LED Dot-Matrix Display

This is a simple HOW-TO make your own personalised LED Dot-Matrix display. I will be adding the complete program with an explaination to light the LEDs with. It's also rather hackable, you can change it to suit yourself.

I decieded to make my own dot matrix display because they look cool, and none can be found in blue, which is the best colour, so I decided, may as well make it myself.

Step 1 Plan

The first task is to plan the project.

I built the cuircuit on Eagle so I could see the connections and test the LED matrix. It also enabled me to learn how to light the individual LEDs.

First thing to do is to add all the support stuff for PIC, so I need power supply, download socket and reset. I also need to arrange the outputs in simple to use rows. This defined the size of the PCBs so I spent as much time as I could reducing the size until I couldn't get it any smaller.

The next step was to place the 20 LEDs in the dot-matrix, connectign all the anodes in columns and all the cathodes in rows. This is impossible to do without using link wires unless your using double layer board or double sided board. I wasn't so I will be using link wires.

Comments

[Gravydude]

The "Blue Dot Matrix" was done by the Germans about 20 years ago. China now makes a 2" cube module. It has 7 l.e.d in a column and 5 in a row. They also make these for segmented applications as well.

[leddisplayscreen]

Yes, you are right.
by the way, we are the led products manufacturer ( led display)
I think you can come to our website for more informations about led. www.leda-display.com

[efdat]

I really need the work you do but does it scroll? because I need that one which scrolls

[slithytove2]

The scrolling would be entirely in the code, not the hardware, so yes it could be made to scroll. I have not worked with this particular uC, so I can't help you figure it out though.

[kukumalu]

Hi! This is a really cool project!
I have a question. If I want to glow only LED (2,2), I must set row 2 at 0 V and column 2 at 5 V (so that current will flow through the LED). Also, other rows- 1,3,4 and 5 should be set to 5 V and columns 1,3,4 and 5 to 0 V. But now all LEDs except the ones in row 2 and column 2 are reverse-biased with 5 V reverse voltage. Most LEDs have maximum reverse voltage of 5 V. Is it safe to use this design?

[jonathan95123]

I was wondering how you solved the random dim LED problem. Im using an arduino and 595 shift register. At first I found the problem to be that there needs to be a 1-2ms delay in between latch pin high and low but after adding more code to control more lights it came back and delays are not the problem. Thanks.

[hr.anup]

y have u used serial out and in................. i seem to ve a problem, how will this display the desired charecters... to get A i will enable col 1,2,3 then i will also for row 1,2,3 then the output will be x x x x x x x x x but i dont want the middle light in the 3ed row to be enabled how to solve the problem...............

[meg51522]

multiplexing is the answer of your problem sir!..

[apender]

http://en.wikipedia.org/wiki/Multiplexed_display

[junits15]

i want to make this, but I dont know how to use a micro controller, i could have board covered with switches, THAT would be cool

[jwoo2023]

same here i cannot use a micro controller so maybe toggle switches? :P

[dacflyer]

pinski1 you mentioned that you was not able to find the blue displays you wanted so you made your own.
well allow me to share with you this site, they make all sorts of displays and in all sized and colors.
heres the link.. enjoy :o)

https://www.lc-led.com/ecommerce2.html

[dombeef]

Yeah, but here you can make your own for less, and besides, there you have to buy atleast 3

[zoltzerino]

 I guess you have problems displaying the character "M".

[cnogoman]

Whats the purpose of the top and side connectors, couldn't you just hook it directly to the picaxe?

[pinski1]

 You you look at the pictures you'll see that the boards are about 1" by 0.75" very very little space for the LEDs, let alone the PICAXE as well, so it needed to go on 2 boards. There was also the problem of only having single sided board.

Of course this was done many many years ago, knowing what I do now, I could probably fit the same thing noto a single PCB in less than 10 millimetres on a side.

