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Topic: Led panel (Read 1 time) previous topic - next topic

fewe

Hi,

I'd like to create a led panel like this one: http://www.nerdkits.com/videos/ledarray2/

For now I only have two columns with 5 rows so 20 LEDS (5 LEDS per column * 2 columns * 2 LED columns per column). I am having trouble when trying to light up only one led at a time. I turn all output pins to LOW and set the related row pin to HIGH so that current will be able to flow. The problem is the following:

Given the fact the 2 columns are setup exactly the same way, the same led on the same row of those 2 columns will lit up... This is why I am trying to set one of the two column pins as an LOW INPUT but this does not help.

Here is the code for clarity:

             for (int i = 0; i < ROWS_NUMBER ;i ++){
               digitalWrite(ROWS_PINS, LOW);
             }
             
             for (int i = 0; i < COLUMNS_PINS_NUMBER ;i ++){
                 digitalWrite(COLUMNS_PINS, LOW);
             }
               
                 digitalWrite(ROWS_PINS[1], HIGH);
                pinMode(COLUMNS_PINS[1],INPUT);
                 digitalWrite(COLUMNS_PINS[1],LOW);

How can I make it so that only one led at a time is lit on?

MarkT

Set all pins as INPUTs, then set only the relevant row and column lines as OUTPUT and HIGH and LOW as required.
[ I won't respond to messages, use the forum please ]

Grumpy_Mike

Only put one column high, the other low. Then put only one row high and the others low.

MarkT


Only put one column high, the other low. Then put only one row high and the others low.


That assumes the max reverse voltage rating for the LEDs is 5V or more (usually the case), my method doesn't assume that though.
[ I won't respond to messages, use the forum please ]

fewe

"Set all pins as INPUTs, then set only the relevant row and column lines as OUTPUT and HIGH and LOW as required."

This is what I do but as I said, but the leds mapped on the column I set as INPUT light up anyway.

"Only put one column high, the other low. Then put only one row high and the others low."

This is also what I've been doing, but the thing is that it works only if you have one column because the patterns then repeats over x columns.

MarkT

Maybe you should clarify the wiring of the LEDs for us?
[ I won't respond to messages, use the forum please ]

Grumpy_Mike

Yes fewe what you report can not happen if it is wired up correctly, so a schematic and a photo would be good.

fewe

The schematics is on the website: http://www.nerdkits.com/videos/ledarray2/mikeyplex.png

I tried to put a 10k resistor but it didn't really help.

Grumpy_Mike

Where are the resistors! You need about 270R in line with each column.
You never said this was a charleyplexing circuit, you drive those very differently from a normal matrix.

AnthonyMartello

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fewe


Where are the resistors! You need about 270R in line with each column.
You never said this was a charleyplexing circuit, you drive those very differently from a normal matrix.


I'll try that but I tried putting 10k resistors on each column to be sure but it didn't so AFAIK a 270R will give the same result.

BTW sorry for the delayed answer

Grumpy_Mike

Quote
but I tried putting 10k resistors on each column

That will give you 0.5mA to share between all the LEDs I would be surprised if you can see anything with that.

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