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Topic: 8x8 Dot Matrix (Read 9330 times)previous topic - next topic

Vincent19

Jul 31, 2013, 08:58 pm
http://arduino.cc/en/Tutorial/RowColumnScanning

Dear all, I am refering to this tutorial when trying my dot matrix.

" so a column needs to be high for any of the LEDs in that column to turn on. The rows are connected to the LEDs anodes, so the row needs to be low for an individual LED to turn on. "

For this, I do not understand it. I think it should be the reverse ? Hope someone can clarify to me and anyone knows how can I test my new bought dot matrix to ensure all the LEDs light up at the same brightness ?

Grumpy_Mike

#1
Jul 31, 2013, 09:09 pm
Quote
For this, I do not understand it. I think it should be the reverse

No it is right.
To light an LED current has to flow through it in the direction of the arrow in the symbol.

Read this for the two ways you can do this:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html

PaulRB

#2
Jul 31, 2013, 11:33 pm
I'm with Vincent. Surely its wrong? Current flows from anode to cathode.

Grumpy_Mike

#3
Jul 31, 2013, 11:40 pm

I'm with Vincent. Surely its wrong? Current flows from anode to cathode.

Mind you those pages are impossible to change. There are several with mistakes on them that older members have been complaining about for years.

Vincent19

#4
Aug 01, 2013, 05:12 am
Any ways to check if my dot matrix is working or not ?

Thanks

PaulRB

#5
Aug 01, 2013, 06:42 am
To check all 64 leds at the same time is not easy without a programmed Arduino and/or driver chips. But you can just use a few jumper wires and eight ~250-300R resistors. Test each column in turn (with resistors on the rows), then each row in turn (with resistors on the columns). If there is any significant difference in brightness you should be able to see it. You must use 8 resistors. With only a single common resistor on the row or column you are testing, you will exadurate any small natural differences between the leds.

Paul

Grumpy_Mike

#6
Aug 01, 2013, 06:44 am
Simple take a resistor from 220R to 1K. Connect one end to an anode, the other to 5V. Then take a wire and connect one end to ground and the other touch on a cathode and one LED should light.

googs

#7
Sep 07, 2013, 07:28 am
i already did what Grumpy_Mike suggested,
obviously, you also need pen and paper and draw it out and map what you find, takes 5 mins...
i had to do it this morning, and think that my 8x8 has LEDs polarity opposite to what i see in all the datasheets/images around the net :S
my 8x8 has part# 1588BS-H4, and i cannot find any reference to it, yet..
(mines a red mono-color)

PaulRB

#8
Sep 07, 2013, 08:04 am
Hi, see this page for the difference between ax and bx variants. Yours is bx, so as you found, opposite to the ax you have seen elsewhere.

http://m.aliexpress.com/item/879542981.html?tracelog=storedetail2mobilesitedetail#description

Paul

turbine495

#9
Jan 27, 2014, 08:00 am
Stupid me, forgot the resistor and fried a pixel

raschemmel

#10
Feb 02, 2014, 08:08 pm
Here's a datasheet
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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