[ShortedOut]

So I have been searching for information on how the manufacturers that make these LED matrices get that smooth look for their LEDs. I found a page describing the process, saying that they use (embed the LED in??) an epoxy resin, either semi-transparent or transparent, and then coat the bottom with black. Does anyone know much about this process? What brand is best? How thin or thick do you spread the coating? And what is used as a mold?

[skillbajo]

pls i'm a novist, i just get started learning the dot matrix
   pls i need some one to put me through on how to write the program code in c language and even the guildline.\
           Thanks

[eagv]

Thank you very much for your help on understanding more about how Led Dot Matrix works.

[jayceemay123]

Hi Po, pashare naman po sa project nyo kung andyan pa.please

[tpirman1982]

Where in my area can I get materials/kits to create LED displays?

[chinnokker999]

Hey i was wondering how you'd make a "T" with this setup... Since there's an even number of horizontal rows, you wouldn't be able to center the vertical line coming down from the top of the "T"...

[pinski1]

Ah, you've found the fatal flaw... Because of my limit on size and the number of outputs, I could only have a 4x5, not the standard 5 by 7, but it does the job, and I like it.

[thermoelectric]

Could You make another one that is 5x7?

[pinski1]

I could, but I won't. The chip I used above, the PICAXE18X doesn't have more than 9 outputs. Ideally you'd need one with 12 outputs, or some further ICs to add to the previous 9 outputs. I'm not making another one, because I really don't see the point there are other things which I'm yet to do, things with ethernet and X10.

[aklem]

Lol just use a multiplexer... and are u using the x10 firecracker?

[Ankush]

I was wondering, can you display a sinusoidal wave-form in ur 4x5 dot matrix. I know u r using it to display alphabets & numbers. But i believe that you cannot have a sine-wave on this type of display device.........as un-neccesary LEDs would glow.

[Ankush]

Well you could display a T with a 4x5 dot matrix.......just that it is the small T...."t"!!!!

[pinski1]

I'm afraid you can do neither. The resolution is far too small to display a capital T let alone sin waves. The LED's wouldn't unnecessarily glow.

[Ankush]

I actually meant small "t".....unless ur looking to display only capital alphabets. Actually if you draw the schematic diagram of your 4x5 matrix you will find that to display only a diagnol 3 LED's , unneccesary 3 other LED's would glow, try it & tell me if thats not true!!.

[pinski1]

if you read the explanation, you'd realize it's is not true... The technique is called multiplexing. it's where you switch on all the LEDs on in a column or row at once, then turn them off and move to the next row, if you do this quickly enough, they eye doesn't see these changes and instead just sees lit LEDs. Try googling multiplexing for more information.

[Ankush]

Ok, yeah thats right. But a standard 5x7 matrix has a problem with diagnol LEDs lighting up....& i mean continuosly ON. Its all because its connected that way. Maybe a circuit diagram would show you what i mean.

[tpirman1982]

Anybody know where can I buy LED Dot-Matrix Display kits like these 20 matrix displays as seen in these pictures on this page?

[chrisapalo]

Hey... That's cool. Just thinkin'... Is there a way to use this with arduino? I have 3x3 matrix that is homemade.

[parcakontor]

i like this item

[Gasburner]

Just reading the buzz, and as to the "T" argument, could you not use a PICAXE 28?

[mman1506]

oh yes the picaxe cip is better but if you need you you can use a pic chip with the same pcb .picaxe chips are pic chips with bootstrap program except you'll need to redo the programmer

[mman1506]

i love picaxe its awesome theyre cheap and easy ive already built 2 robots

[Istarian]

If this hasn't been suggested already, you should learn how to do smd (surface mount) soldering. Then you can use just one circuit board, though you'd probably want to enclose it in a case.

[pinski1]

Back when I did this project (2006) I didn't have access to either easily. Now 3 years on I have, although I do more work with Ethernet and the like now. This was a one off and no longer works, the wire connections between layers were always a little picky and with age a couple have snapped.