resistor on pin 18 of the 7219 to limit the per-segment current to 10mA -- The usb power seems to be able to handle the multiplexed load (only 80 mA) ok.

- high-current loads require good power supply bypassing: .1UF and 330UF capacitors between +5 and GND, located near the 7219 will do it.  

-- please explain in a little more detail (sorry, I'm a rank beginner at this) how to do this - just bridge the +5 and GND with two capacitors in parallel?  

Are there any other tips to try?  Anyone else have this problem?  Did you end up solving this problem, Miche?

Thanks very much in advance,

Noah Luken
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 30
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I also have a bi-color 8x8 matrix that I am trying to get working with just one color for now.  Lite-On LTP14188A-01.  
http://www.liteon.com.tw/opto/spec/databook.nsf/1646fbcd87a370e948256a9a001f2f9b/8ae9d00ce9cd3401482570ce00253c05?OpenDocument
it is "cathode column / anode row" (although the "A" in part number suggests it is common anode?).  when i wire it as per tutorials with a MAX7219 every single LED is on no matter what.  (i thought i had polarities reversed but if i switch, every single LED is *off*.)  i see conflicting info in these posts about if LED anodes (pos) should be connected to SEG or DIG pins on 7219, and likewise about row/col.

i'm confused by the requirement for "common cathode" with the 7219, since in this matrix the anodes are common on the rows, and the cathodes are common on the columns.  so which is it?  

besides that general theory question, is it not possible to use this matrix with the 7219?  can i do some circuit trick to make it common cathode?  i happen to have a lot of them very inexpensively :-p...
« Last Edit: March 29, 2007, 10:35:25 pm by eforman » Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 1
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

hi,

I don't know if this post is still in use.
but I do have the same problem with the bright lighted led as it was discribed before.
does anybody know what the problem is?
it would be get some help because I am not so much into that whole thing yet.

thanks!!

Logged

Pages: 1 [2]   Go Up
Jump to: