I managed to get a 5x7 LED matrix
All the tutorials that I have seen on the itnernet have 12 pin matrices
Mine has got 14 pins, 7 on each of the smaller sides of the display
I managed to get the datasheet (the manufacturer seems to be very secretive about it - it took me three emails and then a phone call to get him to send it) today
Here's it the image I was sent in lieu of the datasheet :
Mine is the one on the row cathode version
Pins 4,11 and 5,12 are shown to be same. Does that mean one of each pair is redundant?
Does it make any sense?
No you wire them both up so the the high current on these pins is shared amongst the pins. It is a common practice to do this sort of thing.
That data sheet is about as good as it gets for most LED matrices.
Grumpy_Mike:
... you wire them both up so the the high current on these pins is shared amongst the pins. ...
Thanks.
You mean I should connect 5,12 to the same digital output pin on the Arduino and likewise for 4,11 ?
And I would need 5 resistors before each anode column or should I put 7 before each cathode row? (I'm guessing it won't make a difference, but just to be sure)..
It didn't come with voltage values for the LEDs so I should probably start with high resistances like 470? What would be the common/average value to go with?
Well you are going to need some sort of driver on either column or row as you can't get enough current out of an arduino pin for more than a couple of LEDs.
The resistors should be placed so that when an LED is on the current for only one
LED passes through a resistor, so yes it dose matter which.
I would start off by assuming 20mA with a forward volt drop of 1.85V
No you wire them both up so the the high current on these pins is shared amongst the pins. It is a common practice to do this sort of thing.
That data sheet is about as good as it gets for most LED matrices.
That's not the reason there are two pins for these lines. It is wired this way so that you can insert the display into the socket either way and it will still work.
All I have is 4 74HC595s and 4051s ..
Can the 595 function as a driver for the matrix.. I'm not sure what a 'driver' means. I've used the 595 to light 8 LEDs at the same time
I'm new to the Arduino and I'll be satisfied even if I managed to light the matrix somehow and then later worry about the brightness, etc.
Without using a LED driver what disadvantage would I have? Just low brightness?
Of course I'm going to be using resistors, unlike the above link..
Also using row-column scanning, I'm lighting up only one LED at any given time, so I didn't understand why I should account for multiple LEDs being on at the same time
A circuit or component that produces the drive (voltage or current) necessary for the output device from the signal from the controlling device (in this case the arduino)
I'm lighting up only one LED at any given time
That is not the way you normally drive a matrix. The normal method is to have one row or one column on at any instant and change that row or column to scan the whole matrix.
If you only have one LED on at a time you will have to refresh it at many times the normal rate so it doesn't appear to flicker. Also with a 5 X 7 matrix the on / off ratio is 34 to one. That means it will only be 1/34 times as bright as if it were on all the time. This is so dim you might not see it.
